Gwenda design progress

[Aramas]

Which is not a lot of progress - or at least not a lot that's visible to the 'untrained eye' (ie not mine smile.gif ). Just refining stuff and fiddling - 'sweetening' mostly). Still lots of placeholders, but you have to do that when you're limited to 20 surfaces. Every time I tweak the sheer I have to adjust the deck and redraw the sheer trim, bulwark and bulwark cap - and eventually the coaming, coach house and cabin top. Argh! I need a Cray so I can use lots of attachments and still have a rotating render.

Currently I'm nutting out how to have a nice pretty standing lug yawl rig that won't drive me nuts trying to reef.

But anyway, It's coming along.
Here's her vital statistics (subject to change - lol):
LOD 7.1m
LWL 6.3m
BOA 2.5m
BWL 2.1m
SA 37 sq m
Lightship 2 t
Loaded Disp 3t

And lots of pics! After I'd grabbed them all with a screenshot grabber (and uploaded them) I noticed that my chat program thingy was on all of them - lol - it was easier to clone it out in photoshop than do it all again.

See what you make of these:
http://www.imagestation.com/picture/sraid93/p58844ff73692c6efa0297f5b1a9147ec/fa4900d1.jpg

http://www.imagestation.com/picture/sraid93/p4092c74d530a5ffd460e1e6dc53ec31a/fa4900cd.jpg

http://www.imagestation.com/picture/sraid93/p17ec44a2ac47d08aa6de701332ae822d/fa4900ca.jpg

http://www.imagestation.com/picture/sraid93/p4caf185732482a6d6507483616736f62/fa4900c8.jpg

[ 12-16-2003, 05:08 AM: Message edited by: Aramas ]

[Aramas]

And a few more:
http://www.imagestation.com/picture/sraid93/p5e6e21d754402a1b9dfe97b32138188e/fa4900c4.jpg

http://www.imagestation.com/picture/sraid93/p1cb87925ea99f94f3327a068ae28fef5/fa4900bf.jpg

http://www.imagestation.com/picture/sraid93/pe6358bedbbec60464030a3b222fe1387/fa4900bc.jpg

http://www.imagestation.com/picture/sraid93/p0ba98fda682561f434b18e3f3596b0e3/fa4900b7.jpg
There were also some grabs of the lines but they come out so dark in a small version that imagestation produces that they're almost unreadable.

[gert]

I like her smile.gif
try a mizzen on her

[Venchka]

Excellent!

Thinking out loud...I wonder if you could make the boat exactly 7m to take advantage of the 7 meter/7 knot provisions of the navigation light rules? At 7.1m the boat would be required to have the same navigation light system as much larger boats.

[Torna]

An aside from the topic at hand, but what is the software you're using? Nice renderings.
-leif

[Aramas]

lol - I should have mentioned the software - it's AutoYacht 8, which is just a cut down version of AutoShip (limit of 20 surfaces). Not having AutoHydro makes doing righting moments tedious, and the 20 surface limit means using a lot of surfaces converted to poly objects (uneditable) that have to be redrawn any time a change is made.

I consider those renderings to be very makeshift - Just quick and dirty work in progress stuff. When it's 'done' I might do better ones of her sitting in a nice tropical lagoon with transparent water and waves, and real woodgrain photo-real textures - if I can be bothered.

Wharram's boats don't have much in the way of lateral area and have a lot of windage so it's not like they point high at the best of times, and it's not really fair to compare cats with monos anyway. The junk rig won't point as high as an off the shelf 3/4 sloop, but such a rig would cost more than the rest of the boat. I'm always trying to come up with 'clever' ways of increasing centreboard and rudder area, and they get a little bigger now and then. I expect they will continue to do so as it becomes more refined. She has 1.8m (6') headroom, so messing with the accommodation is tricky - the galley and head have to be kept in the deepest part of the hull, and fitting a centreboard trunk in there between the settees that convert to a double is awkward - almost down to squeezing out the last millimetre.

The rig is really a placeholder at present - I'd like to do something like Romily and Roxanne - ie a high aspect ratio version of a the standard canoe yawl rig, being a standing lug yawl. I'm even considering a standing lug schooner - if for no other reason than the height limit on the Danube (which I'd like to sail down one day) is 6m, so if I can keep the mast height that low I will - not to mention keeping the masts shorter than the boat and keeping tiller steering. Oh, and I figure a good sailmaker could turn her into a real flyer with a standing lug schooner rig. I'm still unconvinced that a standing lug rig can be effectively reefed from the cockpit, so until that's resolved the junk rig will stay. Gwenda was designed from the outset to be managed completely from the cockpit (apart from anchoring) - hence the narrow side decks, small foredeck and heavily cambered cabin top. Hardly an ideal platform for handling more conventional rigs when the weather is having a hissy fit. So far the junk rig is the only one that is (to my knowledge)proven and meets those requirements.

I've toyed with making her a yawl several times, but she's going to have windvane steering, which is awkward to arrange on a yawl. I'll probably do one just for giggles anyway.

I wasn't aware of the 7m limit for nav lights - is that US only or does it apply elsewhere? She only ended up 7.1m because I was tweaking the stern to get rid of tumblehome and I couldn't bear to shorten the waterline smile.gif I have to shave a cm or 2 off the beam anyway, so shortening her a little will only be almost bearably annoying - there are so many dependencies between lines and surfaces that scaling gets awkward.

[ 12-16-2003, 03:02 PM: Message edited by: Aramas ]

[Venchka]

The 7 meter/7 knot rule straight from the U.S.C.G.:

— INTERNATIONAL —
Lights and Shapes
RULE 25—CONTINUED
(d) (i) A sailing vessel of less than 7 meters in length shall, if practicable, exhibit the lights prescribed in paragraph (a) or (b) of this Rule, but if she does not, she shall have ready at hand
an electric torch or lighted lantern showing a white light which shall be exhibited in sufficient time to prevent collision.
(ii) A vessel under oars may exhibit the lights prescribed in this Rule for sailing vessels, but if she does not, she shall have ready at hand an electric torch or lighted lantern showing a white light which shall be exhibited in sufficient time to prevent collision.
U.S. inland waters, same rule.

