Deck to planking connection ?

[PeterSibley]

It is very likely that I will cold mould my deck from 3 x 1/4" layers, glued with epoxy.I have however been giving thought to the connection between the finished deck and the planking (1" hardwood )

At the moment it seems that plentiful screws , say every 2 1/2" plus a bead of cotton caulking would be best .

Could anyone comment ? Thanks .

[P.L.Lenihan]

If you'll be cold molding your deck then it would only seem reasonable to secure said deck to the hull with epoxy instead of multiple screws and cotton caulking. The combined thickness of your planking and sheer clamp aught to give enough faying surface for a good glue joint. Just my 2cents

Peter

[PeterSibley]

Peter ...I'm not sure ,which of course is why I'm asking ....but I foresee problems with a glued joint .Perhaps if the rest of the construction were epoxy saturated , but with a normal carvel hull ?

[P.L.Lenihan]

Ah,I see now.I presumed the hull to be cold-molded too or at least strip planked. My mistake.
Is it then an issue with possible movement from the sheer strake? Perhaps bedding the cold-molded deck(around the perimeter) in some 5200 would be better. I would perhaps be more concerned with driving screws (No.10- 2"?) into the plank edge on 2 1/2" centers. Perhaps staggering them on 6" centers,with every other screw going into the sheer clamp.Another thought may be to run the deck out flush to the outside edge of the planking and follow through with a rabbeted rubrail screwed into the sheer strake with lots of goop in the rabbet where the lip(rabbet) covers the deck edge.
What do your plans recommend?

Peter

[PeterSibley]

Plans ?? :D .No Peter , this is a learn as you go exercise .

[P.L.Lenihan]

Then you're a braver man than I Peter :) I admire someone who has the determination to tackle boats without plans,per se, and I wish you well with your re-build/restoration/repair or however it may be refered.
I'm just wondering though, would a good comprehensive text on wooden boat building not have perhaps some detailed drawings illustrating some viable methods for you to consider? Unfortunately, no titles come readily to mind at the moment but perhaps others will chime in with useful tips.
Again, sorry for not being able to be of much help but best wishes and success with your boat :)

Peter

[PeterSibley]

I'll be digging out my copy of Bud McIntosh's book soon ....but I thought I'd ask here first .

I must admit I'm hoping Jay drops by .

[Hwyl]

Beam shelf? Or as one of my students called it "deck chine log"

[Jim Ledger]

How do you intend sealing the edge of the deck. Epoxy resin.? Or, radius the deck edge and let the cloth run down onto the sheer plank. Does the rub rail cover the deck/plank seam?

[PeterSibley]

How do you intend sealing the edge of the deck. Epoxy resin.? Or, radius the deck edge and let the cloth run down onto the sheer plank. Does the rub rail cover the deck/plank seam?

I would imagine sealing the edge of the deck as if it were ply ,with multiple coats of epoxy.The lot covered with a bedded rub rail , screw fastened .

It's the actual joint that will be covered that I'm asking about .

Should it be caulked with cotton or using some kind of flexible sticky ....5200 or a polyurethane flexible adhesive ?

[Jim Ledger]

I'm sure that this is an area bound to provoke a wide range of opinions, however, here's a few thoughts.

A ply deck takes the boat out of the "traditional" methods, i.e. covering boards, and presents a new set of problems along with the advantages that plywood offers.

The reason that I asked about the rub rails and deck sheathing, is that these and other details need to be considered in a context with each other.

My thinking for a ply deck would be something like this...

Two or more layers, epoxied together, fastened into a hardwood sheer strake with bronze ring shank nails, each suceeding layer fastened with the same gauge, but longer nails. The first layer should be bedded into 5200 (here's where the disagreement starts. Consider this though, anyone having to replace the sheer strake is going to have such a huge job, that a bit of glue won't make a bit of difference.) Lots of closely spaced small nails would be my aim.

I'd rather radius the ply edge and run the cloth under the rub rail, holding the top of the rail even with the break of the radius. In a similar manner, the toe rail would be set inboard a bit. This way the ply edge is protected with cloth.

Whatever you do, you'll want the edge of the cloth on the deck to be secured under either the toe or rub rail.

Let's see what others have to say.

[Bob Cleek]

Well, FWIW, I'd forget ring shank nails and 5200 completely. You DO NOT want to fasten your deck to the edge of your sheer strake. It is likely to split the plank. The size of the boat may be a consideration, as well. I'm guessing at size, based on your one inch planking. Problem will be, though, that your boat is traditionally constructed with carvel planking on frames, so it will flex, but you are laying a rather rigid plywood deck, so you will be concentrating all the flexing at that deck to sheer plank joint. The task is to trick the boat into thinking it has a real planked deck. (Although a real planked deck is really the best way to go for a lot of reasons, but I guess you're past that, right?)

