30 hp volvo diesel in what skiff/launch

[SaltyD from BC]

So let's just imagine that a guy found a md17c for cheep. Well, fee actually and that it got the boat nut side of his brain going overtime. :confused:

I hear there's a cure but I'm just chippin here so I don't need it yet. No?:confused:

I have in mind a 12 to 15 knot boat that will take some whipped up water from time to time. I have plywood. And epoxy and some cloth. But I like a little framing. And apparantly I have a running MD 17C all of the sudden.

Spira's mullet boats get my attention. I'm trying to get my head around some Atkin designs. But I need help here and suggestions please for an old school power boat type. ..

Thanks.

Dan

[Wiley Baggins]

A developable shape in plywood based on Gartside's "Jennifer" would be nice. Alternately, mmd could certainly draw you something - with no currency exchange issues!

Gartside's Jennifer - http://gartsideboats.com/catpow.php#jennifer

How complicated a boat are you planning on building?

[SaltyD from BC]

Yes Jennifer is a sweet boat. She's a displacement hull though, a 6 knot boat. I was thinking of something that would move a little better as I've already got a displacement (sail) boat. And it appears I'm becomming a partner in another displacement boat (an ex wooden troller).

As far as how difficult a boat, I was hoping for something quite straight forward - work boat style. A rugged 12 to 15 knot boat that would be comfortable hauling a bit of freight and getting bashed around with crab and prawn traps. And something that could get me to my fishing grounds on a good day in an hour instead of two and a half.

John Gardner's 20 foot semi dory for instance would fit the bill nicely. But although he says it would be easy to add a skeg and install a shaft for an inboard he draws the boat for an outboard. I'm not confident enough to figure this out so I'm not going there. If I could find plans for something fairly flat aft, easily pushed with a 30 hp inboard along the lines of a semi dory and preferabley with a bit of V up front I think it would be a very usefull boat for around here. And somewhere to put this volvo :o

[Spokaloo]

Sounds like the perfect setup for Rescue Minor, but Im sure you've already rubbed your brain on that particular piece of paper...

Check with Tad Roberts, he might have something in his pocket thats semi-planing for that hp range as well, and is down in Gabriola isl.

E

[L.W. Baxter]

How fast is that volvo rated to turn? It seems like you would have mucho hp to spare for a small boat at displacement speeds but maybe not enough engine speed to get anything like planing performance. And in the size range you are talking about, 12 knots should be full planing.

I may be mistaken, but I think there's a reason why small, naturally aspirated diesels aren't generally used in planing boats.

[SaltyD from BC]

Sounds like the perfect setup for Rescue Minor, but Im sure you've already rubbed your brain on that particular piece of paper...

Check with Tad Roberts, he might have something in his pocket thats semi-planing for that hp range as well, and is down in Gabriola isl.

E

Ya, the rescue minor is appealing for sure E. But not exactly a simple build as near as I can figure. I've also checked out the Tolman Sea Bright skiff but the info on success of this is limited. Not ruling either out tho. ..

How fast is that volvo rated to turn? It seems like you would have mucho hp to spare for a small boat at displacement speeds but maybe not enough engine speed to get anything like planing performance. And in the size range you are talking about, 12 knots should be full planing.

I may be mistaken, but I think there's a reason why small, naturally aspirated diesels aren't generally used in planing boats.

The volvo will produce 35 hp at max 2500 rpm. So I'm thinking 2000 would be about all you'd want to cruise at. From the Atkin plans there are boats from the day rated for just this kind of hp but without a reduction gear. You can get 1:1 gears with reverse which is what I'd do. At that rpm with the right wheel several of his utility skiffs or launches should make 15 knots. Some a little more.

Ya, let's face it guys I'm looking at old outdated technology here. An outboard would clearly be the way to go. But I like the idea of an inboard diesel, its dependability and putting the weight in the middle of the boat. And the fuel economy should be pretty dang good!

[johnw]

You might look at an older design, like a double-wedge or Hooper Island skiff, not a modern interpretation but something designed for a heavy, low-powered engine.

You might check out this thread.

