Building Foam Kneeblocks
Here's what you'll need to get started:
1. A fairly large piece of 3" minicell foam. The piece pictured is actually not as thick as it comes - so find the thickest stuff you can.
2. Foam Shims. These are most useful when the boat is big - like a creek boat. I don't use them in smaller play boats.
3. Sur-Form. Every paddler should have one of these. You can get them at the hardware store. They are for shaving down foam, and cost less than $5.
4. Foam Cutting Knife. I use a cheap serrated kitchen knife to shape foam. Some people ike to use a hacksaw blade because they can cut curves with it, but I'm not that artsy. Kitchen knife has always worked for me - If I need a curve I just hack it out and sur-form it smooth.
5. DAP Weldwood Contact Cement. This is the best stuff for glueing foam. You can get it at the hardware store or Wal-Mart.
6. DAPlicator. I use a small wedge of foam to spread the DAP on. It sure is cheaper than brushes, and you can use it over and over.
7. Thin Minicell Sheets. You will want to cut a couple of strips about 5" wide by 16" long. Wait to cut until your blocks are built so you can get them exactly the right length. I use self-adhesive minicell, but it would probably be better to use regular foam and DAP.
8. A Sharpie Pen (not pictured, but you know what they look like).
Here's what you're trying to build:
And now for the step-by-step instructions:
1. First, you will need to cut a square of the 3" minicell. I use a 5" by 4" square. This should yield a cube of foam that is 5"x4"x3".
2. Next, you will need to cut your cube diagonally to make the two wedges. Cut parallel to the long (5") axis, so that you have two trianglar wedges that are 4" x 3" x your cut on the ends, and 5" long:
3. Smooth the side you just cut with your sur-form so that it's flat.
4. If you are putting your wedges in a creek boat, glue them onto the foam shims. In the Burn, I cut a corner out of the foam shims before doing this so that they can glue into the boat around the rails for the bulkhead. people taller than me probably won't have this problem (I only have a 29" inseam, so the bulkhead is pretty close). See step 8 before doing a rail cut if you're gonna do it.
5. Shave off the corners of your shim so that they are flush with the 3" and 4" sides of your foam wedge.
6. Next, you're going to need to cut a couple strips from your thin minicell. These need to be 5" wide, and follow the contour of your wedge on the 3" and 4" sides (now slightly bigger than that if you used a shim). You want the strip to be 3-4" longer than needed to cover the wedge ON EACH END - so you're looking at a piece that is (3"+shim)+(4"+shim)+(4"+4" overlaps)=maybe 16" or so long:
7. Glue your thin foam strip onto the wedge, making sure to leave even amounts of overlap on each end.
8. You need to decide which side of the wedge is best for putting your knees on. In play boats, I sometimes use the 3" side against my knee. In the Burn, I use the 4" side. See what feels best to you and gives you the best support. You want the wedge to hold your knee up near the thigh brace, but leave about an inch of slack in there so that you can escape the boat, and in case you wear more clothes later on while paddling. Mark the location where you want to glue the pad in your boat with your sharpie. I put mine just forward of the thigh braces, butted up as close to them as possible.
9. Next you're going to slather the back of your wedge and overlaps with DAP, slather it on the boat, and wait the proper amount of time and glue it in. Once I stick it in there, I sit in the boat and use my knee to press it firmly into place. You will find that the back of the wedge doesn't stick very well since the boat is curved in there and the back of your wedge is flat. It is actually the overlaps of the thin foam that form a good bond to the curved hull and hold this thing in. I end up re-glueing my wedges in every 1-2 months. I could probably get them to stick better if I shaped the wedges to fit flush with the hull, but that seems like a lot of trouble to me.
Good luck with your wedges, and happy paddling!