Bulkheads

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pauls_SPT

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Hello,

I'm going to start rebuilding the interior of my 41' Seaplane Tender soon (See here for details) and one of the jobs I've got ahead of me is rebuilding the bulkheads.

The things I'm wondering, though, are these;

Should the bulkheads go flush against the hull or should there be a gap? I read that there should be a gap to stop stress on the hull, but the article seemed to be referring to GRP boats...

Should the bulkheads go all the way to the keel, seperating the bilge into sections? At the moment, the bilge is partly seperated every fifteen feet or so, to a height of about six inches...

My boat's 9'6" at her widest and cutting a single piece of wood for each bulkhead would be really awkward - is it acceptable to build bulkheads in sections? (A top and a bottom part or port and starboard sections for example?)

Will 18mm ply (West epoxied) be up to the job? Alternatively, should I tip my hat to provenance as t'were, and build the bulkheads out of a more appropriate material, considering my boat's historic nature?

I have frames every 18" and plan to screw and glue the bulkheads to them where they're required - is this the way to do it?

I appreciate that all of this could have been summarised by a posting which read "so these boat things, then - how do you build one those?" but any help and advice will be much appreciated /forums/images/graemlins/smile.gif

Thanks and everything,

Paul
 
Do you know who she was built by? Maybe either Thorneycroft or BPB Co?

If she is British Power Boat then have you tried BMPT for plans? or indeed tried to get hold of Phil Claburn who I think has plans for some of the Scott Paine boats?

I dont know where you are but sounds like it would be worthwhile inspecting some similar boats? (Like the one BMPT have)
 
Hiya,

I wish I knew who she'd been built by!

I think she may be a Walton Yacht Works boat; at least that's what a historian at RAF Hendon suggested, based on the size and shape of the cabin windows shown in pictures of a model I've got of her, which was built by a previous owner.

I've been to see boat 1502 at the old BMPT site (who have now moved on and donated 1502 to the Imperial War Museum as I understand it) and taken huge quantities of photos...except I can't make out from them what I want to know about the bulkhead construction. Indeed, the BMPT built their bulkheads in two parts; top and bottom, but I was wondering what the general opinion of this method was?

I have two excellent plans drawn up by a chap called John Pritchard, one for a 38' SPT and another for a 41' Wide Beam SPT, but neither show the bulkhead construction in great detail...

Really, I'm willing to forego historical accuracy for good/practical building technique, so what do you think?

Thanks for your help,

Paul
 
There's been two or three "Seaplane tenders" at Freebody's at Hurley over the years, and although I was there an hour ago I didn't look, but one (some say the original) was there last time I did look a few months ago, called "Gelyce". I understood they were built by Camper & Nicholls.

Whilst there took photo's of three (!!!) new stems, for brand new slipper launches, clamped up. What other yard are building new traditional boats in such volume? Also the large William Osbourne cruiser "Lady Lucy II" has had her entire port side inner skin replaced, out skin being done whilst there, starboard side still being removed, and new rear cabin sides being clamped up on bench.

IanC
 
Now, Burgundyben will know far more about fast wooden motorboats than I do, but here are some general thoughts, having replaced a bulkhead or two in my time...

1. These are very likely to be "structural" bulkheads, adding to the strength of the hull, because on first principles nothing is on board a fast motor boat that is not paying its way.

2. I suspect that the original bulkheads went to the sides of the hull, and were double diagional planked, for stiffness.

3. If they go right to the bottom, you cut "limber holes" in them, to allow the bilge water to drain aft.
 
Hiya,

thanks for your help /forums/images/graemlins/smile.gif

Limber holes - so they've got a name! My 12" bilge bulkheads have those in them - I assumed they were for control cables and pipes that had long since been removed and sold (everything not actually structural has been ripped out at some point in the past).

So...if I were to butt my bulkheads up against the hull, should I put something in the join, either to promote a better joint or to prevent damage to the hull?

I've drawn this cross section of my hull at one of my frames - the blue is the double-diagonal hull, the brown is the decking and gunwale moulding and the bulkhead is sort of semi-transparent over the top of everything - the join I'm wondering about is arrowed...