[SaltyD from BC]

john, when I google hooper island skiff I get various sail boats. I'm aware of the H I Draketale, is that what you refer to?

[Spokaloo]

Anything sniffed out from the Hand-type boats or maybe something from Westy Farmer?

E

[johnw]

http://www.wye-river-models.com/pages/drake.htm

http://www.wye-river-models.com/images/drake.jpg

I did pull up some crab skiffs and sharpies, but I also pulled up the one above.

Sucher, who published some plans for them in Simplified Boatbuilding, the V-bottomed Boat, called them Hooper Island skiffs. They can have a draketail or a flat transom. The older ones, like I'm talking about, seem to have all been draketails.

They have a strong V at the bow, flatening aft, and the chine runs about parallel with the waterline. The old ones had about a 6/1 beam-length ratio.

[SaltyD from BC]

Thanks for that john ^^ Its a cool boat but I need something a little huskier with more free board.

Back to E, I love most of the Hand designs. Particularly Harry Bryon's Handy Billy versions. (Cause he gives some build info for weekend warriors like me). I wish they were drawn for an inboard option, which he does say they could be done in plywood which works for me.. I wish I was handier at bulding myself lol and I'd maybe go with a 21 HB and figure out a screw and a skeg system :cool:

[johnw]

Don't know if you can get 12-15 knots with a huskier boat. Maybe some of those 1930s inboard runabouts, like Edwin Monk's 18' Tern?

http://books.google.com/books?id=BfSmqiXF06gC&pg=PA65&lpg=PA65&dq=edwin+monk+tern&source=bl&ots=KnRXThi0aj&sig=xX2W8Qzh6z4Q_DRED3p-EO8K93w&hl=en&ei=gCIfSoWYIJ_qsgP7gumFCQ&sa=X&oi=book_result&ct=result&resnum=1#PPA67,M1

[Captain Blight]

Sergeant Faunce! Build a Sergeant Faunce!!

[Spokaloo]

The Sergeant uses 8 hp, not 30.

E

[Wiley Baggins]

I think the Draketail is a real looker - I've seen that basic shape on the Chesapeake.

As for choices, I don't see how you can go wrong on the Atkin's site if you focus on the page featuring Inboard Utilities & Runabouts 20' and Over - http://www.boat-links.com/Atkinco/Utilities/index2.html.

Most are not drawn for plywood though so you'll have to consider converting to developable surfaces (which may or may not be in your comfort zone) or possibly planking with plywood rips.

I thought to moot the FAO fisheries designs but they are all (inboard and outboard) designed for lower power and speeds.

[chicagoross]

"something fairly flat aft, easily pushed with a 30 hp inboard along the lines of a semi dory and preferabley with a bit of V up front "

My flat bottomed 24' Key Largo from Spira will still do over 15 knots loaded (12-15 people) with a 40hp ob. Sounds like his 24' mullet skiff, built for a small inboard, with the v'd bow, might be a good choice. They're pretty easy builds.

You haven't really indicated how big a boat you're thinking of...

[TR]

To achieve speeds in the 11-12 knot range with relatively small power requires a boat that's long and light. The way to achieve light weight is to keep the boat small for her length, thus narrow with low freeboard.

Bob Steward (Robert...of the Boatbuilding Manual) designed and built such a boat for himself about 40 years ago. She was called BarBill, 22' by 5'6" and had a flat plywood bottom 48" wide with very slight rocker but lots of immersion at the transom. Topsides were lapstrake. Freeboard was low, the cockpit sole was right at the waterline (no self bailing!) and the sheer about knee high when you were standing in her. She would run 11.5 knots with a 25HP Gray Lugger Sea Scout turning 1950 RPM.

"take some whipped up water from time to time" is hard to quantify. I would not want to take Barbill across the Strait into 15 knots of NW with a flood against it. But getting out to Thrasher Rock for a few minutes of cod jigging would be okay.

When you are driving a hull at S/L 2.5, without planing (though she is surely experiencing some dynamic lift) transom immersion must be significant to keep trim in control. Barbill runs clean and level.