God only knows what the EU has decreed in this situation for inland waters.

Having given this a bit more thought, I realize that 0.1 meters is 4 inches and I would hate for you to ruin such a lovely boat just to avoid big boat navigation lights.

[Aramas]

Wow - the USCG know what metres are? I'm impressed! It's something to keep in mind anyway - thanks for pointing it out. If small changes can avoid even small headaches then I try to work it in.

And apparently it's a balanced lug rig I'm considering rather than the standing variety smile.gif I really suck with names. Still, it's not like I've actually drawn one yet, so that's my story and I'm sticking to it. Well ok, technically a junk rig is a fully battened balanced lug rig, but that's just rubbing salt in the wound smile.gif

[Venchka]

Oh, you mean a rig like this?

http://www.boat-links.com/PT/PT2000/Caledonia-2.jpg

Sorry folks, I can only resist for so long. :D

Can this rig be reefed from the cockpit? Dunno, but I'm working on it.

[TimothyB]

Junk rigs can be very beautiful, but we have been lately regaled with efficiency beasties, like the hasler, Van Loan, etc rigs.

http://www.naga-pelangi.de/Naga_2/images/naga1.jpg

Now there's a beautiful rig, if you asked me. It seems all you have to do is round her out to really look like a wing, and she takes up nicely in her lines.

--T

[Lion]

Aramas

Looks great ! Especially like the healing angle images. Sort of reminds me of the Norwegian/Danish coastal types with nice firm buttock lines and a swing keel. Assume there is room for the SABB ?

Lion

[Aramas]

Oh, you mean a rig like this?
Yep smile.gif

Sort of reminds me of the Norwegian/Danish coastal types with nice firm buttock lines and a swing keel. Assume there is room for the SABB ? She definitely has a strong baltic/scandinavian influence. And room for a Sabb? How can you even ask? smile.gif

As Braam pointed out, there's also an undeniable influence from the 70's cruisers and IOR cruiser racers that filled the yard that I worked in as a teenager. I spent more hours than I can count sitting under boats on their cradles looking at their shapes - I thought they were the most beautiful things I'd ever seen. The first time I hauled out a H28 was what sent me to the boat bookshop to buy LFH's 'Sensible Cruising Designs' - and the addiction never let up. Of course sitting on St Kilda pier watching the Tumlarens, Folkboats and Dragons dancing in the chop didn't help much smile.gif

Oh yeah - Regarding renders I probably should have mentioned that to get good renders without lots of jagged edges it's essential to have a good fast video card with at least 4x anti-aliasing in OpenGL. Any of the NVidea GeForce 3+ or Radeon 8500+ cards will do - just make sure you turn AA on under 'properties' - lol.

I put the lines grabs through photoshop and turned the contrast up to 11 - at least they're visible now. The waterline is shown by a white + if you look close - station spacing is 0.5m, buttocks are 0.25m and waterlines are 0.1m below the waterline and 0.25 above. She's currently sitting at 2.8 tonnes in saltwater.

Buttocks
http://www.imagestation.com/picture/sraid93/p95ae58d8fc85e5f02943ce821d31e1b4/fa4702b7.jpg

Waterlines
http://www.imagestation.com/picture/sraid93/p481c8c040db9c9321e9a33ffc7f57534/fa4702b4.jpg

Bow Sections
http://www.imagestation.com/picture/sraid93/p0fc888ba412bbad3b22b0e97f856b788/fa4702b1.jpg

Stern Sections
http://www.imagestation.com/picture/sraid93/p454edaf4091d957165721f40668f0020/fa4702ae.jpg

[ 12-17-2003, 03:54 AM: Message edited by: Aramas ]

[Bruce Taylor]

Very nice, Aramas. I can see why you're considering a mizzen...that's a canoe yawl waiting to happen. smile.gif What's her draught at 3t?

[Aramas]

Draft @ 3 tonnes is 0.56m board up and 1.43m down. And that's with the extra 200kg sinking it 1.5 cm - so that's about 130kg to sink it 1cm, or a TPC of 0.13.

I did a quick and dirty balanced lug yawl rig but my grabber won't grab it - I've got too much stuff running atm. I'll try again tomorrow and upload it.

[Lion]

Very sweet lines. Should go like a cut snake! Were you planning to strip plank/cold mould ?

Comment - (hey, you posted them!) - looking at the shear in the line drawings I would prefer to see a little more perk at the bow. Maybe a little along the lines of FCW's 'Annie'.
I don't understand what happens between the drawings and the multi-dimension reality but it seems to me that it visually flattens out and you can somehow lose that nice shearline. Looks a bit exaggerated on the drawing but comes good with a good eye. Too much of course is just as bad.

As to sails I hav't got a clue but I see you have Todd Bradshaw looking at it on your other post. Suspect you are in good hands.

Lion

[Aramas]

Braam - One would have to cross several oceans, a sea or two, sail the length of the Rhine and traverse a canal before entering the Danube smile.gif One would assume a windvane would be helpful.

The bowsprit is just an anchoring derrick and something to make it easier getting to and from shore when beached. It probably does look a little odd, but it's been there from very early on and is a poly object, so I can't edit it without deleting it and doing another one - the old 20 surface limit demon.

