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Re: question about structural integrity of home made aluminum trailer design/process?

Originally Posted by M J D

The big problem with fiberglass just like thin sheet metal is that is does nothing for stiffening the structure.

Seems to be stiff enough in boats to smash through big waves for 100 million stress-strain cycles or 100 years, whichever comes first...

(Actually, the "fiberglass" cloth is exactly for stiffening (like rebar in concrete, to give it tensile strength), and the plastic that holds it together is for flexibility...)

Re: question about structural integrity of home made aluminum trailer design/process?

Thanks, as it is I think i have a build plan that I'm confident I can pull off, and with everyone's input I believe I have a design that will be lightweight and sturdy enough for my needs. I do have a few minor questions to work out (namely how I should secure the triler lighting to the fiberglass panels), but I suspect I'll find those answers as I look into how to work with fibreglass.

I can weld the base frame together, then screw the mdo or plywood floor to it to give it more rigidity, then top it with a shell that has a wood product paneling on the inside, 1.5" thick foam centre, and a fiberglass exterior that is folded under the upper lip of the outside frame's c-channel. the use of angles should keep the structure fairly stable, with the fiberglass giving support to the edges and preventing flexing and the interior panels reinforcing the flat sides to prevent them from caving in. I'll coat it in red-orange tinted truckliner sprinkled with copper paint to match my car, the truck liner helping protect the fibreglass from rocks and damage, giving it an aesthetic I like, and hopefully having some sort of impact on reducing drag. two doors with windows on either side plus a roof vent ont eh angled part should give it plenty of ventilation, while still being insulated enough to be warm if it gets cold at night. I'll problably top the floor with a cork flooring to give it some more insulation

Now to re-make the entire thing in Fusion 360 from scartch - I used mastercam as it's what I'm familiar with, but the free educational edition will only create encrypted .emcx files that cannot be opened by any other software... not even the full version of mastercam.
Attachment 1717252Attachment 1717253

Re: question about structural integrity of home made aluminum trailer design/process?

Originally Posted by Boostinjdm

WTF? That's a bull**** argument and you know it. The stiffness comes from the shape and how the materials are used. I've had enough. I'm out. I'll check back in a few years to see how the project turned out. Good luck OP.

Sure, that's why the sheat houses with plywood or OSB.

Re: question about structural integrity of home made aluminum trailer design/process?

Originally Posted by M J D

The big problem with fiberglass just like thin sheet metal is that is does nothing for stiffening the structure. You would need X bracing and probably lateral bracing with that stuff. As for flexing and vibration, MDO handles it very well, and it won't crack or shatter like plastic or fiberglass could. As for stone chipping, probably as good as any other painted material.

WTF? That's a bull**** argument and you know it. The stiffness comes from the shape and how the materials are used. I've had enough. I'm out. I'll check back in a few years to see how the project turned out. Good luck OP.

Re: question about structural integrity of home made aluminum trailer design/process?

Originally Posted by M J D

The big problem with fiberglass just like thin sheet metal is that is does nothing for stiffening the structure. You would need X bracing and probably lateral bracing with that stuff. As for flexing and vibration, MDO handles it very well, and it won't crack or shatter like plastic or fiberglass could. As for stone chipping, probably as good as any other painted material.

I mean, I could use a mdo based panelling to line the inside and use the aforementioned truck liner to protect the fibreglass from rock chips?

Re: question about structural integrity of home made aluminum trailer design/process?

Trailers.............................Attachment 1717222

Re: question about structural integrity of home made aluminum trailer design/process?

Originally Posted by Boostinjdm

That's great! How many of them go down the highway? How does it handle rock chips or near constant flexing and vibration? How do you repair it?

Fiberglass is a commonly used material for the exterior panels on all types of vehicles. Cars, bikes, boats, and trailers. It's readily available, not too expensive, can be painted, can be repaired, waterproof, can be worked with very basic hand tools, and it can conform to near any shape. Even the wood based teardrops like Sam posted get hit with a layer of resin. The only real downside is the mess.

The big problem with fiberglass just like thin sheet metal is that is does nothing for stiffening the structure. You would need X bracing and probably lateral bracing with that stuff. As for flexing and vibration, MDO handles it very well, and it won't crack or shatter like plastic or fiberglass could. As for stone chipping, probably as good as any other painted material.

