Carbon Fiber/Aluminum build for a family of 5

[fishboat]

My math skills are fading but that mix ratio is bothering me. The second one working back is a bit off to me.

544 x 1.32 = 718g (epoxy crosslink density will be low of target)

800g/1.32g = 606g (epoxy)
800g - 606g = 194g (amine hardener)
606g + 194g = 800g

100/32 = 3.125
606/194 = 3.124
//

[StrongFeather]

Just curious, will you be walking on the floor? (As opposed to some tears where the bed takes up the entire floor)

The bed(s) will essentially cover the entire floor, Michael. Do you think there’s a strength issue? A wise man once said "The Strength is in the Sum of the Parts..." so I’m hoping that it’ll not only be a strong floor but add strength to the entire structure when it’s assembled.

My math skills are fading but that mix ratio is bothering me. The second one working back is a bit off to me.

544 x 1.32 = 718g (epoxy crosslink density will be low of target)

800g/1.32g = 606g (epoxy)
800g - 606g = 194g (amine hardener)
606g + 194g = 800g

100/32 = 3.125
606/194 = 3.124
//

Thanks for the correction, guys. Funny thing is that I was distracted by 4th grade math homework when I typed it up last night. I guess I should have practiced what I preach and checked my work.

Steve


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[StrongFeather]

I was able to make SOME progress on the build this weekend. Here are some picture to get you caught up.

The axle came two days earlier than scheduled, so it was like Christmas in December for this guy!! The axle is a 2k Flexiride torsion axle.


Unfortunately, the weekend was not all jolly. The floor lamination from last weekend didn't go well, so I ended up tossing it out and starting over. $100 down the drain, but much better to redo it now than after the floor is installed. Take two went much better after some tweaks to the process.

I believe the reason for the first failure was two-fold. First, I didn't apply heat right away. Instead, I added weight while the epoxy on the foam was still wet, thinking that it was more important for the uncured epoxy to make contact with the plywood even with a lot of weight with a very flat/heavy counter top to compress everything very evenly. Second, I put a skim coat on the wood and let it cure before laminating it to the foam. This also caused the wood to warp slightly, which didn't allow for full contact of the epoxy. For round two I applied thin epoxy to the plywood, buttered thick epoxy to the foam and applied heat immediately. Much better results this time because both surfaces were wet, which created a chemical bond instead of mechanical, and the heat from the blanket allowed the wood (without cured epoxy on it) to relax and lay flat on the foam. Again, I considered vacuum bagging it, but decided against it even though I believe it would have been a (marginally) better method. Here are some pictures...

Failed first lamination attempt...

32° shop temp...

140° heating blanket...

Lamination take two...


Someone wanted to see a better picture of the sister frame rail. These pictures should give everyone a better idea of where the sister is located in relation to the main rail and the axle. The sister is 4' long, so it'll add some strength and some flexibility in locating the axle for optimal tongue weight.

DSC09840.JPG (133.37 KiB) Viewed 2605 times

And a quick mock-up of the fender to see how much room I'll have for the door. The plan is to build as much of the trailer as possible before actually locating the axle so that I'll know the final weight distribution. I'll probably use some c-clamps to hold it in place until the very end.


Making a pattern for the inside axle mounting plate. The axle manufacture sells a mounting plate for this axle that is about 1/3 this size.

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A shot of the axle mount and mounting plate from outside of the main rail. There will be a similar plate on this side, but I'll probably make an integral fender back that will tie in with the axle mount.

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If you have never mounted a tire on a rim without a tire machine, you should try it. Even more fun is seating the tire bead on the rim with hairspray and a torch!!


On a side note I just want to say I love this site. After reading so many other build journals, I have yet to see any two builds or personalities the same. Everyone has their own twist, their own methods, their own needs/wants, their own backgrounds and their own skills/abilities. Even with all of these differences, the feedback is always very positive and encouraging.


Steve

[Andrew Herrick]

The floor crossmembers simply bolt through the sistered rail like the others. Not sure if you can make that out in the pictures or not.

I thought I posted this picture of the crossmembers yesterday...

They are mounted to the side rail with 1.5" angle aluminum brackets, 5/16" bolts and the aforementioned aluminum spacers. The floor will be secured to the crossmembers using 5/16" bolts from below with T-nuts (or furniture nuts) inserted into the floor from above. Oh, and disregard the fact that the angle brackets in the picture are proud of the side rail... we'll chalk that up to a sloppy chop saw. I might shave them down later, but they probably won't be visible once the frame is flipped over. We'll see.



Steve

As someone who has designed and built several aluminum trailers (and still learning!) ... maybe consider switching from bolt/tee nut combinations to Reamer trailer decking screws? Both work ... but Reamer screws are 3x easier, and unlike an upside-down bolt, can't fall out. Whichever solution you use, be sure to tie the floor into the main rails and not just the cross members.

