Help with fiberglass seat

[paultsmith]

I am going to start to build a fiberglass seat for my xs400 but have a couple of questions.

Here is what I have so far:
Styrofoam foam for making the mold
Fiberglass matting, cloth & resin

I can not get urethane foam and am aware that applying my resin will just eat the styrofoam. Going for another foam or epoxy resin is not an option.
What should I use to coat the foam before I apply the fiberglass and resin? I heard masking tape, aluminum metal tape (used for ducts) and paper mache.

Also after I sort out a way to protect my foam I will begin laying down the fiberglass and resin. I was planning on laying down in this order:
1. Weaved fiberglass mat
2. Strands of the fiberglass fiver cloth
1. Weaved fiberglass mat

When I am laying down the fiberglass should I be using a bunch of small strips and squares or try to use as large pieces as possible?

I plan on sanding the seat smooth between layers of glass. Should I use any bondo between layers too? or just at the end?

Thanks,

 

[carey]

Plastic food wrap , garbage bag, should be a good protector for the foam, and the resin won't stick to it, or the metal tape would work too, or combination of both. About the glass / layup sequence, it really depends on the weave, and the weight (thickness) of the material as to how easy it will be to form and have stay in place unless you vacuum bag it.....and most likely if you know how to bag it and have the tools / equipment to do it you wouldn't be asking these questions. Use the largest pieces you can, but remember that fiberglass does not like to make sharp corners without leaving voids (air pockets) by just laying it down. I wouldn't waste the time sanding it smooth between layers, the only thing this will accomplish is making a lot of dust and taking a lot of time. Now if there are some areas , and there will be, that you need to get rid of, voids, overlaps, etc... then sand those areas before the next layer or so. The strength is in the glass, not the matrix....a good ratio is 60% glass, 40% resin.

Carey

 

[carey]

sorry, missed the bondo question. If you are using polyester resin, bondo is also polyester based so you could use it between coats to smooth things out if you like, but bondo will give you absolutely no strength, and does have the tendency to crack and shrink if it is put on thick. I would use it at the end, or sparingly between coats. There is a product called bondo hair that will give some strength but is also a lot harder to sand and get smooth, but is better than plain old bondo.

Carey

 

[paultsmith]

Thanks for the input.
I will make sure to take lots of photos and fire em up.

 

[JRK5892]

man after you get your shape use short strand fiberglass bondo... cover the whole thing in this... real easy to work with... sand that down then make a mixture of 5 -1 bondo to resin, add the hardenter for both... it will mix up very well, spread it on with a paint brush... when it is about 75% dry sand it with 80 grit sand paper... will gum up the sand paper so be ready to have alot ready... works great! got the trick on here... here is my seat when i was doing it

short strand bondo and a bit of sanding:

after the bondo/resin milkshake mix:
not yet final sanded... still need to fine sand and glaze then prime and paint

 

[xsthomas]

The quickest and easiest thing to use is plaster. I worked in the prosthetic industy for years, and plaster was used to cover the pores in foam to keep the resin from saturating and making the artificial limb too heavy, they need to be as light as possible. just put a thin coat on with your hands and smooth with a sanding screen, sanding screens can be found at Lowes. a good smooth coat of plaster, a few coats of varnish to seal the plaster, some spray on mold release, and go at it.. But if you really want a good saturation in your lamination, vacuum bag it.

 

[Heironymous Josch]

I am going to start to build a fiberglass seat for my xs400 but have a couple of questions.

Here is what I have so far:
Styrofoam foam for making the mold
Fiberglass matting, cloth & resin

I can not get urethane foam and am aware that applying my resin will just eat the styrofoam. Going for another foam or epoxy resin is not an option.

Going for another foam is an option. I use the ultra soft green foam for artificial plants. I've you're making a mold off the bike, I highly recommend this stuff - it's cheap, compatible with poly resins and extremely easy to work with. On the bike, these blocks are so soft, they're hard to keep tightly adhered to each other without a stable, flat base. This said, if you've already built the mold out of polystyrene, I'm sure you don't want to do it again.

