Fabricating a fibreglass seat pan 101

11855 Views 17 Replies 4 Participants Last post by hondamonsta, Jun 26, 2011

66Sprint

Discussion Starter · Dec 9, 2008 (Edited)

This topic will discuss some of the basics involved in building a glass seat pan. For those who wish to follow step by step, I'll be posting a "bill of materials" (by editing this post)... Several methods of forming the "mold" will be discussed, but there ARE other ways.... I'll take a lot of pics, and try to keep the "stages" current with my progress....
Steve

The first thing you will need to do is picture the desired shape in your head, and decide what method of forming the "mold" will work best for you.....
Some of the options.......
For my first-ever pan, I literally threw the glass on a fat rear tire (to get the correct curvature)... Then, I sectioned in strips to widen it and lengthen it and flat panels I'd thrown on a trash bag taped to the floor... I use this as the mold for the tail section, and throw the seat area on the actual frame to get an exact fit (you cover the frame with PVC tape, wax paper, aluminum foil, cardboard, or similar , anything that will "sculpt" to a tight fit... This will become clear as we proceed...) The pics below shows the "blank" tailpiece I made as discribed above, and trimmed for placement on a 450.

Another option is to cover the area on the bike, spray on "good stuff" (styrofoam in a can) and carve/sand that after it hardens.....
Papier-mache can be built-up and smoothed, balsa can be carved, cardboard strips can be cut and glued together, a balloon can be used, plaster can be built-up and carved, almost any method that yields the shape you want can be used....A friend threw glass over a football and got a unique and good looking tailpiece.....
For this one, I am going to attempt to carve hobby store styrofoam blocks and sheet (glued together) to get my mold...... This is mostly because the frame is very narrow, and will require some finessing to get the result I want....
Here we go!......

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66Sprint

Discussion Starter · #2 · Dec 9, 2008

4

For fun, I placed the 450 blank tailpiece on the 90 just to get an idea of how a tail section would look...

Its too long and wide, but nothing that couldn't be fixed by cutting it back down, but I decided a more vintage style would be appropriate for the effect I sought.... Something more like this....

As you can see in the following pix, supporting the pan on the frame will also be an important consideration, and I'll probably have to make it thicker/stronger due to lack of side support...

The 8"x8"x8" styrofoam cube will be carved/fitted as the tail, and the sheets (visable behind the bike) will be used to "build" the cushioned section....

My next post will show Part 1.... shaping/fitting the tailpiece:

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66Sprint

Discussion Starter · #3 · Dec 9, 2008

8

Part 1 : shaping the tailpiece....

Once you have decided which method you'll use to build the pattern mold, it's pretty much a straightforward shot....
Here's some pix of my steps using the "hard cell" styrofoam, and gradually shaping/fitting it....
The design of my frame made i necessary to "fit" the underside of the tailpiece to the fender.... Those of you with "conventional" frames might be able to skip a few steps....
Here are my preliminary guidelines marked...

Once I removed that channel the cube rests tightly to the frame....

and I begin "eyeballing" the desired curvatures and marking them:

Using a handsaw and a rasp, I "rough-out" the shape.....

Once it has been "roughed from all angles, I trial fit for a "look"

Now I hand sand it closer to the final shape, and here's the result (so far)...I'll sleep on the "look" and perhaps alter it slightly before calling it done....

My first impression is "it's close", but we'll see tomorrow....

EDIT: Well, I like the shape, but it's not quite right on this bike.... I've decided to "echo" the shape of the fuel tank a little better, and to reduce the size slightly overall (it somehow looks to "bulky" on that narrow frame). Pix when I'm there....Steve

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66Sprint

Discussion Starter · #4 · Dec 11, 2008

3

OK... I narrowed and lowered the tail and got it to somewhat "echo" the shape of the existing fuel tank and fender cross-sections..... I think the slightly smaller tail "suits" the little bike better..... because I'm so close for the "behind" shot, the back end looks wider than it is...

side view....

Top view....

Tomorrow a final fine sand and It'll be ready for glass!... Steve

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66Sprint

Discussion Starter · #5 · Dec 12, 2008

OK then.... Here is what you'll need before you actually "lay-in" the glass:
fibreglass resin
liquid hardener (MEK)
Glass cloth or mat (I use both)
latex gloves, disposable, several pairs ( I get a whole box )
respirator (paper mask will do)
Mixing pan (I line mine with aluminum foil to make for easy clean-up)
protection for the work area (a plastic "drop" of some sort)
Masking and PVC tape
Aluminum foil

The following discription will be how I do it, not necessarily the only or best way, but it works for me..... LOL.... Steve

I cover my "shape" with PVC tape to expedite "release" (and save the foam mold)... If you are using papier mache', wood, or layered cardboard, this is a necessity, rather than an option.

To be continued...

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66Sprint

Discussion Starter · #6 · Dec 14, 2008

4

Progress so far:........ I have "thrown" the first layer of glass onto the form. Since this particular bike requires additional bracing underneath, and a "bottom" to the cowl area, I'm fabricating sections, which will be trimmed and "glassed together" to achieve the result I want....