[Andrew Herrick]

I'm excited to see your build progress! Very innovative. I'd have to say, though, it seems your technique for laminated panels is a little overdone?

Vacuum infusion is a persnickety process. Have you attempted it on a panel this large before? I'm concerned about your decision to not vacuum-bag. Infusion depends on air being sucked out through an air-permeable skin (e.g. plywood) and the resulting vacuum filled in by a viscous adhesive (e.g. epoxy, in your case). An insufficient vacuum or thick epoxy - and you're dealing with both - means that infusion won't work. You're just relying on the viscosity of the epoxy and the surface energy of the substrates to properly wet out both foam and plywood while hoping that air doesn't get in the way. A properly bagged assembly (hopefully you have filtration in your vacuum system) will be exponentially stronger.

If you don't/can't put together a proper vacuum infusion setup, there are other DIY ways to laminate panels, such as using expanding polyurethane spray foam, 3M 78 adhesive spray, or even Glidden Gripper. You don't necessarily need the Superman-strength of epoxy, since the foam core will fail at 1% of the epoxy strength, anyway.

Granted, you've already purchased epoxy and don't want to waste it! Are you using epoxy fillets and butts to connect the panels? If so, you could save it for reuse ...

[StrongFeather]

Whichever solution you use, be sure to tie the floor into the main rails and not just the cross members.

Thank you, Andrew.

I will look into the screws, and the plan is to tie into the main rails (sides & front/rear) with 1.5” angle aluminum.

On another note, I’m still on the fence about sealing the perimeter of the floor to the frame with some sort of caulk. The benefit would be keeping dust out, and the downside would be keeping (trapping) water in with few options to get out. Thoughts?

I don’t think I’ve come across any of your build journals. I’ll see if I can find them.

Steve


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[StrongFeather]

I'm excited to see your build progress! Very innovative. I'd have to say, though, it seems your technique for laminated panels is a little overdone?...

I somehow managed to miss this post the first time, Andrew. Thanks for the feedback.

To clarify, I wasn’t going to vacuum infuse the floor (that would be crazy), just vacuum bag it to use atmospheric pressure rather than weight to “clamp” it. But, I will be infusing the walls, so stand by for that. It should be a cool experiment. Hopefully not an expensive failed, but still cool, experiment.

Regarding the epoxy use for the floor, I considered TB2 between the foam and wood, but decided to go with epoxy simply because I’ll be skinning both sides and all edges with fiberglass/epoxy for seam strength and waterproofing - so I figured WTH. Plus I wouldn’t feel like part of the group if I didn’t overbuild at least one thing.

Steve


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[Andrew Herrick]

Whichever solution you use, be sure to tie the floor into the main rails and not just the cross members.

Thank you, Andrew.

I will look into the screws, and the plan is to tie into the main rails (sides & front/rear) with 1.5” angle aluminum.

On another note, I’m still on the fence about sealing the perimeter of the floor to the frame with some sort of caulk. The benefit would be keeping dust out, and the downside would be keeping (trapping) water in with few options to get out. Thoughts?

I don’t think I’ve come across any of your build journals. I’ll see if I can find them.

Steve


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1) Good thing to hear about tieing into the side rails! I love working with aluminum.
2) So you plan on using epoxy + an optional coating to protect the floor? Well ... I don't know how you're attaching your walls to your floor, and that makes a big difference as far as waterproofing goes. So I don't have an exact recommendation. With that said ... if you screw/bolt your floor assembly tightly to your aluminum trailer frame, a semi-elastic gasket - whether caulk or butyl - would certainly help keep out water. Sounds like a good idea to me
3) I'm afraid you'll be searching a long time to find any of my build journals When I started building I was too lazy, and then later I was too busy, and now I'm afraid I'm rather protective of some of my tricks, lol.

[Andrew Herrick]

I'm excited to see your build progress! Very innovative. I'd have to say, though, it seems your technique for laminated panels is a little overdone?...

I somehow managed to miss this post the first time, Andrew. Thanks for the feedback.

To clarify, I wasn’t going to vacuum infuse the floor (that would be crazy), just vacuum bag it to use atmospheric pressure rather than weight to “clamp” it. But, I will be infusing the walls, so stand by for that. It should be a cool experiment. Hopefully not an expensive failed, but still cool, experiment.

Regarding the epoxy use for the floor, I considered TB2 between the foam and wood, but decided to go with epoxy simply because I’ll be skinning both sides and all edges with fiberglass/epoxy for seam strength and waterproofing - so I figured WTH. Plus I wouldn’t feel like part of the group if I didn’t overbuild at least one thing.

Steve


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Ah. Point taken! Excited to see your walls - and yes, very cool.

