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Wednesday, August 27, 2014

Kingfisher Drift Boat Build - Plascore Bottom

Plascore Board

I'm using 3/4" Plascore Board for the bottom of the drift boat. It's sort of a honeycomb plastic sheet. There have been many pros and cons discussed on various boat building forums about plywood versus Plascore. The thing that swayed me in that direction was the fact if you hit a piece of rebar or took a hard hit on the bottom and punctured the Linex coating, the Kevlar and fiberglass, with a Plascore bottom you could do a temporary fix and then flip the boat over and do the real repair when you had time. Water migrating into the core won't damage a synthetic material like Plascore. A plywood bottom would keep sucking water like a sponge. Not good! Makes sense to me anyway.

Ordering the Plascore

One problem I had when ordering the material direct from Plascore was determining what specific type of board I needed. After a few emails back and forth with the Plascore Rep we figured it out.

Here's the exact specification from Plascore. I needed 2 sheets.

Specification: 5pcf PP core with film and veil at 3/4" thick X 48" X 96".

The material was shipped from Michigan and I picked it up in Sacramento. The 2 sheets ran $98 plus about $120 for the shipping. So basically about $110 a sheet to Sacramento. Michigan is a long ways away!

Constructing the Plascore Bottom

To construct the drift boat bottom out of plascore you first have to splice together the two 3/4" x 4' x 8' boards into one sheet that is about 4' x 15' 4". You do this by creating a sort of dovetail key joint and lock the two sheets together.

Dovetail Scarf Joints Joined 2 - 4x8 Sheets of Plascore

  • I used the same table that I used when scarfing the plywood. It is 5' wide x 16' long and is about 34' off the floor.
  • The plans provided by Jason Cajune has a layout for the dovetail joints. I laid out the two sheets as per the cut sheet provided.
  • The joints are cut with a razor knife.
  • Once they are cut they have to be fine tuned a bit so they lock together tightly. They sort of snap together.
  • Once they are together place a 3 mil piece of plastic under the joint, A piece about 24" x 5' is about perfect. 

Adding 4 1/2" Strips to the Sides

The Plascore sheets are 48" wide and the drift boat bottom is about 57" wide. The sides need to get extended by adding strips to each side that are about 4 1/2" wide. 48" + 4 1/2" + 4 1/2" = 57" 

  • If you're building a squared off transom you can cut 4 strips 4 1/2" x 48" from one end of the Plascore sheet. The bottom for a square transom is about 14' long so you can cut 4 of them from the end.
  • I'm doing a curved transom which will require an addition 8" or so making the bottom length about 14' 8", so cutting all 4 pieces from the end will be cutting it too close. I'll cut 2 or maybe 3 from the end and 1 or 2 from the sides.
  • These 4 1/2"  pieces will be added to the middle section only based upon the bottom layout provided with the plans. They must be placed in the correct position.
  • Being that the added strips are so close to the sides they can be butted to the larger sheets. They will be covered with enough fiberglass from the side panel/ bottom panel joint for strength. 
  • Hold the strips in place with finish nails or tape.
  • Once all the pieces are laid out and in place put finish nails around the perimeter along the sides to keep the pieces from moving apart when using epoxy peanut butter to glue everything together.
  • Mix up a batch of epoxy peanut butter that is fairly smooth and fill the gaps in the key joints. It will probably take about 3 ounces. Concentrate on the larger gaps.
  • Place additional strips of 3 mil plastic over the areas with the epoxy peanut butter and then place plywood or boards on top of the plastic and weight to hold the sheets flat against the table.
 I'll let this set up overnight, strip off the boards and plastic and get ready to cut the bottom shape.


Monday, August 25, 2014

Kingfisher Drift Boat Build - Flow Coating Epoxy

I've been working on the side panels for the "Kingfisher. The process so far has gone sort of like this;

Steps So Far

(1) Scarf the sheets together
(2) Cut out the side panels to the pattern or dimensions
(3) Sand the scarf joints flat with a 1/2 sheet sander or random orbital sander
(4) Sand the the outside of both sides panels with 100 grit, 120 grit and finish with 160 grit
(5) Vacuum of the surface of the exterior side panels
(6) Cut the fiberglass mesh to size,
(7) Use a dry brush to smooth out the flberglass mesh on the panels being careful not to stretch it too much
(8) Bed the fiberglass with epoxy using a squeegee and natural bristle brush
(9) Let the epoxy set until tacky like the sticky side of duct tape.
(10) Flow Coat epoxy over the fiberglass mesh to fill the epoxy pores.

