Fiberglass over foam construction.

[vwbeamer]

I plan on using the same fiberglass over foam construction method to build my teardrop that coal burner used.. It will be 4 X8 and 44 inches high.

My plan is to build a pretty typical tear drop, less galley out of foam glued together, and cover it with glass mat and resin. I realize will be difficult to bend the ridged foam for the curved top. I have a plan to cut the foam in the rounded teardrop shape. The top foam will be about 2 inches thick and made up of several foam sheets glued together and cut to profile with a heated wire.

I plan to use a hardwood wooden brace glassed across the front floor where the tear drop body meets the tongue, and also some 1X2 bracing glassed in around the door and windows. The rest of the body will be foam and fiberglass to keep weight down.

Once the outside is done. ( less paint and details) I will turn it over and install interior, electrical, and simple cabinets. I then plan on attaching a floor fiberglass and foam floor brace horizontally with some simple 1 X2 wood strapping. it will then rest on a light weight frame like Andrew has shown us. indeed it will be much like the PICO plans Andrew has shared with us, but will use the fiberglass over foam construction. ( Thanks Andrew

What weight and many layers of glass do you think I will need? any pointers or tips? Think this can reasonably be done?

I plan to pull this behind my 2010 TDI Jetta at 80-85 mph, and i want it light and low.


Thanks..

[Ageless]

Remove the plastic sheeting from one side of the foam and it will bend easier.

Do you have a flat floor to work on? If so; lay down and smooth out a plastic sheet. Once you lay the 'glass' on the sidewalls; lay it down and apply weights ( I use 5 gal. buckets of water over a sheet of plywood)

When the resin cures, you will have a very smooth surface.

Do the other side the same way; you will get a very light but very strong and rigid panel.

[vwbeamer]

Maybe i could make a buck to bend the top over? , might be easier than trying to cut the foam shape. I need to pick some up and experiment.

[Ageless]

You could make a form form the top raduis. Apply F/G to the inside first, Remove from the form and mount to sidewalls, then apply outer skin.

[afreegreek]

you want to make a curved panel out of glass and foam I's suggest making a form out of two curved strips of plywood and some stringers. make the form to the curve of the outer line of your shape then get a sheet of GLOSS plastic laminate and apply it to the inside curve of the form. double sided tape will do. apply a few coats of parting wax to the plastic laminate. now you can go ahead and apply your first coat of resin or GELCOAT and start laying up the glass and foam. once you have built up your schedule of glass you can apply the foam core.

for making the foam conform to the curve you can lust cut a series of kerfs or cut the foam into narrow strips with a slight bevel on them. one bevel cut, flip the sheet over cut the second strip and so on. the foam does not need to fit together exactly as long as there's no more than a 16th inch gap you're OK. in fact a little gap will allow the resin to bridge the inner schedule of glass to the outer.. something that is done purposely in some applications..

now use thickened resin to apply the foam to your layup. once that starts to set and won't squirm around on you it's time to do your next glass schedule. or you can wait a little longer and sculpt the foam to shape. like make it a smooth curve. one of those surforms works well shaping the foam, so does 60 grit paper

your part will spring a little when you pull it off the mould but thats why you did this part first. now you can make the sides to this shape and have a perfect fit.

the plastic on the floor mentioned above will also work but you must be sure the plastic sheet you lay will not be eaten by the resin. polyester and vinylester resins contain styrene and will dissolve many types of plastic. epoxy is fine and will not eat plastic. but hey.. you still have that sheet of plastic laminate to layup your flat panels on.

using plastic laminate as a form and laying up your panels from the outside in you'll end up with a perfect finish on the exterior of the panel. all you need to do is give it a little rub with 320 grit paper and you'r ready for paint. however, I'd opt for the gelcoat.

*** if you are going to use polyester or vinylester resin, save yourself some headache and make sure you do your research on when and where you want "WAXED" and "UNWAXED" resin.. or gelcoat..***

[vwbeamer]

I was thinking of making a plug, and then a full size mold, but it seemed like a lot of work.

Making a mold for just the top might be doable.

The front of the trailer might look good with a traditional aluminium skin

Thanks for the ideas.

[angib]

If I was going to do this (and I wouldn't - I don't see the weight saving is worth the huge effort), I would:

- Make myself a flat mould (a sheet of scrap kitchen laminate over cheap ply or MDF is the economical choice) on which I can layup things.

- Lay up a flat double-skin sheet for the floor.

- Lay up flat double-skin sheets for the two sidewalls - these will start with the outer skin so that is perfectly smooth and needs no further prep work - then add the foam and inner skin, all downhand on the mould.