With all that rocker I think the Spira boats will stand on their tails. And I doubt the vee forward is worth bothering with, it's just not enough to make a difference in the ride at speed. You've still got a (essentially) flat bottomed boat that will jar your teeth out at 12 knots in any chop.

[SaltyD from BC]

Thanks a lot for all the information guys, this is fun stuff.

Tad, I pay particular attention to your thoughts here because you know the waters around here and of course because you are a designer! Speaking of which, how about something like your 'Alder' but with a straighter bottom? Maybe even stretched a wee bit?

[TR]

Salty...

Longer is better as long as you keep the weight under control....there is no free lunch. A stretched Alder with a flatter run and less taper (in plan view) aft would work. But don't get any grandiose ideas about her speed in a sea. She will look after you...but only with reasonable handling.

John Atkin's design, Tom Davin, would do the same but her (his?) topsides are intended for lapstrake planking...which would be really nice.

[SaltyD from BC]

I here you theere Tad, speed in a sea is something that isn't on my fun thing to do list.

I'm pleased to hear your thoughts on Tom Davin. I've got the Atkin site on my favorites and usually get hung up on TD when I surf thru over there.


http://www.boat-links.com/Atkinco/Utilities/images/TomDavin-1.gif

http://www.boat-links.com/Atkinco/Utilities/images/TomDavin-2.gif

Man. What's not to like eh ^^? Calls for a universal 4 which is right about the specs of the volvo too. Hmmm......

[TR]

Calls for a universal 4 which is right about the specs of the volvo

Well I nit pick for a living so I'll say....nooo...the 17C is nothing like the Atomic 4. At 630 pounds it's twice the weight, has almost twice the swept volume, and it will turn a substantially larger diameter prop. Approximately 18" as opposed to the 14" wheel the Atomic should turn.

The 14" wheel on the Atomic 4 will absorb about 12 HP at 2500 RPM, whereas the 18" prop. on the volvo will absorb full power at that RPM. As the gas engine runs quieter and smoother I suppose one could run at higher RPM, upping the wear and tear.

If you want full protection for the propeller, larger diameter means a deeper keel, increasing weight and drag. And you've already added weight with the heavier engine. On the up side towing or punching into the wind will be far more satisfying with the diesel.

[SaltyD from BC]

Wow I thought the atomic would be way heavier than that. Showing my ignorance again - thanks for the nit pic'n Tad.

I was thinking from word one on this noodling that I'd have to get some custom work done on a drive train, and likely have to mate a 1 to 1 gear that doesn't have Volvo stamped on it. While I'm looking for odd ball stuff wouldn't there be a smaller diameter wheel that would fit here and perform more like a gas engine?

[TR]

Salty....

There are a number of ways to approach it......I would advise getting some idea of what the boat might be before making moves on a gear and prop.

As a rough guide (for lighter weight boats) about 100 turns at the prop for every knot is reasonable. Thus the standard Volvo 1.91:1 reduction is not a bad match for 12-13 knots.

[SaltyD from BC]

Salty....
As a rough guide (for lighter weight boats) about 100 turns at the prop for every knot is reasonable. Thus the standard Volvo 1.91:1 reduction is not a bad match for 12-13 knots.

Thanks TR, that's a little bit of gold right there :cool:

[ChaseKenyon]

http://bartenderboats.com/construction.html


If the 19 ft.Bartender will do 30 knot with a 40hp it should be fine with your 35 hp. I would gues that the diesel's low end torque over gas engines would allow it to com up on plane quite easily. and you would have a nice super seaworthy boat capable of cruising at 20 to 22 knots fully up on a plane, with very low fuel consumption per mile.

CHase

[ChaseKenyon]

Even if you don't find scalable inboard info in the other BTs I'm sure mike could come oup with a nice package for you and the basic jplans are only $150. Plus for your diesired quick build they have a complete fram kit all cut for you for only $1950.

It is what I would do I I had the engine you have.

Chase

[john l]

check harry bryans website - he has a few diesel powered launches of aprox
the same size as handy billy.

