Thread: Douglas fir/oregon,planking

Traditionally built lapstrakes don't take to trailer borne life very well and this is especially true of those with solid rather then plywood planking. I've just started a new lapstrake build and it'll use glued lap and plywood, though the owner wants a tradisional look. So, to accomidate this need it'll have spruce frames, laminated in, which will simulate a traditional build, but they'll weigh very little and the glued lap method will insure it stays tight and free from leaks.

Also, rather then caulking the seams, most every lapstrake builder (tradisional methods) switched to polysulfide as a seam bedding, once it was available. This made the boats much easier to live with as they didn't need to take up, before you could use it. The seam goo permited sufficent movement to permit the planks to swell as they wet/dry cycled, without leaking. They still suffered the other issues, typical of clench or riveted lapstrakes, but at least you could get on the water quickly.

Thank you PAR.Heidi does used the polysulfide goo,between the planks.It's flat bottom is glassed in the plans,with the glass coming up over the edge of the bottom side plank. http://www.flickr.com/photos/nomadbo...7631207839384/

I'll do the same with my new lapstrake build, 'glass the garboards to the bottom plank, though it will be a full glued lap build, mostly because I want really light, really water tight and not to have to make (or buy) a bunch of ribs, floors, etc. Except for a couple of bulkheads and a couple of ring frames (bulkheads with big holes in them), there's little else inside the boat.

In my opinion if you are going to do the clinker/lap strake planking in Oregon/Douglas Fir I think you are headed for some problems.

Generally the Oregon that we get here in Melbourne is young growth, plantation timber grown in New Zealand. It is coarse open grained and regularly very knotty. I really doubt that it would be good for what you are intending.

a lot of the early speed boats were built with Pacific Maple planking. Many boats including up to the 27' whale re that the Navy used were built with PM planking.
I really would be thinking of PM if you want originality but I would probably use marine plywood purely for availability, consistency of product and ease of use. Also the planking is much less likely to split if made of Marine Ly as opposed to solid timber.

My clinker speed boat was built using Coachwood Marine Ply and despite being at least 40 yo it has no delamination of the plywood or split planks.

Just my thoughts.
If you are in the eastern suburbs of Melbourne and would like to have a look at the planking drop me a pm.
cheers
Peter

Peter,Thank you for the pointers on our Melbourne Oregon.We just had a timber carport rebuilt,(it blew away during a storm late last year.It landed on my ts16) The builder told us not to build in Oregon because of it's open grain.So you do have a point.However,if i were to encapsule it in epoxy(which i was going to do anyway) The open grain would/should fill.I do have a strong leaning towards marineply planking,i guess when painted,only i'm to know its not solid timber.A point raised by Par. was water getting in thru the rivet holes and migrating between the veneers.I am NOT giving up on riveted planks.I will seal them with marine sealant,as for the holes? i've heard of some people squeezing super glue into the holes(its absorbed into surrounding wood,sealing the grain).My idea is to build a "classic styled" skiff,in a traditional manner.I don't want it to be just another glued,ply lapstrake boat.Well it's some time off yet.I just want to get things like materials sorted out BEFORE spending my money.BTW i live in Melton and would love to see your boat some day. John C.

Most every traditional lapstrake builder switched to plywood, once waterproof glues where used and tested. The reason is the material is so much more stable in several regards (no splits, checks, knots, pith, swelling, etc.). You can have your traditional build, but without the headaches, by gluing the plywood planking seams, yet still using ribs and clenches/roves. It's a belt and suspenders approach, but you'll get the best of both worlds.

Superglue in the holes doesn't seal as well as epoxy, nor does it penetrate as far either. It's also brittle, unless you use certain types of cyanoacrylate. Also cyanoacrylates have a limited shear strength, which will be tested around fasteners. I'd be inclined to use epoxy in predrilled fastener holes, to insure they don't leak and the seam remains tight. There are superglues that have silica and other things in them to change viscosity and shear strength, but you'll have to shop around for them.

If not gluing the seams, I'd go full up traditional and just use polysulfide and fasteners. I'll still use plywood, which under putty and paint looks just like solid lumber. The only time I'd use solid lumber on a lapstrake is on very small, very light builds, such as a 8' Lawson tender or something similar.

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I've just started a new lapstrake build and here is the preliminary "line off". It's not finalized yet, you get the idea. I use battens "let" into the station molds to define the plank edges. In fact if you look closely, you can see the garboard batten has been let into the molds, though none of the rest have. This a plank keel design (I have a number of designs like this), so it's bottom is flat, a single plank, which makes beaching easier. These line off battens don't remain in the boat, but just serve to support the sometimes flimsy edges of thin planking stock (6 mm), before getting goo.

I will heed your warnings about not using superglue.I will go for the ply,but polysulphide and copper rivets,not epoxy.Fibreglassed bottom.Plans called for half inch timber planking.I've heard said that as ply is stronger,,you can go thinner.Would 9.5mm be ok? I've used it to bottom my pirogue and it seems strong enough.

Plywood isn't stronger then solid planks, though it's stability and cross grain stiffness are much better. When converting from solid to plywood, no planking thickness deduction is recommended by most designers. This said, if you use two layers of 4 or 5 mm plywood, glued together (epoxy), to make up the planks, you'll be fine with an 8.5 mm - 10.5 (glue line added) plywood plank, assuming 5 veneer stock is used. I've used this technique to make really light hulls and it saves the bother of scarfs or double sided Payson butt joints. I just butt the pieces together and only Payson join the inner and outer seams.

Without a scantlings list for your boat and the general dimensions, it's hard to suggest planking thickness alterations, but the general rule is no reduction. Now, if the seams were epoxied, you could drop down to 3/8" plywood planking, though I'd still use a 1/2" garboard, because of how stressed it is and to offer some penetration resistance.