GRP/FRP shell

[Vindi_andy]

OK guys time to test the grey matter and I know some of you will suck your teeth and go " NOOOO you cant do that with a self build TD" but here are my thoughts anyway.

We have gone through several construction techniques. the ply and insulation sandwich, the ply, frame and insulation sandwich, both with paint over then i had concerns regarding my woodworking skill in terms of the panel meet at the walls and roof so thought about fibreglassing over and gelcoating so the colour was an exact match.

Having spoken to a kitcar friend who works with fibreglass everyday, she make GRP bodies for emergency vehicles in the UK, and she reckons this would be heavy.

She suggested fibreglass over a PU core sandwich construction which would be light and strong. Reasearching the materials it could be more expensive than ply and paint but it would never rot (well the shell wouldnt) plus i like the idea and the challenge fo doing something out of my comfort zone.

What are your thoughts on this idea. Andrew Your input would be greatly appreciated having met you and spoken to you i have some understanding of your background and knowledge of materials and construction strengths.

[angib]

The mian thing about a one-off fiberglass tear is that it would be a huge amount of work to get a decent surface finish - several times as much work as working in wood.

Skining a wood tear with ready-moulded flat sheet fiberglass instead of aluminium is a different matter, but I don't think that's what you're talking about.

Building in wood and then sheathing it with a light layer of glass/epoxy seems to me the easiest way of making a really long-lasting teardrop. It still isn't anywhere as easy as skinning in aluminium, but it is a realistic method. Indeed the alternative of painting plywood is about the same amount of work if you want a high gloss smooth finish - filling the plywood wood grain requires a high build primer and really epoxy is just as easy to use.

Custom building a sandwich fiberglass/foam body is a scary amount of work and involves quite a big learning curve if you haven't worked with those materials before.

Andrew

[WesGrimes]

I am building my tear out of PU Foam, 1/8" and 1/4" plywood covered in fiberglass. I did this for the rotting protection, and for more contours in the design.
It can get pricey, messy, and tiresome. I would be camping already if I did a traditional build.

[glassice]

Vindi_andy cool louts 7
It cam be done lot of cost up front

[Vindi_andy]

glassice thanks for your comments about the car thats the towcar.

I appreciate your comments about how hard it will be and the time it will take. With the regards the steep learning curve I know it will be, building a car from scratch was a steep learning curve for someone who had only done basic maintenance before but i did it. Also having learned those skills i will always have them for when i want to remodel the body of the car

In addition the lady that suggested this has agreed to assist me in this and she work with fibreglass everyday, she makes some of the bodies for some of the emergency vehicles over here.

she sent me a link to a website where a guy did this sort of construction for a car so im thinking it will be structurally strong enough will just take more time. also It will be unique

[glassice]

we have been building our teardrops this way for years But most won"t want to pay the cost .It's hard to compete with a $35.00 wood wall I have seen 8 and now 9 (what happen with the tadpole) I think try and go'ne under with FG. We luck out to sell to a rental co where it rains ever day look in ALB. If you look at litte guy they sell the most just the back is molded fiberglass. 1 of the kit cars we do are loust 7

[Vindi_andy]

This isnt for commrcial purposes this is for a one off just for me and wife but i like the fact that it is different.

The car is one of only 4 on the road as it is a 4 seater so we are different in that.

[kennyrayandersen]

Andrew is right again, of course and one should never easily dismiss his advice (there will be repercussions). In fact I’ve recently got some great ideas from his Piccolo tear! Still, it has been done and if it’s your hobby and you get pleasure out of doing it that way, then great and you should do it. Some people enjoy the build way more than others, so in the end, it really depends on you. It does, or can, allow for greater artistic expression (all artistic expressions come at a price though!).

I’m planning on building this way as well because I’m after the weight-savings – it’s potentially MUCH lighter to build this way! You can get a nice finish on the sides by laying the sandwich up on a flat surface covered with shinny plastic (make the inside your ‘bag’ side), but the top is more problematic.

For the curved top I’m thinking of laying a ply of fiberglass down on the plastic again followed by the foam, but then leaving the top layer off. The foam could then be slit across (slit ¾ deep with a 1 inch thick core). Then using the sides as a form, the panel could then be laid up around the tear with the foam side out and glued at the sides. 1/8 ply could then be glued down as the outer facesheets (what we call the structural plies). I’m even thinking that the gaps made by the core as it wraps around the curvature won’t even need to be filled in (though they could be) – any thoughts on that Andrew?

