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Author Topic: In the midst of making a fibreglass seat. Need advice. What would you guys do?  (Read 4171 times)

Offline Tune-A-Fish©

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Everyone always seems to be against this way, my preferred method.

Step 1: Make plug, the seat you are making in this instance. Get it perfect.

Step 2: Make mold.

Step 3: Wetsand mold, apply release, gel, lay glass.

Step 4: Pop perfect (as perfect as your plug was anyhow) part out of mold. Trim, lightly sand the surface to rough it up, primer, paint, clear, install.

That's why I bought the pans from you for the next two already  ;D
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Offline J-Rod10

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Much appreciated Tune.

Online stroker crazy

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Everyone always seems to be against this way, my preferred method.

Step 1: Make plug, the seat you are making in this instance. Get it perfect.

Step 2: Make mold.

Step 3: Wetsand mold, apply release, gel, lay glass.

Step 4: Pop perfect (as perfect as your plug was anyhow) part out of mold. Trim, lightly sand the surface to rough it up, primer, paint, clear, install.

Listen to the man!

Other methods may get a result, but they are hit-and-miss.

Crazy
“Ride like the Wind” W.H.

Offline RoyalRider

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  • 2010 Royal Enfield Bullet 500 - 1982 Honda CB125s
jpmobius Thanks for the advice that's a lot of great info! yeah I don't plan to deviate too much from the mix but I might make a few mini-batches to see what happens before I put it on the fibreglass.

Tune-A-Fish I like how your seat turned out it looks great.

J-Rod10 Hmmm that might be an option but I just bought a big sheet of plywood last night to make the shape. If I screw up the job again this weekend I will consider using the rest of the wood to make a box for a mould.


Offline J-Rod10

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Optimal temp of poly is 78°. Mixed with the proper amount of MEKP, you have right about 20 minutes before it starts to harden.

Buy a $2.50 pack of waxed cups at Wal-Mart, and mix enough to use in 15 minutes at a time. I typically mix 9oz at a time, two cups makes a seat. If it's warmer, it'll harden quicker, colder, slower. Slower isn't an issue. Quicker, mix less resin at a time.

Online pacomotorstuff

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What J-Rod said about nice master, nice part.
Black seat is the master, white seat is a production part.  A lot of my racing (and street) customers run the as-produced finish on my parts and just add stripes, stickers or their racing numbers.
The seat in the photos has been fitted to a CB125 single about the same vintage as yours and a Honda SS125 twin (from the '60's).
If you can get to Toronto, try Composites Canada on Meyerside for your supplies -  I've dealt with them since the '80's.
Because I use laminating, rather than finishing, ester-based resins, I don't use waxed paper cups (styrene dissolves the wax) and any aircraft company I've worked for (6), waxed containers of any sort have been forbidden for mixing resin - but if you use a finishing resin which already has a bit of dissolved paraffin (wax) in it, it wouldn't matter.
I also use PVA mould release on the mould master after lots of waxing and also on the mould (again, after lots of waxing) for the first couple of pulls to make certain everything releases okay.
We build 26 different seats (and 80 different parts in total) and except for the odd prototype or aircraft reconfiguration project, female tools (moulds) are our preference.
A lot of good info has been posted already and I hope my comments help.
Pat

Offline RoyalRider

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  • 2010 Royal Enfield Bullet 500 - 1982 Honda CB125s
Thank you to all those who have been replying to the thread it has been helpful. For the record I don't use wax cups because the tin can said not to but also for the record I used wax cups back when I was fibreglassing boats in 07-08 and nothing bad happened. Still that was working on school boats that we didn't care if they sunk or crashed...wouldn't use wax cups on a project I care about.

Okay so here's an update :

Basically I wasted a small chunk of money on plywood because I quickly realized that my jigsaw is shitty and I am even shittier at cutting wood. I don't know what I was thinking...making 3D shapes with wood is no simple task at least for me. Here's a picture of me realizing I can't cut a straight line to save my life :

So instead what I did was try the floral foam stuff like the guy from Dime City Cycles used in his seat construction video.

Here are some photos of that process :

Using bristle board for the sides to help shape the floral foam :



I went with HVAC duct tape to cover the whole thing (note that I kept the bristle board because the floral foam is super brittle and I was afraid that pressure when installing pieces of fibreglass would deform it) :


Waxed it with turtle wax :

And I only had time to put down one crappy layer of fibreglass matt. I am happy with the result because as I was laying it I was getting some bubbles and I ended up using a putty scraper thing to smoothen the sides. It looked like it was working but sometimes it felt like I was about to rip off all the fibres...in the end it is much better than previous attempts :




Note that it is not fully covered. I had a hard time with the corners so I thought it would be best to do it in pieces and that it might make it harder if there are some overlapping pieces. This week I plan to finish putting on this layer and then covering it again with another layer of matt before finishing it off with cloth.

