Hi-
I need help making a keel fin for a Vintage M “Madcap” fin type keel, (not bulb)
I’ve cast lead keels before but now that I’m a dad I prefer to let someone else do the casting but I can make the male plug.
Looking for someone to cast me the keel. willing to pay$.
Also on this topic, bulb calculator doesn’t do that type of keel, soes anyone know of a good alternative? I’ve played with Rhino which I happen to have, and 3ds-max which I have, which is great for sculpting but not very precise.
I can adjust the weight later doing it the old trial and error way but it would be cool to get it right the first time
and from that I drawn the lead expected weight that in my opinion should not be less of 55%, better 60%. Hope not infrigment of copyright
Cheers
ClaudioD
PS, You can always fill up the volume with birdshots balls of 2mm, taking into acount that the specific weight is in the order of 8kg/dm3 http://en.wikipedia.org/wiki/Shotgun_shell
Thanks-
I have made keels with buckshot and epoxy. If the keel is solid lead compared to birdshot/buckshot, I can figure the difference in weight between the two with the same design of the keel volume.
the question is if I need to desing the birdshot one the same weght theat the solid one would ahve been, I well need to inccrease its volume by a certain percentage?..
which meand I have to create a whole new keel.
"14.44lbs = 6.55kg
lead min.
14.44lbs pounds sounds about right, but you never know till you float it, not knowing the weight of the rest of the boat.Not sure what 55% = 7.7lbs means?
Hi,
first of all the 55% is the ratio between the boat weight and ballast weight. This ratio determine de lateral stabilty . Greater the ballast ratio better against wind force.
Normal available lead being an alloy, weight about 10.5 kg/dm3 therefore 6.55 x 55% = 3.6kg / 10.5 = 342cm3 volume
Buckshots weight is about 8.5kg/dm3 , there fore 6.55 x 55% = 3.6kg / 8.5 = 423 cm3
Pratically the buckshot ballast has a volume of 423 / 342 = 1.236 alias +24 %
The ballast side surface is about 245cm² - if the thickness would be 1.75cm, you will get a volume of 428cm3 that once multiplied by 8.5 , you reach the ballast weight of 3.64kg
Hope is ok for you. I’m pretty sure that you do not need to make a ballast, Just put the hull on a balance , fix a triplex barrier inside the keel where the ballast should be and then enter the buckshots with some epoxy until you read additional 3.6kg or 7.7lbs unless you made the zeroing of the balance before
Cheers
Claudio
The original plans call for 10 lbs of lead on a 14.6 lb boat, or a ballast ratio of 68% (those old boys built light :-)). Tests I ran for the Yankee III project gave an effective density of no. 7 lead shot as 3.44 oz/cu in, owing to the inability to get optimum packing. This is about 57% the density of solid lead. If you’re going to use lead shot I’d widen the keel at the bottom to form a kind of bulb. Dropping the keel a couple of inches will also help. Madcaps are beautiful boats, BTW, and very, very quick.
-Since I’m planning to carve the hull the old fashioned way out of wood, I can’t pour the shot into the space because there won’t be any space, but good Idea though, anyone know where I can get a glass “madcap” hull?
-Hi Earl- Guess I better carve it paper thin! I’m thinking the way to go might be to make a series of keels first, weigh them, find their centers of gravity, pick the best keel to fit the boat, re-design the boat to fit the keel, then finally make the hull.
Scott Todd has made Madcap hulls, but I don’t know if he still is. PM me for his email. You can make a hollow fiberglass keel easily by glassing with epoxy (not polyester) over a blue insulating foam plug, then digging out most of the foam and using acetone to dissolve the remainder. This can then be attached to a wooden stub keel which is part of the carved hull.
Another way to make a keel of this type is with lead flashing, as used by roofers. This might have a different name in the US, but is used to waterproof gulleys and pitch changes on roofs.
Method: take the shape off the plan, or if you can’t, then do a quick build in wood, and then take the shape from that with soldering wire, and transfer the shape to squared paper.
This is done vertically, spacing the wire to fit with the paper(0.5cm, or1/4 inch, for example).
Trace the shapes onto the paper, and then dot mark the corresponding points to another sheet, and you have a set of horizontal templates which can be used to cut out the flashing to make a lead keel, these are then epoxied together and then either filed or filled with auto putty(filler) to make a smooth result.
It doesn’t take too long, and you don’t have to worry about melting lead; also the density is better than if you are using birdshot. A long SS bolt or two can be inserted if you are worried about the epoxy not being strong enough.
Edward.
PS The soldering wire is also great for templates for making boat stands for long keel boats, and also for motor boats that don’t sit comfortably in sling type stands.