Del's canned ham build

[grant whipp]

Hey, Del!

Why don't you go with this version, use sheet plywood for the roof/front/&rear, then strip-build the curved side-walls, and cover it all with 'glass & epoxy?

Forgive me if this has already been suggested, but it seems to me that you met the challenge of the Roswell/JellyBean with great results, so it would only make sense that strip-building is your next logical step ... ... ...!

Good Luck with it, and as always ...

CHEERS!

Grant

[del]

Hey, Del!

Why don't you go with this version, use sheet plywood for the roof/front/&rear, then strip-build the curved side-walls, and cover it all with 'glass & epoxy?

Forgive me if this has already been suggested, but it seems to me that you met the challenge of the Roswell/JellyBean with great results, so it would only make sense that strip-building is your next logical step ... ... ...!

Good Luck with it, and as always ...

CHEERS!

Grant

Hey Grant, thanks for dropping by. You do know the jelly belly was my first real experience with glass work. Forgive me but I have no idea what strip building is.

del

[angib]

I think the early SMVs are made with all-metal skins, but I suspect the later ones have corner panels made from fiberglass, which is how those corners can be so smooth - fiberglass can be moulded with double-curvature (like a boat hull), whereas metal or ply just won't bend like that. For example, the Roswell is strictly single-curvature: spheres are double curvature and you can't make those from ply!

You can look at many more SMV photos on a SMV fan's site or on the DutchSMVfriends web site, both in their fotoalbum and in their restoration topics of their forum. Of course it's all in Dutch, but Babelfish will translate some of it.

I think you're right that the centre of the walls is flat and only the front/back/top/bottom are curved. All of that is quite easy - it's the four corners that are very hard - those early corners that you don't like are the ones that could be replicated in metal. They could be done in ply too, but getting the geometry right would take a lot of work.

Andrew

[del]

I think the early SMVs are made with all-metal skins, but I suspect the later ones have corner panels made from fiberglass, which is how those corners can be so smooth - fiberglass can be moulded with double-curvature (like a boat hull), whereas metal or ply just won't bend like that. For example, the Roswell is strictly single-curvature: spheres are double curvature and you can't make those from ply! ....
I think you're right that the centre of the walls is flat and only the front/back/top/bottom are curved. All of that is quite easy - it's the four corners that are very hard - those early corners that you don't like are the ones that could be replicated in metal. They could be done in ply too, but getting the geometry right would take a lot of work.

Andrew

I do like the earlier models, imperfections and all. I think the later ones would easier to build (and yet be different enough for me to build, why be normal?), and if some of the imperfections show up on with the newer design, so be it (if I build it, it will never be perfect. Strange and unique, yes) .
Andrew do you have any idea the bulge in the walls, am I even close?

del

[angib]

I think the later ones would easier to build (and yet be different enough for me to build, why be normal?), and if some of the imperfections show up on with the newer design, so be it (if I build it, it will never be perfect.

I was being too tactful before, eh? If you try to build the later design in plywood, the imperfections will be that the pieces will not fit together and there will be a 1-3" step between various panels. And it will be impossible to build.

Are you picking up on my sort of negative, glass-half-empty vibe?

Andrew do you have any idea the bulge in the walls, am I even close?

My guess is that 6" of bulge is right for the early ones but not the later ones. If you look at some of the head-on photos of later ones, I'm not even sure it still has a bulge at the bottom - the door looks nearly flat down there. The tapering of the front panel suggests that only the top has the bulge on these models.

Andrew

[del]

I think the later ones would easier to build (and yet be different enough for me to build, why be normal?), and if some of the imperfections show up on with the newer design, so be it (if I build it, it will never be perfect.

I was being too tactful before, eh? If you try to build the later design in plywood, the imperfections will be that the pieces will not fit together and there will be a 1-3" step between various panels. And it will be impossible to build.

Are you picking up on my sort of negative, glass-half-empty vibe?

I have given up on ply, at least for the corners.

Andrew do you have any idea the bulge in the walls, am I even close?

My guess is that 6" of bulge is right for the early ones but not the later ones. If you look at some of the head-on photos of later ones, I'm not even sure it still has a bulge at the bottom - the door looks nearly flat down there. The tapering of the front panel suggests that only the top has the bulge on these models.

