"Lite House" Ultralight Monocoque build - 6/25/11

[Heifer Boy]

That's looking really good. Fantastic job and ideas.

I like the idea of holding the panels with fender washers. I'd often wondered how to do this with composite panels coz you can't just screw them together like ply.

How did you prepare the panels to take the epoxy? Do they have a gloss coating and are the ends 'open'? Did you have to sand them or is the surface ok as is? Did you just 'glass the top for extra stregnth or had you not laminated this panel before assembly?

I'm really interested in how you doing all this as I would like to build in composite panels one day myself.

PS - Wear a mask... always!!! Mixing, using, sanding... always!!! Trust me on this!!!

 

[StandUpGuy]

What is there for suspension on this trailer?

 

[High Desert-TNT]

Anyone see any problems with this design? (I really hope not!!) I had two options here - do a complicated 2 into 1 with twice as many joints and no continuity of fiber back from the coupler to the trailer, or this, which only involved one precision bevel and a couple plates of homemade G10 , and gives both a continuous run of fiber and a nice box to run the wiring in.

Almost ready to go camping!!

A fascinating build!

Your tongue design is different but as long the ball is on the center line of the trailer it should work fine I'd think (which it appears to be in the pic). You don't have enough weight to worry much about side stress lol. I look forward to seeing more of your work.

 

[Shadow Catcher]

This is a great example of what can be done. Looking forward to seeing the completion.

 

[Thomcat316]

I like the idea of holding the panels with fender washers. I'd often wondered how to do this with composite panels coz you can't just screw them together like ply.

It's one way of many - you could use strips of plywood with tape or poly film on them, or Starboard, or.... The list is long. I just used the screws because it's what I had laying around. They need to be removed as soon as the putty kicks so the gaps can be filled in. Next one I do I'm probably going to use Starboard strips so I don't have to sand bulging putty off the roof.

How did you prepare the panels to take the epoxy? Do they have a gloss coating and are the ends 'open'? Did you have to sand them or is the surface ok as is? Did you just 'glass the top for extra strength or had you not laminated this panel before assembly?

The panels are polyester honeycomb with a non-woven scrim heat-bonded to the ends of the cells. Think of it as end-grain wood core. The surface is better than ideal for bonding face laminates to, and you're not limited to woven reinforcements - the interior might get some panels made up with Formica both sides as cabinet material, haven't decided yet. The central roof panel was cut out and the fan opening was fitted before it was pre-skinned with 9 oz. 'glass, then it was fitted into the curves and fixed in place with putty. All panels were fiberglassed on the interior surface prior to assembly - only the central roof panel and the side panels were 'glassed both sides.

I'm really interested in how you doing all this as I would like to build in composite panels one day myself.

Glad to try and be of assistance! Let me know if there's anything else I can answer...

 

[Thomcat316]

What is there for suspension on this trailer?

Dexter #8 torsion axle, rated at 800 lbs. - the trailer needs capacity for cargo. The next one is going to be rated at 600 lbs.

 

[vtx1029]

Looks great

 

[starleen2]

So - Am I to understand that the "frame rails and the angle are all extruded fiberglass??

 

[Thomcat316]

So - Am I to understand that the "frame rails and the angle are all extruded fiberglass??

Yup - 2"x2" square tubing with 1/4" thick walls, and 3"x3" "L" angle with 1/4" thick legs. Without any miles on it yet it seems pretty robust.

I bonded the tubing to the floor of the trailer for more than half of its length, as well as bonding the ends to the rails, and bonded the rails over the corners for their full (5 ft.) length. There's some vertical flex, but not more than I get with my boat trailer. There's no detectable horizontal flex.

 

[aggie79-HILO]

This is one of the most unique and intriguing approaches to building a teardrop that I've seen.

Obviously, this isn't your "first dance" with epoxy, composites, vacu-forming, etc. Other than the curves, do you think this approach is possible for a comparative newbie to fiberglass?

I had been looking into vacuum resin infusion, but your method seems to be much better for what I may be doing on my second build. I don't mean to go off-track on your build, but would you mind commenting on vacuum pumps - particularly less expensive options than continuous-use commercial-grade pumps?

Thank you,
Tom

 

[Thomcat316]

This is one of the most unique and intriguing approaches to building a teardrop that I've seen.

Obviously, this isn't your "first dance" with epoxy, composites, vacu-forming, etc. Other than the curves, do you think this approach is possible for a comparative newbie to fiberglass?

I'd say it would be good to approach this the same way I have - start small, with projects that don't really matter (i.e., cost) too much, then build up to making whatever you want. (afterthought - build fenders first - good way to gain experience and you'll have parts to sell if you do it right.)

