CB450 Fiberglass Seat Build

Hi everyone,

Well I'm very close to starting a "Big Arse Project" thread for my CB450 build, but before getting into that, I thought I'd do a write-up on my seat build for the project.

The materials are all about the same as I used on my tank, so refer to http://dotheton.com/index.php?topic=6339.0 for that.

First step, of course, was to grind all of the original seat mounting tabs off of the frame:


I'm going to keep the stock rear fender, incorporate the brake light into the seat and mount the battery and electronics under the seat cowl, so I came up with a battery tray that will mount to the rear frame bow and and the brake light mounting holes in the fender.

I made a cardboard mock-up of the battery I planned to buy for sizing:


I bridged the area between the frame bow and brake light mounting with cardboard and covered it with tape:




I waxed the taped form and applied about four layers of fiberglass and epoxy:


After everything cured, I removed all the tape, repositioned the tray on the frame and drilled the mounting holes:


Next the tray was marked and trimmed to the final shape:




Later on I'll lay up a fiberglass battery box that will bond to the top of the tray.

CC

The battery box was started by cutting out a block of styrofoam about 1/4" bigger than the battery all around and rounding over the corners:


Then about four layers of fiberglass and epoxy were applied:


When the epoxy cured the box was sanded and trimmed and all of the styrofoam was cleaned out:


Leaving the semi-finished box:


The box will be bonded to the top of the battery tray and assorted brackets will be bonded to the box for solenoid, rectifier, regulator and hold down strap attachment.

CC

Alright! Another installment of "How To Do Your Own Fiberglass the Right Way".

The black stuff looks like CF and not glass.

my guess is that you are wetting out your glass before placing it. do you ahve any pics of this? do you use a brush or a squeegee? you are not worried about heat and the fiberglass? looks real pro-like. cant wait to see the finished seat

I wish I could be as neat as that when I do it. Very impressive work. Very professional.

Did you tint the resin to get it black, looks very cool.

Well done mate you're a credit to the art.

Rod from OZ 8)

Flugtechnik said:

The black stuff looks like CF and not glass.

Click to expand...

The color is from the resin not the fabric. One of the great things about epoxy is it's long shelf life. Although it retains it's structural properties, it does tend to discolor over the years. The resin I used for the battery tray was left over from a project I did about 15 years ago.

CC

dcmspikes said:

my guess is that you are wetting out your glass before placing it. do you ahve any pics of this? do you use a brush or a squeegee? you are not worried about heat and the fiberglass? looks real pro-like. cant wait to see the finished seat

Click to expand...

I'm actually wetting the fabric in place on the mold. I use cheap 2 inch "chip" brushes from Harbor Freight, cut the bristles back to about 1" long and use a "dabbing" motion rather than a brushing motion to apply the resin. I think this technique is refered to as "stippling" and allows the use of minimun resin and also reduces the displacement of the fibers in the cloth.

I don't think things will get hot enough near the glass to worry about (at least I hope not).

CC

Thanks for the kind words everyone.

I'll try to post some more tomorrow, but I worked a long shift last night and now its time for bed.

CC

dcmspikes said:

my guess is that you are wetting out your glass before placing it. do you ahve any pics of this? do you use a brush or a squeegee? you are not worried about heat and the fiberglass? looks real pro-like. cant wait to see the finished seat

Click to expand...

I'll go a little off topic here to add something to my previous response. I built a license plate holder using a technique for wetting out the glass before placing it. This works really well for simple shapes with few compound curves. I don't have many good pix but you should get the idea.

Use some fairly heavy transparent visqueen from the hardware store to make an envelope to sandwich the lay up in. Cut out your glass to shape and wet out the layers one at a time between the sheets of visqueen. Working on the outside of the visqueen envelope squeege out the excess resin (or use very little resin and work the resin into the lay up with the squeege) After the glass is wetted out, peel off the visqueen and form the glass into the shape you want. With this technique you can make a very clean lay up and use about 1/2 the resin you normally would in a traditional "wet" lay up.