Andrew

I see no bulge at the bottom too. I had figured out in my head how to build the frame work for the bulge all the way around (sorry I do not know how to put it down on paper, but I can build it), but just at the top and tapering off on the ends, I do not think I even want that. What I want is a hybrid of the two, more like the older style with less bulge.


My thoughts on wall frame work. Typing this out so I can read it later, it may read like incomprehensible babble (now you have been warned). The following is proof of why I am not an engineer.

First build a frame work of the side profile, like this (outside perimeter only), only in the profile Andrew gave earlier.

Then build a second frame work smaller than the first frame by twice the major axis of the eclipse used. Using eclipses made out of ply spacing the two frameworks apart. The ply eclipses spaced apart every (say 12"). The ends will require some pieces at a 45, placed where the seams are on the older SMV (see red and white SMV this post). My current thought on the eclipse is 4" minor, with a 15" major. Andrew if your still laughing (reading) this do not worry about drawing this, all I need to work out is spacing of the eclipse pieces and the eclipse itself. I know this goes against the engineering credo but I think I will frame this then figure out what to skin it in.

del

[doug hodder]

What about cold molding in ply? Just an idea....Doug

http://www.nwmarinedesign.com/coldmold.htm

[del]

What about cold molding in ply? Just an idea....Doug

http://www.nwmarinedesign.com/coldmold.htm

What if I install the inside wall, fill the void with some sort of insulation that is moldable. sand to shape and cover with this cold ply? Doug do know what they are gluing the wood together with?

del

[doug hodder]

Del...cold molding is usually done with multiple thin layers of ply with some sort of rib system behind it to attach to. Boats need more strength to the hull than a tear body however...but that's just my opinion. I'd think that you could shape some foam for those compound areas, since they are not that large and cover it in glass mat and cloth and epoxy it up into the shape you want. Either grind out or melt the foam out of the interior using lacquer thinner and build it up for some thickness with some chop. I'm sort of playing with the idea on a new build. I do know that you want enough resin over the cloth on the exterior to minimize "printing" of the cloth to appear in your paint coat.

I could be completely wrong on this, but I think the idea/technique of cold molding sort of came into its heyday with the advent of epoxies or polyester resins, maybe it was earlier. Epoxies really made it possible for a thin lightweight hull in ply. I'm sure Andrew would have some info on this subject. I don't know the history on it all...just know what I think I can do with it and how I'm going to approach the problem...may not be the prescribed method, I'll just figure it out as I go, but my technique involves a thrift store basket ball cut into segments for the compound curve pattern, your curves may not be as hard however. I guess I'll learn something new. Doug

[del]

Del...cold molding is usually done with multiple thin layers of ply with some sort of rib system behind it to attach to. Boats need more strength to the hull than a tear body however...but that's just my opinion. I'd think that you could shape some foam for those compound areas, since they are not that large and cover it in glass mat and cloth and epoxy it up into the shape you want. Either grind out or melt the foam out of the interior using lacquer thinner and build it up for some thickness with some chop. I'm sort of playing with the idea on a new build. I do know that you want enough resin over the cloth on the exterior to minimize "printing" of the cloth to appear in your paint coat.

I could be completely wrong on this, but I think the idea/technique of cold molding sort of came into its heyday with the advent of epoxies or polyester resins, maybe it was earlier. Epoxies really made it possible for a thin lightweight hull in ply. I'm sure Andrew would have some info on this subject. I don't know the history on it all...just know what I think I can do with it and how I'm going to approach the problem...may not be the prescribed method, I'll just figure it out as I go, I guess I'll learn something new. Doug

Doug right now I know what it should look like, but how to get there is filled with uncertainty. But hey if I do as I have always done, the results will be boring, so I am here to learn. And Doug your comments are always encouraging and/or informative, so keep it up.

del

[doug hodder]

Del....your results aren't boring by any means...so who else has tackled a build like the Jelly Belly? You provided a great wealth of info for lots of builders out there, curves, angles, fit up situations. In addition to bringing out a lot of information from people like Andrew, you have learned a ton of info on using epoxies and working with curved features. Just apply what you have learned into your new project, but just tweak it a bit for what you want. That's how I learn anyway. For me...I build from the outside in. I know how I want it to look for the road appearance..I make that look, then fit the rest of the stuff inside. If someone doesn't like it...tough! It's what you wanted, it's what you built. If they have an issue...ask where theirs is! Besides...you've got a lot of miles on yours, much more that some people have...so it's a proven trailer! Doug

[grant whipp]

...Hey Grant, thanks for dropping by. You do know the jelly belly was my first real experience with glass work. Forgive me but I have no idea what strip building is...