It's going well though! I am stoked :)
« Last Edit: Sep 28, 2015, 21:24:03 by RoyalRider »

Online pacomotorstuff

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I know what you mean about florist's foam being so fragile, so carefully brush a coat or 2 of resin on the foam and let it cure - helps a lot but still pretty fragile.
Packing ("Scotch") 2 inch wide tape works great over a master to stop the resin from sticking to it.
For your next project (and I know you couldn't for your seat because of the foamboard bracing), radius all of the shape edges on your master - at least 1/4 inch - or more if it fits into your design.  It allows the fiberglass to drape a lot better around the corners and makes a far stronger part to boot.  Make paper patterns first for the proposed lay up plies, to see where you have to put cuts (darts) in the reinforcement.
In those infrequent cases where I'm building something on a male tool - which is what you're doing right now and what a customer wants me to do tomorrow after I said I wasn't going to them anymore LOL - I just use glass cloth, not mat, as I find it drapes a lot easier, doesn't lump up and requires less final sanding.  Usually I use 3733 weave 6 ounce cloth, each ply laid on and tailored a little differently.  I try to use peel ply at the end of the lay up regardless of whether it's epoxy or polyester resin, but can't always do it.  To fill in the weave pattern, I mix my own filler and give the part a good sanding before it gets primed and painted.
Don't give up; you're making some real progress there and will have a great, one of a kind seat when you're done.
Pat


















Offline RoyalRider

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  • 2010 Royal Enfield Bullet 500 - 1982 Honda CB125s
Thanks for the kind words and info Pat! I appreciate it a lot.

Yeah I know I said another layer of mat but...I hate the stuff, it's really hard to work with. Last time I used the cloth it worked fine with the edges it was just that I didn't think of imbibing it completely before laying it down. The cloth is also extremely tough (my first attempt at a seat was made out of just 2 layers of cloth was able to withstand a full on hammer blow with all my strength and also didn't crack when I stood on top of it and jumped up and down)

I think I will just complete this layer of mat and then do 2 layers of the cloth since it's much easier to work with. I also found it didn't shrink as much once it began curing...with the mat I have to have a lot of excess draped down on the sides or else it shrinks and pulls itself off the top.
« Last Edit: Sep 29, 2015, 14:48:11 by RoyalRider »

Offline jpmobius

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You've got some really sharp corners that make it difficult to force the glass around and stay tight before the resin cures.  I like very light weight cloth over matt because it is less messy and for me easier to make follow complex shapes - plus it is easier to keep the weight down on the finished part.  I like to wet out my layers first before  lay them on the part - easier to get complete saturation for me.  Usually I spend some time planning out what I want to do and cut up all the pieces first and then set them aside in order of application.  Speeds things along and lets me get everything layed up before the resin kicks - though I invariably use epoxy which allows a bit more time to work.  For a part like yours with the sharp corners, you might want to take a plastic garbage bag and stretch it over your part on top of your still wet layup.  You can simply hold it tight until the resin kicks enough to bind everything together.  Once it sets hard, you can just mow it off with some #36 grit sandpaper.  Not exactly like vacuum bagging, but since you will be doing a lot of sanding anyway to get it smooth and straight, it isn't much extra work. 

I like florists foam.  You can buy urethane foam in higher densities, but the really nice stuff is expensive.  You can buy big thick sheets of lower density - more like florists foam but finer grain - from an industrial insulation supplier for much more reasonable money.  Florists foam is really fragile, so it takes a little getting used to, but you can capitalize on its frailty.  For one, it is super easy to shape with #36 grit paper on a sanding block, and if you are willing to be gentle you can make extremely accurate and refined shapes very quickly and finish up with #80 - #120 grit paper.  Once you get that first layer of glass on it, you can treat it pretty roughly.  The second thing is that because it IS so fragile, you can hollow out a part very easily after it is done.  Or, if needed add some more glass to the inside to build up some strength and not change the outside shape.  I made this 2 into 1 manifold out of foam, glassed over it and dug out the foam with a screwdriver after it set  up.  Carved up the foam original with a hack saw blade and some sandpaper and just kept test fitting it to the bike.  It was a little tricky to not damage it, but had it finished except for paint in a mornings work.  The inside was quite smooth once I scrapped out the foam, but I sanded it and it is just as smooth inside as it is on the outside.  I used lots of very small patches of super light matt the size of a dime - really just scraps for the layups, and there is probably 2+ layers.  Turned out really strong and durable.  Wish I had a better pic of it off the bike.
« Last Edit: Oct 06, 2015, 01:23:22 by jpmobius »
Mobius


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