Again, thanks for your help /forums/images/graemlins/smile.gif

Paul
 
There are really two ways to go. Either stop the bulkhead on the frame well clear of the planking, or bring it right out to the planking and use plenty of mastic behind it. The reason being that you want to avoid a nasty little space that traps dirt and damp. It rather depends how much frame you've got to fasten into. With a round bilge boat with steamed timbers you've no choice because the frames are small in section, but with a big hard chine boat like yours you may have plenty of frame to fasten to.

Be really, really, sure that the boat is the right shape before fitting bulkheads, cos that's the shape she's going to be from now on...
 
Thanks for that /forums/images/graemlins/smile.gif

Getting the boat set up right is what I'm trying to figure out at the moment - the problem with measuring her to check how straight the hull is, is doing it with any accuracy - tying taught ropes from stem to stern and measuring to the gunwales seems like a good start, but in practice, the measurements I'm getting are only accurate to about an inch or so I'd imagine...

Have you got any ideas as to how I might check everything's square before I go fixing bulkheads in place?

Thanks again,

Paul
 
Can you set up a datum board? There is a method which is much favoured by British wooden boat builders, described in Watts and Jurd, called a "building board" in which a plank is set up on edge, above the boat, from stem to stern, and all measurements are taken to that. I've seen it done with a large wooden powerboat hull which was being restored professionally. You can get a dead straight line down the board with string and chalk (mark it in permanently of course!) and get that horizontal.

Having done that, it's a matter of measuring to the datum and the old 3:4:5 trick for making an instant set square of large size, as favoured by the ancient Egyptians, etc. /forums/images/graemlins/wink.gif
 
There used to be one based on the River Severn at Stourport Yacht Club, owned by Norman Kidd. name 441. She was kept in near original condition subject to the demands of civilian use. Last heard she was ashore, may be worth an enquiry as to whether she is still about. I should imagine the lack of salt water will have affected her planking by know and the years will have taken their toll but could be worth a visit if she / he is still around. A check on the club forum has just revealed that she was recently purchased to be restored. Worth contacting stourport http://www.stourportyachtclub.co.uk to find out the new owners for shared knowledge.
Takes me back to the 70's when we were members with Maid of the Mist (40' Gibbs TSDY) and Hypotenuse (Nauticus 27)
 
Mirelle is right, you could choose to go either route, given that she is an old boat and likely to be treated with respect (and not chased by machine gun equipped Jerry's) I'd suggest butting the bulkheads right up against the inside of the frames.

Having not seen your boat of course its hard to say, but my caveat here would be that the most important thing for you to get right is the fastening of the frames into the planks and the security of the joints (biscuited?) between the constituent bits of frame?

Girt big limber holes are essential, suggest 2" round holes adjacent to and either side of the keelson.
 
Yes. Exactly.

Many of these boast were built by cabinet making firms, working as subcontractors to the lead yards, during WW2, and the construction techniques were adapted accordingly.

A careful reading of Michael Verney's books comes in handy at times like this!

One huge advantage of using double diagonal planked bulkheads, if you are my sort of wooden boat owner (as opposed to the Victorious/Transcur/Kestrel sort! /forums/images/graemlins/blush.gif)
is that you are dealing with smaller bits of wood, easy to manhandle and mark up, and the cost of mistakes is less than wrecking a sheet of plywood.

If it's good enough for Larry Pardey*, it's good enough for me!

"Details of classic yacht construction - the hull" - another good book.
 
Plus had another thought....

I take it she is DD from keel to chine and DD from chine to deck?

If she is a BPB Co boat maybe worth removing one of the outer planks from the bottom to see what is between the two layers of wood.

I can tell you this, both my 23 and 20* foot racing boats build by BPB Co had a layer of calico cloth impregnated with oil, linseed I think, between the two layers. Needless to say after 70 years it was well past its best and with hull upside down I took the chance to remove it and the new outer planks were epoxied back on and fastened with bronze screws. (sides are different as they are seam battened not DD).

I'm sure the early whalebacks had this cloth too. Maybe now would be a good opportunity to sort this out?