So this is the stage I'm at. I'm going to back track a bit and talk about epoxying down the fiberglass mesh first. This process is a little bit like you have enough information to be dangerous. It's like you think you've got it all figured out and then you start and realize you're sort of winging it.

The fiberglass mesh is just laying on top of the side panels dry. The first coat of epoxy will be poured onto the fiberglass mesh. I mixed up about 12 ounces of epoxy to start spreading it with a squeegee and that went pretty smoothly. Spreading it with a squeegee was pretty intuitive. You spread it from the center towards the sides and edges, smoothing it as you go and being careful not to stretch out the fiberglass mesh. They call it a "modified waitress wiping motion". When I got done the only problem I had is that I had some wrinkles at the edges and a few small, quarter sized areas where the glass floated up. I think this is par for course.

I then waited until the sheet tacked up and then did the first flow coat. This second coat of epoxy essentially fills the rest of the fiberglass mesh so you can then sand it once it dries without digging into the glass. I mixed up a batch of epoxy about 9 ounces and got started.

Flow Coating

  • Mix up about 9 to 12 ounces of epoxy. Mix it for 2 to 3 minutes.
  • Get your epoxy pallet ready, I like plastic plates on top of a scrap piece of plywood.
  • Get your tools, 3/16" nap foam roller and a 2" disposable bristle brush
  • Pour some epoxy down the center line of the sheet
  • Use the foam roller to spread the epoxy around until it is a thin even coating. 
  • Work an area and then use the 2" disposable brush to even out the epoxy.You do this by "tipping", just use the tip of the brush in light strokes moving in one direction,towards the direction of which you are applying the epoxy.
  • Spread the batch of epoxy and then mix another batch and keep going.
  • Keep a wet edge.
Next I'll let it dry overnight. This second Flow Coat eliminates sanding between the first and second coats.

Flo Coating the 3rd and 4th Coats

I chose to let the 2nd coat dry and harden overnight. This allowed me to sand the surface and get some of the imperfections taken care of before I got too far along. The outside of my Kingfisher will be painted but I want a real smooth finish so I want to take extra care with this process. The top edge of the side panels will be covered with a 1 3/8" gunwale. The bottom edge will be covered with about 4" of truck bed liner. So the middle sections of the panels are the critical areas. With that said I'm still going to try to get them as perfect as I can.

The next day I sanded the two exterior side panels with a random orbital sander. I used a 5" random orbital sander with 80 grit paper. I got my two fans running but on my respirator and got after it. I sanded down to the fiberglass in a number of areas but really tried not to go too far. The fiberglass is what gives the panel it's strength. It went pretty quick but I went through about 8 sanding disks. This is normal. If it isn't cutting change the paper. 

I talked to the guys at Raka Epoxy about the next step. The epoxy I'm using is their non-blushing type. So all I needed to do was vacuum the panels and then wipe them down with Acetone. You can also use Denatured Alcohol.  The Acetone cleans the panels and evaporates quickly.

I put on my Tyvek Clown Suit, rubber gloves, glasses, mask and got after it. Same process as listed above. I did one flow coat and waited about 4 hours and did the fourth coat. Looks pretty darn good. I'll wait until tomorrow and then take a photo. Then I can flip the two sides over and give the insides  two flow coats. They won't be fiber-glassed.

Kingfisher Drift Boat Build - Modeling Transom

I'm cutting out the sides and bottom for the "Kingfisher" drift boat and I'm sort of wondering how do these parts come together to look like a drift boat? The bottom looks like a drift boat bottom, but the sides look like long rectangles.

I've also got to decide on whether to build the transom as a  (a) "Square Transom" like the plans I've got, or whether to experiment and build either a (b) "Rounded Transom" or a (c) "Beavertail Transom". The "Beavertail" is how my "Hyde" drift boat is built. I like it a lot.

I've built models of the "Rounded Transom" and the "Beavertail Transom". I've shot a video to take a closer look at it.

I think I like the "Rounded Transom". Now I just have to figure out how the heck to build it.