Jet Boat Fiberglass Seat Shells

This is the finished prototype seat set into place in the hull. It clears the sides of the gunnels by a couple of inches total to allow for upholstery. I will have to fab a set of stands for my boat since I don't have stringers that run the full length of the hull. The seat bottom back corner just misses resting on the front edge of the stringer. I guess a short stringer would be all that is needed on this small of a boat with this type of drive set up, please comment.

The seat bucket shells are an almost exact replica of the octagonal shaped seats out of my 1972 Sleekcraft Rebel, but are the same as many other jet boats of the era. I say, "almost exact", because the seats shells I have built are actually using a fiberglass mesh of woven threads as opposed to the originals chopped strand or bat construction. You can litereally see the reinforced glass mesh in the finished product.

The rear bench seat is a complete custom fabrication fashioned to mimmick the front bucket seat shells. By using the existing seat as a template for a mold, I simply widened a bucket seat into a bench model so the lines are an exact match making it all look good together and maintaining the clean lines your boat was designed with. The use of the bench seat also eleminates a lot of the wood structure in your boat making it lighter, thus faster or able to carry more gear, both a plus. I understand my particular hull is heavy anyway, so this will be a welcome weight savings.

Bare Seat Shell Description

The bucket seats are roughly 18" wide x 18" deep x 18" tall. The rear bench, as built, measures 63" wide x 18" deep x 18" tall. My new mold for the seats will allow me to build a bench or buckets to any desired width, within reason.

The glass used in the prototype was a 24 oz per square yard bi-axial mat with a thick chopped strand mat on one side. The backside of the mat was covered by some 5 oz/sq yd chopped strand mat laid to cover the dips in the resin made by the large strands on the backside of the mat (inside of the seat shell). The Next seat will be of a thicker 32 oz/sq yd bi-axial mat with even thicker chopped strand on one side.

The prototype seat mold was a simple plywood buck that I made from some scraps laying around, I knew thay would come in handy. I did not envision going into any kind of production with these so temporary, one time use mold was on my mind. I Bondo-ed the inperfections in the wood and sealed the surface with fiberglass resin. Little did I know that the resin when coupled with the wax I was using as a mold release could re-react with each other binding EVERYTHING together. Luckily however the only places the mold stuck was at the overlaps were the heat was greatest. None the less, the mold is essentailly useless for even a second run as the heat from curing loosened the Bondo from the wood surface and the potential problems could just cascade from there. After attempting to scrape the proto mold clean and re-prep the surface, I just gave up and built a new, better mold to avoid any problems and will prepare it properly as a permanant mold system.

A Closer Look at the Rear Bench Seat Shell

I realized while laying out the glass for my protypte that the seat back may be a little weak due to the distance between the angles at each end which provide plenty of support for the back on the bucket seat, but on the bench, it flexes way too much. My quick fix on the prototype was to add three more layers of woven mesh to the top edge. This did stiffen the upper portion of the seat back but still allowed some flex. That is what the prototype is for, finding the problems before they get to the customer. Therefore, the new mold will have a small half round channel built into the seat rear to add a stiffening element without having to resort to a 2x4 support across the back of the seat or spanning the gunnels of your boat. My personal goal was to design a clean looking seat that would install easily within one days time without adding a lot of ugly bracketry and/or lumber supports that will just rust or rot away from the wet enviroment.

A First Attempt at Upholstery

I bought a Singer 401 off ebay and got some material just to see if I could get the hang of sewing upholstery. I tried a few passes to get the machine setup for the sewfoam and vinyl and in no time I was sewing pleats and piping and putting it all together. I only ran into a problem when I could not get the machine to punch through the two layers of sew foam, four layers of marine vinyl, and the 5/16 inch piping core. It may have been the needle I had switched to, a 14 from a 16. The machine sewed beatifully even if it was amost 60 years old. Shame that things are not built to the same standard of quality today.

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