We did a bunch of custom work on a Harley Davidson Softail Rocker. We did a custom gas tank as well as installed a
Russ Wernimont Designs (RSD) strutless rear fender kit, so an off the shelf seat would no longer fit, so we made one. A metal seat pan would have been very difficult to build, and would be hard to make fit as tight and right as we would like, so we broke out some fiberglass. Once you have decided to try it, you will want to go out and pick up some supplies first. Remember, this will work on any bike, from a chopper to a cafe racer, or a stock bike to a trike, so try it. I like to use fiberglass cloth, as well as mat, so buy both, along with the correct resin, as well as some extra hardener ( it's always good to have extra of all this stuff, it sucks to run out in the middle of a project). You will also want to buy some measuring/mixing tubs and stirring sticks ( not pictured here). You will want some Aluminum Tape ( which is for heating/cooling duct work) some blue masking tape (the kind that removes easy), Some high quality duct tape (not pictured here). You will want a drop cloth large enough to completely cover the bike, you do not want to accidentally drop activated resin anywhere on your bike, we used a 10ft by 6 ft. You will want to get quite a few pairs of rubber gloves, this stuff is not fun to get off your skin. You will need a fine tipped sharpie, a pair a scissors, and a new razor blade.
Here is a before shot so you get an idea of what we were working with, yours may be different, but the steps will be the same. The way we are building this one, on this particular bike, we decided against a external mounting bracket. If you need one, and normally you will, plan it ahead of time and have the bracket fabricated already, as well as the mount holes already done. When you are glassing up the seat, simply place the bracket into the glass as your working. You would want several layers of glass below and above the bracket to make sure it doesn't move. Fiberglass sticks very well to metal, but don't be shy will applying extra mat.
We like to use cardboard to provide some structure to the bottom of the pan. This will make everything flatter and easier to shape, as well as provide some spacing for when you finish the underside of the pan with material to keep the seat where you wanted it, low and tight to the frame.
Here you can see we have the shape of the cardboard done, and are starting to use the blue tape to fasten it down to the bike. Be sure to pull the tape down tight on the first few pieces. This will be critical to holding it in the exact place where you intend it to be.
Now we are finished applying the masking tape. We got well beyond where we plan on working, you do not want to get anything on your painted surfaces or chrome, as this stuff will rip paint off and destroy surfaces. You can also see I have used the sharpie marker to put a reference mark on the bike. This will be used to lay down the first layer of fiberglass cloth, and get it exactly where I wanted it to be.
Here is a shot of the Fiberglass Cloth, Resin and Hardener we used. Normally the resin comes with hardener, but I have found you run out of hardener before all the resin is gone. We also used Fiberglass Matt as well. The cloth is used only on the first, bottom layer to provide a nice uniform bottom of the pan. The mat is the used for every other layer, to provide strength.
Lay the cloth out on the bike. If you cannot get it to lay how you want when it's dry, it most likely will not lay differently when it's covered in resin.
Here I have transferred the reference mark in the center to the cloth. Holding it firmly in place, I then make another mark around where I think the outside of the seat will be. I normally try to go at least .250 inches past where I will want it to be when finished. I will now cut my pattern out of the cloth. and set it aside for later.
We are now ready to start installing the aluminum foil tape. You can see as I go, we will continue to put the reference mark on top of the new tape. If you wait to long, you won't know where the line is below, so after you install every piece, redraw the lines.
Special attention needs to be paid to this step! If anywhere on your pan will "hook" under something, chances are when you try to remove the pan when its cured, your not going to be able to remove it, or it will break. You do not want that to happen. Here you can see, where the frame rails go under this seat, we pull the tape straight down from the center line of the tubing. This will still allow the pan to hug the frame rails tight, but will allow you to remove it.
Pay great attention to detail, and now tape off the rest of the area. Again, be sure to do farther out than your seat pan will go.
Now I will drape the drop cloth over the bike, and use a high quality duct tape to fasten it to the bike. Be sure to be well away from where you want your finished pan to be. But don't worry if you can't, and fiberglass gets laid on top of the duct tape, it won't hurt anything,
But remember, the glass does come of the aluminum tape easier.
We use plain old Turtle Wax as our mold releasing agent. It works good, is readily available, and is pretty inexpensive compared to Mold Release Wax. We apply it ( using their supplied applicator), not to heavy, let it glaze over for awhile, then rub it off will a good clean cloth towel.We do this a minimum of 5 times. Be sure to pay attention and apply it everywhere, even over the duct tape holding down the drop cloth. After you have done all these steps, you are ready to get the fiberglass mat pieces ready to install.
Be sure to check back for part 2, where will lay down the fiberglass, then shape the pan and get it ready to be covered.
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