What should I use to coat the foam before I apply the fiberglass and resin? I heard masking tape, aluminum metal tape (used for ducts) and paper mache.

Masking tape works well, so does plastic film like Saharan Wrap. Paper mache is a bitch, the plaster is ultra brittle and doesn't adhere to foam very well. Aluminum tape works well but will create large irregularities everywhere because it's a couple of mm's thick. If you've got your mold exactly as you want it, you can even use elmer's glue to seal it but you have to make sure and get 100% coverage and you won't be able to tool it once it's dry as it's pretty brittle. Also, correctly applied mold release wax and pva should seal the foam but you're taking a huge risk if you're not 100% certain resin isn't going to seep in anywhere.

Also after I sort out a way to protect my foam I will begin laying down the fiberglass and resin. I was planning on laying down in this order:
1. Weaved fiberglass mat
2. Strands of the fiberglass fiver cloth
1. Weaved fiberglass mat

This should provide ample strength for sure. If the seat is being made over top a positive mold, you may want to use a surface veil for your top layer - the veil makes the surface easier to tool, doesn't splinter out like fiber matting and clothes do when sanded and makes for a smooth finish.

When I am laying down the fiberglass should I be using a bunch of small strips and squares or try to use as large pieces as possible?

This is up to you. I use as many large pieces as I can. I cut newspaper to shapes that are easily shaped on the mold and overlap at all joints. Once I have the newspaper shapes, I cut the fiber from them. This process makes application easier and adds to overall strength.

I plan on sanding the seat smooth between layers of glass. Should I use any bondo between layers too? or just at the end?

I wouldn't advice either. Sanding between layers may give you a smoother final product but you're shearing glass fibers along the way, diminishing strength. The bondo will only add weight and may diminish strength as well. You want to saturate the fibers will no excess resin above or below each layer, this will give you the most strength, minimize weight and give you a relatively smooth surface. Do all your bondo on the outside. If you want a perfect outer surface, use the mold you already have to create a negative or cast and lay a gel coat and fiber into it to form your seat.

 

[HerrDeacon]

This is up to you. I use as many large pieces as I can. I cut newspaper to shapes that are easily shaped on the mold and overlap at all joints. Once I have the newspaper shapes, I cut the fiber from them. This process makes application easier and adds to overall strength.

That's a great tip.

 

[sharperdill]

I coat the foam with 5 - 10 coats of primer. NOT SPAY PRIMER. I use Zinsser fast prime 2, it comes in a blue can. This stuff is sandable and makes for a great foam sealer against the resin or gel coat.

 

[mathil]

Just a couple other things you should have on hand that haven't been mentioned...

1)Brushes
2)ACETONE
3)Plastic containers to mix resin in. (I use milk jugs with the tops cut off. Cheapest disposable containers.)
4)Not totally necessary, but I have a plethora of composites rollers to roll out bubbles and such. If I were to reccomend getting ONE kind, I would reccomend a 1" bristle roller.

 

[Jonesy]

Hey, slightly off topic, but I've been considering cafe-ing my XS400.

Do you have a build thread on here? I'd love to see some pictures.

 

[grayskull]

i saw a video on youtube .if you are cvering foam.as in your case. you use alluminum foil .cover the foam with it and then you can start glassing. the foil protects the foam. if you dont the hardner will eat the foam.I have got to do my sons gs 650 .I split his l model seat into 2 pieces.The back half has had the foam carved and sanded into a tail section. now i can put the glass to it .after that we are going to carbon fiber it.Its going to look trick..

 

[Merrickx]

I've been thinking of making a fiberglass seat for my XS 400 also. Let me know how it goes?

Also, you wouldn't happen to have stumbled upon any kind of manx-ish tank that fits your XS 400 have you?