MyIceBoat: Rear runners in the making.

After a couple of more trips to the scrap yard this is what I ended up with! Two flat iron bars. The wider one is 90 x 6 mm and will be used for blades and the other one is 30 X 5 mm and will be used for stiffeners. I would have liked to have gotten a higher flat bar for the blades for example 130 x 6 mm but that was not available. These runners wont allow much snow on the ice! Normal carbon steel is used. Stainless steel would be easier to maintain. I have read or heard that the frictional coefficient for carbon steel on ice would be lower than for stainless steel on ice. Although not confirmed I hope it is true since it should make the boat faster.

I started by cutting the bar in correct length (600 mm).

Next step was to shape the blade. The instructions state that blade should have a curve of 2 mm on a length of 400 mm measured from below the bolt of runner. I achieve this by taking of material of the blades with a belt sander with 40 grit sand paper.

Both runners were shaped at the same time.

Every now and then I checked the measures until I was satisfied.

I made a small deviation from building instructions by leaving a 10 cm part straight below where the fastening bolt will come on the blade. This is how I know some of the DN sailors shape their runners when they sharpen them! Also good to point out here is that I'm only shaping the curve of the blade to desired shape now. The blade still has to be sharpened before it is ready.

Stiffeners. These are there for strengthening the blade in side ways. If and when the boat tips up on two runners during sailing due to strong winds, the sideways force on forward part of the rear runner still on the ice might become so big that it bends the blade if no stiffeners are used.

I'm using a bolt joint to fasten the stiffeners. Here I'm making M5 threads in one of the stiffeners and the other side will have counter sunk bolt head.