Lion - yes, either strip planked or cold moulded - it depends on what timber I can get and in what sizes. My preference would be to triple layer cold mould with either qld kauri or white beech, but since they're both rainforest timbers it would mean finding recycled stuff or stock from an old timer.
The sheer is amazingly sensitive and I've experimented with it quite a lot. It's actually what I recently learned is called a 'planar sheer', and any change from what's there now has a peculiar effect on her looks. I'm talking millimetres. 'Annie' is much fuller in the ends than Gwenda, and so needs a lot more turnup fwd to balance it. You might be right though - I'm not going for a cutesy 'character boat' look - what I want is more in line with the ethos of scandinavian designs of the period between the wars, like the Tumlaren, Folkboat, Dragon, sq metre boats etc. The renderings are from a perspective view, so the sheer is already flattened by the optical illusion you mentioned - ay least if your face is close enough to the screen smile.gif

Here's the quick and dirty lug yawl rig - I managed it by using just one of my precious surfaces. Everything else is done with clones and scaling. The main is just the junk rig without the battens or roach, and the mizzen is just a scaled down clone. The spars aren't proportioned yet - they're rather skinny - lol. It was just to get an idea of the look. Of course there's no way of steering it yet smile.gif

http://www.imagestation.com/picture/sraid93/p505b8a9ed3b42da8cee95e3885b6b0d9/fa453e5b.jpg

http://www.imagestation.com/picture/sraid93/pefff3a25798655e37d752a0566dec3b9/fa453e58.jpg

I think it's quite pretty.

[Bruce Hooke]

While the 7 meter rule does apply in US and International waters, it may not apply in some countries so be careful if you are thinking of visting foriegn lands. Furthermore, if you are going to do much night sailing it really is safer to have proper lights, so if you can arrange for them then I certainly would. The biggest issue on a small boat is generally the source of electricity.

That's a nice looking design you've got coming along.

As to junk rigs, one of my all time favorite WoodenBoat issues is #66, because it has a series of absolutely stunning pictures of genuine working Chinese Junks in China.

[L.W. Baxter]

Very classy, Aramas! What construction technique? Somebody mentioned another thread of yours, but I missed it. I was busy getting stoned in the bilge. I mean it, some guy was throwing rocks at me! Don't go down there, keep working on this boat, she's a beaut already!

--Lee

Geez, my brain is going soft! I see you've answered that question already!

[ 12-18-2003, 01:10 AM: Message edited by: L.W. Baxter ]

[Aramas]

Yeah junk rigs are nice on the right boat. I've never really been happy with the weight of the junk rig on Gwenda - the real mast I drew to Hasler's scantlings (and subsequently 'lost') is so huge it looks like a power pole stuck in the foredeck - I'm talking Freedom 40 huge. The aesthetics always grated with me too - it really didn't suit the boat imo.

I love yawls and I simply adore canoe yawls. They do have some drawbacks though, mainly steering arrangements and the difficulty of fitting a windvane. I'm not too keen on the whacky 'tiller with a big slot in it' arrangements I've seen. She's not deep enough to have an inboard rudder (which I'm not keen on anyway) without having it curving up at the back (eeww). Perhaps the neatest steering arrangement I've seen is an outboard rudder with a tiller going through a slot in the sternpost - it avoids all the linkages and their associated friction, and doesn't seem too ugly if done with a bit of thought.

With regard to a winvane, about the only approach that appeals to me is fitting one to the top of the mizzen with a shaft coming out of the bottom of the step, with a crank connected through the sternpost slot to a trim tab on the back of the rudder - Still 2 linkages but not too horrible I suppose. Robin Knox-Johnson had a vane on each side on his ketch 'Suahili' (sp?) but I consider that to be a rather inelegant approach.

If I built Gwenda as a yawl I suspect I'd dispense with the windvane but still build in the means to add it if necessary. Her lines are quite undistorted, her centreboard is somewhat forward, and combined with the balancing qualities of the yawl rig and a means of fixing the rudder she would probably take care of herself on most points of sail - albeit after an inordinate amount of quasi-mystical fiddling smile.gif

Oh and Braam - I won't mention how warm it is here in Australia, but suffice to say I live in the tropics. There were several occasions last winter when I had to put a shirt on smile.gif

And as a perhaps feeble attempt at redeeming my somewhat tarnished nautical nomenclaturalism, I just thought I'd quote Phil Bolger from '100 Small Boat Rigs': "Strictly speaking, all lugs that aren't dipped in tacking are standing lugs, but it's usual to use the term for the type with the tack at the mast" So I figure I'm only half ignorant smile.gif

[ 12-18-2003, 03:27 AM: Message edited by: Aramas ]

[Aramas]

Just thought I'd put up a 'bald nosed' version for Braam, since he didn't like her pointy bit.

http://www.imagestation.com/picture/sraid93/p0944afa9b85f7aa23ee5225ae50041b3/fa3c599a.jpg

My group trees were turning into a hedge, so I had to do some aggressive trimming. Now I've got a whole bunch of those 'difficult design decisions' to wade through.

Bugger tongue.gif

[ 12-22-2003, 12:38 AM: Message edited by: Aramas ]

[Meerkat]

The "7 metre" rule is part of COLREGS, which is an international treaty signed by all ocean going countries...(?). Signatory nations conform their domestic regulations for all waters open to navigation from the ocean to follow COLREGS for the most part. I believe the only place they don't apply in the US are the Great Lakes and the Mississippi River system (both have rules that predate COLREGS), and possibly the Intra Coastal Waterway.

http://www.oz.net/~papillon/kbmanual/colregs.html :


Rule 23

Power-driven Vessels Underway

(a)A power-driven vessel underway shall exhibit:

(i) a masthead light forward;

(ii) a second masthead light abaft of and higher than the forward one;

except that a vessel of less than 50 meters in length shall not be obliged to exhibit such a light but may do so;

(iii) sidelights: and

(iv) a sternlight.

(b) An air-cushion vessel when operating in nondisplacement mode shall, in addition to the lights prescribed in paragraph (a) of this Rule, exhibit an all-round flashing yellow light.