Re: question about structural integrity of home made aluminum trailer design/process?

Originally Posted by M J D

MDO is used outdoors all the time. Painted billboards and wood signs are made from it.

That's great! How many of them go down the highway? How does it handle rock chips or near constant flexing and vibration? How do you repair it?

Fiberglass is a commonly used material for the exterior panels on all types of vehicles. Cars, bikes, boats, and trailers. It's readily available, not too expensive, can be painted, can be repaired, waterproof, can be worked with very basic hand tools, and it can conform to near any shape. Even the wood based teardrops like Sam posted get hit with a layer of resin. The only real downside is the mess.

Re: question about structural integrity of home made aluminum trailer design/process?

Originally Posted by Boostinjdm

What's the obsession with mdo? If it is what I think it is, it's not a material I would use on anything outdoors. I don't even like it indoors. Stick to waterproof materials.

If I was going to do it, I'd build a sturdy, flat, frame that could survive on it's own. No twisting allowed. So probably square or rectangle tube. Then marine grade plywood floor. Then top it off with a shell of 1-1/2" or 2" blue or pink foam board wrapped in 2-4 layers of fiberglass cloth and resin. Then paint it.

You go thick enough on the foam or fiberglass and an upper frame isn't needed. That's just my opinion, it's worth what you paid for it.

MDO is used outdoors all the time. Painted billboards and wood signs are made from it.

Re: question about structural integrity of home made aluminum trailer design/process?

Originally Posted by Boostinjdm

What's the obsession with mdo? If it is what I think it is, it's not a material I would use on anything outdoors. I don't even like it indoors. Stick to waterproof materials.

If I was going to do it, I'd build a sturdy, flat, frame that could survive on it's own. No twisting allowed. So probably square or rectangle tube. Then marine grade plywood floor. Then top it off with a shell of 1-1/2" or 2" blue or pink foam board wrapped in 2-4 layers of fiberglass cloth and resin. Then paint it.

You go thick enough on the foam or fiberglass and an upper frame isn't needed. That's just my opinion, it's worth what you paid for it.

Thanks

Yeah marine grade plywood should be good enough. I'll admit that I had been trying to minmax the weight and strength but this is a one off and I'm not that much if an expert and the differences will be largely neligeable, but the marine grade would be good as it helps prevent deterioration issues I'd like to avoid. I originally wanted to use an aluminum frame but my complete lack of experience with aluminum makes it a poor decision.

The tubular frame was closer to my original plan before I was talked out of it (water collection or rusting from the inside out) I'm still thinking channel might be better for that then? I haven't used fibreglass before but I think my dad has used it way back when, so that might be a better method - especially as it allows me to curve all edges pretty easily (something I was bashing my head in trying to figure out on a metal support frame). Admittedly the use of truck liner was more of an aesthetics choice as it would allow for a roughened surface to improve aerodynamics with the golfball effect. No harm in still using a coating over the fibreglass to help protect it?

One of the earlier posters had mentioned that fibreglass will sometimes delaminate. Is that easily avoidable with proper preperation?

Re: question about structural integrity of home made aluminum trailer design/process?

Might even be a channel frame, but it definitely is a regular utility style frame.........then the wooden stuff is piled on top of it. Pretty much the same way my little enclosed box trailer is built.......I think it's an Interstate.

Re: question about structural integrity of home made aluminum trailer design/process?

Looks like this guy just built what you're talking about on a small tubular trailer frame.

https://forum.ih8mud.com/threads/bui...railer.607202/

Re: question about structural integrity of home made aluminum trailer design/process?

https://www.clp-inc.com/what-is-mdo-plywood/

Re: question about structural integrity of home made aluminum trailer design/process?

Originally Posted by grahamf

Hmm... How about 3/4" angle for the upper shell and sandwiching the foam with 1/8" mdo glued on either side, then the spray liner on the outside?

I haven't worked with 1/2" much but just for a frame of reference how difficult it is to bend say a 36" length by hand without using a knee or anchor?

What's the obsession with mdo? If it is what I think it is, it's not a material I would use on anything outdoors. I don't even like it indoors. Stick to waterproof materials.

If I was going to do it, I'd build a sturdy, flat, frame that could survive on it's own. No twisting allowed. So probably square or rectangle tube. Then marine grade plywood floor. Then top it off with a shell of 1-1/2" or 2" blue or pink foam board wrapped in 2-4 layers of fiberglass cloth and resin. Then paint it.

