Taller Wall ....

[Larry C]

you could always use a scraf joint as well -- that way you could even splice 1/8 inch plywood and could easily do a sandwich structure, which would be much lighter...

Kenny,
I think just a butt joint with epoxy/ fiberglass is all thats needed. Scarfing is difficult to keep straight. I built a Pygmy kayak kit 15 years ago that uses butt joints with 4MM Okume plywood.

Also I remember some scientific testing that was done on scarfing vs butt joints in boat building. It was a controlled test of various thickness plywoods.
The result was plywood under 1/2" was stronger with properly done a butt joints ( glass both sides), than a scarf joint.

I know that can bring a lot of arguments as it did on the boat building forum. However, from my personal experience, using thin ply, I think the butt joint is the way to go.

Here's butt joints being used to make long panels for a S&G kayak:




Larry C.

Sure, if you are going to glass both sides!! Tear walls aren't going to see much bending though, and if you were to scarf them, then bond them to foam and then glass over the outside... I'm guessing that would do as well. I was thinking to do a good scarf joint you'd have to make a router jig, but it wouldn't be that hard. In composited we use a 20/1 scarf -- I'm guessing that would work in plywood as well. Do you remember what the scraf ratio was in the test you read about? I'm guessing it's perhaps less than 20/1.

A butt joint with fiberglass fabric on either side would no doubt be robust enough.

I don't know the scarf ratio that was used, but I bet it was what ever is typical in boat building. The problem I see with scarfing thin ply is to get the strength to hold the panels together, the scarf will be steep which will make sharp fragile edges.

What I mean about butt joints is just using tape or narrow strips of glass at the butt joint, not glassing both sides of the whole panel. When I did the butt joints, I was able to lift the panels without worrying about breaking the joint. I don't think I would feel that secure with just a scarf holding the thin panel.

Isn't what we are trying to accomplish just holding the lengthened panel together till its bonded to the foam core? I think this should follow the "KISS" concept. The time it would take me to set up a jig to router the scarf, I could have the panels butted with thickened epoxy and taped applied to both sides of the joint.

Both methods are fine for thin ply, I am just comfortable with a different method than you.

[Billy K]

Okay, my pea brain came up with a thought.....

What if; (just adding 6" in height)....

- Using a 2"x8"x8' to go along the length.(to be assembled lying down)
- Cut a notch on the inside upper edge the thickness of my 1/4 x 3/4 x1/4
and @2" deep.
- spread thickened epoxy in the cut out.
- lay the frame and outter skin into the notch.
- pocket screws from wall lower frame board into 2x
- attach inner skin
- stand wall and screw the 2x to the side of the trailer and into the floor
- attach spars....etc.etc......

does that make any sense??

[afreegreek]

good God!.. reading this stuff make my head hurt.. you'd think you all were making your trailer to withstand a sabot round from an Abraham's tank..

[kennyrayandersen]

Larry,
Yeah, I knew what you meant. I've got no problem with it. As far as glassing the whole thing it depends on what a person plans to do to the outside. Personally, and I know this discussions has been had many times, I would glass the whole thing if I were only going to paint the outside or even epoxy it for that matter, but that's me. It's not a strength issue to be sure, but there have been too many people that have had water penetration issues to risk it IMO. Too much work and repair has had to be done. I'm REALLY not into doing anything more than once.

[vtx1029]

What about doing a lap joint? Just router the top of one sheet and the bottom of another and then glue them together...

[Lou Park]

What about doing a lap joint? Just router the top of one sheet and the bottom of another and then glue them together...

Ahh, finally, the best way to do it.

[Billy K]

The reason for the original question was to avoid any seams.

I do appreciate the scarfing,laps, and butt joints for what they do. Seamless is my intent...other than where necessary, as much as it can be acheived; for my woody walls.

As for the tank round...don't own one of those. But, I may wanna stop a .50 cal lead ball or 600grain longbow fired arrow
Thanx for the concern though.

[kennyrayandersen]

What about doing a lap joint? Just router the top of one sheet and the bottom of another and then glue them together...

Ahh, finally, the best way to do it.

When you are splicing an 1/8 inch thick piece that don't leave too much to work with... It could be done though and as long as you weren't bending it it would be OK. If you started to wrap it around with that kind of splice, and expecially that thin, I wouldn't be surprised to see 'issues'.

