2+2H low weight, how to improve the design?

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2+2H low weight, how to improve the design?

Postby adjangs » Wed Feb 03, 2016 8:29 pm

Image
Image

The particulars:
-Using a 5x8 Northern Tool trailer
-Overall height 6'
-Overall width 5'9"
-154 sq feet of area in the walls/roof, so ~5 sheet's worth in weight
-monocoque construction out of 1/4" ply, no spars, epoxy fillet construction? I will have to scarf the plywood to keep the bends fair.
Both beds have 21" of foot space, much more head space (2.5' on the top, 4' on the bottom) the beds overlap by 31": this is not yet accounting for frame and mattress widths.
Bottom bed has room for full queen, top is 5'4" long and 6 ft wide on top, 5 ft wide on bottom
There is about 21" inches between the trailer frames, so I think high quality 3/8" plywood is appropriate for flooring. I have not yet worked out the framing needed for the upper bed



Thanks to the forum member _Ryan_ for uploading the 5x8 Norther Tool sketchup model this is built upon.
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Re: 2+2H low weight, how to improve the design?

Postby Pmullen503 » Wed Feb 03, 2016 9:28 pm

Very similar to CLC's new camper project: http://www.clcboats.com/shop/boats/development-projects/clc-teardrop-trailer.html#line_drawings.

One problem I see it that the door is too far forward; hard to get in and out of. You could move the wheels back. May need to to get the right tongue weight.
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Re: 2+2H low weight, how to improve the design?

Postby adjangs » Thu Feb 04, 2016 3:10 pm

Thanks for your excellent suggestions. I agree completely. Moving the wheels back 10" allows for the door to be bigger and centered around 36" back.

I redrew with the above in mind and stretched it 6" lengthwise, it now has 160 sq ft of surface in the walls/roof, still about 5 sheets' worth. I feel good about those changes.
Image

CLC's tear was part of the inspiration for sure. I haven't seen a weight on that yet but I'm sure it is fantastically light. I wanted to see what could be done for a small family. I made the whole thing a little simpler and bigger.
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Re: 2+2H low weight, how to improve the design?

Postby kudzu » Fri Feb 05, 2016 10:16 am

I think you could and likely should move the axle back even more. And now looking at the CLC design I can see that, while the sketches show the wheels closer to mid-cabin, the actual trailer in their video has the wheels near the back of the trailer. In most TD designs I see the majority of weight is to the rear of the camper. The only exceptions I've seen are ones storage boxes on the tongue & with no galley.
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Re: 2+2H low weight, how to improve the design?

Postby Pmullen503 » Fri Feb 05, 2016 12:33 pm

What is the height of the door? You might want to make a cardboard or plywood mockup to be sure it's easy to get in and out. Mine is 27" x 40" and I'm glad I made it as large as practical. It is low enough to sit in the doorway to put on my boots.

What's the rear going to look like?
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Re: 2+2H low weight, how to improve the design?

Postby KCStudly » Fri Feb 05, 2016 7:18 pm

On that same note, you will probably have to give up some more headroom for the inner door seal flange and around it so that you can stick with a flat door. In other words, I don't think you will be able to run the door right up against the facet seam the way you are showing it, at least not without some very tricky carpentry work.

Neat idea. I'd like to follow along as you work thru the design details.
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Re: 2+2H low weight, how to improve the design?

Postby adjangs » Fri Feb 05, 2016 11:17 pm

Thanks for these great suggestions, everyone.

If the axle is moved back a total of 11", the outer shell happens to be perfectly balanced on the axle, 80 sq ft front and back of it, leaving the rear bed (say it is a 80 pound structure) against the bulk of the trailer frame; I'm estimating the tongue weight of 75 pounds with these considerations. If I need more tongue weight from there, I would be glad to tongue mount a large lead-acid battery, but if I can keep on the light end of angib's weight graph I would be around 750 lbs total, so 75 lb tongue would be about right.

I redrew the door as big as seems practical with these lines and it came out at 35" at the peak above the bed frame and 25" wide; seems doable with some head tilting in and out. Keeping the door outline near the facet makes sense since that will be one of the stiffest areas, but yes I was forgetting to account for the needs of a recessed door.

On second thought, I was thinking I would leave the rear nearly flat, maybe some curved stiffeners behind it to prevent oil canning. Then maybe have light storage access, 20 cubic feet empty back there. Or, maybe a light pull-out galley on heavy duty drawer slides; as drawn the pullout outline is 40" off the ground, about right for a counter.

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Re: 2+2H low weight, how to improve the design?

Postby KCStudly » Sat Feb 06, 2016 12:51 am

My doors are pretty large for a TD, and yet while building, with the cabin set closer to the floor than it would be while on the trailer (equal to a shorter door) when I go to sit down in the doorway and roll back in it is no problem; but if I lean in to organize or retrieve something, there have been several occasions when I clobbered the back of my head on the seal flange when standing back up straight. For me and my relatively tall chassis I don't expect that it will be a problem once the cabin is mounted on the chassis, but I could see this being a frustration for short doors on a normal height chassis.