You go thick enough on the foam or fiberglass and an upper frame isn't needed. That's just my opinion, it's worth what you paid for it.

Re: question about structural integrity of home made aluminum trailer design/process?

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Re: question about structural integrity of home made aluminum trailer design/process?

Originally Posted by Boostinjdm

1/2" angle isn't going to be good for much. Neither is the bed liner over foam. A couple layers of fiberglass over foam would be much better.

Hmm... How about 3/4" angle for the upper shell and sandwiching the foam with 1/8" mdo glued on either side, then the spray liner on the outside?

I haven't worked with 1/2" much but just for a frame of reference how difficult it is to bend say a 36" length by hand without using a knee or anchor?

Re: question about structural integrity of home made aluminum trailer design/process?

Originally Posted by grahamf

I do have to put some more 1/2" angle bar in to support the door, fenders, lighting, etc but otherwise my plan would be to coat it in antirust paint, screw on 1/2" MDO flooring, place rigid .75" insulation for the panels backed by glued on 1/8" wood paneling on the inside, then coat the entire thing in spray/roll on truck liner to protect the frame and add rigidity to the shell.

It of course will still be some time before I actually build this so I do have time to get more feedback and make adjustments as needed

1/2" angle isn't going to be good for much. Neither is the bed liner over foam. A couple layers of fiberglass over foam would be much better.

Re: question about structural integrity of home made aluminum trailer design/process?

Ok that is very light trailer
You can make it a tandem axle very light wheels

Most trailer I built had load of 14,000 pounds or more.

That light trailers has other problems out of my range.

Dave

Originally Posted by grahamf

I feel like I should remind you that the trailer is only about 500lbs and, excluding the tongue, is 8.3 feet long.

Re: question about structural integrity of home made aluminum trailer design/process?

I do have to put some more 1/2" angle bar in to support the door, fenders, lighting, etc but otherwise my plan would be to coat it in antirust paint, screw on 1/2" MDO flooring, place rigid .75" insulation for the panels backed by glued on 1/8" wood paneling on the inside, then coat the entire thing in spray/roll on truck liner to protect the frame and add rigidity to the shell.

It of course will still be some time before I actually build this so I do have time to get more feedback and make adjustments as needed

Re: question about structural integrity of home made aluminum trailer design/process?

1/2" MDO should be all you need.

The design needs some intelligent refinement, though.

Re: question about structural integrity of home made aluminum trailer design/process?

Attachment 1717144
I think this should be stable? Have to figure out if I'll use .5" MDO or .75" MDO but otherwise I'm figuring out how to do the top shell now and how to secure the door
Attachment 1717149

Re: question about structural integrity of home made aluminum trailer design/process?

Originally Posted by grahamf

oh I see countersunk machine screws from the top instead of wood screws from the bottom

Yes, that's what I would do. Get some self tapping trailer deck screws.

Re: question about structural integrity of home made aluminum trailer design/process?

oh I see countersunk machine screws from the top instead of wood screws from the bottom

Re: question about structural integrity of home made aluminum trailer design/process?

Originally Posted by grahamf

hmm... I don't think i can easily screw the MDO to the channel without seriously messing up it's structural integrity, but I can screw into the angle iron and gussets. how does this look?
Attachment 1717130
I modeled it using 2"x1"x.0125" channel instead of .188" channel, but I might switch to .188" channel when I get to actual construction

You don't need those angle braces and clips on the cross members. Just screw whatever sheeting right to the cross member. I would run diagonal bracing to the sides of the tounge or make it vee shaped

Re: question about structural integrity of home made aluminum trailer design/process?

Originally Posted by grahamf

Well it's a camper that will be carrying a foam mattress and some camping gear and luggage and will have one or two male adults sleeping in it at night.

When it is not moving it is a statically loaded structure. When it is being towed over roads it is a cyclically loaded structure subject to premature fatigue failure unless you can triangulate every joint. Alum aircraft manufacturers take great care to limit the cyclically loaded stresses that cause fatigue or incorporate designs to limit stress risers. But specifically if there is welding on alum involved then judicious amounts of heat treating is used.

What are your alloys, fillers, and post weld heat treatings? You might want to pick up a copy of AWS D1.2.