Monday 30 July 2012

Hi,
I've had 3 test sessions so far and we are getting the bugs out slowly. First, the hulls are dry inside, and they seems to move easily through the water. On Saturday Kevin and I were both on the boat and we took turns pedaling while the other tended to some issue. Then while I was pedaling Kevin took pictures and video of the wake at various speeds. Unfortunately I couldn't seem to get the GPS on my phone to cooperate so we don't know the speed although folks along the shore were complaining that the wake was making it unsafe to swim......
We tried several props and it does make a big difference how much the boat and cargo weigh. The 16x14 APC pattern prop was just too aggressive with two people on board. The boat seemed to move right along but I could not reach a cadence I liked and still keep that up for an hour with two people on board. Now if there were two drive units we would be going faster and that might have worked. In the end we were using a 16x12 prop that had been previously cut down to about 13 inches. It was a bit light for a single rider but good for two. I bought a few larger props but I won't use them unless I back off on the gearing. At some point I would like to tow the boat through the water and see what the drag is at different speeds.

I dropped the frame down about 5 inches and could go a bit lower but I don't think I will. It's great for flat water but too low for white caps I expect. I will keep the original frame extensions and make 4 more so that I can switch if I have to.

On Sunday Jane and I went back to the lake and did a bit of a tour. The issue of dragging the prop prompted me to take another stab at supporting the shaft which seems to work quite well. Basically I changed the support so that the only restriction was to keep the prop tips from falling more than 6 inches below the surface. Other than that the shaft and prop came move where ever it likes. At the shore I got Jane to pedal while I held the boat and the drive shaft bowed out enough that the prop moves ahead almost a foot! But it seems to be okay at this.......... We went out around some islands and back with the only issue being that I forgot to tighten up one of the bolts on the rudder bar and the forward end came off so it bent the tie rod at the back to about 90 degrees. But we borrowed  a bolt from something else and wade it back fine.

Pictures to follow and maybe video if I figure out how to upload it.

Monday 23 July 2012

First wet test

So.......first wet test on Saturday morning. Jane, myself and Kevin went to Cox Lake near Tantallon where we met Bill who had paddled over to help. We put the hulls and frame parts together without incident and then clamped on the boom with all the drive train, the seat, and the support tube that held the steady bearing bar for the prop shaft. We had the center of the main frame marked and positioned the assembly with the center of mass where we thought it should be. Right on the money, because when it was thrown in the water it was about 1 inch out of the water on the bow and stern. This was installed with duct tape, c-clamps, retchet straps etc!
I kept one rudder dry and installed a telescoping tent pole to the other with a ball style tie rod end. Since this was still not long enough we duct taped a paddle to the end of the handle.. Nothing but the best.....

The prop was an APC plastic model airplane prop ( 16 x 12) and I should have taken a picture of it before it went in the water. It is on the end of an 11 foot aluminum shaft, 3/8 in diameter, or just under 10mm.
52 tooth crank sprocket, to a 14 tooth sprocket on a 2:1 Miterpak right angle gear box.

The prop is installed on a stainless steel stub shaft which goes through a Delrin block. This is bolted to a 1.5 x .125 aluminum flat bar going up to the frame. This is what I wanted to use to set the maximum depth of the prop. All the joints used 1/4-20 bolts with self-locking nuts so they could all move without falling out.

The first thing I noticed was how easily the boat moved through the water. A very light effort with a canoe paddle would move it right allong. I started to pedal gingerly and everything worked great. However, when I used just slightly more effort I could hear the prop hitting so I went back to shore. Turns out that when pedalling, the bow in the shaft is very much exagerated and this effectively shortens the shaft which changes the angle on the aluminum flat bar. So we experimented with woving the hinge point forward but eventually ended up taking the guide off altogether. This worked great for about 10 minutes and while I was starting to push just a little, one blade snapped off the prop!! On examination we could see that the other blade was white and soft at the same location and it broke a few minutes later. by this time we were just using a loop of rope to lift the prop for shallow water. I really don't want the prop dragging on the bottom when I stop pedalling....

I think maybe the gearbox is just too far above the surface and the blades are working too hard to try and straighten shaft when pedalling. There was more flopping of the drive shaft than I expected but this could be due to not enough of the shaft in the water.

Over all I was extremely happy with the first outing and now will start the refinements!