Here's a picture of what this is about, before I say why I'm building it, and what the design criteria were.
It's a third, front wheel dolly that fits in the front hatch, uses the front hatch shock cords to hold it in place, and has a kind of ratchet that puts a brake on allowing only one way movement if I want that happening.
WHY--The AI 2 is heavier than the AI 1 (not as heavy as the TI) but still, if you are using the heavy duty rear dolly that Hobie sells, the bow has some real weight--especially if you have gear in the front hatch. The boat launches fine from my trailer, but if I launch with the dolly I save two trips from trailer parking to the ramp. And there are places I can't use the trailer.
Recently, on a crowded day, I was landing the boat and trying to pull it on the dolly by hand up the ramp slope quickly because there were other boaters waiting etc. Both lifting and bow and pulling uphill is doable, but not that fun. Also, If I set the bow down to rest a second, it just goes into reverse sliding away, or else I'm bending over holding it still. Anyway, on that day I decided it would help a lot to have a front wheel, and furthermore one that would not roll backwards if I so desired. With the creases in the underside of the hull as natural places for longitudinal support for the dolly, and the shock cords already there--underneath the front hatch is perfect for one.
BUILDING IT--Started by taking off the hull profile and figuring out how high I wanted the bow to be to reach my hand easily when I'm towing. That resulted in the full sized templates shown below (did the best I could to bring out the pencil lines in the pic)
You are seeing one of the semicircular, longitudinal pipe supports already built here. The basic structure is 5/4" US clear pine, sandwiched between 1/4' marine ply. Yes it could have been 3/4" pine as well in terms of strength, but that gave less bearing surface where the mount hits the hull.
This is one of the test fits
I cut out parts of this template to outline the band saw cuts on the wood, and then tape them back in place afterwards. Here's a dry fit clamp up of the central section before gluing the three pieces of 5/4 together to get the necessary width.
Below, the marine ply has been added and a test fit shows the profile to be pretty good. The white pipes fit in the hull creases which are just about parallel at this point.
Above you can see how the marine ply on the semicircular longitudinal supports extends vertically upwards to create a cradle for the pipe. I'll put rubber on the part that hits the hull directly--the same stuff Hobie sells for the TI cradles (or did sell anyway).
Here's two more shots of the thing mounted.
Works great in the driveway, and I should be able to try it on a launching ramp tomorrow. Below it is stowed away in the front hatch. It just fits (made that way on purpose)
And now here's the simple, funky ratchet gizmo, shown below first in action, and then stowed off to the side.
Since the dolly itself is symmetric fore and aft, I can turn it around and get this braking action in either direction if I want it. It's easy enough to lift the boat in order to make turns, and going downhill on a ramp, it's easy enough to just life the bow also. So that means I can just set the bow down and park the boat heading down hill if there's congestion on the ramp area.
After some more testing, this whole thing will get one coat of MAS epoxy, a light sanding, and then one or two coats of Epifanes varnish. Have really enjoyed building this, and I love it that the same shock cords that hold the hatch cover down can hold the dolly in place. That is so perfect.