- Lay up a flat single-skin sheet for the roof - the single skin will be the inside of the roof. Thickness will be much, much less than 2" - 3/8" to 1/2" is enough (we used to make big yacht cockpit floors 6'x15' with 5/8" foam).

- Bond the sidewalls to the floor.

- Wrap the roof panel around the edge of the sidewalls and bond in place - because it doesn't have a second skin, it will bend fairly easily, though only round big radiuses - tight radiuses are out.

- Laminate the second layer on the roof and make the join with the sidewalls.

- Spend hundreds and hundreds of hours getting the roof flat and smooth, plus some more hundreds of hours repairing the sidewalls where the roof-sidewall joint spoilt the nice finish.

This only involves hundreds and hundreds of hours - what you've proposed sounds more like thousands and thousands....

Oh, and did I mention the hundreds and hundreds of dollars of structural foam to make the core of the sandwich? Of course you could use insulation foam but that will be so weak that you will have to make each skin so thick that they could get by on their own without the foam.

Not too negative, I hope......

Andrew

[Ageless]

IMPORTANT!!

If you use a material like laminate for the mold; give it a coat of paste wax (simonize) This will keep the resin from bonding to the laminate. We made 1000s of glass molds and that's how we release it from the plug.

[vwbeamer]

No, not at all. I have great respect for you ideas.

I have given a great deaal of thought to this since posting, and agree with you.

I'm still thinking of making a mold for the top and molding a fiberglass top, but with a gel coat, much like a boat would be made. maybe with a plywood core of some type.

If I was going to do this (and I wouldn't - I don't see the weight saving is worth the huge effort), I would:

- Make myself a flat mould (a sheet of scrap kitchen laminate over cheap ply or MDF is the economical choice) on which I can layup things.

- Lay up a flat double-skin sheet for the floor.

- Lay up flat double-skin sheets for the two sidewalls - these will start with the outer skin so that is perfectly smooth and needs no further prep work - then add the foam and inner skin, all downhand on the mould.

- Lay up a flat single-skin sheet for the roof - the single skin will be the inside of the roof. Thickness will be much, much less than 2" - 3/8" to 1/2" is enough (we used to make big yacht cockpit floors 6'x15' with 5/8" foam).

- Bond the sidewalls to the floor.

- Wrap the roof panel around the edge of the sidewalls and bond in place - because it doesn't have a second skin, it will bend fairly easily, though only round big radiuses - tight radiuses are out.

- Laminate the second layer on the roof and make the join with the sidewalls.

- Spend hundreds and hundreds of hours getting the roof flat and smooth, plus some more hundreds of hours repairing the sidewalls where the roof-sidewall joint spoilt the nice finish.

This only involves hundreds and hundreds of hours - what you've proposed sounds more like thousands and thousands....

Oh, and did I mention the hundreds and hundreds of dollars of structural foam to make the core of the sandwich? Of course you could use insulation foam but that will be so weak that you will have to make each skin so thick that they could get by on their own without the foam.

Not too negative, I hope......

Andrew

[vwbeamer]

thanks, you input has me moving towards and metal sidewall with a fiberglass top.

IMPORTANT!!

If you use a material like laminate for the mold; give it a coat of paste wax (simonize) This will keep the resin from bonding to the laminate. We made 1000s of glass molds and that's how we release it from the plug.

[McBrew]

I plan to pull this behind my 2010 TDI Jetta at 80-85 mph, and i want it light and low.

Don't forget, your Jetta TDI is rated to tow 3,270 pounds or 3,300 pounds (depending on whether you have the 6-speed manual or DSG, respectively). Of course, I understand why you might want to keep it light -- fuel economy, towing in hilly country, etc. Just wanted to mention that.

Glass over foam construction has been floating around in my head for a while... I'll have to get the first tear finished before I think too hard about a whole new construction technique... but I'll keep reading!

[Ageless]

When I get into the 'decor' panels on the Palace; I will be making up a 4' mandrel and bagging the panels. While it isn't a foam core; I'll need to take pix of the process. I have a pump to pull a vacuum so it will be a fun project

[afreegreek]

When I get into the 'decor' panels on the Palace; I will be making up a 4' mandrel and bagging the panels. While it isn't a foam core; I'll need to take pix of the process. I have a pump to pull a vacuum so it will be a fun project

careful!! vacuum bagging is highly addictive. next thing you know you'll be doing resin infusions..

[BigAl]

For your curved foam roof have you thought about the bead and cove technique used by boat builders to get curves from flat foam?

You could cut those using a hot ni-chrome wire, but please be careful, pink foam insulation produces some nasty vapours.

[DasBaldGuy]

This is an awesome idea....go for it....I'd love to see the build thread!

I plan to use fibreglass on my Tear (as I have much experience building speaker boxes and other projects with it). Great stuff!