Teardrops n Tiny Travel Trailers

by **Marck** » Sun Jul 05, 2009 11:46 am

I mean how besides the obvious things like something punching through, how much more structurally "stiff" does the second layer make the trailer???

I am using 2 layers , just got to wondering is all

by **48Rob** » Sun Jul 05, 2009 12:47 pm

Marck,

If the two are laminated/glued together, it makes it far stiffer.

I have two sheets of 1/8" on my roof, and can walk on it, carefully, with all my 180 pounds.

Rob

by **Geron** » Sun Jul 05, 2009 1:18 pm

Second layer hides the "dimples" from staples/nails/screws/fasteners for a "smoother" dimple free finish. That is if it's glued on top of the first layer.

g

by **Roly Nelson** » Sun Jul 05, 2009 5:03 pm

My little 1/4 Nelson Stacker, has only one layer of 1/8 inch plywood on the roof, and I can push on it hard enough to make it "oil-can", which isn't good. If I were to do it again, it would be a 2 layer roof, and gosh, maybe the wooden cabin would then weigh 105 lbs instead of the present 95 lbs. Oh well, after all building teadrops is an experiment, right?
Roly

by **Arne** » Sun Jul 05, 2009 7:37 pm

mine has one 1/8th layer on the roof. where it is curved, no problem. I can depress it slightly where i flattened it for the vent... I'd still go with one layer (fully filled with foam insulation on the ceiling and I would not leave the flat area for the fantastic fan... it would all have a curve, and I'd just caulk the gap where the fan mounts as the curve would be so slight on the top.

by **Mauleskinner** » Mon Jul 06, 2009 12:58 am

I could definitely feel the difference before and after adding the second layer of plywood to mine...I'd definitely recommend two layers.

You just never know... :thinking:

by **Marck** » Mon Jul 06, 2009 3:26 am

which kind of glue did you all use between the 2 layers of ply??

I used good ole gorilla glue (poly glue) to glue it down to the spars..(along with a healthy supply of nails/screws. But was leaning towards probond 2 for the next step of glueing the layers together

by **Mauleskinner** » Mon Jul 06, 2009 10:23 am

I used West System epoxy, thickened.

by **halfdome, Danny** » Mon Jul 06, 2009 11:21 am

Like said before, two layers of 1/8" makes a stiffer roof and smooths out the previous seams. I start the Baltic Birch from one direction for the first layer and the other direction for the second so that all first layer joints are covered. I use Tightbond ll for the glue, spread with a plastic Bondo spreader. Makes for a strong teardrop with minimal extra weight.

Danny

by **bbarry** » Mon Jul 06, 2009 4:42 pm

I was surprised how stiff 1/8" ply is when bent into a curve or properly braced. When flat, as Arne says, it has some flex to it. I went with only one layer (skinned in aluminum) and am quite happy with the result. If epoxying and painting, I'd probably go for two layers.

Brad

by **Marck** » Tue Jul 07, 2009 9:13 pm

I start the Baltic Birch from one direction for the first layer and the other direction for the second so that all first layer joints are covered. I use Tightbond ll for the glue, spread with a plastic Bondo spreader.

EXACTLY what I did yesterday and today I see exactly how much "stiffer" it made things to have 2 layers .... now if I was going to go with aluminium (which I would love to but can't on this one) I think one layer might just be enough

by **kennyrayandersen** » Thu Jul 09, 2009 8:23 pm

The stiffness and strength change as a ratio of the thickness cubed
(.25)^3 / (.125)^3 = 8
It’s about 8 times as strong when the thickness is doubled. That only applies if the two sheets are glued together. If they are not fastened or glued then the strength only doubles.
:thinking:

by **halfdome, Danny** » Thu Jul 09, 2009 8:33 pm

kennyrayandersen wrote:The stiffness and strength change as a ratio of the thickness cubed
(.25)^3 / (.125)^3 = 8
It’s about 8 times as strong when the thickness is doubled. That only applies if the two sheets are glued together. If they are not fastened or glued then the strength only doubles.

Does that include the radius too? It seems it would be greatest at the tightest radius.

Danny

by **doug hodder** » Thu Jul 09, 2009 8:39 pm

I used 2 layers of the 1/8 baltic on all the radaii on the Voyager and 1/4" ply on the rest. Like mentioned, the 2nd layer hides a lot and on those tighter curves, it's way tough. Doug

by **kennyrayandersen** » Thu Jul 09, 2009 11:18 pm

halfdome, Danny wrote:
kennyrayandersen wrote:The stiffness and strength change as a ratio of the thickness cubed
(.25)^3 / (.125)^3 = 8
It’s about 8 times as strong when the thickness is doubled. That only applies if the two sheets are glued together. If they are not fastened or glued then the strength only doubles.

Does that include the radius too? It seems it would be greatest at the tightest radius. Danny

That calculation is just for the base material. Curves make the panel stronger (curved plate is stronger than a flat one). I thought the whole curved panel stiffness derivation might be a be beyond the call of duty! :lol:

I was just giving a simple way to compare how changed in thickness change the strength. Anyway, 1/4 is WAY stronger than 1/8, not whether or not it is needed is an entirely diofferent question

Teardrops n Tiny Travel Trailers

Does a second layer of 1/8 in ply make a real difference

Does a second layer of 1/8 in ply make a real difference

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