Building a centreboard

[The Bigfella]

We've glued up the centreboard blank for the Payne Yellowtail. I'll post a couple of photos as construction proceeds.

We started with some 6" x 1" Oregon (Douglas Fir) quartersawn boards - which we machined down to 18mm.

The finished size of the board is 1130mm x 400mm x 35mm - then a couple of layers of glass take it back to about 40mm. In Americanese that's 44 1/2" x 15 3/4" x 1 1/2" or thereabouts.

The board takes a 35mm block of lead - 180 mm x 150 mm - call that 7" x 6"- down near the tip. I've melted up some old lead flashing ready to go - but we will shape the board first.

We joined the planks for each half of the board blank yesterday - 3 boards in each half.

A quick clean off this morning and a slathering of epoxy - we used enough to fill a 300g yoghurt container - which gave a good ooze factor.

http://i240.photobucket.com/albums/ff112/igatenby/board1.jpg


http://i240.photobucket.com/albums/ff112/igatenby/board2.jpg

We didn't have a bag for the vacuum table .... so it was clamps...

http://i240.photobucket.com/albums/ff112/igatenby/board3.jpg

Grain direction is opposed between planks.. and the joins between the halves are offset - we could have offset them further if I'd used another plank, but, not really needed here.

More photos to come... (when we do more work...)

[Mike Field]

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Good one, Ian.

You did all the work while Bazza was getting his payoff, right? :)
.

[The Bigfella]

Well, I did the tailing out on the thicknesser and table saw, and I mixed the glue and did the clamping and cleanup today.....

Oh yeah - I plotted and drew up the template yesterday - but its Bazza's bandsaw..

I was bringing it home to do the shaping tomorrow - until I realised that my planes are on the boat - so that may well happen at Bazza's too. I had to do a flying visit to the boat today just to get fibre for the glue... and didn't even give the planes a thought.

We must talk about that mast at some stage... and some bronze fittings...

[Wooden Boat Fittings]

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I'll post a photo of the mast I had in mind, Ian (after I take it.) From what you've said I think it might possibly do. And when you've worked out what bronzeware you need I'll give you a quote that should come out about 10% below Briggs list prices. But we'd better do this by email, I guess. (Is your address still the old Optus one that I have from years back?)

Mike

[Larks]

What glue did you use on that Ian?

[The Bigfella]

Mike - it is - the email that is. btw I ran across someone else who had gone to the UK for a quote - I've tried to steer them local...

Larks - it is Botecote - with the non-yellowing hardener, not that it is needed for there. I've been using mainly West on Grantala - although I did use 30 litres of Botecote there at one stage, but this boat has been built with Botecote, so I'll continue with that. I used West 403 fibre in it today..

[Wooden Boat Fittings]

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Local isn't what you'd call cheap. But if you're overseas it is, given the present exchange rate. And for Aussies, it's half the landed price of imported stuff, and probably better quality into the bargain.
.

[The Bigfella]

Geez I wish Bazza would learn how to use my camera, so he could take a photo of me working...

Here's where we started this morning...

trimming to width - 400mm, after planing the first edge:

http://i240.photobucket.com/albums/ff112/igatenby/cb2.jpg

drawing the board....

http://i240.photobucket.com/albums/ff112/igatenby/cb3.jpg

and I reckon the plans have an error. My plans are dated '99 - so I would expect this to have been fixed. The radius given for the foot of the board from the pivot point is 1020 mm. Using a radius of 1050 mm gives a board that measures as per the plan - which is what we ended up doing.

Then the corner radius is drawn with an 80mm radius...

http://i240.photobucket.com/albums/ff112/igatenby/cb4.jpg

through the bandsaw

http://i240.photobucket.com/albums/ff112/igatenby/cb5.jpg

finished blank

http://i240.photobucket.com/albums/ff112/igatenby/cb6.jpg

and a test of the glue...

http://i240.photobucket.com/albums/ff112/igatenby/cb7.jpg

yep - that's a pass, it didn't break on the glue line.

Profiling starts about 10" down from the top of the board - with 4" of that as a transition from profiled to square - the last 6" being left square (OK, rectangular)... and that's next..

[The Bigfella]

btw - weighed the blank - about 19 lbs.

and here's the profile template.

http://i240.photobucket.com/albums/ff112/igatenby/cb1.jpg

[The Bigfella]

I picked up a new cheapie electric plane yesterday - my last one melted its plastic bearing housing on some Grantala project..... and I roughed out the blank

http://i240.photobucket.com/albums/ff112/igatenby/cb1-1.jpg

http://i240.photobucket.com/albums/ff112/igatenby/cb2-1.jpg

Bazza came over to check on progress today and couldn't help himself!