(c)

(i) A power-driven vessel of less than 12 meters in length may in lieu of the lights prescribed in paragraph (a) of this Rule exhibit an all-round white light and sidelights.

(ii) a power-driven vessel of less than 7 meters in length whose maximum speed does not exceed 7 knots may in lieu of the lights prescribed in paragraph (a) of this Rule exhibit an all-round white light and shall, if practicable, also exhibit sidelights.

(iii) the masthead light or all-round white light on a power-driven vessel of less than 12 meters in length may be displaced from the fore and aft centerline of the vessel if centerline fitting is not practicable, provided the sidelights are combined in one lantern which shall be carried on the fore and aft centerline of the vessel or located as nearly as practicable in the same fore and aft line as the masthead light or all-round white light.
----------------------------------
Rule 25

Sailing Vessels Underway and Vessels Under Oars

(a) a sailing vessel underway shall exhibit:

(i) sidelights;

(ii) a sternlight.

(b) In a sailing vessel of less than 20 meters in length the lights prescribed in paragraph (a) of this Rule may be combined in one lantern carried at or near the top of the mast where it can best be seen.

(c) A sailing vessel underway may, in addition to the lights prescribed in paragraph (a) of this Rule, exhibit at or near the top of the mast, where they can best be seen, two all-round lights in a vertical line, the upper being red and the lower Green, but these lights shall not be exhibited in conjunction with the combined lantern permitted by paragraph (b) of this Rule.

(d)

(i) A sailing vessel of less than 7 meters in length shall, if practicable, exhibit the lights prescribed in paragraph (a) or (b) of this Rule, but if she does not, she shall have ready at hand an electric torch or lighted lantern showing a white light which shall be exhibited in sufficient time to prevent collision.

(ii) A vessel under oars may exhibit the lights prescribed in this rule for sailing vessels, but if she does not, she shall have ready at hand an electric torch or lighted lantern showing a white light which shall be exhibited in sufficient time to prevent collision.

(e) A vessel proceeding under sail when also being propelled by machinery shall exhibit forward where it can best be seen a conical shape, apex downwards.You might also want to look at Annex 1 at http://www.oz.net/~papillon/kbmanual/annex1.html that covers light shapes, intensity, colors and placement.

[ 12-22-2003, 03:04 AM: Message edited by: Meerkat ]

[Meerkat]

Going for something like this?:
http://www.selway-fisher.com/Beaump3.jpg
http://www.selway-fisher.com/Beaump1.jpg

[Aramas]

Going for something like this?:
Not really, although I do drop by the Selway Fisher page from time to time smile.gif

[Meerkat]

Well, the proportions are quite similar and, from what you've posted, the rig is near dead on! tongue.gif

[Aramas]

Well it's about the same length at least smile.gif

It's narrower, about 3/4 of the weight with half the ballast and 2/3 of the sail area. It also has a transom, lower freeboard and raised deck cabin.

It also has the mast right in the bow and uses a boomless standing lug rig with the tack fixed at the mast.

Overall I'd say that the aesthetics are incompatible with my personal taste (Is that polite enough? tongue.gif )

So in summary, it's about the same length :cool:

[ 12-23-2003, 03:05 AM: Message edited by: Aramas ]

[Meerkat]

Thanks for being polite about it. I was just trying to be helpful.

Raised deck cabined boat designs are hit and miss with me - some I like, most I don't.

Here's one I like ;) :
http://www.classicmarine.co.uk/boatlists/images/golant.jpg

[Buddy]

Oh Aramas, I do like her. These questions are meant to be constructive:

How is she ballasted? Seams very round bottomed and "light" on form stability.
The rig seems so tall. How is the mast stayed? Is it to be a big free standing timber? Has she stability enough for such a high center of effort? Seems more usual to have lower rigs on these buxom hulls.
The cockpit itself has such a lovely coaming. Taken with the narrowness of the sidedecks aft, what is the need of the high bulwark continuing aft? Looks like it might actually be hard to use.
Could you abide putting the centerboard trunk off center 6"- 8" or so for your double berth problem?
I am concerned about the fullnes of the waterlines in the bow. Wouldn't more hollow down low make her easier to push to hull speed? Have you looked at how that works in your diagonala?

She'll be a real looker.

[Aramas]

Hiya Buddy - rather than use quotes and answers I'll just try to answer everything. Ed Burnett expressed similar reservations in another thread. The design is still early days and there's a lot of work still to be done.

She has around a tonne of lead on the bottom of the keel along about the middle 1/3 of her. She is rather round bottomed, and the reasons for that are somewhat convoluted, so I won't go into them. Several months ago I did preliminary stability calculations based on a rather sketchy weight estimate and it turned out ok. She's changed quite a bit since then and sometime in the next couple of weeks I'll do a more accurate stability run. While the sections are quite round the centre of bouyancy does move outboard quite quickly and with the rail down I'm quite happy with the bouyancy distribution.

The mast is free standing and in the last rendering was sized for a free standing gaff of the same area - actual spar design is a ways off yet.

In the same render the sail area is just arranged as a starting point - in order to balance the lead (currently 18% as drawn) either the mizzen has to be a bit bigger or the main smaller. Part of the next stability run will involve trying to find a pleasing balance of aspect ratio and sail area. If I can get over 30 square metres without hardening the bilges or shortening the rig too much then I'll be happy, otherwise I'll have to firm it up and sacrifice some of the other characteristics of the form.

The narrowest part of the side deck is 20cm, or about 8", with bulwarks 10cm (4") high. The purpose of the bulwarks is to help keep water off deck, keep other stuff (lines etc) on deck, and aesthetics. It looks kinda naked without them. The deck doesn't have a lot of area, but there's enough to sit up on the stern quarters either side of the mizzen. All sail handling will be done from the cockpit so the only reason to go forward is anchor handling, and even that can be done from the cockpit.