I've done stitch-and-glue plywood/epoxy/fiberglass kayaks, vacuum molded various bits for them out of fiberglass and carbon over foam molds, and fabricated all sorts of other little bits, but this was my first step up to this scale. I was going to be all fancy with this first build, with a radiused transition to the roof, and even built a partial mold to test the concept, but in the end I ran myself out of time and went with square corners. Expedience rules!

I had been looking into vacuum resin infusion, but your method seems to be much better for what I may be doing on my second build. I don't mean to go off-track on your build, but would you mind commenting on vacuum pumps - particularly less expensive options than continuous-use commercial-grade pumps?

Get experience in traditional vacuum bagging first, then transition to infusion. If I were building these for resale I'd definitely go to infusion, as I think I could get a much better part finish without fairing labor, as well as more consistent parts. I would also thermoform the core if it weren't just for a one-off.

As for vacuum pumps - here's a short list of links to various suppliers and DIY options:
http://www.berkut13.com/sucker.htm
http://www.joewoodworker.com/veneering/ ... mpress.htm
http://www.dream-models.com/eco/vacuumpump.html
http://www.fiberglasssupply.com/Product ... gging.html
http://www.acp-composites.com/home.php?cat=4732

eBay search for: "AC vacuum", "refrigeration vacuum", etc. - here's a link I found:
http://cgi.ebay.com/Vintage-Robinair-2- ... 35ae40a5a4 (I own one of these that I paid even less for, but haven't hooked into an automated system yet. It's bulletproof and moves a LOT of air out of a bag FAST.)

If you decide to do the DIY route with the compressor let me suggest that your air outlet be run through a bronze wool oil trap into a homemade collection cup that's mounted to the vacuum inlet with a needle valve. If you do it right you'll have a self-recirculating open system that doesn't get oil all over the place.

For laminate materials, make sure you test what you're using before shooting a big part with it.

As a last word - don't underestimate the volume (and cost) of epoxy for a project of this size. I have a distributor next door, and was able to buy on-the-fly, but if I had to do it mail order I'd've been in trouble several times over.

 

[Larry C-TNT]

I really like your design and building method. I am trying to build a light weight Tear, but I am using light weight woods, 1/8" strips and 1/8" ply covered in light tight weave glass. My chassis is built the same yours, but it's welded steel.
Your offset tongue coupler is really "cool" I hope it proves to work fine.

I have few questions and concerns:

How much does your chassis weigh? I am wondering how much lighter it is than my 1X2X1/8" steel tongue.

I assume your tongue is epoxied to the angle, and the floor. That look's strong enough, but my concern is the 800# Dexter 8 axle with 12" wheels. Unless you are always loaded with weight, the trailer will probably be bouncing quite a bit.



Hit a good size pot hole or such and the stresses that will be put on your axle to angle point, especially with small wheels, will be extreme. Your layup schedule for the connection point seems good, but this area is too small to be able to absorb extreme stresses.

Would a larger piece of aluminum angle on the inside attached to both the side and bottom spread the load better? Maybe another aluminum plate on the outside as well.

My similar design is welded steel and this stress area has me concerned. Others have had welded axle attachment points fail when hitting a pot hole.
I will probably use 13" wheels with radial car tires to get the best ride, but the best wheel size is still open to discussion. Also, I am thinking a 600-700# axle.
Here's my chassis (upside down). The cross piece is a temporary brace that will be removed.

Larry C

 

[aggie79-HILO]

Thank you for the information and advise. I appreciate your insight.

Now...back to the build. Your design is incredible as well as your approach. I look forward to updates.

Thank you,
Tom

 

[Thomcat316]

I have few questions and concerns:

How much does your chassis weigh? I am wondering how much lighter it is than my 1X2X1/8" steel tongue.

I didn't weigh it separately, but looking at the spec weights of the materials it's about 40# including coupler and plates.

I assume your tongue is epoxied to the angle, and the floor. That looks strong enough, but my concern is the 800# Dexter 8 axle with 12" wheels. Unless you are always loaded with weight, the trailer will probably be bouncing quite a bit.

The reason for the 800# axle is that the trailer will be used for cargo from time to time (trade show booth) which will take the gross weight up to about 900-950 lbs. According to a conversation I had with a Dexter engineer this is an acceptable periodic overload for on-road use.

I am going to try the trailer out this weekend with appropriately deflated tires, and if it misbehaves too badly I'll have to figure out which tires to migrate to.

Hit a good size pot hole or such and the stresses that will be put on your axle to angle point, especially with small wheels, will be extreme. Your layup schedule for the connection point seems good, but this area is too small to be able to absorb extreme stresses.