It adds a little weight (12 Lb/sheet of 1/8 inch plywood), but would likely speed the build.

Alternately, rather than use the plywood, one could just fill in the gaps in the foam and come back over it with fiberglass. The outer surface might not be quite as nice, but this is probably the lightest way to build – it will take a lot of surface prep if you don’t want it to look like a sack of walnuts going down the road. The corners could be finished off with 2-3 inch fiberglass tape (inside and out) I’d ¼ inch radius the outside and ¼ fillet the inside before taping. Anyway, those are just some thoughts and ideas how you might do it and still get a decent surface to finish.

T%his stuff in fact says it for bending and only bends at 16 inch radius -- it's only 1/8 inch think -- just imagine bending something 16 times stiffer -- it ain't going to happen -- you'd have to cut some slots in is to get it to bend. Anyway -- I recommend the thin stuff especially if you have any smaller radii.

http://www.plywoodcompany.com/application/home/itemdetails.aspx?categoryid=197&itemid=163

[2bits]

"NOOOO you cant do that with a self build TD" Is not in our dictionary! !! ! Self build that bad boy! ! !

[glassice]

If you find( how I built a fiberglass teardrop) in my old post we did are 1st one with one piece of melamine and a roller. But one of the gods here was plaining to start to build them to sell so I got lot of ca----------- all the pic are in my alb.are of the build over 97 out the door and the god is steal trying to get his fist When I thy to show how to do glass on the cheep and 38 years of trick i get BS from god buds. and less than 7 hr of block sanding down to wet 2000 gr to pull a mold of it. 23 man ( person ) hr working time Most over think it.to many engineers

[kennyrayandersen]

Glassice,
I hadn’t seen your album before, but there were some good techniques and you’ve got much of what I was suggesting in there. Did you use 1 or 2 inch thick foam for the floor? Did you go pretty much frame-less, or something like Andrew’s light-weight frame (minimalist). Anyway – kudos, it looks like some good work and along the lines I was thinking. Do post if you ran into any show stoppers or BIG issues that you had to work around.

[glassice]

Just foam 1" in the floor the one we do now are 2" for under 4o out side day temper and off road .There a kid in sac that Just got a shell from us no foam he plaining to use EMT for the walls try to get him to post it here the fist 30 ' x 5' fish farms tanks we did with same 1 piece of No BIG issues that you had to work around I think a board 5 year old could do for $2000 are so any tear has a lot of area X 7 even use the same 1 peace of melamine when we did the 3/4 scale The Fairchild C-119 Transport Plane for a production co it has over a 1000 coats of wax been put on it and just 2 corners mess up
WoW I am cheep

[kennyrayandersen]

I think I’ll go 2 inch in the floor just because I’m not planning to have much frame structure. Everything else will just be the 1 inch. I was also thinking of 2 plies on the floor (inside and out – inside due to step loads, and outside due to FOD damage) with 1 ply everywhere else except the corners where the sides and center section come together – there I was thinking of 3 plies outer, and 2 plies inner. Also, there would probably be some local reinforcement (both plies and core) at attach points.

[glassice]

the bulkheads add a lot we use 1.5oz.
4 layers on the out side and 3 ins and 1 to 3 layers of top val
and up to 10 layers in some place and core mat and woven I make the trailers to last over 100 years you have to look out for the sun and 1 are 2 layers will die in a few years

[kennyrayandersen]

That might be a little overkill. I just spent a couple of years analyzing a cowling for a helicopter (high vibration, environmental exposure, FOD) with around 250 mph max velocity!. It was generally 2 plies on the outside (graphite) with just one ply on the inside. Of course where there are fasteners or fittings etc. (high local load introduction) the are multi-ply reinforcements as you are suggesting. I think the key, that you alluded to is to make sure it is painted well to prevent any UV damage. I would keep mine indoors anyway, and since I'm pulling behind a FIAT 500 it REALLY important for weight to keep it light. Also, I'd like to mention that one should use inserts or potting compound (epoxy with filler in it) between the face-sheets so the the core doesn't crush which will also damage the face-sheets.