Definitely no off-centreboards smile.gif The arrangement is a little hard to explain so I'll wait until there are drawings, but it should work ok as is. The settes will each convert to a 'double' that's around a metre wide at the head, leaving the opposite settee and table in place if desired. Alternatively the whole thing can be turned into a bed that has the cb trunk angling out of the head of it at around 40 degrees 30cm from the end.

Hollow in the bow waterlines wouldn't actually do anything positive at all, and unless it was added by extending the waterline it would effectively increase the apparent angle of entry. Hollow waterlines are mostly a dead fashion. Half angle of entry is presently at 32 degrees which is higher than I'd like but not unacceptably so (about of par with a lot of traditional load carrying cruising boats without hollow). She's not a racer. At the moment I can't actually find my old resistance and propulsion notes that contain the plot of optimum half angle of entry vs V/root L, but I did check it some time ago and it wasn't too bad. To compare the actual wave making characteristics of a hull with hollow waterlines the hollow should be ignored and the actual waterline in the bow quarter should be extended to the centreline. have a look at Fenwick Williams' 24' gaff yawl (aka 'Annie') in the Wooden Boat plans catalogue and Fifty Wooden Boats - she's very similar on the waterline to Gwenda - about the same angle and only a hint of hollow. She also has a much fuller deckline forward, so the angle of entry when heeled would probably be quite a bit larger than Gwenda's when heeled, and by all acounts she sails well. Fining out the bow would tend to lower Cp, waterplane area, displacement, Ixx, stability and TPC (carrying ability) so it's swings and roundabouts. About the only way to pull it off without sucking down the negative aspects would be to draw the bow out and make her longer, but you have to draw the line somewhere.

Diagonals are things that were used to fair paper drawings, and imo they give no indication of actual water flow whatsoever. If I did draw them though they would look perfect due to the inherent fairness of the hull form - which would mean precisely nothing. I've looked at heeled waterlines, buttock and sections at different angles of heel, and while I'd like to remove most of the accommodation and fine up the bow if it didn't have any drawbacks, it's not going to happen.

And thanks for the encouragement. Posting early stuff is a bit of a 2 edged sword, but I was running out of steam and trying to get motivated. Overall I think it helped smile.gif

[ 12-24-2003, 03:23 AM: Message edited by: Aramas ]

[Aramas]

Meer:
Here's one I like smile.gif That's the Golent gaffer right? Pretty boat.

[Buddy]

I'm familiar with Annie. Beyond the calculation of numbers, I suppose it's our entrenched traditionalism that appreciates the touch of hollow in the bow of Annie and the way a line of shadow from the sheer plays along the turn from hollow to full that makes us stop to take another look. Too much of an artist's concern.

I would think, absent freeing ports or such, those aft bulwarks are going to hold water, not keep it off the deck, particularly looking at where the rig and hull form suggest the heel is going to settles in, not unlike the traditional boat features this one appears to adopt.

I find it a great comfort on my catboat to be able to put a boat cushion outboard of my 3" coaming on to my 10" side deck and be able to sit"heavy" and enjoy a bit of fun in a gusty breeze. The same might work for you.

I'll look forward to see how you bring her along.

[Aramas]

Actually there will be freeing ports, but since I have to redraw the bulwarks and trim every time I adjust the sheer then little details like that will just have to wait smile.gif The joys of showing early work.

I think hollow is useful when fairing in wineglass sections to a bow with little or no overhang, but it stil doesn't seem to serve much purpose apart from aesthetics (which I agree on btw). It's tempting to put in wineglass stern sections just to look pretty, but I think it will turn out ok without them and perhaps be a little easier to build.

Wider side decks would be nice but that would make the enclosed head rather more cramped and perhaps alienate the decision-making gender smile.gif

[Meerkat]

Originally posted by Aramas:
Meer:
</font><blockquote>quote:</font><hr /> Here's one I like smile.gif That's the Golent gaffer right? Pretty boat.</font>[/QUOTE]Yup, the Golant Gaffer - I own the rights to sail number 88 smile.gif

[Aramas]

Well I modelled all of the structure apart from the floors with McNaughtons scantlings for a 3 tonne displacement, and with her as drawn in the last pic posted (SA 33 m sq & 1.1 tonnes ballast) she has a Dellenbaugh Angle of 22 degrees, which is within the range in Larsson and Eliasson. She'll be pretty tender empty though. I'll just have to ballast her with beer. For some strange reason most canoe yawls don't seem to be designed to cross oceans. Funny that tongue.gif

I still have to do stability up to 180 degrees, but I doubt there will be any surprises.

[Bruce Taylor]

Sounds good. "Dellenbaugh" is news to me, though. Santa got me a gift certificate for the WB store...maybe I should buy the Larsson/Eliasson book with it.

I like the yawl rig on her. A gaff main wd. look nice.

You should post your rendering on Boatdesign.net, if you haven't already. There are some pretty sharp designers there, & they're not shy.

[Aramas]

Yeah the Dellenbaugh thingie doesn't really mean much imo. It's supposed to be the angle of heel the boat would assume going to windward under full sail in 8 knots of wind :rolleyes: , but I guess it's really just an empirical index to compare similar boats. In Gwenda's case there aren't any similar ones that have data available. Skene's at least gives some details like length and whether it's a centreboarder, but it still doesn't mean much. If a boat is rigged with large working sails and doesn't use light weather sails, then the Dellenbaugh method would show that it was very tender. It's kind of like all that piffle about slack or firm bilges - it means nothing unless it's compared to a similar hullform.

I pop over to boatdesign.net occasionally, but those guys are technicians, not artists smile.gif

I like it here.

[Buddy]

Do you see a little red flag when running the numbers on a 6000 pound, beamy 23 foot boat design, it calculates out to be tender? Why not consider adding some form stability to that round section and tehn running those numbers before you start building something?

