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PostPosted: Sat May 08, 2021 5:42 pm 
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Joined: Sun Apr 20, 2008 6:18 am
Posts: 3058
Location: Sarasota,Key West FL
The retractable weighted keel works just like a traditional sail boat. I don’t know if the pics are still there with me sitting and standing on the gunwail of my TI in our pool. But the thing actually worked really well. I just got a steel carpenters square from home depot, (it happens to be made from spring steel). Bought a bunch of scuba weight belt weights, ( the little beads in a bag). Made myself a little mold, (pointed on the ends) from two sheets of plastic taped together on the ends. I mixed the lead beads with some polyester resin from home depot, took maybe a quart I think, but I don’t remember for sure. With the carpenders square in the middle standing straight up I poured the lead bead, polyester mix into the mold. Took about two hours to make the thing.
I then took an old mirage drive plug, re-enforced a little by filling it with 2 part urethane foam. With a cutout for the carpenters square in the center, (I wrapped the carpenters square with plastic to prevent it from sticking to the foam).
I drilled 3 or 4 hole thru the side of the carpenters square so I could set heights, then just shove a pin thru the hole when I want to adjust the height. The mirage drive plug is easily removed with the built in latches.
Later on I designed a hinge so it would be a swinging keel, but that was kind of a waste of time and effort, and didn’t do much.

Lead costs around $4 bucks a lb you know, and we needed 50 lbs for the TI’s, and 20 lbs for our revo’s, and around 30 lbs for either an AI or Oasis. With the carpenters sq fully down, the boats were totally un-capsizable.
We were avid scuba divers, so we already had most of the lead weights laying around our shop.
Hope this helps
FE

Note: on the revo’s we needed the mirage drive for kayak sailing, (our favorite thing to do). So instead we just poured the lead weights into PVC tubing, ( just the beads, no polyester resin), then capped the ends. We then suspended the keel under the boat with grey spectra string, (hobie rudder line). Look up the weight of lead, then select the PVC diameter and length based on the volume, (easy math), because I don’t remember the dimensions for sure, (I think it was around 2in dia pvc 2 ft long for our two revo’s). The weight was low enough to clear underneath the mirage fins.

For safety reasons, don’t eat the beads, (just kidding)


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PostPosted: Sun May 09, 2021 3:06 pm 
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Site Rank - Admiral

Joined: Mon Jul 25, 2005 8:20 pm
Posts: 155
Location: Campbell, CA
You've got the gears spinning in my mind ( they were 3D printed so they will eventually strip ) but hopefully not before I build something. Will post photos here if I do.

Dan


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PostPosted: Sat May 06, 2023 8:08 am 
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Joined: Sun May 25, 2014 4:35 am
Posts: 129
Location: Singapore
Hi Dan,

Sorry I missed your post - I lived somewhere where I couldn't sail for 7 years and have only just got back into it. Search through my old posts and you'll see that I sail my AI without Amas or Akas. The secret for control is some kind of boom, especially downwind, footstraps, and of course reefing early! It's pretty forgiving - I've had water coming over the gunwales in gusts and still not capsized, helped by the square topped AI sail that spills winds in gusts

I was in Naples, Italy when I last sailed my AI, and am now in Singapore where the winds are much gustier, but anyone with experience of sailing really tippy racing dinghies shouldn't have issues sailing an AI without the akas/amas, as long as you fit a boom and use a combination of tiller and mainsheet control and are prepared to move a lot around the boat.

So...
1. Some kind of boom is needed to stop death rolls downwind.
All my booms have been made from fishing rod blanks glued into their extended position with G-Flex epoxy

Initially I used (1) a simple sprit boom held on to the mast with a Prusik knot, with a 2:1 reduction mainsheet attached near the clew with another Prusik then routed along the boom then down to a traveller on the front cross beam to give some vanging downwind, with the clew of the sail held to the boom with another Prusik. it worked OK but the vanging effect was limited and I had to go into the wind to furl it, so had to reef cautiously on downwind runs

Recently I moved to (2)a twin boom system with a front cross bar inspired by Sydney Herreshoff's Amphicraft set up from 1934, but without the wires holding the booms to the mast, and using the mastcap rotating (spinnaker) head to attach the dyneeema wires going down to the front of the booms. That worked great once I'd worked out the right reduction ratios for the sheeting(self-vanging, mainsheet also provided outhaul function, and I could furl/unfurl on any point of sail), but it didn't allow for a jib, which I've since found helpful in light airs

So now I've gone back to (1) but with the addition of a vang plus dyneema wires coming down from the Hobie spinnaker masthead to the front of the boom for the vang to work against, plus a furling jib made from a Revo sail. It all works OK but I still need to make a few changes. I can only unfurl facing the wind, but can furl on any point of sail. The jib is only for light airs, where it really helps

I've also just fitted a hiking plank (a 144 cm wakeboard) just behind the seat and strapped to the hull. I'm extremely pleased with as it means hiking out is much less athletic and I can hike out further (I tried cut down outrigger tubes years ago but they were uncomfortable)

Next week I'll start work on fitting a separate outhaul to control sail camber and play with the mainsheet routing (similar to (1) above, which together with the dyneema wires coming down from the masthead, means I might not need a separate vang. I'll also start on rigging up a dummy steering head mounted on the rear hatch, using 1/2 thick wall pvc pipe + flange an+d 4 way tee. with cables going back to the rudder and a tiller + tiller extension going forward. Up to now I've been using a tiller extensioon on the risible excuse for a tiller Hobie fit as standard, but it's in the wrong place and doesn't offer the control I want.

That just leaves modifying the Mirage drive plug so that I can fit the standard daggerboard there (deeper and further forward for better balance when sailing upwind with the jib). Not sure how I'll go about that yet...

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Simon


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