making a tailpiece / bump stop seat for GS400

[Andy]

Well it's not for a KZ650, but since the process would be the same I thought this would be ok. 

I'm building a cafe out of a GS400L I picked up for a song and dance so my Fiancee has a nice little bike to ride (and motivate her to get a license!).  It's a 'custom' type cruiser and came with apehangers and a massive king/queen seat which is not my style at all.

I am taking a different route than I have seen anyone on here take when building a seat so here goes.

I had some 2 inch pink foam sheet left over from another project, something like $20 a sheet.  I cut three pieces that were the approximate length and width I would want the seat / tailpiece to be and glued them together.  I then took the sandwich of foam and put it where It would sit on the frame.  Then I beat on the top of it.  This imprinted the foam where it was making contact with the frame, air cleaner cover, brackets etc on the frame.   Then I carved out some foam and did it again. I got this idea from my dentist when he capped my two front teeth, he made me grind with carbon paper then he ground off the carbon marks on the caps.  I hate that bastard but at least he helped me out here, not that I'd tell him or I'd get a bill.

anyway, once it sat flush on the frame I planted my butt on top, put my feet on the pegs and grabbed the front signals to simulate clipons or clubmans.  I marked where the end of my ass was on the top of the seat and used that point as the back of the seat portion.  Then I got to carving the tail.  I started with a small electric hand planer but it's really noisy and was no good for doing curves.  I moved to a random orbital palm sander with 40 grit pads and my shop vac to suck the dust.  This moved through the foam fast!  It worked great.  Lots of shaping, I have spent about 2 hours so far shaping it although that does include getting frame fitment.

I'm waiting for some glue to dry so can't do much more today.  Here's the progress so far.

Pic 1 - Rough block showing fitment notching in the base.
Pic 2 - Rough block on the 4-hunge

Pic 3 - after some shaping. 
At this point I realized the block didn't come down far enough and the exposed tubing of the frame was not what I was going for.  I peeled one sheet off the top and glued another one in one layer above the bottom.  Then I marked the edges of the frame tubes on the bottom and used my circular saw to cut a bunch of grooves to the correct depth to hide the frame tubes.  I sanded down to the bottom of the grooves until I had a flat surface and did the place-on-frame-and-beat-then-carve technique again to adjust the fit.  The more shaping!

Pic 4 - more shaping of the taller hump.  Still doesn't look right.  I'm no Artiste but that is an ugly little bump.  doesn't match the tank or the arch of the wheel.

[Andy]

Wow those pics look bad, but you get the idea from the thumbnails.

Here it is after yet more shaping with sit test in progress!

[rstnick]

Cool project.
I want to try one one day, a Cafe with single seat.
Keep it coming.

[H2RICK]

Great work, Andy, and it's interesting to see the whole process. You're an inventive and creative guy, no doubt of that.
If/when I get hold of a 650 for a cafe project I'd be waaaayyyyy too lazy to go through all of that to have a bum-stop seat. .....Plus I really don't have a creative/artistic bone in my body.
I'll just spend the bux at Airtech and buy something off the shelf that will do the job.
Maybe not as satisfying as building your own but then I've never been too fond of fibreglassing, either.
My feeble .02 worth....

[HerrDeacon]

Very nice Andy, that's going to look real nice. That is a very similar process to how I made mine for the KZ (http://dotheton.com/index.php?topic=3374.0). Look forward to watching your process.

[antiq]

Looking good so far. I'd form a pan of 3/4 inch plywood so that I'd have something to hold the hinges and lock.

[Andy]

I finally got some more work done on the bum-stop seat.
I got side tracked pretty good by a $100 enduro, a 1973 Kawi F7.  But that's another story

I finished shaping the seat. It's not symmetrical, but I had to stop or else I was going to shave it down so much I'd have to get a pocket bike for it.  Kinda like trimming your own sideburns and ending up with a Mohawk.

Next I took aluminum tape and covered the top and sides to keep the resin from melting the styrofoam plug.  I saw this a few years back where some guy was making a solo seat for his 2000 something Z1000.  I had the same bike at the time and that helped me understand everything he was doing.

Once the tape was on I took a 2x4 foot sheet of fibreglass cloth and laid it over the whole seat.  I used T-pins to pin the front of the cloth down, then worked on stretching it and working it to take the shape of the styrofoam plug.  I also learned that from the Z1000 guy.  Once it was good and stretched I took an old paint roller (complete with dried up paint) and used it to roll the resin on.  It actually worked a lot better than I hoped.  I have used a brush before but it distorts the cloth and pulls the cloth around on you.  The roller pressed the cloth and resin to the plug.  It did pull it up a little but only if I rolled away from the edges.  I stuck to rolling from the center toward the edges and it worked great.  I didn't even get any crap on my hands!  totally worth it IMO.

When dry I cut the excess cloth with scissors and test fit.  
Looks ok on the bike, I'm not stunned by the beauty but hey it's my first try.  I kinda already decided this one was too small but I figured I'd carry on as a learning exercise.
Ok, well time to see how I look on IT.  I'm not sure if the bum stop is too small or my arse is too big.  I'd wager on the latter.  good thing the Fiancee has a smaller butt than me, we'll see how SHE looks on it in a few weeks when she's back from work.

anyhow, that's it so far.
If you do any glassing then I'd say go on the generous side with the hardener.  I mixed it up per specs and it's a bit soft now that it's dry.
I'll do another coat or two of cloth and see how tough it is.  I have the seat foam from the stock seat to shape up, yes there is going to be a bit of padding in there!

