Replacing a plywood deck on a steel boat.

Thank you so much everyone for your thoughts..... veering towards a straight replacement of ply ..... any advises if I do this? I guess glue and bolt first layer then glue and screw top layer, offset to any joins? then epoxy with mat over the lot and lip? then paint the lot with epoxy paint inside and out... is that how its done? or is there better method. Any advise on glues epoxys etc or pointer to good literature.
cheers
 
No experience of doing this, just thinking out loud :-

With the extreme camber of the deck of the Seal / Zeehond, Bending 9mm ply to conform will leave stresses that will be trying to lift the deck off the steel shelf, maybe 3 layers of 6mm ply would conform to the camber easier.

Screwing into ply has little holding power, either use temporary screws into temporary wood blocks underneath or numerous temporary staples or permanent ss-staples.

I cant think of any way to make a sufficiently flexible joint between hull and deck. Given that there will be movement here, think of ways to stop water entering the ply, any bolt holes make them oversize and coat holes with epoxy, lay epoxy and cloth on the hull shelf as a bed for the first ply layer, fold over the cloth, and epoxy down after the top ply layer to protect the end grain.

Plank
 
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Thanks you everyone for your help this job took took much more work than i could ever have imagined..... however for better or worse Wanda now has a new ply deck.... with 2x 9mm marine ply from Robbins. Wood is first class though expensive ... Robbins customer service delivery charges and after sales ...appalling. photo of deck.jpg

Now for the treadmaster .... which will cost as much as the wood!
 
I built my last boat in steel. Use pre-blasted and primed steel from new and epoxy coat the burnt areas at the end of each days welding. Use 'Tee' sections inside for stiffening as these make fastening panels very easy. Basic stick welding is very easy after a few hours practice, despite what the professionals might tell you. Keep the steel weight similar to the ply and timber bearers weight and you won't be far out.
 
I also have a steel boat but the deck and superstructure is steel. If I were to do it again I would use aluminium for the deck and superstructure and insulating the steel hull from the aluminium superstructure.
 
fanakaman said:
Thanks you everyone for your help this job took took much more work than i could ever have imagined..... however for better or worse Wanda now has a new ply deck.... with 2x 9mm marine ply from Robbins. Wood is first class though expensive ... Robbins customer service delivery charges and after sales ...appalling.
Now for the treadmaster .... which will cost as much as the wood!
Click to expand...

I didn't see this thread until now but was going to post that if the boat was designed for ply decks then replacing them like for like seems like a good idea, gglad to hear you had the same thought and it all turned out well in the end. An alternative to Treadmaster and quite a bit cheaper is Kiwigrip which I intend to use on my boat when I get round to it.

Boo2
 
fanakaman said:
Thanks you everyone for your help this job took took much more work than i could ever have imagined..... however for better or worse Wanda now has a new ply deck.... with 2x 9mm marine ply from Robbins. Wood is first class though expensive ... Robbins customer service delivery charges and after sales ...appalling. View attachment 55329

Now for the treadmaster .... which will cost as much as the wood!
Click to expand...

Hurrah! You shall ride the ocean swells once more :cool:

Good luck with the rest, and plans to head off again?
 
Hi, Boo2 - we've already bought tread master- we stick it down tomorrow, if the weather allows; then there's the little matter of almost a complete internal refit and the rig to sort, not to mention working for a few years to top up the cruising kitty before we go off again! Nice to meet you recently GHA
 
Hi,
I've only just seen your thread about replacing your deck. I built a 36 foot seal many years ago and my drawings gave two options for deck material, ply or steel. I chose steel. It was 3mm thick, I have a couple of photos of the deck being built. If your interested, send me your email by PM and I'll send them.
Cheers
Paul
 
As long as there are sisterships with steel decks ( highly likely with a VDS) and no problems, a steel deck would be no problem for you , and your best bet. If the hull is foamed, avoiding setting the foam on fire demands precautions( lots of wet blankets over it).
I used 3.2mmm hot galvanized steel for my decks, no problems . Galv needs a TSP, then vinegar wash , before painting.
I weld all my beams and longitudinals on before installing the deck panels. Eliminates a lot of overhead welding.
I have put all the steel decks on a 36 footer in 8 hours, much simper than with any other material. It also lets you weld down all your fittings, eliminating deck leaks.
Changing materials at the hull-deck joint is a big mistake.
 
The only wooden area on my steel ketch is the cockpit sole and its teak on ply.

Unfortunately after 30years, its time to rip it up due to rain ingress.

The decks & coach roof are epoxied and then have treadmaster applied (in blocks rather than over the entire surface) and its worked well. Contrasting Toplac is used between the treadmaster panels.
 
The hull deck joint takes almost the entire twisting load on a hull, and is the spot most prone to corrosion, and leaks, which makes it a bad spot to change materials. The cabin sides are not all that heavy, especially with the windows cut out , so no advantage in changing materials there. I have changed the cabintop on gazzele from heavy, soggy plywood, to 3/16th aluminium, with good results, a big reduction in weight and maintenance.
It is the longitudinal shrinkage along the sides of side decks which cause distortion. Thus side decks need longitudinals, one for an18 inch side deck, 2 for a 24 inch side deck.
Most steel boats here have 1/8th inch( 3.2mm ) steel decks, including all VDS designs . Anything much less would give severe distortion problems, and would be impossible to keep fair. Any corrosion would go thru rather quickly, not giving you much time to catch it in time.
 
Its another dead thread raised by Brent Swain. The deck has long been fixed in a quality marine ply.

Nothing Swain has said on the revised thread has contributed to the earlier discussion, or even added new information, just reinforced the fact he consistently raises dead threads.
 
BlowingOldBoots said:
Its another dead thread raised by Brent Swain. The deck has long been fixed in a quality marine ply.

Nothing Swain has said on the revised thread has contributed to the earlier discussion, or even added new information, just reinforced the fact he consistently raises dead threads.
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More childish jeering?
No, you are not going to be the last one to ever seek info on dealing with this issue. No, we wont accept your implied claim that now that you have dealt with the problem, no on else has the right to more info on the subject. No, your having done it in plywood, and its having lasted a brief time, doesn't mean what you have done is the final word on the issue, and will last forever, nor that it wont give you problems..
What I have suggested will last much longer, will not rot and leak, is much stronger, and will give far fewer problems, in the long run.
Sure, to late for you, but not for others who have similar questions.
No, I don't buy the attitude that as long as you are OK, screw everyone else.
Yes, you will have regrets, for not using what I have suggested, eventually.
Yes, what I have posted is useless to you ,( too late) but not for others.
No, you won't be the only one who ever matters, on this issue!

When I put the aluminium top on the Gazelle, I used stainless flat bar where the aluminium was bolted down. One should use stainless wherever you can't get at it easily, in the future
 
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ianj99 said:
The only wooden area on my steel ketch is the cockpit sole and its teak on ply.

Unfortunately after 30years, its time to rip it up due to rain ingress.

The decks & coach roof are epoxied and then have treadmaster applied (in blocks rather than over the entire surface) and its worked well. Contrasting Toplac is used between the treadmaster panels.
Click to expand...

Change it for non vegetative material.
 
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