wavy skin

[Miriam C.]

I get it---bendy Birch is going to feel bouncy because it is not as rigid as normal plywood. You might see sagging too. However if you can't go under the inside and add a spar (sounds like they are close enough anyway) then I would live with it or add a layer.

Personally I used Tightbond lll on mine. Put it on with a cheap paint brush and clamped it with straps and boards and wedges. Now with the bendy you will need to be careful with straps as them might put too much pressure on some spots making it sag some more.

Good luck!

[looped]

Well i went by the shop today and took some measurements,, putting one on there crossgrain will not be a good idea since when measuring 4 feet from the galley would put the seam too high on the nose of it.. dont want to do the entire nose in metal so im going to put another layer on in the same direction.

Thinking to put the center brace back in there and place a piece of ply on top and then break out the never used weights to clamp it. also going to strap clamp the edges so they get a good seal as well.


Was going to do some work today but my bud was doing something in the garage already so i just moved stuff around and out of his way.

Im seeing that he really wants his garage back so im gonna have to kick this into high gear esle i wont have a place to build the next one

[johnb]

I found the birch to be really flimsy and annoying to wrap smoothly on the inside of the tear so I put 1/8 inch oak ply on the outside followed by 1/8 luan followed by .065 aluminum. Yes this is way overbuilt but the oak layer was very firm and my 6 year old can walk on top. Next time I'll just do the oak and thinner al.

Good luck!

[looped]

I found the birch to be really flimsy and annoying to wrap smoothly on the inside of the tear so I put 1/8 inch oak ply on the outside followed by 1/8 luan followed by .065 aluminum. Yes this is way overbuilt but the oak layer was very firm and my 6 year old can walk on top. Next time I'll just do the oak and thinner al.

Good luck!

okay my gears are turning again,, this could be a very good thing or complete disaster in the making.

last trip to the lumber place i got 2 sheets of birch thinking one layer would do it. now i am getting an idea..

what other 1/8th wood is nearly as flexible as the birch? im thinking i could do the second layer in it and save the trouble of a high flex surface.

on the curve it is doing fine just the flat top it is giving me grief.

Would a second layer of bendy birch stiffen it up enough?


when i did contruction the most exotic woods we worked with was redwood and sometimes oak. this project is teaching me new things and at this point i am feeling like a total noob

[looped]

okay im trying to figure stuff out here,, if i am getting annoying with the questions then i am sorry but if i dont ask i might make a big mistake here.



for a moment lets go back to the previous idea of using 2 pieces of birch put cross grain it would be a little stiffer in this direction. i previously discarded that idea cos the seam fell onto the curve of the front. that was measuring from the back. in a little thinking session i considered putting it on from the front lower edge and working my way up then back. by my rough guesstimation this would put the seam right above the curve and a little bit onto the top.

here is a pic that i drew a couple lines on. the blue line is about where the seam would be if i went from the hatch forward. somewhere between the red lines is where the seam would be if i went from the front back.

Would either location be a suitable place for a seam or should i ditch this idea all together and go with a solid piece. whereever they meet i will, i guess, need to use some epoxy and membrane to seal it up?




Hmm another idea would be to put the crossgrain on there then follow it up with another one sheet layer.. that would make the outer skin 3/8 though. but it would be alot smoother..

[S. Heisley]

Hi, Looped:

When you aren't sure what the answer is, working with a small 'scrap' wall can be better, faster, and physically/financially cheaper.

Re: Adding another layer of ply
I would be hesitant to add another layer of 1/8" ply as it would be just as bendable and therefore may follow the unwanted bulges of what you already have on there. Gluing the first layer to the second on your TD might just make it permanently curvy as well as heavier.

Try it on a test piece first:
If you have a few scraps, you can duplicate the problem by building a small scale 'scrap' wall with the bulge. I would try adding the second layer over top of the 'scrap' wall and see what happens. That way, you won't have caused bigger problems on your existing TD and your can find out faster and with less over-all effort if it works.

Another test with the 'sandwich filling':
You've said that your walls are already sandwiched and sealed; but, are they sealed between the spars? In other words, can you push out a piece of the styrofoam between the studs? If you try it and see that the styrofoam will push out, use that sandwiched 'scrap' wall for another experiment. Push the styrofoam out of the scrap wall, spray it with that special styrofoam glue (it's in another thread...I'll see if I can find it) and push the styrofoam back in between the wood of the scrap wall, pressing the wood against it to get good contact. What I'm thinking here is that the styrofoam may pull the waves out of the plywood if you can glue the plywood to it. (You may have to use the spray on both sides of the 'foam so the two ply sides pull on each other to keep everything in place.) Again, do this on a test piece as I may be way off base.

Wishing you Success,
...Sharon

[S. Heisley]

The styrofoam glue was in this thread:

http://tnttt.com/viewto ... c&start=15

[looped]

thank you,, the walls are completely sealed in top bottom side and side.

I will go play with some scrap wood now, as for the rest i will just wing it and hope for the best..





thank you