Antiq, I have no plans for hinges, I am thinking I'll embed metal clips to hold it direct to the frame.  I'm thinking I'll drill lots of holes in the seat base and fill with resin, or else carve out some foam for some bracing.

I was going to mount the battery under the hump and ditch the airbox so I could empty that area of the frame but from what I have heard you don't mess with the airbox on CV carbs.  So that battery will stay and maybe some number plates put on or make some sidecovers the same way I made the seat.

Pic 1 - partly taped up with aluminum tape
Pic 2 - fibreglass cloth all stretched out.  those T pins are super handy, I got them at michaels.  I know it's a craft store, but this project is one step above macrame and tole painting
Pic 3 - Dried and excess trimmed, final trim will be done with sander after a few more coats

[Andy]

Pic 4 - on the bike.  Meh.  Thought it might be better, but ok let's see what we can do with this as practice i.e frenching in a taillight?  Hey look a kz650!
Pic 5 - stress testing.  Yup, my butt is too big / the stop is too small.   Ok, now I know for next time to go another 2" higher.  Perhaps I'll just make a new basee layer, glue on, and shave down the seat part.  It took a lot of work to get here.

Oh, and for shaping the foam a hand drywall rasp works best.  The sanders make dust and that get's everywhere (like in your lungs).  The raps makes coarser pieces that still get everywhere except inside you.

[H2RICK]

Kinda like trimming your own sideburns and ending up with a Mohawk.

I know it's a craft store, but this project is one step above macrame and tole painting

I'd never knock Michaels. I needed some very fine gauge wire for a certain use and none of my usual sources could help. Lo and behold, Michaels had 25 feet of the correct wire, in stainless steel yet, for the princely sum of $2.00. I've now got enough wire to last me the rest of my life.
Now SWMBO wants to know if I need any "bike parts" as she heads out the door to Michaels. I tell her that I'll be right along with her. They have tons of little knibby-ticker bits that you can use for all kinds of things and while she's shopping I'm browsing to see what I might find useful.....and their prices for this kind of stuff are very reasonable.
Another place for stuff like that is a model train/airplane hobby store. Lee Valley also has some weird little bits and bobs as well.

[HerrDeacon]

That looks amazing Andy. I really like the shape, it really suits the bike, nice job.

You mentioned that "I mixed it up per specs and it's a bit soft now that it's dry.". This has me wondering what type of resin your using. There are two types: laminating and surfacing. If you used a laminating resin (i.e. no wax in it) then the top surface won't fully cure as its in contact with the air. To fully cure it will need to be sealed from the air.

Not sure if this is the issue your having, but thought I'd mention it.

[rstnick]

Nice work.
Does the stuff smell bad when your working with it?

[Andy]

That looks amazing Andy. I really like the shape, it really suits the bike, nice job.

You mentioned that "I mixed it up per specs and it's a bit soft now that it's dry.". This has me wondering what type of resin your using. There are two types: laminating and surfacing. If you used a laminating resin (i.e. no wax in it) then the top surface won't fully cure as its in contact with the air. To fully cure it will need to be sealed from the air.

Not sure if this is the issue your having, but thought I'd mention it.

Deacon, good question, I don't know.  I grabbed the can in my shed and I think you just may be onto something!

[Andy]

Nice work.
Does the stuff smell bad when your working with it?

Rob

The resin reeks, horribly bad, I put it on real quick in my basement and put the piece outside, then ended up opening all my door for 1/2 hour so I wasn't getting too stoned.

the styrofoam is basically odorless, especially if you don't use a power sander (can make enough friction to melt slightly).

My brother is in the aerospace biz and his hobbies are aligned with that.  He made a foam cutter to make wings for model planes.  All he used was a transformer, maybe out of our trainset from when we were kids (???), a hockey stick, two bolts, and a resistive wire.

bolts through the stick, string the wire tight between the bolts, hook up to transformer and the wire gets hot and cuts the foam.  He;d glue a cross section of the wing to each end of the foam and just trace over it with the hot wire.  Works amazing, but not great for compound curves.

My next attempt I think I will draw up "formers" to make of light wood and glue in between blocks of styrofoam to help ensure symmetry.

[HerrDeacon]

Deacon, good question, I don't know.  I grabbed the can in my shed and I think you just may be onto something!

If the top layer is still a bit gummy, I'm guessing its laminating resin. This resin is used for when you want to come back later and apply more layers. Since the last layer is not fully cured the bond will be much better than if it was fully dried.

You could try covering it with something to block it from the air, like plastic wrap or something. I've done that before.

As for the smell, the polyester resins can really smell and it goes everywhere. I like the smell but my family doesn't  Next time I glass anything I'm going to try epoxy resins, they are supposed to be far less fragrant.

[beckley528]

duratech makes an additive that allowes you to spray gelcoat and it works great. it only comes in gallons and is mixed 1-1. make sure you have some acetone handy to clean your gun. I like to use a cheap gravity feed gun that is made for shooting primer. get a mask and vent the work area please.