Lightweight Design

[mikeschn]

I had a little time to do some more of the design... pictures will come later... meanwhile here are the weights I have... weight in pounds.
btw, the floor, the shelf and the counter are SIPs.

1/2" plywood walls 75
doors 16
windows 7
roof skin 31
subfloor 21
spars 25
chassis without tongue 139
floor 28
door frames 9
inside shelf 7
galley counter 7
bulkhead with 1 skin 15
inside shelf support 2
galley counter support 5
hatch spars 8
hatch skin 6
wheels 32
fenders ?
=====
Total 433


I did an alternate wall scheme, with pine framing and an aluminum skin, an was able to knock off 3 pounds.

i.e.
.040" alum wall and door skins for both sides = 36#
pine and plywood wall framing for both sides = 36#

Here's the picture of the alternate construction... using 3/4" thick pine framing as shown, and a 1/2" plywood door as shown.

[Elumia]

so your 1/2" ply version is just wood sides? It would need some sort of weather protection. Is the top skin Alum only?

do you have an axle in the 139 lbs for the chassis?

You have to add in all the edge mouldings, latches, hardware and screws too. easily add 50 lbs.

Seems to me that achieving a well built, durable 800lb tear is very doable.
Add a few hundred pounds for gear and most any car can pull that.

Mark

[Roly Nelson]

Thinwater, that is sure a slick looking little boat you have built. I had one similar back in 1948, we called it a hydroplane, was powered by a Huge 10 hp Mercury motor and was the fastest thing on the water. Did you design it yourself and what is it powered with?

To all wooden teardrop builders, it is possible to build one that weighs less than 250 lbs, if it is only 6 ft long, has a floor made out of a hollow-core door and is on a 145 lb, 48" x 40" Harbor Freight frame. The wood alone only weighs 95 lbs, accoring to my bathroom scale. See some pics of it in my gallery photos.

Roly ~~

[mikeschn]

Yep, that's definitely light, albeit a little small for 2 people.

How light could you make a cub/modernistic?

Mike...

[mikeschn]

Here is the lightweight cub/modernistic so far...



Mike...

[GPW]

Mike , that's a BEAUTY!!! What about cutting some large oval lightening holes in that rear bottom galley wall, save a little ply weight and you could use that bottom rear compartment for storage ... shouldn't affect the strength of the wall much ..That and a large cargo net across the front wall and you could store a lot of gear ...and if you bull nosed all the interior framing , then a nice light paint job would finish it off and look good too...

[thinwater]

My wife may prevent the build of the true teardrop as she has decided that she needs a bathroom inside the camper. Size is looking like it will be 6 x 12. I will still make it a teardrop style but it will be a lot bigger than i wanted. Any bigger than 6 x 12 and it starts to get expensive and in the two axle range. I may make the frame out of aluminum c channel to save weight. My welder is not big enough to weld this safely. I will have to tack it with my MIG and take it to a friend with a TIG for the final welding. i already have the metal so it won't be to expensive to make.

Roy Nelson, The boat is a "Minimost" designed in the 1950's and published in a magizine. It does over 31 with me (230 lbs) and a 15 yamaha. I have made three of them. I am finishing another one this week.

JIM

[GPW]

While we're talking about lightweight, might as well weigh all the stuff we're gonna' carry too ...forget that cast iron ...

[caseydog]

That honeycomb material that Heikki mentioned has me thinking it would be a good replacement for the Coroplast I was thinking about. I have seen it used in Trade Show displays, but only in flat panels. I had no idea it could be "bent" into a curved surface.

Heikki, do you know if they actually bend it, or form it in a curve when they make it?

G

[mikeschn]

Jim,

Did you check out the ET?

My wife may prevent the build of the true teardrop as she has decided that she needs a bathroom inside the camper.

[angib]

do you know if they actually bend it, or form it in a curve when they make it?

Honeycomb-cored panels cannot be bent after they're made - they break first, as they are much too strong to bend.

To make a curved honeycomb-cored panel, the two skins and the core have to be bonded together in their final shape, so usually this is done in a mould.

Andrew

[GPW]

There is a honeycomb material out there used to make aircraft, I believe it's called Nomex... might be able to put a curved skin down over the framing, lay on the Nomex and add another skin on top ... like wings are made...strong, light , and fireproof...

[ARKPAT]

angib Posted: Sat Sep 29, 2007 8:21 am Post subject:

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caseydog wrote:
do you know if they actually bend it, or form it in a curve when they make it?

Honeycomb-cored panels cannot be bent after they're made - they break first, as they are much too strong to bend.

To make a curved honeycomb-cored panel, the two skins and the core have to be bonded together in their final shape, so usually this is done in a mould.

Andrew

Andrew you could build polyfoam board and shave it down as a curve then apply thin veneer inside and outside as a foam core door. Would this work with a adheasive that would be compatable with both materials?

It would make the surface light and strong.



Pat

[angib]

Yes, ply/foam/ply sandwich panels are just like laminate/honeycomb/laminate sandwich panels except they don't have quite such a good strength-to-weigh ratio. The advantage of ply/foam/ply is that it's nearly ready-finished as all you have to do is coat the ply, rather than spending three months fairing and sanding laminate. But you still have to build some sort of mould or jig in which to assemble the sandwich panels and possibly buy a vacuum pump to squeeze them together during gluing.

But going back to the key issue on sandwich panels - how strong do you want your outside skin to be? Neither foam nor honeycomb cores provide enormous amounts of local strength - if you want your outer skin to be resistant to, say, flying stones, you will have to make it thick enough to have its own puncture resistance, and isn't that going to lead you to the same 1/8" ply that people here have used for their roof without sandwich construction? Veneer/foam/veneer will be strong enough overall, but you will be able to stick your car key straight through it.

Andrew

[GPW]

Angib is spot on with the local strength issue, and as with all structural designs, some compromises have to be made...How many flying projectiles do we expect to encounter??? We must defer to the history of TD's ...Were there problems in the past ...how were they solved...??? Even a thinly constructed TD provides more "security" than a tent ...