How-to build a custom fiberglass seat pan for your motorcycle Part 2

Welcome back for step two in the process of building a custom fiberglass seat pan for your motorcycle. Whether it's a stock bike you want to do something different for, a chopper or custom that no one builds a seat for, or anything in between this article should help you out. If you have questions  track us down on our website or Facebook and we will be more than happy to help if we can.

 In the last article we showed you the prep work involved in getting ready to lay down the fiberglass mat and cloth to be able to make a strong seat pan.  Here you can see I layed the cloth down on the bike to get a rough idea of how big I needed, then I marked it with a permanent marker to guide me when I lay it down. As seen in the last article I had drawn the "t" in the center of tape I used to cover the frame. I do this so I don't have to make the seat pan bigger than needed, which in turn makes it harder to remove from the bike when done. I draw the line 1/4" - 1/2" out from where I need, depending on the area. I then leave another 1/4" or so outside of that, just in case.

 I like to have everything laying out right where I can get to it easy. Once you get started you only have a certain amount of time until the resin gets hard. Once it's hard, you have to stop and let it cure. You can then rough it up with sandpaper, etc to make it so the next layer you add is able to bond. Of course if you get it done and it's thick enough and shaped right the first time, you shouldn't have to add more layers. So think about everything before you get started. I also like to have 3 people handy to get this job done. 

 One to cut pieces as you go to make sure you get pieces that fit right to help you get it thick enough to strong and handle the load. If you are working with resin, and get it on your gloves ( be sure to wear gloves, this stuff is nasty) you will have a hard time handling the mat or cloth. One person the apply the resin the the glass (as seen in the above pic) and to help lay it down on the bike. It can be hard to do when you are working with larger pieces. The third person will be using your tool to squeegee to the air bubble's out of the mat or cloth that can get stuck in your piece (which is not good). The third person will also work with the first person to identify the areas that need more material to make it stronger and the size and shape of the pieces to make it work well.

 Here you can see we are applying the first large piece to the bike. Here you can see one of the tricks to the job, wax paper. When we applied the resin to the first large piece ( and any other large piece that you may need to use) we laid a sheet of wax paper under our cloth to make it easier to transport to the bike. Be sure to remember that the was paper will be on top when your applying it, so make sure your cloth is upside down to how it will be on the bike. It's not easy to undo, so take a second to plan this before you get started.

 Here you can see Hugh using the squeegee to remove air bubbles in the cloth. You can also see the "t" on the bike and on the cloth line up. It really does make it easier to get you pan right the first time. The lines on the outside work well also to make sure things are lining up where you want it to.

 In this shot Kody is applying extra resin to areas that got a little dry during the installation. Remember, the resin isn't what makes the strength, it's the cloth and mat. Adding resin does help the got be some, or makes transitions thicker, which is nice. If when your working the mat/cloth and it's sliding around alot, try putting some more resin on. It's tricky, as to much is not good, but enough to make everything wet is needed. Practice will make you better at this. 

 Here you can see Hugh applying resin to make, that we will then install on the pan. Between the mat and cloth the initial see pan we did was 3 layers thick all over, with small pieces making it even thicker where extra strength was need. Note, that we did go back and did a second set of fiberglass over the first, as this seat required great strength because of the design of the bike. We like to overbuild things, as it sucks to have to do a job twice, when if done right the first time it wouldn't have been needed.

 This shot shows how well you need to cover everything. This resin is nasty stuff and will peel paint and damage chrome if it gets on it.

 This is what it looked like after we let it cure overnight. Be sure to let it take time and let it cure. Fiberglass gets hard quickly on the outside, but the inside will still be wet/soft. Let it cure.  We use cutters like these to remove excess fiberglass. Here you can get an idea of how much we go past where we want the seat to be when we get done. It's easy while making it to go bigger, but once your done, it's a bummer when you need a little bit more but have to go through the whole process to make it that little bit larger. Here is where we decided we wanted to do a second round of glass work to strengthen our pan up.

We trimmed the pan down to close to what we needed, then we re-waxed the form ( which is important, don't forget). We then did all the steps over again to essentially make it twice as thick as it was before. This pan ended up with roughly four layers of cloth and at least two more of mat, with up to six more in critical areas.

Be sure to check back for part 3, where will will finish trim the seat pan, as well as add foam to finish it up and make it fit the rider perfectly.

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How-to build a custom fiberglass seat pan for your motorcycle

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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