Here's what you do. (Or at least what is done by the finestkind pros in similar situations.) Lay a 1" thick covering board in the usual way, on top of your shelf and/or clamp and deck beams. This will give you some room to move at the hull to deck joint, identical to a real planked deck. At the inboard edge of the covering board, work a rabet, maybe two inches wide and maybe 1/2" deep. Run your ply deck up against the inboard edge of the rabet in the covering board. (You will need to decide along the way if you want your deck a bit higher than the covering board or level with it, in which case you will have to adjust the thickness of the ply deck to match the top of the covering board.) This will create a 2" "trough" between the edge of the plywood and the edge of the rabet. Fasten your ply deck with screws into the deck beams. Then lay dynel and epoxy over your ply deck, running the edge of the dynel into the bottom of the trough in the covering board. Finish it off with a batten bedded in a lot of goop (I'd use Dolphinite or equivalent... NEVER anything that will prevent getting it up if you ever need to.). Screw and bung the batten in the trough. Pay the seams on either side of the batten with deck seam compound (Jeffries or Teak Systems polysulfide.) This will work with canvased decks as well. If you ever need to recover the deck, or, God forbid, to replace rotten plywood decking, all you have to do is take up the batten and you have a clear shot at working on the deck without having to tear up the covering board, toe rails, a lot of cleats (mounted on the toe rails) and so on.

The covering board edge, of course, is laid over the top edge of the sheer strake and that seam is caulked in the traditional manner. If you ever have to remove the sheer strake, this can then be done without disturbing the covering board or decking at all.

Bob's yer uncle!

[PeterSibley]

Bob , that's pretty well the MacIntosh method .Sounds like a good way to do things ..although the covering boards are lot more work .Thanks .

[Jay Greer]

What I have done in the past has been to lay a fore and aft layer of quarter inch thick T&G Port Orford Cedar followed with a double diagonal layer of opposed 3/16" cedar set in thick epoxy. These layers were attached were ring shank nails for the first course and monel gundriven staples for the next two. A layer of Dynel Cloth set in epoxy was then layed down followed by the deck planking set in dolfinite and attached to through the sub deck into the deck beams with #10 Everdure screws.
The decks were caulked in the traditional manner using cotton and were payed with Jefferie's Marine glue. Prior to switching to Jefferie's I used Cuhl's Elastic Seam Compound which, sadly, is no longer made. The decks I have laid are still in use. I expect they will last at least fifty years or until they are sanded too thin to be of service.
Jay

[PeterSibley]

What I have done in the past has been to lay a fore and aft layer of quarter inch thick T&G Port Orford Cedar followed with a double diagonal layer of opposed 3/16" cedar set in thick epoxy. These layers were attached were ring shank nails for the first course and monel gundriven staples for the next two. A layer of Dynel Cloth set in epoxy was then layed down followed by the deck planking set in dolfinite and attached to through the sub deck into the deck beams with #10 Everdure screws.
The decks were caulked in the traditional manner using cotton and were payed with Jefferie's Marine glue. Prior to switching to Jefferie's I used Cuhl's Elastic Seam Compound which, sadly, is no longer made. The decks I have laid are still in use. I expect they will last at least fifty years or until they are sanded too thin to be of service.
Jay
Jay , that sounds like Best Practice , as described to me by others .

Could you elaborate on the connection to the hull planking ? Screws , nails , caulking or 5200 ?

Thanks .Peter.

[pipefitter]

With 2 different constructions, it is better to isolate the parts. The deck could be incorporated with the rub rail as a semi monocoque so that there is no weather at the joint with enough room under the transition for plank movement with a soft and possibly traditional sealing system between the 2. A semi-floating sheer deck/cap that is semi isolated without a chance of an exposed joint to the weather could be looked at as one advantage. The trick would be knowing how much the planking moves between wet/dry cycles and how much room it needs. Just a thought. When I hear cold molded, I think glass and it seems there would be an advantage to carry this on over the rubrail/sheer batten whatever to nix any future problem/maintenance concerns.

[PeterSibley]

The version of cold moulded that I have in mind is 3 layers of 1/4" .The first , fore and aft and arised ie a v edge ,the next diagonal, the top layer fore and aft again .The layers of the top and bottom lined up .The idea being that should the top layer print through ,it would look quite presentable .

The system outlined by Bob seems the best .A rebated covering board ,with the deck itself 1/4 "or so higher than the covering board.

[redbopeep]

Bob , that's pretty well the MacIntosh method .Sounds like a good way to do things ..although the covering boards are lot more work .Thanks .

MacIntosh shows two methods for plywood decks, the first being taking the plywood to the edge w/o covering board and putting a rubrail to cover that edge/end grain of the plywood. The second way he shows is that which Bob describes with a rabbet in the covering board and small batten over it. I don't have the book here at the ready, but I thought MacIntosh preferred the first method but can't recall why.

