GRP/FRP shell

[kennyrayandersen]

but is it possible to make the internal shelves in glass over foam .That how we make ours make it a real stiff shell best way to tie the side wall together

I agree and that's how I plan on doing mine. If you use the 1 inch thick foam and close that out with 1X1s [and glass over the whole thing] then you can join the shelf to the side of body with biscuits (you would put a corresponding 1X1 in the side of wall as well so the biscuit has something to go into (plus the biscuit will react traverse shear as well. You could also put screws in until the epoxy dries. If the shelf sags, you can biscuit a 1X2 lip onto it. I'm thinking fir for the wood as it's pretty strong per unit weight (nearly up there with spruce, but a lot cheaper and it can be bought in larger pieces and cut to exact sizes).

In case there was some confusion, I was thinking 2 inch thick foam in the floor (thus the 1X2s) and 1 inch thick everywhere else using 1X1s as inserts and closeouts.

[Ageless]

Kenny; the white foam board, with the plastic removed will bend a bit without needing kerf cuts so if you aren't using too much radii that made not be needed.

[kennyrayandersen]

Kenny; the white foam board, with the plastic removed will bend a bit without needing kerf cuts so if you aren't using too much radii that made not be needed.

true dat. I'm thinking about my profile, and there are some areas where I think it will be necessary. Also, the white foam (with the beads, no?) isn't as structural as the blue or pink extruded stuff (that's why it's more flexible).

Actually that brings up a 3rd possibility and that's to put the glass ply to the outside and let the foam, which isn't so stiff, go into compression and just bend it where you want. I just am hesitant because I think you would have to have a relatively good support to hold it as you bend it. The advantage with that method is it would save you from having to fill all of the gaps and it would give you a good (tool side) exterior surface. It would probably take a little experimenting whereas I'm pretty confident that the other method would work straight up since it doesn't tend to pre-load anything.

[glassice]

Why use wood we use no wood and works great ? Are trailer are use as rental units in Costa Rica few roads get beat to hell for over 6 years for some it rains all the time even have one bob in the sea for 10 days had to fix the tongue and a tire never park at low tide

[kennyrayandersen]

Why use wood we use no wood and works great ? Are trailer are use as rental units in Costa Rica few roads get beat to hell for over 6 years for some it rains all the time even have one bob in the sea for 10 days had to fix the tongue and a tire never park at low tide

Funny, I never thought about it but I don’t think you could sink one of these bodies made from a foam sandwich if you tried!

With regard to your question, first, I’m using less plies that you apparently are if I understand you correctly. Second – I could be over killing it a bit, but I usually err on the side of conservatism. I like the idea of being able to biscuit and screw the floor to the sides as well as the shelves to the sides. Additionally, it gives something substantial to bolt a minimalist frame to. Like I was saying earlier, stuff usually fails at the joints, not out in the field area; plus, you tend not to save much weight in the joints but over a large area (on a wing for instance, if you are able to reduce just a little thickness on the skin, there is a huge impart to the weight since the area is so large). On a teardrop, there is a lot of area that doesn’t require much strength. By putting the robustness in the joints and not in the field area, the overall weight should be less. There is more than one way to solve a problem, and as you have found out with your configuration you can fix it by adding plies. In the end, it might be lighter than I’m doing it – it would take some ciphering (as Jethro would say) to know which in the end is lighter. However, I really don’t like to load up the sandwich in tension – it’s generally not good design practice; so, if you close each particular panel out in wood, you can get a really good attachment joint. Again, both will work, it’s just my preference. You could probably use plywood or other commercially available inserts to attach the body to the frame, or ramp the foam down to nothing and add extra plies to that solid laminate area, but the other thing I’m trying to do is to make is simple and easy to manufacture in a non-production (garage) environment – simple rectangular panels closed out with 1X1 or 1X2 fir and skinned over with glass is about as easy and simpler as it gets and no tooling other than a flat bench is required.

[glassice]

. remember soft wood expands I think 300% more than most resin so it will pop and resin will not stop watter from get in

[kennyrayandersen]

you are doing a glass over foam floor bond on top and bottom of the floor then fill the gabs with 2 part foam if it has wood biscuits that be your week link with the other you have a full bond of the glass and it's intention and compress at the same time . remember soft wood expands I think 300% more than most resin so it will pop and resin will not stop watter from get in

Sorry, I don’t even know what you said so I likely can’t exactly respond to your comment/question. The foam is the rigid pink/blue stuff sold at Home Depot/Lowes. The wood will be covered with fiberglass as will the core. The biscuits go in the wood, not the foam. The wood merely closes out the foam panel.

[glassice]

with the wood inside of the glass it expand more than the glass IT will pop

[kennyrayandersen]

with the wood inside of the glass it expand more than the glass IT will pop If you take your foam for the floor lay your glass over the top then flip it over lay that up no glass on the sides . put it between the walls lay up a strip of glass to bond floor to wall then flip your trailer over do the same then fell in with 2 part foam . The wood biscuit is a week joint next to 2 layers of glass and foam the whole length of your trailer

The glass won't be on the sides of the floor panel wood, just over the top and bottom -- I'll have to sand away some of the side panel glass to get mostly wood-to-wood contact with double biscuits on the side along the length of the tear. According to wood worker mag that did some structural tests, double biscuits are just about the strongest joint out there – much stronger than dowels. I suppose I could go with a full spline joint, but I think biscuits every 8-12 inches will shred the wood long before the joint will fail. Additionally, I plan on doing a radius filler with two plies of fabric tape in the interior corner as well as a .25 inch radius and two plies of fabric tape on the exterior corner (probably overkill again, but I am a stress engineer so I can’t resist a little beef-up). The tear will be primarily white with a red strip (ala Abarth) down the side so I don’t expect any significant thermal issues.