Operation a success!

Well, that was fairly painless.

I carefully measured the curve of the hull using my flexible drafting curve and traced the curve onto the steel frame. Then I cut out the long tube completely, and carved out the curve on the end tubes using my Dremel cutting wheel.

The cuts worked out perfectly!

I filled the open sections of the cut tubes with a new strip of 1/16" steel and welded them closed. Then I re-inserted the long cut-out section to match the angle of the hull. It fit perfectly. I welded it in place and now the drive leg bay fits nice and flat against the curved hull.

I only had to move the whole drive leg back about 8" - not so bad.

Now I am filling the hollow tubes with epoxy, then I will epoxy plywood panels into the frame to enclose the frame. I'll do this before I mount the frame on the hull, as it is much easier to do with the bay frame out of the hull. Here are the next steps:

1. Using the frame as a template, I am going to cut out a 1/16" stainless steel flange. This flange will screw to the bay frame from BELOW the kayak hull - sandwiching the fiberglass kayak in between the flange and the bay frame. The flange will have the exact same inside dimension of the frame, but will extend about 1 inch outside the frame on all sides. I will also pre-drill countersunk screw holes into the flange.

2. Position the bay frame down onto the hull with a thin layer of epoxy/micro to level out all the small bumps, etc on the fiberglass floor. I'll let this cure so that the drive leg is bonded to the kayak floor.

3. Flip the boat over and position the flange on the bottom of the kayak hull onto a bed of epoxy (sand the gel coat on the bottom of the kayak first). Using the flange holes as a template, drill through the flange, the kayak hull and into the drive leg bay frame.

4. Screw the flange into the hull & bay frame. (fill the holes with epoxy as you insert the screws

5. Now, cut out the drive leg hole in the kayak floor using the bay frame and flange as a template. This is the structural connection between the frame and the kayak - well most of the structure. The front and rear of the drive leg bay will also be bonded to a bulkhead that will connect the side walls of the kayak to the drive leg frame. This should be extremely strong - probably stronger than the kayak itself.

6. To water proof the bay, I will wrap a layer of fiberglass over the flange and up the insides of the drive leg bay frame walls, over the top, down the other side and across the floor of the kayak. Then I'll radius all the corners using some thick epoxy/micro mix.

I should weld the seat rails to the front of the bay frame before I do all of this, but I would rather have that drive leg bay fixed and in place before messing with the seat. So instead, I think I will weld some tabs to the ends of the seat rails and bolt them to the bay frame. I should weld some nuts to the bay frame before filling with epoxy.


6 Responses to “Operation a success!”

  1. # Anonymous Anonymous

    Hi Greg,

    It is possible that the properties of your stainless steel is affected during welding. It is possible that your welds will corrode. (some stainless steels do, others don't) You might need some thermal treatment.

    Cheers, Klaas.  

  2. # Anonymous mikael

    Hi Greg
    Looking at your pictures it seems you intend to have the prop offset to one side. Is that so or is there something that I haven't understood. On a bike the chainline is normally offset to the right but here it seeme you have placed the chainline centrally in the kayak which places the prop offset to the left which also your bayframe position indicates.
    How will that affect handling?  

  3. # Blogger Adventures of Greg

    Hi Mikael: It is important that the bottom bracket and both cranks/pedals are CENTERED right-left in the hull or my balance would be off. The chain runs straight down from the chain ring to a right angle gear box which positions the prop at about 3/4" to the left of the center line of the boat. That won't make any difference in performance or handling. Some HPB's have the prop at the SIDE of the boat.


  4. # Anonymous Mikael

    Hi again
    A few more questions if you can bear with me.
    1. That whopping big hole you intend to cut in the hull, how do you intend to seal it when the drive leg is in normal position? It can hardly be left open since it will create enormous drag.
    2. When raising and lowering the drive leg, how do you intend to stop water from entering the kayak? OK the top of the bay is higher than the normal waterline but in any kind of seaway the pressure from passing waves will make the water in the bay slosh around quite a lot.

  5. # Blogger Adventures of Greg


    1. When the drive leg is in place, the hole in the back is filled with a plug that is faired to the bottom of the boat. To remove the drive leg, the plug is removed, drive leg rotated out of the water, and plug re-inserted. there would also be a smaller plug to replace DL once it is fully removed from it's narrow slot.  

  6. # Blogger Adventures of Greg

    Mikael: Your comment about the offset made me think twice. I went back to the hull today and realized that I had been centering the narrow SLOT of the DL bay frame in the center of the kayak hull rather than the center of the bottom bracket!

    Duh! Anyhow - this worked out well. I can now move my frame back to where it was originally designed to go and still take advantage of the frame mods I made to account for the sloping hull sides.  

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