[Aramas]

No buddy. I don't. 22 degrees is not tender. I said tender empty, but then I don't plan on sailing her empty - she'll have 300 litres of water an 100 kg of anchor and chain for starters. All storage is below the waterline (and is watertight). Most boats her size are designed to carry a lot less, and so are lighter built and ballasted. Grey Seal has similar dimensions, but is lightly built with half the ballast and a capsize ratio of 2 (borderline) - and by all accounts she's a good boat, but I wouldn't go offshore in her. People still overload lightly built boats though, which poses not only stabilty problems, but also structural problems. Gwenda is designed from the outset to carry a tonne or as close to it as I can get without compromising strength. She's a cruising boat, not a weekender.

Gwenda has a 2 foot draft and unlike your catboat it's required to be self righting. Anyone can design a beamy hull with high form stability, but unfortunatelty it would be just as stable inverted.

As I mentioned previously I believe the Dellenbaugh angle is a crock anyway. It only shows initial stability, not heeled stability - which is higher at large angles of heel with the 'round' bilges than it would be if they were harder.

I actually did do a firm bilge version yesterday (took about 10 minutes). It had about the same dellenbaugh angle as the original, since it floated higher, changing the metacentric height and the centre of gravity (relative to WL). It also had much lower stability from about 60 degrees onward.

I find it amusing that a shallow hull like mine elicits such comments while a wineglass or deadrise hull with gobs of bouyancy down low (which is a lot worse, since as soon as the boat heels it's on the wrong side of G - ie heeling the boat) is considered normal.

If you want to see an incredibly slack bilge then have a look at the lines of the Tumlaren - there's no turn of bilge until a couple of inches below the sheer, and they're excellent boats. While you're at it check out George Holmes' Iris and the round sectioned version of Ethel. They actually look a lot like low freeeboard versions of Gwenda. LFH's Wagon Box is only prevented from lying on her side at anchor by the lead in her guts - not a lot of form stability there. LFH was evidently quite fond of slack bilges - funny, I've never heard him criticised for it smile.gif

Stability can't be evaluated by how hard the turn of bilge is - it's actually a function of bouyancy distribution when heeled and the centre of gravity. By hardening the bilge there will usually (assuming the same hull type) be higher stability up to a certain angle and then less after - usually considerably less at 90 degrees. A stiffer boat will also have a more violent motion and will require more string twiddling since it won't depower in gusts as well from heeling. It's not as simple as what most people would like to believe.

Incidentally I'll be running more numbers than you can imagine. I already have pages of the suckers and there'll be many pages more before I'm done. I spent 3 years at college studying naval architecture, so I probably have a somewhat different view of stability when compared with the average armchair designer. Imo most of what people believe about almost every aspect of yacht design is just nautical myth, and at best it only applies when comparing similar hulls. Assuming that stiff = good and tender = bad is exceptionally silly, since many fine cruising boats would be considered tender - particularly those who's working rig is intended to continue working in light winds. Attributing stability characteristics solely to the 'turn of bilge' is no doubt convenient (certainly easier than having a basic understanding of stability smile.gif ), but it really doesn't count for much. smile.gif

Why is it that when shown a 'work in progress', many people tend to make superficial judgements on the assumption that it's not only finished, but that someone is trying to sell it to them? tongue.gif

[ 01-11-2004, 09:31 PM: Message edited by: Aramas ]

[Lion]

Love it!

Like the look of the lug yawl although have no idea how it is for performance and handling. Self steering is something to consider (other than natural balance) - read a good book by a guy, Rowdy ?????, from Sydney who had been partially paralysed in a rock climing accident but got back sufficient movment to build and sail a small steel sloop single-handed around the world in about 1990. His biggest problem was the self steering which had been damaged by a launch when he was in Stanley harbour, Falklands. In certain conditions he became dangerously exhausted.

Hollow waterlines at the bow ? Dunno how they work but my FCW 18' catboat hull has them and they are puurity ! He was however criticized at the time for having much fuller bow lines that the Crosby's etc (one catboat was called 'Buxom Lass') but he claimed it was not a problem and kept the bow from burying etc. On a comparative basis his boats were fast and stable. How fashion changes !

Go build it !!!!

[Aramas]

Thanks Lion smile.gif

I won't be starting building this week, but I hope to get underway this year.

I haven't read that book, but if he was in the Falklands then he probably rounded the Horn and spent a lot of time in the Southern Ocean - I find just thinking about that exhausting! I've developed a taste for the tropics and have no aspirations to visit high latitudes.

Self steering is a tough one, and I'm actually starting to favour an inboard rudder, since I've figured out how to work in a trim tab and linkages without too much drama - only one linkage. Still, I'd like to try her without. I get the feeling she'll mostly look after herself once she's sorted. I'll have to reread 'Trekka Round the World' yet again - I've had it since I was 10 and I can't imagine how many times I've read it. Trekka was a yawl with no self steering, and she did rather well, although Guzzwell did say that he later tried a vane on Trekka and that he would go for a cutter next time. I don't mind trading course holding accuracy for 'simplication'.

Antoine de Saint-Xupery, pioneer aviator and author of 'The Little Prince' once said something along the lines of "An object reaches a state of perfection not when everything that can be added has been added, but when everything that can be taken away has been taken away."

I try to live by that.

[Buddy]

It must be that in my brevity, I rubbed you the wrong way. Because I understood that you were offering a work in progress and inviting comment, I voiced my concerns solely for your evaluation and perhaps benefit. Certainly I am not feeling your are asking me to buy, or buy into, anything you have put forth.

You seem to frame my comments in context of a 1200 pound 15' catboat daysailor which I own.