I recommend that you make some cardboard mock-ups and live with them for a while.
Last edited by KCStudly on Fri Feb 12, 2016 9:52 am, edited 1 time in total.
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Re: 2+2H low weight, how to improve the design?

Postby rowerwet » Wed Feb 10, 2016 5:54 am

My own door designing came from sitting on my bed with a tape measure.
Put your head on the pillow like you're sleeping, now sit up and swing your feet over to the floor. Measure from the head of the mattress to your closer hip. Subtract 4", that is your forward door post location.
Measure to your further hip, add 6", that's the aft door post location.
Still sitting in place, measure from the mattress between your legs to the top of your head, sitting up straight. Add 5" and that is the height you need to not bash your head.
For me that works out to 33" wide doors, perfectly placed, with no sliding, scootching, or inch worming, getting in or out of bed. Also these doors allow my tear to swallow any gear I want to take camping, including bikes.
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Re: 2+2H low weight, how to improve the design?

Postby rowerwet » Wed Feb 10, 2016 5:56 am

I hope you plan on many more windows, ventilation is an issue with two in a 5x8, 4 will be a sauna.
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Re: 2+2H low weight, how to improve the design?

Postby mezmo » Thu Feb 11, 2016 10:39 pm

Here s the CLC web site for the TD.

http://www.clcboats.com/teardrop

It has links to the current and old galleys on it. Both have lots of pics,
especially construction pics that can be of interest for anyone interested
in the stitch-and-glue method. This is the first that I've seen pics of that
method as applied to TDs/TTTs.

Thanks for the original link to this. It's a neat design and we now have
the build method too.
If you have a house - you have a hobby.
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Re: 2+2H low weight, how to improve the design?

Postby KCStudly » Fri Feb 12, 2016 10:26 am

It looks like keeping the door to door jamb fit is a real problem for them. The faceted door probably needs some stiffening ribs to help it keep its shape, especially at the outer edges where it needs to hold tight to the seal. Keeping the door as one piece on the flat, like you (OP) have done seems prudent, but you will likely still have to stiffen the door panel and jamb against warping.

To give you some perspective on this, my walls are 1-1/2 thk foam with a 5mm inner skin laminated. At the galley wall opening I have a laminated formed arch about 2x2 nominal capping the edge of each wall, with the counter top and upper galley shelf face frames adding support (although the outer fiberglass skin has not been applied yet). Throughout the course of a day with shifting sunlight and temperatures I can sometimes see my galley walls wing in or out from the hatch edge, sometimes up to almost 1/16 inch. (I expect this to stabilize significantly with the application of the fiberglass and counter top.) On a marginal door seal that could make the difference between water and dust coming in or not. Seeing what looks like 3/4 to over an inch of "wing" in their thin panel doors, it just can't be good.
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Re: 2+2H low weight, how to improve the design?

Postby Pmullen503 » Fri Feb 12, 2016 1:09 pm

I've been working on a similar design in foam (curved panels) with only 5 strakes. I've found on models that the curve is lost when the door is cut out. What I've considered is sectioning in a wood door frame that keeps the door panel flat on the inside and then use a long sanding block and sanding the door blank to match the curve on the outside. The door ends up somewhat thinner on the edges but is still flat on the inner edge where the door seals are.

Just have to figure out how to do it on the full sized trailer.

I also noticed that the CLC door system looks suspect. The edges don't appear to line up in some of the photos. Having build a CLC kayak I know that when you cut out for a deck hatch, the hatch piece flattens out and so no longer fits perfectly. Not a big deal on a small hatch.
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Re: 2+2H low weight, how to improve the design?

Postby adjangs » Sun Feb 14, 2016 9:15 pm

This is all really good feedback to improve my process. I went back to square one with a tapemeasure in hand and really put in some thought. What I came up with isn't really a 2+2H anymore; more like putting kids' bunks where normally a galley and cabinets would go, but the end result seems to be more efficient with material all around, and more ergonomic. I kept in mind that an RV bunk should have 30" high openings, and that a teardrop door needs to be bigger than I originally thought to make it comfortable. There is also more space for easily accessible storage than before. The bunks are just 5' long now by 30" wide but the main bed remains essentially queen-sized. The whole thing is 6' tall and about 5' wide now, 150 sq ft of surface area. I didn't put these in but I think it needs a rooftop vent fan with inconspicuous intake vents, and possibly even a 5000 BTU window air conditioner (12" high) mounted on the tongue.
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Re: 2+2H low weight, how to improve the design?

Postby KCStudly » Sun Feb 14, 2016 11:12 pm

I think you would be more comfortable if you raise the rear roof enough to put both bunks in the rear without such big "shelf" over the main bunk head area' unless you were planning to have the pillows for the main bunk in the rear by that bunk, but then the side doors placement would be off again (at least to my eye).

You want to be able to sit bolt upright in the middle of the night w/o cracking your skull. :?
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