[Jim Ledger]

MacIntosh shows two methods for plywood decks, the first being taking the plywood to the edge w/o covering board and putting a rubrail to cover that edge/end grain of the plywood. The second way he shows is that which Bob describes with a rabbet in the covering board and small batten over it. I don't have the book here at the ready, but I thought MacIntosh preferred the first method but can't recall why.


The covering board method was shown as a way to build without needing a rub rail to cover the exposed ply edge. The covering board he shows is quite thick and requires the deck beams be notched to accomodate the thickness.

[redbopeep]

The covering board method was shown as a way to build without needing a rub rail to cover the exposed ply edge. The covering board he shows is quite thick and requires the deck beams be notched to accomodate the thickness.

Thanks for the info. I agree with the other posters about not nailing the plywood into the top edge of the shearplank because some independent movement would be expected. Having said that, it seems that if the person building the ply/cold moulded deck system has adequate knees from deck beams to frames it minimizes that movement, too.

I'm glad of this topic because we've been (just now) re-installing the decking systems on our boat and she had three! different systems in place AND we have been considering all the fasteners and loading these systems were designed for.

Her original deck design was a sandwich of 3/8" 3ply under a regular 1" thick laid deck. The ply was old fashioned cold-moulded or home made plywood back in 1931 when she was built.

The deck to planking interface changed depending upon where on the boat you were. On the foredeck which has solid bulwarks, the plywood goes to the edge of the deck with a covering board on top of it and the laid deck was inboard adjacent to the covering board in a traditional fashion though the covering board sat about 1/4 inch HIGHER than the planking. The planking including the bulwark planking protected the edge of the plywood and of course the covering board covers the top of the plywood protecting it though that seam between covering board and bulwark is a risky point. We've considered fasteners from the bottom of that bulwark plank thru to the covering board but think that could cause different problems. The scuppers were pipes through the decks (which is why we figure the covering board was a bit higher than the planking) and a single big freeing port on each side that sat about 1" above the level of the covering board in the bulwark planking.

Midships, on a raised deck, the plywood and laid deck both stopped adjacent of the covering board with all sorts of blocking between the frames/deckbeams supporting the underside of the deck. Traditional and straightforward looking from the top.

The cockpit went all the way across the boat, breaking the deck such that the deck aft of the cockpit isn't connected to the midships deck. Back there, the plywood and laid deck went UNDER the covering board butting up against the shearplank which ended a the same height as the top of the laid deck. There, the 1.5" tall x 7" wide covering board sitting on top of the planking acted more like a toe rail. The shearplank itself protected the edge of the plywood (and laid deck for that matter). The covering board (and forward caprail on foredeck) has a bullnose that sticks out maybe 1" beyond the top of the planking sort of like a rub rail but the boat's actual rubrail is about 14" below and surface applied to the planking.

The midships deck had a small toerail on top of the inset covering board whereas the foredeck had the bulwarks.

Now that we're replacing all these systems, we've done the foredeck as it was but we've reduced the size of the cockpit (it now has decking on each side of it) so the aftdeck and midships deck needed the same construction.

Our new deck is 3/4" cedar T&G overhead under two 9 mm marine plywood glued together. The waterproofing will be a layer of dynel set in epoxy and because I like the look/feel of (real) canvas the whole thing will be covered with traditional canvas set in paint. (Long story on that decision with no laid deck on top but no need to go there in this thread about covering boards and deck/plank transition!)

We ended up deciding to combine the midships/aft deck setup so that the shear plank is adjacent the 3/4" t&g overhead but below the 3/4" plywood. A quite thick and wide covering board is shaped protecting the end of the plywood by the shape of the covering board system which essentially has an outboard rubrail part to protect the plywood; the plywood sits atop the shear plank but is not mechanically fastened to the shear plank. All covering board and deck fastenings are to the deck beams and each other, none to the shear plank. A small toerail sits on the inboard edge of this covering board and scuppers are the same thru-deck pipes that previously existed. With our boat's strong deckbeam to frame interface, a good shelf and sturdy knees we hope that the movement will be minimized.

A weakness of our system is that when we replace the "sacrificial" canvas which sits atop the dynel deck, we will have to remove the covering boards. The "rubrail" part of the covering board/toe rail system can be removed from the covering board if we need to work on part of the shearplank. The shearplank would be a bear to remove since it's a 35' plank with scarfed on shorter front and aft section to make 52' length from quarterlog to stem.

We've put down the 3/4" cedar overhead everywhere, done the plywood on the foredeck and are just getting to the plywood on the rest of the deck this upcoming week (rain, rain, rain has delayed this project alot).

In addition to differences in deck/shear plank interface on this boat, the whole interface between the deck and house, scuttle, deck lights, all have been interesting because on this boat they're ALL different--all designed with the plywood subdeck going under (cabin, scuttle, deck light, all) but some with original laid deck going under (like deck lights and scuttle) others with laid deck adjacent (like cabin).

Thanks again to you guys for bringing up the reasons NOT to attach the planking to the deck directly. Good luck in your projects, too.