And yes, overbuilding is the key to membership on TNTTT And since epoxy is arguably the most forgiving DIY structural material out there, it sure is tempting to don belt and suspenders. Glad you didn't use TB2 though; I don't think it adheres that well long-term to XPS insulation. And it's a hard thing to fix if it goes awry.

[John61CT]

better picture of the sister frame rail. These pictures should give everyone a better idea of where the sister is located in relation to the main rail and the axle
…
And a quick mock-up of the fender to see how much room I'll have for the door. The plan is to build as much of the trailer as possible before actually locating the axle so that I'll know the final weight distribution

Excellent, thanks all clear now.

Personally I'd shoot for being able to easily relocate the axle's longitudinal placement as desired even after the whole build is complete.

Heavy stuff like batteries, water tanks, propane bottles may be added or relocated later on.

I think your design allows for that if slightly modified. Put two cross-beams instead of one between the "sister rails", equidistant from the axle mount point, or even a third one at the mount point for plenty of anti-twisting stability.

This "inner frame" is fixed wrt the axle mount position.

Then the "outer frame" can slide back and forth, its cross-beams if any will set the maximum limits for that longitudinal positioning.

Fixing point bolts hold the the axle plate to both the inner and outer frame rails, as well as many as you like between the outer rail and inner "sister" rail.

[StrongFeather]

I think I’m picking up what you’re throwing down, John, and I realize that it’s hard to see what my final arrangement will look like with the pictures I provided, but I think it’s very similar to what you described if I understand you correctly.

What is not shown is two missing crossmembers (they’re each 2’ apart). Also, just to clarify, the beam you can see in the pictures above is the axle beam, not a floor crossmember.

Anyhow, that plate that is mocked-up in the pictures will bolt to the frame as well as the axle bracket (the part welded to the axle beam). If I ever need to relocate the axle, all I need to do is drill some new holes in the plate or make a new plate.

It’s hard to describe in words, so I’ll try to get some pictures in a day or two.

Steve


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[John61CT]

Aha. The Timbren units I plan to use attach with 6 bolts only via one angle-plate, from outside and underneath the main rail only.

No cross beam at axle height as long as you're comfortable with the rigidity of your design.

Greater ground clearance and/or ability to drop the floor if/when sticking to paved roads.

[Andrew Herrick]

Aha. The Timbren units I plan to use attach with 6 bolts only via one angle-plate, from outside and underneath the main rail only.

No cross beam at axle height as long as you're comfortable with the rigidity of your design.

Greater ground clearance and/or ability to drop the floor if/when sticking to paved roads.

I use the Timbren Axle-Less suspension system. I love it, but it's a little more finicky than a traditional axle. Not using a thru-axle with the Timbren puts an ENORMOUS amount of stress on your main rail. Most small camper frames don't have the torsional rigidity to deal with the deflections. I have no idea what your frame looks like, John, but for everyone else reading: Unless you have the numbers to back up your assumption that your main rail can handle the stress, best to go with the 2x2 steel thru-axle recommended by Timbren.

It's worth pointing out that the "axle" used by Timbren is still several inches higher than a traditional axle.

[StrongFeather]

Hey all! It was a relatively productive Friday on the build.

The floor is finally laminated! It does have a slight bow to it though. I'm not sure why, but the first side laminated flat as can be, but the second side caused the whole thing to bow slightly (~1.5" over 10'). I don't think it'll cause any problems, and I'm hoping that it'll actually be beneficial by adding some pre-stress that'll help to support the front and rear ends of the frame - although I don't think it's necessary. I'll install with the crown down so that the stress will provide lift to the front and rear. If the bow is going to be an issue, it'll probably delaminate when I attach it to the frame, so we'll see. Here's a very unglamorous picture of her majesty. At some point, I'll lay the frame on it, trace the final size with a pencil and cut it to size with a circular saw before adding a layer of fiberglass and epoxy to add a little strength to the seams and waterproof the wood.


I was also able to get the axle mounting plates done and mounted! Here's a shot of the first plate being fitted and bolted to the axle mounting bracket.

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Here's the axle sitting between the frame rails (upside down) with both brackets. I plan on using 4 c-clamps to hold it in place until I have a better idea of the weight distribution, at which time I'll be able to locate the axle properly.


This shot shows the axle plate sitting inside of the sister rail. It can slide fore an aft, so once the weight distribution is known, it will just be a matter of drilling holes to attach the plate to the frame rail and to install the last floor cross member.

DSC09858.JPG (122.63 KiB) Viewed 2588 times

And last but not least, the main tongue beam is pretty much done.

DSC09863.JPG (159.12 KiB) Viewed 2588 times

I really appreciate all of the input from everyone. I'm loving this build.


Steve

[redbicycle]

With your tongue being aluminum I don't think it will be strong enough without support.


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