[Billy K]

Well, nobody has said; it won't work....the 2 x ? method, I mean.

the pros I see,
1) it would give me 6"(+ or -) more height
2) it'd reduce waisted 1/4" plywood
3) the rabbet backwall would become exterior trim
4) I could use a 9' long 2x and butt join the length at the
galley wall: adding a framing 3/4" stud right under
the hatch hinge, where the splice would be

the cons
1) the same back wall would need to be notched for the
doors to be just above the floor
2) maybe too much wall weight above the joint

Anybody else think of others?
With drawers under the doors and galley; I think this will allow for lots of storage and not add too much cost or waist.

[Larry C]

What about doing a lap joint? Just router the top of one sheet and the bottom of another and then glue them together...

Ahh, finally, the best way to do it.

Maybe with 1/2 " plywood, but it's not a good idea for 1/8" ply.

[Larry C]

The reason for the original question was to avoid any seams.

I do appreciate the scarfing,laps, and butt joints for what they do. Seamless is my intent...other than where necessary, as much as it can be acheived; for my woody walls.

As for the tank round...don't own one of those. But, I may wanna stop a .50 cal lead ball or 600grain longbow fired arrow
Thanx for the concern though.

Billy K wrote:

"The reason for the original question was to avoid any seams"



I guess I don't understand what you mean, how would you increase the size of a sheet of plywood without having a seam?? please explain.

We have offered several methods to increase the size of the sheets, but they all will have seams.

Now, if you really want to avoid plywood seams on a "woodie" , you could strip build the exterior walls.

Larry C

[Billy K]

What I'm after is a full side of wood grain. Unbroken by trim or a change in direction. A seam would be next to impossible for grain continuity.

That's how I came up with the 2x added to the bottom. I could use 4'x8' sandwich walls and get a bit taller; while still holding to the full field of grain. This would not allow for any added length though; without a seam of some sort.

Woodbutcher mentioned some 4x10 that he'd found. Maybe that would allow me to use the 2x "bottom rail" thought I have; AND go to @9' in length.

Does that clear up my thoughts? Am I nutz and making this harder than need be? I can/could do any of the joint methods but, wanna try to do it without seams.

If, I go with sandwich walls (1/4 x 3/4 x 1/4) 54" H x 9' L; the skins would most likely need to be butt jointed. That would blow my "full field" plan.

Thanks to all who've had suggestions.

[bobhenry]

Am I nutz

Well of course you are your building a wierd little tiny trailer arn't you.

So join the club.

What you are trying to do probably won't happen. You might try minimizing the seam by planning the outer skin layout to fall right at your door edge. Let the door hide the area where the two sheets butt together right under the trim.
A fancy brass or stainless door kick panel below the door and plop your "porch" light right on the seam above and there won't be enough left to see but a few 3" sections. The viewers eye will be so distracted by the accessories that the seam will 'disappear".

[Billy K]

You may be right,Bob; BUT.....I have time and determination on my side!!

I did find out that ping pong table board is 3/4" x 5' x 9' !!

Also, like we talked about; I found veneer big enough to cover that!

So, now the question becomes: How do I ensure water tightness?

Will epoxy and auto clear coat be enough over a veneer?

[Larry C]

You may be right,Bob; BUT.....I have time and determination on my side!!

I did find out that ping pong table board is 3/4" x 5' x 9' !!

Also, like we talked about; I found veneer big enough to cover that!

So, now the question becomes: How do I ensure water tightness?

Will epoxy and auto clear coat be enough over a veneer?

I think you are going to a lot of expense by using Veneer. Also, what glue are going to use on the veneer that heat from the sun won't soften?
Have you considered using wood strips for the sides as Juneaudave did.

Check out this superb build. It sets the bar for "Woodies"

http://sites.google.com/site/slumbermax/Home

If you book match your strips there will be no visible seams and you can create beautiful graphic inlaid designs. The size of the project is not an issue with this method. Also, depending on the chosen wood species, the cost is minimal if you mill your own strips. This is the method I will be using. I will cover the strips with glass/epoxy

If you go with the veneer, I would cover it with glass/epoxy, not just epoxy, even if its just thin glass. You really need the glass on the seams, but glassing the whole surface is much better.

Auto clear is a great idea although it's expensive compared to marine spar varnish and it's more difficult to repair. Both will protect the epoxy from UV and must be renewed periodically.