IF YOUR bike has a wide or two-rail frame, and you intend to leave the bottom open, you could have simply thrown the entire first layer (glass cloth) directly over the pattern (mold), let it "tack" for a half hour, and have already applied the second outer layer (also glass cloth) and it would now be drying overnight....
Tomorrow, you could add a couple layers of glass mat inside the hardened form, let it cure, trim and be sanding it...
It will several more steps for me to get that far, but glassing , while messy, is fairly easy......
Here's what I've done so far:
(1) cover the foam mold with Saran wrap held tightly pulled (as smooth as possible) with PVC tape

(2) "laid" the first layer of resin soaked glass cloth, allowed it to "set" for a half hour, marked the intended edges with a silver Sharpie, gently lifted it from the mold, and trimmed the semi-hard glass with scissors.....

The glass will now be placed back on the mold to fully harden..... (because I need the mold again to finish the "bottom") If you are having a fully open underside, you can just wait a half hour, add a second layer, and allow it to cure in place......

Here's mine drying overnight on the form...(Notice the saran protecting the fender)

Here's another angle.....

Tomorrow, I'll build the "bridge" that will support and reinforce the seat pan........
STAY TUNED!....... :lol: Steve

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66Sprint

Discussion Starter · #7 · Jan 11, 2009

Now that I have a computer again, I'll get back to this topic...... I have to upload a BUNCH of pics to Photobucket, and I'll start this back-up Sunday....

66Sprint

Discussion Starter · #8 · Jan 11, 2009

7

Remember... Your seats will be LOTS easier to fabricate.... The multitude of steps shown below is to fit a pan to my single support frame..... Here we go.....

I left off with fabricating a "bridge" for the narrow frame....Essentially, I just wanted the seat to bear on the "flats" of the stamping, rather than on the welded seam.......

I made up a foam blank that fit the frame, and glassed it up.......Later, I'll add it to the underside of the pan .....

Same steps as before..... form glass cloth to the mold, then add an internal layer using mat to strengthen it.....

Next, I threw a blank for the back flat on a piece of aluminum foil, and glassed the rough seat area on foil covered foam

The foil was peeled, and the pieces were trimmed and fitted for looks....

The "bridge" was added.....

More trimming, and fitting, then taped and bonded together.....the undersides of the joints will get two strips of mat for strength....

Now, it's just "painting' on some coats of resin to smooth the imperfections, sanding, Glazing putty or bondo for dips and waves in critical areas, and painting the primer and color coats...... I almost continuously recheck fit and "adjust" as necessary.......
Pics of the results in next post..... Steve

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66Sprint

Discussion Starter · #9 · Jan 11, 2009

3

Here's the pix of the result.....

It still needs color sanded and cleared, but not too bad for about half what a purchased one would cost, AND, it's an EXACT, custom fit!....
I'll add a pic once it's upholstered........Steve

ANY QUESTIONS?........

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66Sprint

Discussion Starter · #10 · Jan 12, 2009

Since I like my result, I'll simply cover it in PVC tape and "throw" an overlay duplicate. The duplicate will be slightly larger (about 1/16th in in every direction) and have an open bottom, but will provide an easy "cut-modify-paste" basis for the next one...... Materials cost on the duplicates are only about $15 each, and the time savings is HUGE!........

Any questions or comments?.....Now is the time!...

...Steve

bill440cars

· #11 · Jan 12, 2009

That is Truly an AWESOME job there Steve!

So, when do you start production?

Just kidding, GREAT JOB though!

66Sprint

Discussion Starter · #12 · Jan 12, 2009

2

Thanks Bill!... I could make up some "extra" copies for members with smaller bikes.... I'll trial fit it on a 175 frame today (I think that's about the biggest bike this cowling would fit)...I can throw some 450 size copies as well if there's enough interest....

I think it's getting close to the vintage cafe' look......Maybe with a bit of British influence too....In any case, I like the "flow" it gives to the back of the bike.....

I'll add a pic of the seat on the 175 tonight...... :lol: Steve

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66Sprint

Discussion Starter · #13 · Jan 13, 2009

No Pix.... It was too narrow for the 175 frame by a good 5/8 to 3/4 inch on each side (by eyeball measurements). but I like for the cowl to cover to the outsides of the top shock mounts..... No problem though... It can either mount behind the shocks, or I can simply cut a copy in half down the frame centerline and graft in an 1&1/2" widening strip, and blend it in....Spacing (length) from tank to shock tops was spot-on, and the side view was good as well..... I think it would fit right on the 100/125 models, But I don't have a frame to trial fit it....

66Sprint

Discussion Starter · #14 · Jan 24, 2009

Update.... The seat went for upholstery today....Will post pics as soon as I get it back....

bill440cars

· #15 · Jan 24, 2009

Steve, I have to admit that I was skeptical about how this bike could turn into a decent build. :| And, once again, you are making that sucker "Strut It's Stiff!"

Carry on there Guy!

Take care, Bill

66Sprint

Discussion Starter · #16 · Jan 25, 2009

Thanks Bill, I'm working on the low-to-the-tire fibreglass front fender while I wait for the upholstery....and still considering what to do about fabricating a "sporty" looking exhaust that will perform decently...the stock muffler is both ugly (rusted) and proportionally huge.....Plus, I'd like to boost the top speed up from 55 to nearer 70/75 MPH even though the intended riding path (The Blue Ridge Parkway) has a 45 MPH speed limit....LOL.... Don't want it wound-up like a watch spring ALL the time.... Steve

Znabb

· #17 · Nov 23, 2010

Wow, great topic Steve!

hondamonsta

· #18 · Jun 26, 2011

The seat you fabricated came out perfect. You mentioned in the post that you may mold something for the 450 frame. Did you ever get around to that? All I need is a seat for my build and I'm without a workshop right now.

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