This boat is not my prime frame of reference with regard to your cruiser. I have a good deal of hands on experience in owning and sailing, and amateur experience in designing and building, boats in the 22-26 foot range, from about 2500 to 4500 pounds
. It's this business which triggers my concern of a 22 degree sailing heel on a 6000 pound 23 footer. The boats of my experience will all recover from a masthead knockdown, and on paper at least, continue on around to self right if completely rolled. Have to to qualify as a racer/crusier and get a certificate .Never have had that bad of an actual experience, but have had some wild rides. None of these boats required anywhere near that 22 degree angle of heel for ordinary, competitive sailing. Specifically, they all had more form stability, without sacrificing ultimate stability, than that.
My old standby is a 22 foot sloop of 3400 pounds with 900 pounds of ballast, all in the canoe body drawing only 10 inches. The daggerboard is neautally buoyant and with waterline beam is 6 feet. She is initially tender to me, but fetches up on those flaring topsides at 10 degrees. At now time does burying the rail produce speed on this boat. If you can put crew to weather fine, but keep the heel off her by shorting or dumpimg sail. otherwise. Anything else is just kidding yourself.

Performance expectations, and corresponding beam and ballast parameters, and sail area to displacement ratios have changed much over the years since 1971 when I first bought such a boat and began accumulating my opinions. But never have I seen much popularity for a tender boat. After about 10 degrees of sailing heel the ladies become uncomfortable, and after 15 the men consider reducing sail because we're slowing down from being off our lines. (Speaking of boats which can occasionally surf, but not really plane here).

I can think of a similar traditional boat, the Flicka, of 20 feet and 8000-8500 pounds. Salty, and stoutly shaped and built as all get out but,she has amazed( alarmed?) many. I have seen a couple quickly traded away when their intial tenderness has discomforted the crew with a large angle of heel while still only poking along in an average breeze in or along shore. I fully understand that the passagemakers consider this a great little bluewater boat of ultimate safety in high winds and high seas, but for the conditions in which most people use their boat, reasonable speed and a reasonably comfortable usual angle of heel are a lot to ask to trade off.

In any case, I feel my previous post has annoyed you and regret doing so.

I want you to understand that I'm sure you have the talent to create exactly what suits your purpose and pleases the artist in you, and that making me my "comfortable" with your design is not necessary.

I'd hate for anybody, especially me, to detract from what is a very satisfying, very personal project by raining on your parade.

Good luck with her as always.

[Aramas]

Buddy, sorry if I seem a little terse. It comes of years of struggling to explain things that I take for granted and indeed consider self evident. Ten years ago I believed all that quasi-mystical poetic claptrap about 'powerful bilges', 'elegant wineglass sections' and 'graceful hint of hollow forward' that graces the pages of our favourite books and magazines and gets bandied about in yacht club bars. However, as my understanding of the mechanics of stability and fluid flow developed I came to understand that it was all simplistic nonsense. Like anything else stability and hydromechanics are cases of being simple once you understand them, but trying to explain them can be quite frustrating and perhaps ulimately futile. They were expressed mathematically to me, and so converting that into English can be quite difficult. As an example, the basic mechanics of wavemaking are frighteningly simple when expressed as 3d differential equations, but extremely difficult to explain in Engish.

The Dellenbaugh angle really doesn't indicate what some claim it does. It's only for comparitive purposes, and a DA of 22 degrees is near the middle of the accepted range for that waterline length, so by that index is neither tender nor stiff. The idea that it indicates the angle of heel to windward in 8 knots of wind may have once applied to a particular class of boat (or not) but it certainly doesn't now. As I mentioned previosly the DA is based on small-angle stability (a fraction of a degree), and doesn't account for actual form or ballast stability at large angles of heel. It's also clumsy in that it's dimensional and varies with waterline length. Perhaps eventually someone will work out a 'Dellenbaugh Coefficient' that is both non-dimensional and independent of length - ie < X tender and > Y stiff for all vessels.

The acceptable range given in Larsson and Eliasson for a 6m waterline is 18 - 26 degrees. ie a DA of less than 18 degrees is deemed to be too stiff, over 26 degrees is too tender (assuming an average working rig)

The example of Flicka is an interesting one. She's another vessel that has been designed to carry a good load. Consequently she would float high empty and be rather tender in that condition. It's unfortunate that people have sold them on without trying them loaded as designed. Just filling the water tanks would probably be enough to stiffen them up, but for weekend use she should probably be fitted with internal ballast. I expect Gwenda will be much the same way, but I don't intend using her without at least a half load. A ship would never put to sea empty, and so uses water ballast to bring her down to her lines.

I actually wonder if that's why nearly all yachts in the 20-30' range are designed with such a small payload that they're really only weekenders, since people are just not accustomed to anything else. It's not unusual to see production 30 footers that are 6 inches below their designed wl at the start of a voyage. What they don't seem to account for is that at such a displacement the boats are not only slow, wet and hard to control, but also dangerously overloaded, since their scantlings are sized for the designed displacement.

In designing a small vessel with a good load carrying ability it must be assumed that the skipper has sufficient seamanship to operate her in her intended displacement range - as with any seagoing vessel. It would seem that this is too much to expect of the general public, which probably accounts for the plethora of production yachts aimed at the weekend yachtsman and charter markets. Most of them are hard pressed to find storage for a couple of overnight bags let alone water and supplies for an ocean crossing.

[ 01-13-2004, 12:59 AM: Message edited by: Aramas ]

[Buddy]

Whew, I'm worn out.This average armchair designer is struggling, with what appears to be ultimate futility, to express in English respect for such quasi-mystical claptrap as "powerful..graceful...elegant" (As an aside, these terms seem very similar to praise for fine horses to me.)

I do understand how another crock of my superficial piffle won't mean much in your opinion, and I simply can't imagine how more comment from me on this subject would be amusing for anyone else here.

Here's looking for your boat to be as beautiful as the Herreshoff and Williams boats we both find inspiring. She appears to be well on her way.

