Plascore Hull White Water Boat Project

Larry Hedrick
Park City Utah

Desolation Canyon
The spring flow of 2011
40000 CFS
Jeremy and Ky in the boat running Joe Hutch















This is the bottom view of the front hatch. The plywood edging is 3/8. The flat plywood is 1/8 (4mm) 3 ply. The layup was to epoxy 1/2 X 1/2 inch mahogany strips around the plascore with thickend epoxy in the joint. The frame was pinned with 23 guage pins directly to the work bench, then a layer of 10 Oz. glass was applied and the 1/8 plywood was epoxied and pined to the wood frame. It was coverd with plastic and weighed down. The next day the piece was lifted from the work table and the pins were clipped of and set with a punch. Next the 3/8 plywood strips were epoxied on the sides. Glass was applied over the top and down the plywood sides. All the joints seem very strong. When it is cured I will stand on it and test it out.





I placed a block under the stem then picked up the back end. I think it is about 250 pounds at this point.


This is the center where the locks will be located. Thin spacer inserts were place between the inside and outside gunwales. Each end of the spacer is tapered. The spacer should have been longer. A gap developed as the gunwales were pulled together. The space will be filled with thickened epoxy. The spacers are installed so that when the hole is drilled for the oarlock socket it will not cut into the gunwales so they will not lose strenght.


This image shows the wood strip which has beed epoxied to the top edge of the inside gunwale to cover the exposed cells of the plascore. The outside gunwale will get bolted on and finish the gunwale system.


Still could have used more clamps.
The inside gunwales are epoxied in place and go above the plascore by 1/2. A strip of wood will then be epoxied on to cover the exposed cells. The inside is epoxied in place to add strength. The outside will be bolted through so it can be replaced when I smash it.


The cut is 12:1 for 5/8 stock.


All the deck segmens have been cut an sized. The ones at the rear of the boat have been glassed and are epoxied down to the deck joists. The joist system has worked fine and the deck is solid enough to stand on. There is now more glassing and taping to do and a lot of filet work. All out of 10 Oz glass at this point so it may be time to move on to the gunwales untill I get the glass.




$$$$$$$$$$$$$$$$ 43.78

That's 43.73 total not 39.38 each! I picked up 22 of these Southco latches for 1.79 each. Talk about a score!




This images is of a wood joist hanger which will hold the plascore beam.

This is a joist laminated from 3 6 inch pieces of plascore each with 6 inch glass tape between each layer. I should have used unidirectional tape but all I had was standard over under weave. This is the place for carbon fiber. Carbon would have made a much stiffer joist but, it's strong enough. The compartment under the rower is vary large and this joist will support the deck.


This is a bottom view of the rowers foot well. Wood strips have been added to increase the epoxy surface area. A butt joint with plascore has no bond strength in the same way as end grain plywood. On a previous boat my foot well which was only held together with epoxy filets developed a crack while in the Grand Canyon. The plywood had too much flex. The cross members will add support to the floor.

This view is looking straight down into the foot well. Triangular pieces of wood have been epoxied into the long joint to add a surface bond to the side and bottom of the plascore. All the other joints have an epoxy filet.
Sorry for the out of focus image. My high-tech SLR sent the focus beam to the back wall of the shop and not the subject. Didn't find out until I got home.

Three bulkheads installed and one more to go. It might be difficult to see in the images but, the bulkheads do not go all the way to the floor. The space will be filled with a foam insert and sealed with 3M 4500. This will allow the floor to move up and down on impact limiting damage.

The saved cut out is on top of the opening. It can be framed with wood, glassed and attached to the deck below with hinges. I am still working on the sealing system.

This is what will be the under side of the deck, the opening is made stronger with a border of 3/8 inch scrap plywood. Seems plenty strong.

An opening for a hatch has been cut from a sample scrap of plascore. The cut out has been saved for use as a lid. The plascore is being sealed off with 1/2 X 1/2 inch wood stock. The honeycomb was filled with thickened epoxy, the inside frame pieces are pressed in place and a layer of 10 Oz glass was applied on top and bottom.

Stem had a twist of about 1 inch. A serious engineering solution had to be found! The steel ball is from a valve which was requisitioned (not by me) from United Park City Mines at some time in the past. After the front bulkhead gets glassed in place I may be able to get rid of the steel ball. It might make a good anchor, it's about 100 years old and very cool. Since it came from a silver mine I don't know why it's not silver.

Hull weight at this point is 110 pounds.

This is an end view of the chine sample. I hit it was a hammer and it just bounced off. The outside has 7 layers of glass and kevlar. the inside has 3 layers of glass over a fillet.

This is a top view of a sample chine test joint.

The chine is covered with a layer of the kevlar up from the bottom. The side glass goes over the kevlar then a second layer of bottom glass goes up and over. 3 layers of side glass and kevlar cover the chine with 3 more layres of heavy biaxial 6 inch tape. 2 more layers are installed over filites on the inside. A total of 8 layers of fabric.

The chine edge of the plascore has been rounded with a grinder exposing the cells. The cells have been filled with epoxy thickened with micro spheres. Ground glass will make a solid filler but, it's too hard. The micro spheres will cure to a softer material which has a bit more ability to compress which is the reason it was the only thing added to the epoxy.

The bottom of the boat is 3/4 inch plascore. The stock was joined with a square wave box joint and it was going to be used to beef up the bottom of a friends boat. He decided to use Kevlar instead. So I took back the plascore and used it on this boat but it was 2 inches too short. This is why a small piece was bonded on the front under the stem. Had I known it was going to be short, I would have just taken 2 inches off the side panels. The plascore is so easy to work with it's no problem to bond sheets together. After the cells are locked together with thicked epoxy and glass goes on top and bottome it all locks together.

This a prototype of the oarlock socket. The oarlock shaft will be in-line with the side panel.

The inserts are plywood blocks. They will extend below the gunwale and allow for drilling out holes for attachment of flip lines, spare oares etc. Without them drilling would expose the cells of the honeycomb which will be more difficult to close off then plywood end grain.