William_H
Well-known member
Just to give you some ideas. My 21ft trailer sailer has a 100kg centre board vertical dropping. There is another 250kg lead under the floor. The total weight being around 950kg.
At 90 degrees of heel it exhibits 30kg up thrust at the hounds (not ast head) being fractioanl rigged. This is just enough to meet YA safety requirments for stability. keel lcked down of course.
The foil shaped keel was originally made by moulding 2 halfs to make the skin. Lead blocks were then fitted and epoxied in and halfs joined togher. The upper half of the boatd is wooden centred for strength.
At one stage I added 15kg of lead to the tip of the cb. I used the existing tip shape to make a fibreglass mould. I then removed this mould and moved it up (board upside down) by about 40 cms. I screwed some large screws into the CB tip for attachment. I drilled a hole in the mould and poured molten lead into the f/g mould. There was a huge amount of smoke and the f/g mold was singed but before it was destroyed the lead set. I removed the burnt f/g leaving a perfect shaped new cb tip. Actually I ground the lead down a bit and covered it with fibreglass and faired the whole thing off. The tip does get a bashing when i hit rocks etc but has been repairable with more f/g covering.
So if you were building a new ballasted c/b I would make a male mould out of plaster and or wood. The make a female mould of fibreglass and polyester resin. Then pour the molten lead in very carefully adding steel rods inside for strength. The lead would only extend a small distance from the tip so I would then fill the rest of the upper cb mould with foam. Remove the f/g mould (destructively) Then lay up carbon fibre and fibre glass over the core. Carbon fibre will be excellent for the sides of the cb but being stiff it will not bend so you need a twill weave glass to do the curved laeding edge and bottom. Skin should end up quite thick at about 3mm at least. You will nead reinforcing at the pivot area and lift wire attacment.
However for a dinghy perhaps just a little lead at the tip may help. What is really important is to make wide side decks and sealed self draining cockpit. Dinghies when capsizing generally lose their form stability as the water rushes into the hull. The other difficulty is that the crew tend to end up standing on the lower inside gunwhale so inadvertently forcing the capsize. A leaning out over the top gunwhale is the way the experts avoid capsize. Indeed a skilled crew can climb over the top gunwhale as she oes over such that they can right it again without getting wet. (quite a trick) I think you (OP) should get more capsize practice in. I know we have warmer water but always in teaching dinghy sailing to kids capsize drills came before sailing. Including righting from fully inverted. In fact one of my party tricks was to dive under and come up inside the inverted hull. Couldn't always get the kids to do it but it is a fun. A lovely blue light from the water.
anyway good luck with the dreaming over the winter olewill
At 90 degrees of heel it exhibits 30kg up thrust at the hounds (not ast head) being fractioanl rigged. This is just enough to meet YA safety requirments for stability. keel lcked down of course.
The foil shaped keel was originally made by moulding 2 halfs to make the skin. Lead blocks were then fitted and epoxied in and halfs joined togher. The upper half of the boatd is wooden centred for strength.
At one stage I added 15kg of lead to the tip of the cb. I used the existing tip shape to make a fibreglass mould. I then removed this mould and moved it up (board upside down) by about 40 cms. I screwed some large screws into the CB tip for attachment. I drilled a hole in the mould and poured molten lead into the f/g mould. There was a huge amount of smoke and the f/g mold was singed but before it was destroyed the lead set. I removed the burnt f/g leaving a perfect shaped new cb tip. Actually I ground the lead down a bit and covered it with fibreglass and faired the whole thing off. The tip does get a bashing when i hit rocks etc but has been repairable with more f/g covering.
So if you were building a new ballasted c/b I would make a male mould out of plaster and or wood. The make a female mould of fibreglass and polyester resin. Then pour the molten lead in very carefully adding steel rods inside for strength. The lead would only extend a small distance from the tip so I would then fill the rest of the upper cb mould with foam. Remove the f/g mould (destructively) Then lay up carbon fibre and fibre glass over the core. Carbon fibre will be excellent for the sides of the cb but being stiff it will not bend so you need a twill weave glass to do the curved laeding edge and bottom. Skin should end up quite thick at about 3mm at least. You will nead reinforcing at the pivot area and lift wire attacment.
However for a dinghy perhaps just a little lead at the tip may help. What is really important is to make wide side decks and sealed self draining cockpit. Dinghies when capsizing generally lose their form stability as the water rushes into the hull. The other difficulty is that the crew tend to end up standing on the lower inside gunwhale so inadvertently forcing the capsize. A leaning out over the top gunwhale is the way the experts avoid capsize. Indeed a skilled crew can climb over the top gunwhale as she oes over such that they can right it again without getting wet. (quite a trick) I think you (OP) should get more capsize practice in. I know we have warmer water but always in teaching dinghy sailing to kids capsize drills came before sailing. Including righting from fully inverted. In fact one of my party tricks was to dive under and come up inside the inverted hull. Couldn't always get the kids to do it but it is a fun. A lovely blue light from the water.
anyway good luck with the dreaming over the winter olewill
). That's fine, but as I've also no real interest in racing either, I'm keen to escape from the customary mentality of two-man involvement in this boat's use.