Fiberglass "Cafe" Seat (need some help!)

RONNOC206

I am working on a seat for my 78' cb400.
Started with a rusty seat pan i bought off Ebay wanted the latches and being able to lock the seat on.
Cut away some metal and did some bondo work to improve the profile for the glass.
Now it already weighs more than the original seat, oh well.
I'm using styrofoam for the tail and wondering if the epoxy resin will eat right through it, if so whats a good way to protect the foam?
Also can I sand and prime right on the fiberglass or do I need to buy more bondo... Shocked

If anyone can share thier own experiances with fiberglass or even post pictures it would help a ton!

Thanks, Connor

mixer · Posted: Sun Apr 17, 2011 7:57 am Post subject:

Styrofoam will get destroyed QUICK by epoxy, the easiest way to protect it is (are you ready for this?) BONDO! a thin layer will make it easier to shape, give it epoxy resistance and be able to be removed after a few coats of fiberglass harden (ok you could chip it out after one)

you will need a bit of bondo/spot putty on TOP of the glass to make it perfectly smooth since youre using the foam on the inside to build a shape. needs to be primed AND painted before you can use it.

Link to cafe hump this has a few good pics as to how to make the mold about half way down the page

fiberglass seat pan this is a link to a step by step how to make a custom fitted seat pan.

youll probably have to do a combination of both, lay the pan, make your shell, mold in plaster, make the seat by first laying the outer shell in glass in the mold then molding in the pan if you have to have the locks and hinges working.

otherwise just follow the kind of instructions for the cafe racer seat and call it a day.
PURE fiberglass can be light, a hybrid wont be, and it doubtfully will be as strong where the hump meets the seat pan.

Good luck and have fun! post pics of the finished results!

dkrager · Posted: Sun Apr 17, 2011 1:54 pm Post subject:

Actually Styrofoam will not get destroyed by epoxy resin. I used to use it all the time as molds for R/c Aircraft fuselages and then burn the foam out with acetone once I had enough layers of glass built up. It's also the material of choice for vacuum bagging wings and used as surfboard blanks. It's the polyester resin that will do a number on foam if I am not mistaken.

Cheers,

Dave

dkrager · Posted: Sun Apr 17, 2011 10:56 pm Post subject:

Oh, BTW a good source for epoxy is your local hobby shop they sell a laminating type resin in huge bottles that is especially designed for doing composite work. Itâ€™s thinner so you can brush it on and is the slow cure variety that will give you a really tough part that wonâ€™t melt in the sun. They will also have glass in a couple of different flavors.

Iâ€™m just making mention of the hobby shops because if you are only making small parts itâ€™s a good source for materials without having a bunch of leftovers that you may never use.

But nah, epoxy is absolutely safe for foam. I have been using white foam as molds for small parts for years. Only tips I can give is go easy when carving your mold. Foam is really fragile so itâ€™s really easy to take big chunks out of it so use low abrasives. When you lay your glass only put enough resin on so that the glass goes clear and no more. You donâ€™t want bubbles or pools between the layers so keep it as dry as possible but saturated. Once you put your layer of resin on take a paper towel and lightly wipe off any excess resin. You should be able to see the weave. This also helps bond the layer of glass down to the next. Once the epoxy sets, lightly sand and then do the next layer. This will get you a very strong and light part.

Anyway once you are satisfied that you have enough layers of glass built up then brush the epoxy on liberally like you are painting the piece. Then let it setup and sand. Then do it again and sand and probably again. LOL

Itâ€™s sort of labor intensive but yea, foam and epoxy are the materials of choice when it comes to one shot molds.

Cheers,

Dave

RONNOC206 · Posted: Mon Apr 18, 2011 1:51 am Post subject:

Dave, thanks for the good tips. I already went to my local marine supply for the fiberglass and epoxy resin the brand is West Systems and chose to go with the slow hardener. May have gotten a bit more epoxy than needed but wanted to be safe. The fiberglass is fine inter woven mat and some the kind with fibers going every which way, i was thinking to cut into strips for the tricky areas.

Question. For putting a layer of epoxy on after and sanding is this just to make it smoother or stronger?

As far as shaping the foam I've been using an electric palm sander with coarse paper, its been working like a charm. I'll get some pictures up soon of the progress

dkrager · Posted: Mon Apr 18, 2011 10:09 pm Post subject:

The last layers of epoxy resin give you your finish coat. Itâ€™s mostly for cosmetic reasons but does add to the stiffness of the piece. Yes, you will have to cut the glass down to smaller sizes for difficult surfaces just try and overlap the joints cleanly and grind off the joints cleanly between layers.

The thing is, donâ€™t get in a rush. Glass is one of those things like paint where attention to detail can make or break it. Cool

Cheers,

Dave

JimMc · Posted: Mon Apr 18, 2011 11:28 pm Post subject:

You can't bondo over rust. Eventually it will crack.

holysmokes · Posted: Tue Apr 19, 2011 7:56 am Post subject:

i have a good seat pan and foam..with original honda cover on it..i got it when i bought a load of 400 450 hondas

you can pm me if you want to buy or not

RONNOC206 · Posted: Tue Apr 19, 2011 11:49 pm Post subject:

I grinded a good amount of rust away where I laid the bondo.
Thanks holysmokes but i kept the stock seat intact.

Thanks again Dave for the tips definitely using them and taking my time on the fiberglass process.

Has anyone heard of running pods on this bike or is that a no-no. I know your not supposed to tinker with these but they slapped on so much emissions stuff to hold them back could it increase the HP if done right? Is there a re-jet kit for these?

Here's the current stage of the foam piece. I may make the back slope slightly more dramatic. The tanks have a spine on the top that fades toward the end and so I continued the effect on the foam. Putting a 50's style pontiac tail light on the back.

RONNOC206 · Posted: Tue Jun 14, 2011 9:51 pm Post subject:

Update on my seat, actually just finshed and got the pad on today!

RONNOC206 · Posted: Tue Jun 14, 2011 9:53 pm Post subject:

Thinking of repainting everything.. but for now, FIN!!!!

iatrucker · Posted: Fri Jun 17, 2011 4:53 am Post subject:

Lovin the little bit of raised part on the top.