Nah - actually, I asked him....

http://i240.photobucket.com/albums/ff112/igatenby/cb3-1.jpg

I finally got a bit of an edge on one of Dad's old spokeshaves

http://i240.photobucket.com/albums/ff112/igatenby/cb4-1.jpg

and Bazza left me at this stage to do the other side myself.

http://i240.photobucket.com/albums/ff112/igatenby/cb5-1.jpg

[Wooden Boat Fittings]

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Looking good, mate.

Don't forget to leave the trailing edge nearly square (as someone here was saying recently,) will you?
.

[Larks]

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Looking good, mate.

Don't forget to leave the trailing edge nearly square (as someone here was saying recently,) will you?
.

Why's that? (I missed the post involved) My gal' steel one is knife sharp (though admittedly probably because of rust being cleaned off over the years)

[Wild Wassa]

When a trailing edge is too sharp/too thin (on a hand shaped CB which will be far from being a perfect foil), separation happens far too readily even before a boat reaches max hull speed ... on foils that aren't perfectly perfect.

Flutter, galloping, shudder and clumping, the four aberrations that result in reducing a hydrofoil's efficiency are much reduced or can even be totally alleviated when the trailing edge of a small CB is a 2-3mm flat (going on the small size of that wooden CB of course).

There is no way that the small wooden CB can be shaped to being a perfect foil, so employing a flat trailing edge is important to improve the foil's hydrodynamic efficiency.

Warren.

PS, If you are in my neck-of -the woods, drop into the Canberra Yacht Club and take a look at the foils and boats that I'm currently doing. There is even some wood. Several WB Forumites have called in lately. Rock on over dudes and let's discuss perfect.

[The Bigfella]

Yep - there's a square trailing edge - the plan shows it as about 6 mm.

I was going to attack it again today.... but work beckons. We will be vacuum bagging the glass on this board - two layers are specified - 200 and 300 gsm - but that's a ways off yet.

[The Bigfella]

No progress today - other than two beers with Bazza.

Back to building foils - I'm hoping Barry will come on over tomorrow, because I'd much rather he finished the other side. There isn't even a poofteenth gap anywhere between the template and the foil on the side he's done. I think he might just know what he's doing here. He built the wooden 18' skiff that he won one of his two world titles on - and he worked at McConaghy's and Beashell's - making centreboards among other things.

The trailer is progressing well over at Steve's too. I called over after work, because the timber for the new keel had arrived. I must've kissed a tooth fairy or something - because there was no invoice with the timber.

http://i240.photobucket.com/albums/ff112/igatenby/wood1.jpg

http://i240.photobucket.com/albums/ff112/igatenby/traIER.jpg

Still some more crossmembers to go on - and the lowered draw bar at the front. The rear gets cut in a bit at the centre for the putt putt. The trailer is being designed to handle both the 3.8m Markham Whaler (40hp catamaran) and the 4.26m Payne Yellowtail that the centreboard is being built for. Bunks for each boat are removeable.

[The Bigfella]

Damn - I picked up the camera and shot this without looking - and my son had been playing with the camera and left it on the wrong setting. I'll post it anyhow - it's one of Barry's old templates for foils - another world championship winning profile, I might add...

http://i240.photobucket.com/albums/ff112/igatenby/ca2.jpg

Here's the holes drilled for the cutout - drilled until the point just appears, then finished from the other side.

http://i240.photobucket.com/albums/ff112/igatenby/ca3.jpg

and me pouring the lead. Wearing safety skin legins of course....

http://i240.photobucket.com/albums/ff112/igatenby/ca4.jpg

[Larks]

Mate, I'm sure all will be revealed in due course, but what stops the lead dropping out when you lift the CB, I assume the lead will shrink as it cools? Or have you cunningly recessed the cutout or something?

[Wooden Boat Fittings]

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Ian, are you going to cover the lead with wood on each side? If not, let me tell you a story about my grandmother's grand piano.

Its keys were all counter-weighted with lead plugs that had been poured into holes drilled horizontally through each key in the wood beneath the ivory, and all in the same relative position on each key. Over time the lead slumped out each end of each hole, and eventually started rubbing on the lead doing the same thing on the next key. All the keys started sticking, and the thing got really annoying to try to play.

The technician's "fix" was to file the projecting lead off each key every few years. Before long the counter-weights had become so ineffective for want of lead that playing the piano was a bit like playing an old tracker-action organ.

The real fix would be to spotface each end of each hole, fix a disk of gal at one end, pour in new lead, then fix a second disk on the other end after the pour. No more lead flow, no more sticking, and no more pounding the keys to get any sound.

If your c/b starts sticking in its slot after a while, you'll remember my grandmother's piano won't you....?
.

[The Bigfella]

Guys.....

The lead will be covered by two layers of epoxied glass - 300gsm and 200gsm. It isn't going anywhere. Its a damn heavy board now.... though.