[Aramas]

lol - don't take it personally buddy. I think there's a rule somewhere that anyone that does this sort of stuff has to be ...um "somewhat opinionated" smile.gif

I respect the same designs as you do, I just don't subscribe to the traditional 'lines analysis' school of thought, nor do I find endearing the quasi-mystical beat-ups that that seem to characterise the writing style of many books and magazines on our favourite subject. That doesn't necessarily make me right, but it probably does make me irritating at times. I can live with that smile.gif

[ 01-14-2004, 05:51 PM: Message edited by: Aramas ]

[Buddy]

I'm laughing out loud too. If my sailing club had a bar and you could make it over this way, we could share a brew or two and do this better. I can identify with the sobriet of opinionated.

Please keep the cards and letters coming (picture too) of your progress. 1000 pounds of provisions and clothes to get her in trim huh? I thought I couldn't pack light.

Take care, Buddy

[Eric Sea Frog]

It only shows initial stability, not heeled stability - which is higher at large angles of heel with the 'round' bilges than it would be if they were harder.
Aramas,

Why do you deem round bilges steadier than hard ones?
Is it only because of formal stability, as the boat is harder to right back once it's leaning on its side?
Is that what you mean by stability at 90 degrees?

Eric

[Aramas]

I was generalising smile.gif

If you think of ultimately slack bilges as a triangular midsection, and ultimately hard bilges as rectangular, then at 90 degrees the triangular section has it's centre of bouyancy closer to the deck, and so has more form stability.

When someone says that Gwenda needs harder bilges, I guess they're assuming that nothing is lost by hardening them up. I've done several hard bilge versions, and generally they have a lot more volume down low, so they sit higher in the water, raising G with respect to B and lowering B when heeled (so less form stability at 60 degrees +). Admittedly I could make her a deadrise form with hard bilges, but that effects her ability to dry out upright and makes the cabin sole extremely narrow. So then there's the option of 2 hard turns in the bilge which would produce a kind of dory form, which would work but I don't see any advantage in it.

It all comes down to bouyancy distribution when heeled, and whether the sections are round, straight or have a hard bilge or chine doesn't mean much at all as long as the centre of bouyancy shifts rapidly to leeward and stays close to the deck at high angles of heel.

What I find a little peculiar when discussing this sort of thing is that there are hundreds of well regarded boats by well regarded designers that run the gamut of firm/slack bilges or whatever characteristic is being criticised, but those well regarded boats seem to be beyond criticism even when they have the same characteristics as Gwenda. eg Buddy didn't like the full entry and low bulwarks, but he liked Fenwick Williams' 'Annie', which has the same angle of entry and bulwarks. Go figure.

I bet I get a lot of flak when I post the accommodation plan, but having looked at hundreds of other designs, I think she's better in that respect than most. People seem to base criticism on a non existent idealised boat, and yet conveniently overlook the limitations of the existing designs that they like. Funny that smile.gif

[Buddy]

The part about the low bulwarks I questioned was running them aft "parallel" to cockpit coamings ( which the Annie I've seen doesn't have) and in effect creating a channel much less than a foot wide to a few inches. It would be difficult to sit outboard of the cockpit on occasion and it might trap a foot walking aft. I thought maybe the bulwarks could end about where the coamings became or a tad bit aft of that so a fanny, or a fanny on a throwable cushion could sit outboard of the caoming on the side deck.

Doesn't Annie have some hollow in the bows (even if the angle is 32 degrees)? OF course the stem profile is different to enable that to be so.

[Aramas]

As I pointed out, the narrowest part of Gwenda's side deck is around where the cockpit joins the cabin and is 20 cm (8") wide. I'd like to widen them a little if I can manage it without turning the head into an upright coffin. The only reason she has sidedecks rather than a raised deck is aesthetic reasons - lowering inverted stability is just a bonus. As I also pointed out there is plenty of room in the stern deck quarters to sit out if desired. I also pointed out why the side decks are as narrow as they are. I also mentioned that the only reason to go forward is to anchor. I don't think that I mentioned that the cockpit is 2 metres wide and 1.8 metres long though. Annie's cockpit is tiny, she has about 18" less headroom, has no enclosed head, draws 20" more, displaces a ton more with the same sail area, and I don't like her boxy cabin or cockpit coamings at all. Having the dinghy tied down athwartships from rail to rail would certainly make going forward to douse that jib quite a pain, not to metion the wave impact loadings on the side of the dinghy when taking water over the bow. I'm quite familar with Annie's drawings since I had her plans hanging on my living room wall for several years smile.gif

Annie has the slightest hint of hollow in the fwd waterline (ie almost none at all), and even including the hollow she is still as full or fuller in the fwd waterline as Gwenda. As I've explained (ineffectually it would seem), fining the entry with hollow does nothing positive at all, and on a given waterline length actually increases wavemaking resistance by creating a shoulder behind the hollow which makes a larger angle than would be the case if the waterlines were straight, and causes more pressure variations (which is what makes waves). Gluing a sheet of ply on the stem and fairing it in might give a nice low angle of entry and a longer lwl on paper, but it actually does nothing except increase wetted surface. In order to effect wavemaking resistance in a positive way, the area over which hollow is used must make up a significant portion of the vessel's displacement, and about the only instance in which this is the case is where bulbs are faired into a bow. Annie is also far, far fuller at the deck, meaning that when heeled her angle of entry will be far larger than Gwenda's. She also has a lot of bouyancy down low which would shift to windward of G when heeled, decreasing form stability, and countering any percieved 'firmness' of her bilge (as is the case with any deadrise or wineglass form). That's not to say she's a bad boat (I've heard she's quite a good one), but to make direct comparisons with a different hullform is meaningless. There are just so many factors to be balanced, and not all of them are self evident and some are even counter-intuitive.

I actually like Annie, and she has certainly been an influence but I wouldn't want to own one.

[ 01-19-2004, 10:42 PM: Message edited by: Aramas ]