Attaching roof skin. Thoughts?

[western traveler]

I am about to add the insulation between the spars on my TD build. It’s a woody build as many of you know.
I am vacillating between two layers of 3mm baltic Birch as Steve Fredricks lays out in his book and one layer as Tony.Latham describes.
With Steve’s method I would have no visible staples anywhere on the roofline. However I can hid staples along the perimeter of the roof with Tony’s method as it will get molding on the edge of the roof and walls.
I do not want any showing across the spars.

Here is my plan;
Lay PL Premium along the edges and spars. Lay one layer of birch down and tack the edges with crown staples. Then use ratchet straps down the length of the roof to make contact with the spars and fasten the rest of the edges with crown staples.

When I got to looking at the roofline last night my fear is the straps will create a valley down the length of the roof. The spars are 1X2 poplar and a 5’ span.

Can I expect spring back and a flat roof with this method if I go gentle on the ratchet straps?

Any other thoughts?

Ralph

[tony.latham]

I am vacillating between two layers of 3mm baltic...

The reason I use one layer is the combined strength of the system. Once the top layer is installed over the foam, ribs, and headliner, the structure becomes a (mostly curved) torsion box. I'm sure I could walk on it. It's that strong. (But no... I'm not that dumb.)

I can't forecast the valley issue you are concerned about. I understand your wish to hide staples, but if you thunk them neatly and in rows, they won't be obnoxious. If you choose to use straps with stickers under them, I don't think you'll need much force to hold it down. I'd be concerned about the top layer floating on the PL3 even if applied with a notched spreader –-perhaps that's not a problem-- but It really doesn't like to squeeze down over a large surface.

You might visit Tom and Shelly's build. I think they added a second layer and get an opinion from them.

http://www.tnttt.com/viewtopic.php?t=70278



Tony

[western traveler]

I am vacillating between two layers of 3mm baltic...

The reason I use one layer is the combined strength of the system. Once the top layer is installed over the foam, ribs, and headliner, the structure becomes a (mostly curved) torsion box. I'm sure I could walk on it. It's that strong. (But no... I'm not that dumb.)

I can't forecast the valley issue you are concerned about. I understand your wish to hide staples, but if you thunk them neatly and in rows, they won't be obnoxious. If you choose to use straps with stickers under them, I don't think you'll need much force to hold it down. I'd be concerned about the top layer floating on the PL3 even if applied with a notched spreader –-perhaps that's not a problem-- but It really doesn't like to squeeze down over a large surface.

You might visit Tom and Shelly's build. I think they added a second layer and get an opinion from them.

http://www.tnttt.com/viewtopic.php?t=70278

I understand one 3mm ply being plenty strong enough. It is this fastener thing that I was trying to find a way around.

Steve Fredricks didn’t mention what he applied to bond the two sheets together or I missed it. Just that the fasteners weren’t exposed as he fastened to the overhang of the first sheet.
Now having read Tom and Shelly’s experience with the PL premium swelling and slightly lifting the birch where not fastened I have more questions.

I am leaning towards single layer of Baltic birch and crown staples as you suggest.

So do I use PL premium on the walls edges and TB III on the spars? Stapling it all down?

Then my concern is the tiny voids left above the staples. I had good luck not wetting out the surface first when I glassed the walls with 4oz cloth. Of course there were no fasteners to glass over.

Now I will be using 6oz cloth. I am thinking I will need to fill the staple voids before doing the glasswork so as not to depend on the wetting out process to simply fill them, and can this just be resin and then glassed over normally within 12 hours?

Thoughts on this appreciated…

[tony.latham]

So do I use PL premium on the walls edges and TB III on the spars? Stapling it all down?

I used PL from the headliner up. It does a better job when there's a hair of a gap (especially the flat of the spar and the bend of the roof) than TB2 or 3 does. The Tightbond glues really don't have enough of an open time either. PL Premium does. And yes, pneumatic crown staples.

Then my concern is the tiny voids left above the staples.

You could fill those with epoxy thickened with wood flour and I'll bet they end up being hard to find.

Tony

[Tom&Shelly]

You might visit Tom and Shelly's build. I think they added a second layer and get an opinion from them.
http://www.tnttt.com/viewtopic.php?t=70278



Tony

We were thinking of a 2nd layer, but only used one in the end, and with fiberglass and bedliner over it, it's fine.

We did have an issue with the PL expanding and pushing out the 1/8 inch Baltic birch between that and the ribs. We had (temporary) dry wall screws every 6 inches or so, and the glue pushed up a little around them. If we were to do it over, I'd use Titebond III for that job. Our fix involved thickened epoxy (IIRC) and lots of work sanding. But that doesn't sound like it's relevant here.

Tom

[Pmullen503]

Having done 11 cedar strip boats I know a little about dealing with staple holes.

My advice is to apply the staples in a neat line. After they are pulled, wet the area with water to swell to wood around the hole. A hot iron helps too to steam the wood. That won't close the holes all the way but helps.

I've never found a fill that is invisible. I just let the holes fill with epoxy when I glass. You'll forget those little dots where the staples were are even there after a while.

[noseoil]

I would do a "dry run" with a single layer first, to check the fit, edges & center pull-down. If it's good, then lift it from one end, add the glue of choice & lay it down a spar at a time as you roll the sheet into place.

