Tongue & Groove Bulheads

[EASLOOP]

Good morning,

I have acquired a quantity of tongue and groove 3/4" by 3" mahogony floor boards that I intend to use to build the bulkheads in my refitted East Anglian. I had intended to glue the T&G to form a rigid bulkhead across the boat but speaking with someone today they said that I should not do this as any movement in the planks could result in cracking and splitting. I know that mahogony is very stable, especially this stuff as it is about 100 years old, and so I am seeking any advice from those of you that have experience in this area. I.e. to glue or not to glue - does not gluing create a moveable bulkhead resulting in loss of supprt/rigidity etc etc.
Looking forward to your replies

John

<hr width=100% size=1><P ID="edit"><FONT SIZE=-1>Edited by EASLOOP on 22/02/2003 10:00 (server time).</FONT></P>

 

[snowleopard]

100 year old mahogany? nothing but trouble, wouldn't let it anywhere near a boat. tell me where it is and i'll come and cart it away for you, no charge ;-)

<hr width=100% size=1>

 

[Jools_of_Top_Cat]

The dive charter boat I used to skipper was owned by a joiner, had lovely woodwork in the wheel house and down below. In the f'ward cabin he used tongue and groove, softwood too, but before application epoxied the back of each plank and heavy varnish to the front, with mahogany you should not have this worry.

We fitted them with tacks, they were fitted to the ribs thus making up walls and tidying up the cabin, they were also used on the bulkhead, fitted to a stud wall. When tacking we put the tack through the tongue right up against where the plank begins as it were. only the first and last plank had visible tacks, although these dissapeared with a dot punch.

The tongue and groove worked well and looked good, the vessel was 45ft so may have been able to handle this amount of timber better than a smaller vessel, but my advice would be to make them solid, use glue by all means I just thought I would share how I saw a proffessional do it, it may not have been 100% marine technoligy, but it worked well in my opinion.

<hr width=100% size=1><font color=blue> Julian </font color=blue>

<A target="_blank" HREF=http://www.ukstaffords.com>http://www.ukstaffords.com</A>

 

[EASLOOP]

Har Har

Have a good day



<hr width=100% size=1>

 

[neil_s]

My old Hilliard had lots of t and g pine. None of it was glued. It was all secret nailed to 2 X 4 in battens fastened to the frames. None of it formed part of the load bearing structure, though. Is your bulkhead a structural part of the boat? If so, perhaps it would be better to retain it as is and use your t and g as a decorative surface finish.

Neil


<hr width=100% size=1>

 

[EASLOOP]

Thanks for your input. The T&G I am using is 3/4" x 3" 100 year old mahogony and so is very stable. I am building the bulkheads with T&G as it is impossible to get a one piece ply bulkhead into position. This is because I am trying to move a 7' 5" wide piece of ply into a 7' hole (cannot drop it into place as the coachroof is still where it started) bearing in mind that the bow of the boat is not unlike a cone which is diminishing in size as one moves forward. So T&G was a good option.

Yes, the two bulkheads do reinforce the hulll athwartships, but the planks will be secured to the sole bearers, the deckhead beams, deck beams and hull frames, all of which line up to form an effective circle. There will be an aperature in the bulkhead, sort of a smaller hole, through which one gains access to the forepeak, heads etc. In all probability I could glue as well as I expect very little movement given the way the planks will be secured, i.e. using s/s wood screws through the planks directly into the beams - not hidden nails. Most of the advice is against gluing however.

Hope it all works well

Best wishes,
John

<hr width=100% size=1>

 

[Plum]

Although your 100 year old mahogany will certainly be very well seasoned! the age of the wood will not affect its resistance to expand and contract with respect to changes in moisture content (this is proved by the fact that even a 100 year old mahogany planked hull will "take up" and become more watertight due to the expansion of the wood as it takes up moisture). Even if you glue the planks together and then encased the while lot in epoxy resin, you will still get a ceratin amount of movement. Now, assuming that your boat is of traditional timber construction, I beleive you should consider what effect this bulkhead will have on the overall hul structure. If you glue a very stiff bulkead into a traditional wood hull you may create unreasonable stress points and do damage to the hull (this applies to GRP hull too). Was the hull designed to have a structural bulkhead in this position?

<hr width=100% size=1>

 

[EASLOOP]

Thanks for your input. Yes, I am aware of the take up issue with mahogony, my sloop is mahogony on oak frames with a laid teak deck. I have completely gutted her and have now completed some very substantial works. I have been fortunate enough to get a complete set of full size plans for the boat from Alan Buchanan, the designer. In those plans two bulkheads are shown one just ahead of the keel stepped mast and the second just aft of the mast. These two B/heads are about 30" apart. Annotation on the plans are that the forward bulkhead be fastened to frames and beams all around using 3/4" ply with an open section for a door. There is no such annotation for the aft b/head. I assume from this that the forward b/head is structural. In any event, I am not a shipwright and so by default some (most) of my joinery has a fair degree of freedom as it were. By default then there is adequate (I hope) room for movement dur to moisture ingress. I have decided not to glue the planks together because this will add a stress point (hard spots) that could be a problem. The reason I am using the mahogony is because I was able to get it for less than the price of many other solutions. All though I am changing the material I will be putting the bulheads back where the originals were fitted on the basis that this must be the best place to put them. My concern is that there may be TOO much movement thus adversely affecting rigidity.

Rgds
John

<hr width=100% size=1>

 

[Plum]

Nice little project you have there! Just looked at a picture of an East Anglian called "Mirembe" in Classic Boat magazine so now know what you have. Sounds as if you have been doing a lot of homework/research in order to refit your interior in a way that is sympathetic to the hull and your decision not to glue the plans together sounds reasonable. There is one thing for sure, the planked mahogany bulkhead will look so much better than a sheet of plywood! Good luck.

<hr width=100% size=1>