Hi, Del!

"Strip-building" is the process of using narrow strips of wood (usually about 1/4" to 3/8" thick and about 3/4" to 1-1/2" wide) glued & stapled together to form the curving hull and/or deck of a wooden boat (think kayak or canoe). When the glue/epoxy is set, you pull the staples and sand the wood smooth and cover with fiberglass cloth & epoxy. To get the the curves and keep the strips in some kind of alignment, various pieces need to be tapered in various places (depending on how compound the curve is). It is an extreme exercise of patience and persistence, but some very graceful (and sometimes very complex) forms can be achieved this way.

I couldn't find the one I was really looking for as an example (not too long ago, a fellow built his whole teardrop strip-style - with rounded sides, roof & galley lid - and caused quite a stir 'round here), but here are a couple of examples of teardrops built on this Forum using strip-building for their flat sides and roofs:





There are several others, like JuneauDave's, but these were found on a quick tour through the Hall of Fame album.

If it were me trying to build an SMV-type trailer, I'd do something similar to what you've suggested and get a couple profile frames up, then attach as many curved side frames as was necessary (most temporary - only the ones holding/making the door frame would be permanent) ... skin the roof & ends with flat sheet ... then start in the middle of the sides with the strips and work downwards & upwards.

There are many books available that can walk you through the whole process, some in bookstores, but mostly through wooden boat magazines. I think it is the ideal method to achieve the results you are after.

Good Luck with this new project! As always ...

CHEERS!

Grant

[angib]

What about cold molding in ply?

In order to cold mould a shape like this trailer side, you need a former to provide the shape. These couple of photos of cold molding yachts (OK, one of them is cold moulding, 'cos it's in Britain...) show the process of fitting narrow strips of thin wood (or ply) to the former - effectively it's 'make your own custom plywood':





Having made the former, you're 90% of the way to having made a mould for fiberglass - and you haven't yet started the laborious process of cold moulding. Cold moulding has dropped out of use on anything except amateur builds or very top-end yachts because it takes a long time (and plenty of skill) to do.

Really, it would be easier to make a mould and lay up a complete fiberglass side panel.

Note that cold moulding and strip planking are quite different. In cold moulding the primary joint is to the strip underneath or on top - in strip planking it is to the strips either side.

--------------------------------------------

Going back to the SMV-style side panel, here is what I think could be done. I stress it is impossible to make ply fit the SMV-shape exactly - where smooth curves are wanted, there will be some unexpected hollows and things like that. If the panels are made small enough, the unwanted features won't be too noticeable and could even be faired out with filler.



This uses a 15" offset from the outer shape and a 6" depth of bulge. Each orange line would be:
a) a joint between ply panels (so there are lots more than four), and
b) a rib under the ply panels giving them the curved shape.

The significance of this design is that each rib is the same as the others - they're all just arcs of the same (21.75") radius.

The green line shows the extent of the flat centre panel - it could have a pure curved shape, but will be easier segmented as shown.

Del, if you wanted a shape for the green curve, I can't give it - a 15" offset from an ellipse is not itself an ellipse, it's just a curved line.

Andrew

[del]

The significance of this design is that each rib is the same as the others - they're all just arcs of the same (21.75") radius.

Andrew

If I am reading this right the orange pieces (ribs) are part of a circle, not a eclipse?

del

[angib]

Yes, the orange lines are ribs - and also the joints between the 16 pieces of ply that make up the rolled edge.

I've made the shape of the ribs circular as the skin can bend most easily to that shape. If the ribs were elliptical, the side skin would curve right round onto the top/bottom/front/rear. This would look wonderful, but the radius at the end would be something like 1", so nothing would bend round that.

Here's a sketch of how I see this being built. This is a view looking backwards through the top (side/roof) corner, but the side panel would be built lying on flat building base/surface, using your (red) outer ring frame as a base.

Each orange rib then (a) provides reinforcement to the assembly when finished, but also (b) acts as a jig during assembly to support the inner ring frame the right distance off the building base.



After assembly is competed, the excess bit of each rib is cut off - not easy, as access is poor, but then life isn't easy......

Does that make sense?

Andrew