Tom Lathrop Posted February 2, 2008 Report Share Posted February 2, 2008 Haven't had time to do any more work on Lapwing lately. here is the reason. A group of local woodworkers is building a fleet of Optimist Prams to get the younguns out sailing. I have built the mold and made the patterns to get things rolling. Much of the assembly will take place in John Burritt's shop where there is more room and John can supervise. I go for back surgery on Feb 13 and will be out of action for a while. We plan on 6 to 8 boats for a start this Spring. I have to say that the International Optimist plans are the worse that I have ever built from. I guess that is what happens when a committee of "concerned parents" gets involved. I once coached little league basketball so I know how that can be. There is one measurement that has a tolerance of plus/minus 1mm. Most are plus/minus 2.5mm which is hard enough on a boat. Be thankful that you build for a good set of plans. Quote Link to comment Share on other sites More sharing options...
Tom Lathrop Posted February 3, 2008 Author Report Share Posted February 3, 2008 Hmm, Female mold. I can see that's not Grahams Idea. How did you guess : On the other hand, I can pull the hull, with all interior assembled and no (that's zero) screw holes in it, from the mold after two days. Those aren't two full days, it just takes that long for the epoxy to cure well enough to pull it. Sometimes the male mold works better and sometimes the female of the species is superior. With real tight tolerances, this mold guarantees a more uniform product. With all the interior in place, the boat is rigid when it comes out of the mold. Not true with a male mold which turns out a wobbly shell that must be handled with care until you get the interior in place. If the boat does not have to meet rigid measurement specs, the two kinds of molds are more even but I usually find the female easier. Of course that only works in boats ;D ;D Quote Link to comment Share on other sites More sharing options...
Charlie Jones Posted February 3, 2008 Report Share Posted February 3, 2008 lol- Old Shorty kinda really started something with his PD racer eh? All over the world now it seems, with fleets in Oz and elsewhere. You oughta see Shorty sailing one- He's NOT a little guy- maybe 6'4" and about 250 pounds. Here's a pic of me standing beside a HIGHLY modified one on our beach, last Duckworks Messabout we attended/ Quote Link to comment Share on other sites More sharing options...
Tom Lathrop Posted February 3, 2008 Author Report Share Posted February 3, 2008 Yeah Ray, having a boat with a lot of twist in the forefoot changes the balance in favor of a male mold. It is hard to force a panel with that much twist into a female mold, in that case, the male is better. In a historical sense, the plywood/resin/glass-tape composite boat was started in Norway in the 1950's in female molds. That was before anyone thought of stitch and glue. They did not have epoxy, so polyester was used. It required great care to make good joins but the Brits made lots of successful racing boats that way. In the 2nd photo above, the panels in the mold are patterns made by cut and try to exactly fit the mold.. These are used as routing patterns for the final patterns which are done in stacks of several at one time for series production like we are doing. Very simple and accurate. As I said, one size does not fit all. Charlie, That looks a lot more like a military vehicle, including a big gun ;D I completely agree on the issue of making a boat that everybody can enjoy. The Optimist Pram was like that before the internationals got into it and actually created a new boat and class. Plans are still available for the original but the local organizer wanted a boat that could be raced in sanctioned IO races, so that is what I built. Quote Link to comment Share on other sites More sharing options...
Charlie Jones Posted February 3, 2008 Report Share Posted February 3, 2008 Tom - I would think also, that with the tolerances you mentioned earlier, a female mold would be far more likely to actually MEET those tolerances boat after boat. I can see how practical it would be for a production run of small boats. Quote Link to comment Share on other sites More sharing options...
Doug Cameron Posted February 3, 2008 Report Share Posted February 3, 2008 In the 70s and early 80s we built a lot of whitewater kayaks and C-1s using female molds and polyester (and later vinylester). We used a waxy mold release. With more tenacious epoxy, is there a way of preventing leaks through the joints from adhering to the mold? I am in favor of any boat that gets kids involved in outdoor sports like sailing. Just as long as parents don't make it too unpleasant with their rules and quibbling. There are no umpires or scrutineers out there on the open water, and I hope it stays that way. Little League had great potential, but it ruined baseball for many kids. Quote Link to comment Share on other sites More sharing options...
Tom Lathrop Posted February 3, 2008 Author Report Share Posted February 3, 2008 In the 70s and early 80s we built a lot of whitewater kayaks and C-1s using female molds and polyester (and later vinylester). We used a waxy mold release. With more tenacious epoxy, is there a way of preventing leaks through the joints from adhering to the mold? I am in favor of any boat that gets kids involved in outdoor sports like sailing. Just as long as parents don't make it too unpleasant with their rules and quibbling. There are no umpires or scrutineers out there on the open water, and I hope it stays that way. Little League had great potential, but it ruined baseball for many kids. We usually use duct tape to avoid sticking to the mold. If the patterns are accurate enough, no epoxy will come through if care is used. On a male mold, it can happen anywhere along the chine or keel, while on this female mold, sticking can occur only at the 1/2" thick station molds so it is a far smaller problem anyway. Actually, I don't remember having this problem on the school male mold for the Spindrift 10 and we pulled many-many boats off that mold for the last 18 years. Hey guys, I know why I'm sitting at the computer. My back hurts and I trying to rest but don't you have some useful work you can do in the boatshop ???;D ;D Quote Link to comment Share on other sites More sharing options...
Charlie Jones Posted February 3, 2008 Report Share Posted February 3, 2008 waiting for the tide to come in enough so we can haul a 34 foot tri. We still need a bout 4 inches more water. Tide may not wait on any man, but man sure waits on tide ;D Quote Link to comment Share on other sites More sharing options...
Doug Cameron Posted February 4, 2008 Report Share Posted February 4, 2008 I wrote my note at lunch. Took the boat rowing yesterday, but I still have lots of small things to do. I've been in the shop all day except for lunch and a fire call (student reheated a pizza without taking it out of the box!). Quote Link to comment Share on other sites More sharing options...
Oyster Posted February 4, 2008 Report Share Posted February 4, 2008 Opps, wrong thread. You guys are talking about work making me feel a bit guilty tonight with spending almost all day on the water and holding hands with my lady friend on the beach. ;D Quote Link to comment Share on other sites More sharing options...
Tom Lathrop Posted February 4, 2008 Author Report Share Posted February 4, 2008 I'm really glad you guys found productive work to do today other than watch the Superbrawl. Like erster, I've been lazy. Even lazier since I did no useful work at all. Well, I did lay out a rudder and daggerboard but was watching TV at the same time, so that doesn't count full points. Now we will see if I met all those ridiculous + 0, -2mm tolerances. Quote Link to comment Share on other sites More sharing options...
Charlie Jones Posted February 4, 2008 Report Share Posted February 4, 2008 Well - the tri is on dry land. We had to put four flat tires on the trailer to get it to sit low enough, then used a power boat to shove the thing up onto the trailer- had a pair of supports up under the wings. Then pulled it out- yeah- simple- hauled with a diesel dually Ram and a motor home chained to the front to give the Dodge traction. Got the flat tires up onto the concrete part of the ramp MOSTLY out of water, then jacked the whole rig and changed to real tires- four of them. THEN hauled it over to a flat part, away from the launch ramp and parked it. In the morning we'll haul it to the shop down the street. Gonna be fun - it's a 20 foot beam and one street is 22 feet between mail boxes. Permits? We don't need no stinking permits way out here ;D Started about 1800 and finished at 2130. Not too bad really. Did I mention this is a 34 foot Cross trimaran? Quote Link to comment Share on other sites More sharing options...
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