With 2 layers, glue, ratchet straps & too much tension in the center, you will create a permanent bow in the spars which will not relax when the straps are released. A single sheet would be best, if you can set one end of the sheet (hatch end or front end at the bottom, what I will call the "fixed" end) & use a "pull" to put the entire sheet into tension from the "floating" end. This will give a uniform tension on the entire sheet to fasten it. PL would likely be best, for reasons Tony has already mentioned. Folding wedges, gravity & weights or some type of pull will allow it to settle properly & set up over enough time while the glue is wet. Leave the sheet long on one end so you can grip it for the pull.

[western traveler]

Having done 11 cedar strip boats I know a little about dealing with staple holes.

My advice is to apply the staples in a neat line. After they are pulled, wet the area with water to swell to wood around the hole. A hot iron helps too to steam the wood. That won't close the holes all the way but helps.

I've never found a fill that is invisible. I just let the holes fill with epoxy when I glass. You'll forget those little dots where the staples were are even there after a while.

Thank you Tony and Tom for your responses.

Tom, I think your experience is very relevant here. Do you think the experience would have been different if there were fasteners every 3”? What you described as a fix sounds like no fun at all and would not work with this build. Glad you found a solution!

As with Tony my thoughts of fasteners was always crown staples and there is no pulling those without damage to the surrounding area to my knowledge.

Pmullen,
You sir have just placed me at a fork in the road. The interwebz is our friend.
I hadn’t considered a mechanical stapler and I think that is the type you are referring to as I just watched a couple of YouTube videos of removing staples from a mechanical gun in a strip cedar build. I then made a call to a neighbor that recently completed a cedar canoe build. (I went and looked for staples in his build the other day while he was out of town and couldn’t find any, Now I know why).

I just did a test on some scrap 3mm Baltic birch with my stapler and it got good penetration still leaving enough space in the head to pull it using 1/2” staples and feel like if it was glue under it I would ultimately have a tight bond.

Now the question becomes what type of glue/adhesive to use. I am not sure the stapler can flatten PL Premium max. I do have PL 3x as well.
I fear TB III will leave too many voids and fail to secure the panels.

Thoughts?

Glad I asked all you experienced folks first as I still have a couple days to figure this out.

[western traveler]

@noseoil,
Clearly I am a slow composer…

[Pmullen503]

Another tip on stapling: collect some of the plastic straping used to secure heavy boxes. Cut it into 2" or so pieces and when you staple, put a piece between the legs of the staple when you staple (don't staple through the plastic strap.)

That does two things, first it protects the wood from being dented by the staple or stapler. Second, it will insure the staple will sit above the wood (if you can set the right force on the stapler.) Or if the staple is driven all the way home, you can use the plastic to remove the staple without having to dig into the wood.

As far as glue goes, original gorilla glue is thin enough to squish out when you staple and it will foam to fill any voids.

[Tom&Shelly]

Tom, I think your experience is very relevant here. Do you think the experience would have been different if there were fasteners every 3”? What you described as a fix sounds like no fun at all and would not work with this build. Glad you found a solution!

It certainly would have been better. We also used PL Premium over the foam, not just along the ribs, so it pushed up there. If we didn't do that, and used fasteners every 3 inches, we would have been a lot better off.

BTW, in other places, we used very fine gauge wire nails. I should have put Shelly through some training with those before glue down. While I was applying clamps, she was all over the place with that nail gun, but, I found out later, didn't know to put several in near each other at different angles. Not a problem, of course, if you are using staples.

Tom

[western traveler]

Update,
I went with Pmullen’s advice and attached the forward skin yesterday using a T50 stapler with 9/16” staples which penetrated the Baltic birch easily and didn’t bury themselves too deeply into the poplar spars. They distorted just enough to give a solid anchor. The glue I used was original Gorilla glue. I used a few straps for a bit of tension and didn’t see any excessive lifting. Today I proceeded to place the other roof panels. If I have the same results with them I will be very happy.
I did pull a number of staples from yesterday and the holes are hardly noticeable.

[Tomterrific]

I guess I'm too late to help but here is some things that helped me.
I pre bent the roof curve. I found the curve too sharp for the Revolution Ply so I bent it half way over night. I used ratchet straps and 2x4s across the roof.
This should have been first. After I got the ceiling bent/forced into position, I glued little blocks around the edge of the curve for more glue surface. I used PL 3 and 5 like most and really spread it on, like caulk. I think the wide glue joint between the roof, wall, ceiling and rib (spar) gave strength to my flimsy construction.
To spread out the PL I used a 3" drywall screw threads as a notched trowel. I threw away quite a few but I have many.

Tt

[booyah]

FWIW I did the single layer and staples as well, pulled the staples after the glue dried and before doing epoxy/fg

its been 6 years and I concur its way stronger than you'd expect, I have laid down on it before, but was nervous

[western traveler]

Thanks boohyah and everyone else for your thoughts and responses.
As mentioned above I used the staples and Original Gorilla glue for the roof. I pulled the staples and wiped down with a damp cloth to close the holes a bit as pmullen had suggested. It seems to have a solid bond to the spars. Having since been glassed it is even more rigid.

There was one issue I hadn’t considered in time to perhaps avoid.
I used Trans Tint for color enhancement. Perhaps had I stained the panels prior to installing it would have made a difference. I didn’t think of it in time and when I did I was faced with the possibility anything used to seal the holes would likely hinder the dye penetration. So I applied the tint and let it dry. When I used a green pad to knock it down the dye accentuated the holes enough that if I look hard enough they are visible. Not enough to be upsetting but dang.
I think I will add this to my build journal…