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

...ask your questions in the appropriate forums BUT document your build here...preferably in a single thread...dates for updates, are appreciated....

Postby Thomcat316 » Wed Jun 29, 2011 7:41 am

aggie79 wrote: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.
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Postby Larry C » Wed Jun 29, 2011 9:55 am

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.
Image

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Postby aggie79 » Wed Jun 29, 2011 9:59 am

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
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Postby Thomcat316 » Wed Jun 29, 2011 1:06 pm

Larry C wrote: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.
Image


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.
Image

Same area from underneath.
Image

Closeup of the backing plate showing neoprene damper.
Image[/quote]
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Postby Larry C » Wed Jun 29, 2011 5:07 pm

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?


Image[/img]

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Postby Thomcat316 » Wed Jun 29, 2011 5:26 pm

Larry C wrote: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.... :(
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Postby Rock » Fri Jul 01, 2011 1:16 pm

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 :lol: 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
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Postby Larry C » Fri Jul 01, 2011 1:24 pm

Rock wrote: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 :lol: 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.

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Postby Thomcat316 » Fri Jul 01, 2011 3:01 pm

Rock wrote: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
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Postby sdakotadoug » Mon Jul 04, 2011 10:08 am

FACINATING, Love it :applause:
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Postby pete42 » Mon Jul 04, 2011 10:53 am

Very nice, no make that super nice. :thumbsup:

I hope I will always be surprized at what you builders have come up with and the one's still perking in someone's mind. :awesome:
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Postby Cliffmeister2000 » Mon Jul 04, 2011 10:58 am

Well, I'm not overly impressed.... because "overly impressed" doesn't do my appreciation justice! Amazed, in awe, jealous, those don't quite get there either. Great job!

Oh, I love your shop!

What, exactly, do you do that you attend trade shows for? :thinking:
God Bless

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Postby Thomcat316 » Tue Jul 05, 2011 10:45 am

Doug, Pete, Cliff, and any others handing out compliments - I'm humbled.

I'm brand new at this, and trying out a concept that may or may not work well over a period of time - y'all are the folks I look to when I don't know something, which in the course of this build was a LOT more often than the times I had knowledge...

I'm VERY glad to have had folks there to learn from and lean on!! :D

As for the shop, the "shop" photos (mold-building phase) are of our next-door neighbor's shop, Seafarer Marine, who are a very good supplier in addition to being great friends. (<---plug here, buy from them if it's practical.) The "warehouse" photos (layup/assembly phase) are mostly of our receiving bay here at work, with much debt owed to the patience of our "Man of Many Hats", Jay Finkelstein, who put up with my "damn trailer mess" for three weeks longer than I told him he'd have to.

There's still a galley to build, wiring and plumbing to run, interior electric to fit, and fenders to build (starting to sound a bit like "The Princess Bride," eh?) so this isn't the end of this thread....
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First Trip Photos - July Fourth Weekend!

Postby Thomcat316 » Wed Jul 20, 2011 1:40 pm

Here's a few (in)action shots:

First Night - Canoe Creek Service Plaza, Florida Turnpike. We got stuck behind a bad crash and ended up running out of time to be "on time" for the park we were heading for, so we slept 'mongst the Big Dogs for the night.
Image


And here's a couple actual campsite photos from the Spirit of the Suwannee Music Park in Live Oak, FL.
Image

Image
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Postby S. Heisley » Wed Jul 20, 2011 3:12 pm

Congratulations on your first camping trip. :thumbsup: :applause: Your TD is such a cool build and it looks so cute, parked between the "Big Guys"! 8)

The walls appear to be like a tent's (somewhat see-through, especially if a light is on inside?). If so, what are your plans to combat that?
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