[Wiley Baggins]

Well, I’ve been away from this thread long enough for –

a. Some smart people (read as TR) to affirm my belief that you’ll get more bang for your horsepower dollar out of the diesel in terms of propping at the cost of more weight.

b. To find the Atkin’s design, (Brent) that called for ballast – 2000 pounds.

I was going to suggest Brent as I see it meets your speed criteria and the ballast should allow you to easily load it up with whatever you (reasonably) want for fishing and offset the weight difference of your diesel compared to a lighter gas engine. I doubt that the torque differential is enough for your 30hp engine to overcome the power difference between it and the 65hp gas engine specified (operating at 2400rpm). However, someone with a better grasp of these matters can certainly contest that.

Brent does have a slimmer cousin, Ketewomoke, that is supposed to be a load carrier too and is rated for a gas engine between 25hp-45hp. Atkin describes her as a bit slower, but maybe the torque difference and associated propping might do the trick.

Brent – http://www.boat-links.com/Atkinco/Utilities/Brent.html

Ketewomoke - http://www.boat-links.com/Atkinco/Utilities/Ketewomoke.html

Lastly, there is Easy, rated for gas engines rated at 30hp-40hp. You would definitely give up some carrying capacity to engine weight and she’s round-bilged so you’d have to lap your plywood, but the speed should be close.

Easy- http://www.boat-links.com/Atkinco/Utilities/Easy.html

Have you developed a short list yet?

Thanks for mooting this topic. I’ve had a design I’ve been tinkering with on-and-off for quite some time and these three (and others) offer some good comparative data as well as inspiration.

[SaltyD from BC]

Thanks for the ideas once again.

Back to Chase, yes I've coveted the Bartenders for a long time. The only draw back for what I'm doing here is they're a pretty small boat inside. I'd prefer a little more cockpit space for a lot of crab and prawn traps. We tend to go a little nuts on the trap fishing sometimes. lol. .

And Wiley I've spent hours going over the Atkin plans. My latest favorite is one of your suggestions, Ketewomoke. That's today anyway :confused:

And in other news I met with a buddy from another town not far away today that says he has 3 different Borg Warner gears kicking around that might work with some mods ... :)

[flyinwall]

i have been following this thread religiously as i have a perkins 4.108 that needs a hull to go into and i looked at "BRENT" and was wondering if a small wheelhouse with a v berth inside would upset the balance of the boat much

[Spokaloo]

On the Bartender.

They are hypersensitive to weight, and would NOT perform well with a big diesel lump. The performance numbers come from light weight engines and minimal accomodations. If a Bartender is your choice, sell the lump and get an outboard or small gas inboard. Calkins talks at length about light weight being the key to his boats.

I still think Rm or Shoals Runner are great hulls for your needs, fast with minimal hp and shallow running, not to mention protection from running shallow or going over flotsam.

E

[SaltyD from BC]

Hey flyinwall, Atkin shows a small cabin on "Sand Dollar" which is a similar sized boat as Brent:

http://www.boat-links.com/Atkinco/Utilities/images/SandDollar-1.gif

Maybe something like that on Brent would work going with a V berth in the cabin and controls on the back of the cabin. A windshield and dodger could cover the 'wheelhouse'.

[Spokaloo]

What if we drop off a little speed to keep the ply on frame building schedule and have something terribly seaworthy and good looking?

http://bartenderboats.com/images/tc%20troller%201lo.jpg

Timber coast is looking pretty sweet nowadays.

E

[SaltyD from BC]

Dam straight E! Odly enough I was just surfing through Bill's site and was checking Timber Coast out. She wasn't there last time I looked some months back. And the Volvo would do well in her albeit on the higher end of required power. Which isn't a bad thing.

Problem is I seem to becomming a partner of sorts in my buddy's boat, the Sea Lion no 111

http://i28.photobucket.com/albums/c242/Salty303/sealion.jpg

Which isn't a bad thing :D:D She's an ex troller built in 1950. So as you see we've kind of got the displacement (very) seaworthy thing covered.

I have visions of the likes of one of Atkin's utilitys or such in tow with the Volvo stuffed in it. Camp on the Sea Lion, run around at 12 or 15 knots with the 'tender' fishing and hauling traps. :cool: