T@b Plans?

[angib]

For Arne,

Here are some good pictures from a really good Dutch trailer website http://www.caravantrekker.nl - of course it's in Dutch, but Babelfish does offer a Dutch translation, though it does have a problem with quite a few technical words!

Poor streamlining - little or no rounding at the sides:



Average streamlining - rounding of the sides, but not at window or roof level:



Very good streamlining - rounding continues right into roof and front part of roof sloped down:



For Steve,

Designing bodies for stitch and glue construction is quite easy. Here is some free software that takes a multi-chine hull design and produces panel expansions: Hull Designer

Of course you have to learn to use the software (not hard) and, for non-boaters, you have to learn to think of your trailer as a boat (not hard either).

I've used this software to produce the panel drawings for the Trailerboat panels:



I think I might have a go at a design like a miniature Bowles Aero:



You will notice that the problem with these more streamlined trailers is that it's hard to design a door that can be realistically sealed!

Andrew

[Arne]

The difficulty with all those designs is how to build the interior walls after the exterior is done, with proper spacing and insulation. Plus, they don't have the teardrop shape I need (to get the kudos/g/).

I have come up with a plan. It involves having an exterior wall, with 1/8 on the outside of the framing, and kerfing the frame down to the 1/8 every 3/4 inch. That would allow the 1/8 to bend and form the front wall curve. It won't be much, probably only 1-1.5 feet of the front wall with the front edge in about 6 inches. But that coupled with a short tongue should help noticeably. I plan on doing a test piece to see how it works out, to get the kerf spacing right.

The curve can only start in front of the door, else the complexity multiplies.

[steve wolverton]

Designing bodies for stitch and glue construction is quite easy. Here is some free software that takes a multi-chine hull design and produces panel expansions: Hull Designer

Ah yes, I remember that program!

I think I might have a go at a design like a miniature Bowles Aero:

That would be great Andrew! I've decided that my next build will be a stitch-n-glue. There is no reason to keep building tears in the conventional manner when a monocoque structure would be just as strong, and much lighter.

As for the door, I don't think I'd attempt to place the door at the front/back of that design. I'd be more comfortable with it on the sides of the camper. Hinging would be the problem, maybe a split door like an aircraft. The bottom half fold down as a ramp, and the top half raise up.

I'm thinking an 8-10 foot stitch-n-glue Airstream type tiny trailer. The building forms could double as bulkheads. Very similar to large sailboat construction. It may be a couple of years before I build it, but I'm game.

Something like this: http://dixdesign.com/didi38build1.htm

And, Steve, I am super intrigued by that stitch and glue idea. Could you use some sort of a spray on insulation and not really have an inner skin?

Not sure as I've never used spray on insulation. I imagine you could use sheet foam and cover it with fabric like I did on the Cowper.



The sheet foam would be cut as the same size as the wooden panels, the wooden panels could even be used as the templates. Of course you wouldn't have the spars (that's the beauty of stitch-n-glue) so your ceiling would be one (well, a series of panels) piece.

[angib]

Here's a 3D model of a stitch and glue body with tapering both forward and backwards. For low drag behind a motorcycle, this would be ideal, but I'm not so sure it wouldn't turn out to be very sensitive to crosswinds.





Andrew

[Arne]

Andrew, those sides coming in are exactly what I'm talking about, but the profile would still have a tear shape. Can you cobble up something with a tear profile for me?.. I'd like to see what it looks like...

I have no plans to try anything so complicated on the back. I don't think it would be worth the effort.

[angib]

Arne,

A fairly conventional teardrop profile at 4x8 but with the sides curving in 6" over the leading 18" of side. Note this means the sides are now 97 3/8" long, dammit.





Andrew

PS for Mike: Yes I do like 'Shell' a lot!

[steve wolverton]

Oh man, this is starting to look really good.

[doug hodder]

If you are going to do this in Stitch and Glue...what thickness material are you thinking about? Doug

[steve wolverton]

If you are going to do this in Stitch and Glue...what thickness material are you thinking about? Doug

I was hoping for 3/4" or 7/8" ply. I just wanna see if Arne can bend it.

1/4" would be fine IMHO, what are your thoughts Doug?

[Miriam C.]

Steve you could alway upholster the inside. Add some padding.

[Arne]

Andrew, can you tuck the bottom of the front under a bit? I don't like the flat slab on the bottom?

Do you think it would affect the areo much to have the front / bottom flat instead of tucked under....? Flat would make construction easier...

my design is around 125 inches long, so there will be a seam at the front of the door anyway (on the door post).

-----------

The only decent way to bend heavy ply would be to kerf it, in my opinion, anything over 1/4"... I think you could bend 1/4 a bit the short way, but not the long way.

I had bent 1/8 the long way on my roof. when I chopped the top off, the ply sprung back almost flat.. I thought it would have assumed the shape after over one year, but it was protected from moisture by the uniflex, and wanted to be straight again.

[angib]

Andrew, can you tuck the bottom of the front under a bit? I don't like the flat slab on the bottom?

Do you think it would affect the areo much to have the front / bottom flat instead of tucked under....? Flat would make construction easier...

Assuming the bottom of the front is in the wake of the tow vehicle, I don't think it matters at all.

Splitting the side panel at the door post is useful as you could switch from thicker material making the flat rear side to thinner ply to do the curve in the front of the side.

Have you thought about how you would reinforce the top/front? Once the sides start curving in, the ends of any roof spars become very, very complex angles.....

Andrew

[Arne]

I have given it some thought.. I figure if I do it, I'll deal with each piece individually.. I really need spars and an inside wall in the front, as I will have shelves up front, as I sleep head to rear... and the shelves will hold tv, which is a bit more weighty than clothes. I kind of like the bottom tucked under better, but it does take floor room (that is where the dog sleeps).

[doug hodder]

I'm certainly no expert on Stitch and Glue construction but as with a lot of boat construction, you can go thinner on the materials since there is a curve to it which increases it's strength on the convex (water)side. I would think you would need something to support those areas where the material is flat on this design as that would be the weak point, the curves are going to be plenty strong. In looking at a lot of small dinghys and jet boats in stitch and glue, all the panels have some curvature to them. Of course, there isn't going to be the pounds/sq in pressure on those flat areas like there are on a boat, so maybe it doesn't mean anything, but I'd be willing to bet the flat areas would have some movement to them in 1/4" without some interior structure. I'll bow out now...Doug

[Arne]

The stitch and glue was something I was thinking of, but I still need an interior wall with a space in between inside and outside. the easiest way for me to do that is to build a regular frame on an outside wall, and kerf the frame in the front. that eliminates the stitch and glue thing. then make templates in place for the interior walls.

In kayaks, its easier because the flat areas are much narrower, and often reinforced with fiberglass cloth. I think the front of a tear with curves could be done that way, but not big flat sections....

I thought of doing the front of the tear with s&g, but it would be difficult to make the compound curve side framing in place, so have more or less given up on it. having the front side walls curve in is a good idea, I think, but I'm still going to do some testing to see what can of worms I'm opening up.. I'm not that much of a masochist, but want my next tear to be my last build.. have lots of other things I should be attending to..

curving the wall in creates the problem of the ceiling/front wall not having a flat surface to attach to... so I'll have to sand it flat, or fill it some how.