*a project to be started in 3006
 
Hiya,

thanks again for all your advice /forums/images/graemlins/smile.gif

As you surmise, my hull is DD all over. I'm a little unsure about taking off all the outer planks to renew the calico - my boat's 40'6" long - that's a lot of planking to re-fasten! Admittedly, this is something I should do, but the cost is prohibitive - is there something to be said for not disturbing it? If I were to strip the hull to this extent, I'd certainly be looking to win funding from the HLF or similar and, having looked into this, I'm not sure that it's the route I want to go down...

That said, if work such as this is a neccessity, then I'd have no choice - I was rather hoping I could get away without going to such extents, though /forums/images/graemlins/frown.gif

Can I just go over some of what BurgundyBen wrote, as I'm a little unclear as to what he means;

"I'd suggest butting the bulkheads right up against the inside of the frames"
Do you mean hard against the hull?

"the most important thing for you to get right is the fastening of the frames into the planks and the security of the joints (biscuited?) between the constituent bits of frame"
Which planks do you mean? The frames are all brass screwed and glued (I would imagine) and are very strong as they are.

Could anybody suggest any good books I might be able to get hold of? I have one on wooden boat restoration, but it's really just a brief guide to 101 jobs you could possibly want to do on a wooden boat...

As always, many thanks for your advice and time /forums/images/graemlins/smile.gif

Paul
 
I'm going to (cautiously!) differ from Burgundy Ben; I would leave the planking undisturbed. Ben is "into" very high powered craft, operating at their original design speeds, so he needs to have everything 100%.

Your vessel, whilst "in the same family", so to speak is a more moderate version of the same thing, and I dare say you will be content to operate at moderate speeds.

Take a look at Michael Verney's "Practical Conversions and Yacht Repairs" - its long out of print but it was a common book in its day and your local library or secondhand bookshop should be able to turn one up.
 
Thought about it some more and its a question of how much time and money to spend. Starting point is how many HP is going in? If only enough to give displacement speeds, maybe 10 to 12 knots, then removing outer planks probably not required and whether bulkheads are hard up against inside of hull not so important.

However, if bigger HP is going in and planning speeds, say anything over 20 knots, then I would suggest that the critical point here is security of the planks to frames and if that part of the job is done right then butting the bulkheads right up against the inside of the planks is right as it will be spreading the load of the bulkhead and frames onto the planks over a wider area.

Basis I suppose of my approach is that there is no point in ensuring the integrity of only some areas of the hull, the whole thing must be right, otherwise it will be a case of damage transferring to other places.

On my Scott Paine boat the hull has been upside down, all outer planks off, bottom inner planks refastened, outer planks re fastened and new sides, all done with SB screws (of which I still have a 1000...).

Clearly its a different size job altogether on a 40 footer and maybe not required if a pair of smaller engines going in.

Incidently I still want a Napier Lion engine.
 
To be honest, I was looking at a pair of 100hp diesels - whatever was available, although S6M's (rare though they are) would be in keeping...

I can see you point though and, to be honest again, I have visions (really nasty ones) of my boat disassembling itself, plank by plank, the first time I open the throttles with any enthusiasm.

How did you get your boat upside down? Did it sit nicely on it's gunwales or did you support it at the keel at all? I really can't see me doing this (the logistics alone don't bear thinking about!) but it'd be nice to know what's involved.

Thanks again,

Paul

ps - what are SB screws?
 
SB - silicon bronze.

Engines - reckon a good choice would be ford dorset or dover blocks, non turbo fine if you want 100hp each, spares situation is good for base engine and marinising bits from Mermaid probly the best. Should think a reasonable pair with g'boxes about £3k? If you were buying new then the Perkins M135 pretty good, but ~£10k each! Lancing Marine Fords are cheaper new.

I built two big plywood discs around the boat and rolled her over, should think with a boat size of yours you'd need three or four and maybe a crane! totally different task with my 23 footer than your boat.
 
Thanks /forums/images/graemlins/smile.gif

I can picture the crowds I'd draw, rolling a 40' boat over with truely epic ply discs - I imagine I'd get into the local papers!

I'll have to have a bit of a think about that...
 
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