Allright lets get back to designing and testing. The other group can work on their youth and parent programs and finding sponsors to finance it.





Alright, for a long time now I really wanted to use metal glues in beachcats. Actually I have tried several glued setups on my own cats, both Prindle 16 and F16. Till now the results are promising.

I also really want to make the F12 platform as much like a normal A-cat platform in appearence as possible.

I really see alot of advantages of the unstayed class 5 rig mainly because the whole setup can be homebuild in a day including having mom sew the mainsail while Dad and kid build up the mast and boom from standardised alu tubes that we bought at the hardware store.

I want to use the same pod to hold the unstayed mast as used on the "Standard" Landyacht (standard is a name) as shown in the picture earlier.

On landyachts this pod is simple welded to the tubing or the other way around. I know it looks fragile but I have yet to see one of those break.

Having said this the pod needs to be made of stainless steel as you can't weld corrosive resistant aluminium very well. However stainless steel is too heavy and too expensive to use for the mainbeam itself. So ideal would be to attach a steel pod to the aluminium mainbeam. Sadly these two materials react to eachother and accellerate corrosion. That is unless they two materials are seperated by an layer of non-conductive material. And a layer of metal glue is just that kind of thing.

The glue that I have used in the past holds up well to salt water and was available in my local hardware store. It was discussed recently in some other thread on this forum. This glue is quoted to hold 160 kg per sq. centimeter. in shear stresses. It will undoubtable be weaker under tensile stresses.

But if we use round 80x2 mm alu tubing for the mainbeam (common as mud) and we weld a 60 mm stainless steel pod to a peice of stainless steel that was first bend halveway around the mainbeam then we can glue those two parts together and avoid tensile stresses in the layer of glue. For the later thing to happen we need round beams, but that is alright as we round alu beams because they are easy to get and cheap.

If run the numbers and a 60 x 60 mm stainless steel base plate should be able to handle the torsional forces. But we need to find out how far we can push it. We can always make the base plate larger and solve our problems that way, but stainless is expensive and the less we have to bend it around the beam the better.

This setup for the mast is simple and effective but it does put alot of torsion on the beamlanding as all the mainsheet tension will be transformed into torsion that must be withstood by the beam being secured to the hulls. The rearbeams are just the same as on catamarans, this included stresses, so we can just copy that of say F16's or F18's. But the F12 mainbeam is significantly different then those of the normal cats.

I would really like to have the mainbeam detachable so the boat can be broken down in hulls and beams and be transported that way. Will make putting the boat on the car top (part by part) alot easier. We can of course glue the mainbeam into place, as we have done with the mast pod but then we will never be able to disassemble it.

It is hard to simulate these parts by mathematics are most assumptions used in these models don't apply anymore. So just building it and test it is far more attractive.

It is this I want to test in simple test setups.

But I also would love to test glueing the alu beam to say a block of tropical wood and have that laminated into the hull (or a jig if it is a test setup) and see if it will hold. Afterall glueing the beams in will be really attractive from a cost and homebuild point of view. We just need to learn whether such a block can be laminated well into the hull itself. The math suggests that it can be done that way. But again math has problems with respect to local stress concentrations as the hulls are not simply a uniform material like metal. If it all where metal then I would know from the simulation but the hulls really aren't.

I think all the other items have been solved. At least I think so.

Can you help me in this respect Flatlander 18 ? See also my private reply.

Wouter