Keel Length and Bulb Weight

Does anyone have a recommendation or rule on the keel length and the bulb Weight?

Gizmons,

I don?t know of any rules of thumb, but if you can tell us what size/class boat you are building, I?m sure one of us will be able to point you in the right direction.

<hr noshade size=“1”><font size=“1”>Moderator
-Dan
Sherman Yachts</font id=“size1”>

On my Footys, fins are about 7" deep, bulb weight +/- 6 ounces, depending on target displacement of the boat.

Bill

ok stupid me i didn’t notice that this thread was in the footy section. [:-paperbag]

<hr noshade size=“1”><font size=“1”>Moderator
-Dan
Sherman Yachts</font id=“size1”>

I myself think that about a 6inch fin is ideal.
Bill some of “HalfPints” nosediving(very minor problem I understand and no worse than any of mine most likely!!) could come from the long fin…not sure but just a thought.Boats can “trip over” long fins.

Cheers
Brett

Thanks for the tip, Brett. I made my fins removable, so I’ll make a shorter one and compare (one of these days.) Should be interesting to test. Since I have 2 Halfpint boats, I can put the long fin on one, short on the other, and compare in same conditions.

Bill

Do you think that fiberglass strip or epoxy electronics board would be stiff enough? probably two thin pieces glued together.

thx

I think a fiberglass board sandwich should work fine. These fins are not very long and support little weight, so it doesn’t take a lot. I did see a Footy with a wood fin about 9" long, 1 1/2" wide, and less than 1/8" thick that had a lot of flex, though. I would consider that undesirable. You need to find the combination of material to give you the stiffness needed for the size fin you are building.

Bill

I have made some fins and rudder for 1Ms out of two sheet 1/16 ply and one inner sheet of 1/16 stiff plastic. It was good enough for the 2kg bulb. the layers help when sanding the foil shape.

Maybe a sandwich of glass and thin Ali?

thx

Hi Bill,
I am building my first sailboat (a Footy) and would like to know how you make the fins removable? I was thinking of useing a rod inside the fin (connecting to the bulb) and running it into a tube in the hull?
Regards,
Gerald

Ahoy Gerald ,

My Footy design “Sneaker” has a removable keel made from an 1/8" x 1" Aluminum flat stock. My fiberglass fin can slide on and off the stock and I can change fin profiles very easily. I built a wooden keel trunk that doubles as the servo rails. It is held in place by a 4-40 bolt that is epoxied into a slot I cut at the top of the aluminum stock and fits into the cap of the trunk.

Fairwinds, Rob Amaral

Hi Gerald, I made my fins from basswood that inserts thru the hull into a fin box made from styrene sheet. It’s about 3/4 by 3/4 by 1/4" and the fin is held by a screw thru the top of the keelbox and into the top of the fin. I glue the fin box to the hull with a fillet of superglue (but don’t do that with the fin inserted into the box!)

Bill