Then again - the bilge pump I picked up yesterday is no lightweight either a bronze Simac "0" - it weighs 5.5 kilos - although I'm not 100% cxertain I'll use it.

http://i16.ebayimg.com/01/i/001/19/a3/3cad_1.JPG

[Larks]

Guys.....

The lead will be covered by two layers of epoxied glass - 300gsm and 200gsm. It isn't going anywhere. Its a damn heavy board now.... though.

Mate, I had little doubt, just interested in the process:)

[The Bigfella]

OK, so I lied. It isn't covered in glass - its now covered in carbon fibre. One layer 195 gsm = 6 oz.

Here she is, about 8:00am. Under the board is the Carbon, the peel ply, the release film and the breather fabric. The pivot point on the board has been drilled and filled with epoxy glue mix.

http://i240.photobucket.com/albums/ff112/igatenby/s1-1.jpg

Here's Bazza's vacuum pump. It originally saw service producing television vacuum tubes.

http://i240.photobucket.com/albums/ff112/igatenby/s3-1.jpg

And, this is Barry putting the resin on....

http://i240.photobucket.com/albums/ff112/igatenby/s2.jpg

Both sides resined and stuffing the bag

http://i240.photobucket.com/albums/ff112/igatenby/s4.jpg

Sealing the bag with a bit of tacky tape..

http://i240.photobucket.com/albums/ff112/igatenby/s5.jpg

Vacuum applied and this was at about 8:45am....

....plenty of resin coming through the peel ply

http://i240.photobucket.com/albums/ff112/igatenby/s6.jpg

[The Bigfella]

... and one last shot from today - there's lots of vacuum there to suck this much resin through...

http://i240.photobucket.com/albums/ff112/igatenby/s7.jpg

Why carbon instead of glass?

Dunno, just having a bit of fun.

Of course, using carbon introduces a whole new ballgame as far as galvanic corrosion is concerned - carbon is right up there at the noble end of the tables. I don't expect any problems, given that we will bush the lifting shackle and the carbon is isolated by the resin.

I probably won't do the rudder in carbon, given that there will be a bronze fitting at the bottom - although it is easy enough to isolate it using a bit of glass cloth...

[rufustr]

As long as the galley and my bunk on Grantala are finished, I'm pleased you have achieved this much progress on our toy for this years EBS.:D:D:D

[The Bigfella]

I figured we'd have a bunk building weekend....

I just found another source for Queensland Maple.... so I might get busy there again. I better do some work to scrape up the readies for another cubic metre or two.....

I thought you guys would have put a higher priority on me getting some new anchor chain and cable to wire up the winch?

[J. Dillon]

Looking good Big fella. You're sure taking pains to get it perfect. Thanks for the images of your work.:D Just how much des it weigh in lbs.

JD

[rufustr]

No, we can pull the anchor up!.:)

We need space for the chef, and a bunks to crash in when we get tired of telling lies.:D:D

[rufustr]

Hey JD.

How about a trip to Australia to coincide with our EBS.

We can show you just how basic an Australian EBS can be.:D:D

[The Bigfella]

Jack - I'm not sure, I'll weigh it after we finish it. There's about 23lb of lead in the bottom end - so all up it would be pushing towards 30lb I guess.

Rufus... if'n you'd drunk enough of that Bushmills, I wouldn't have had a sore head the next morning and you wouldn't have cared where you slept either....

[The Bigfella]

Hey JD.

How about a trip to Australia to coincide with our EBS.

We can show you just how basic an Australian EBS can be.:D:D


Just because Duncan got THE chair.... you complain non stop...


http://i240.photobucket.com/albums/ff112/igatenby/ebs3.jpg

[rufustr]

Yep, that's me, Winge, Winge, Winge.

[The Bigfella]

Sheesh - if you are going to whinge, you have to spell it write.

[The Bigfella]

The unwrapping occurred this morning... bag off

http://i240.photobucket.com/albums/ff112/igatenby/z1.jpg

.. breather gone ...

http://i240.photobucket.com/albums/ff112/igatenby/z2.jpg

... getting serious now ...

http://i240.photobucket.com/albums/ff112/igatenby/z3.jpg

Barry swinging the diamond blade .....

http://i240.photobucket.com/albums/ff112/igatenby/z4.jpg

The pile of rubbish....

http://i240.photobucket.com/albums/ff112/igatenby/z5.jpg

A quick sand, some work to do on the isolation issue (making sure there is no electrical connectivity from carbon fibre to any metal), filling the weave and then a paint and she will be done .... I'll leave the painting until I re-paint the hull

[The Bigfella]

OK, after the official weigh-in, it weighs 17.6 kilos = 38 3/4 pounds.

Its sanded - not that there was much of that to do - and stashed in the shed waiting for me to get inspired again.