More later,

CC

shorten the bristles. that should help. sometimes when im stippling the mat will pull away from the part. anyhow, your technique and results look great. thanks for the tips

Nice work! what brand resin are you using for that?

rockcitycafe said:

Nice work! what brand resin are you using for that?

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Thanks!

I used West System Epoxy from West Marine for the bulk of the seat. The battery tray was some old left over Hexel Epolite resin.

CC

Getting back to the seat, after the frame tabs were ground off, I inserted some foam rubber about 1/2" thick between the frame and fender to allow for some clearance for wiring below the seat:


Next I wrapped a layer of sheet rubber about 1/16" thick around the frame anywhere the seat pan would touch for a little chaffing protection. Then I formed the mold for the pan from some aluminum flashing covered in masking tape:


I formed a little skirt around the frame below the seat from aluminum flashing and covered the whole form with masking tape:


The form was waxed and the frame was protected from drips with a few trash bags and about four layers of fiberglass were applied:


The pan after curing with the form removed from the frame and the rear edge of the pan trimmed:


Blocks of styrofoam were glued to the back of the pan and shaped to form the cowl:








A little filler of epoxy and microballoons between the seat pan and cowl and were ready for some more glass:


Yes, I know the hump is huge, but so is the tank and I think they look pretty good as a matched set.

CC

After the seat pan was roughed up with 80 grit sandpaper, another four layers of glass were applied over the seat pan and cowl:




The seat removed from the frame and marked for trimming:


The styrofoam was removed from the hump by digging it out with a wood chisel:


The roughly trimmed seat pan back on the frame:


The pan mounts to the frame at the front by the stock gas tank rear attachment:


And at the rear by the old turn signal attachment points:


After lots of bondo and sanding and the first primer coat:


The cowl had a bit of side to side flex, so I added some stiffening ribs formed from 1/2" styrofoam and covered with a couple layers of glass:




A hole was cut into the rear of the cowl for a low budget 4" trailer rear/brake light:


With the brake light mocked up:


The seat pan in it's latest adornment of red primer:


Next time, the upholstery pan.

CC

Looking great CC. Can't wait to see the seat and tank all painted and on the bike. You make it look so easy!

HerrDeacon said:

Looking great CC. Can't wait to see the seat and tank all painted and on the bike. You make it look so easy!

Click to expand...

I think you'll like. ( I'm planning on copying your paint scheme! )

CC

To make the pan for padding and upholstery, I installed the seat pan and tank on the frame and covered the tank mounting tab and bolts with a piece of 1/4" foam for clearance. Then I covered everything with masking tape:


The form was waxed and a couple layers of glass cloth were applied:


After curing, the upholstery pan was pried off and trimmed to fit:


For some limited access to the battery/electronics area, I cut an opening in the front of the hump. The top back of the upholstery pan will be held in place with 3/4" diameter rare earth magnets that will be epoxied into the hole at the top of the hump and into the upholstery pan:


The front of the upholstery pan is attached to the seat pan with a couple of #10 pan head machine screws that are epoxied/fiberglassed through the upholstery pan. The wings of the wing nuts are drilled and safetied to each other with a small spring to prevent backing off:


The upholstery pan is padded with one layer of "sleeping pad foam" from Wal-mart on the front of the hump and three layers on the seat. The padding was attached with 3M Super 77 spray contact cement. Shaping was done with a sharp knife and some very coarse sandpaper:


On top of the seat, I added two layers of some carpet padding I found that has almost a "memory foam" feel to it:


Well that's about where the seat stands for now. Upholstery will be three pieces of vinyl stiched together at the seam between the seat and hump and at the front of the seat and attached to the pan with Super 77. I'm hoping to get that done this week.

CC

That's one of the better lay-ups I've seen....nice work!