The axle is mounted using a layer of neoprene as a shock load mitigation, and the angle is bonded to both the floor and the wall along its entire length. Given the tendency of fiberglass composites to flex under impact as well as the built-in stiffness of the 1-1/2" thick floor panel, I'm not too terribly worried about the potential failure of the framing at the axle point.

Would a larger piece of aluminum angle on the inside attached to both the side and bottom spread the load better? Maybe another aluminum plate on the outside as well.

I'd actually be worried about introducing too large a hard point in the structure - it's meant to flex a bit, and preventing that might not be of benefit.

My similar design is welded steel and this stress area has me concerned. Others have had welded axle attachment points fail when hitting a pot hole.
I will probably use 13" wheels with radial car tires to get the best ride, but the best wheel size is still open to discussion. Also, I am thinking a 600-700# axle.

I may go to softer-riding tires after this weekend as well. If I were using your build method I'd possibly consider bonding the shell to the frame with some sort of elastomer - Sikaflex, 3M 4200, Teakdecking Systems SIS440, etc. For composite structures I'm much more a fan of bonded joints than bolted - strengthens the structure over the whole of the joint and makes the joint very hard to catastrophically damage.

Here's my chassis (upside down). The cross piece is a temporary brace that will be removed.

Just like mine, but I built the box first...

Here are better-detailed photos of the joints in question:

Axle coming out from under frame member, shows bonding fillet.

Same area from underneath.

Closeup of the backing plate showing neoprene damper.

[/quote]

 

[Larry C-TNT]

Thomcat,
I see you used the low profile standard axle bracket orientation. I am going to use the low profile reverse orientation that Andrew suggested I use. I assume it's so the bracket angle is directly below the chassis angle. Don't know if it makes much difference though.

Let me know your thoughts on how the 12" wheels ride. I am torn between using the light weight (35# pair) 12" wheels and 13" or 14" wheels with radial car tires that will be heavier, but probably better all the way around...I think.

BTW: where/how are you attaching fenders?

[/img]

Larry C

 

[Thomcat316]

BTW: where/how are you attaching fenders?

Well, I kinda like the "Rat Rod" look....

Had I thought of it, I would've ordered the axles with brake plates - as far as I can tell it's the best place to attach "motorcycle" style fenders, which would have been really pretty cool.

Without the brake mounts I will be attaching the fenders (when they are finished) to the frame angle. I'm vacillating between molding up a set out of fiberglass and carbon with coremat and making a nice cold-molded wood pair. I'll also have a single bolt on either side going through the wall to keep the fenders from vibrating and fatiguing.

Either way, they will be solid backed and they'll mirror the shape of the trailer.

And yes, before y'all warn me, I've read the experiences some folks have had on here with fenders fatiguing and otherwise being built too light and disintegrating.

Don't want that....

 

[Rock-TNT]

For what's it's worth my camper hit a pothole that sent the curb side bouncing at least 18" into the air on my way from Boston to Cape Cod just now. After I finish my lunch I'll go out and take a look In any event it went another 100 miles after that and got here. Low mass has many advantages.

For those that don't know I used parts from the HF 1195# trailer kit. Currently the camper is about 500 lbs and I've been running 25 lbs of air for the whole 1,600 miles of this trip so far. She's still pretty bouncy.....

Eric

 

[Larry C-TNT]

For what's it's worth my camper hit a pothole that sent the curb side bouncing at least 18" into the air on my way from Boston to Cape Cod just now. After I finish my lunch I'll go out and take a look In any event it went another 100 miles after that and got here. Low mass has many advantages.

For those that don't know I used parts from the HF 1195# trailer kit. Currently the camper is about 500 lbs and I've been running 25 lbs of air for the whole 1,600 miles of this trip so far. She's still pretty bouncy.....

Eric

Hi Eric,
Your running leaf springs, and you removed 1 or 2 leaves right? Are you running 25# in those 12" wheels?
I hadn't thought about low mass helping when hitting a pot hole, but it does make sense. I think I want to tweak my axle rating (when I order it) to something close to my total loaded weight of the tear.

Larry C

 

[Thomcat316]

For those that don't know I used parts from the HF 1195# trailer kit. Currently the camper is about 500 lbs and I've been running 25 lbs of air for the whole 1,600 miles of this trip so far. She's still pretty bouncy.....

Eric

This gets right to a question I've agonized over a fair bit this last week - at well under 500 lbs. travel weight at the moment and an 800 lb. rated Dexter torsion axle, would it make sense to start out at 25 PSI in the 4.80x12 tires and let more out as needed, or perhaps start even lower?

Depending on how things go this trip I may get a pair of Yokohama 145SR12 passenger car tires, which I know I can run at really low pressures without much risk.

Whitney

 

[sdakotadoug]

FACINATING, Love it