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Constant Camber (tm)

Posted: Fri Nov 09, 2018 9:07 pm
by dave367
Does anyone have experience either in building or designing for Constant Camber (tm) hulls? I had some thoughts but surely there's a paper, or owners manual or plans addendum out there somewhere, to give me a leg up?

Thanks!

Dave Culp

Re: Constant Camber (tm)

Posted: Sat Nov 10, 2018 8:32 pm
by Robert Biegler
There is some information in this book: http://outrigmedia.com/outrig/wp-conten ... me-two.pdf It's not a manual, though. The patent is here: https://patents.google.com/patent/US4471710

I found what looks like the exact same idea, only using a female mold, patented in 1997: http://www.freepatentsonline.com/6021732.pdf

There is a little information here: https://newageofsail.com/constant-camber-technology/

Somewhere on the Searunner site, there is mention of assistance with constant camber building.

There is a 12 page manual for the cylinder mold construction method: file:///C:/temp/Cylinder%20Mold%20Construction%20Manual.pdf It mentions a manual on video or DVD.

I have wondered whether it would make sense to combine cylinder molding with Rob Denney's intelligent infusion by using curved, female mold laminating surfaces.

Re: Constant Camber (tm)

Posted: Sun Nov 18, 2018 5:17 pm
by John Perry
Have no personal experience but my freind Simon attended one of the AYRS meetings we held in Devon a few years back and he told us all about how he and his friend Andy built a 10m catamaran using the 'cylynder mold' method. Basically he hated that method of boat building and wished that he had built his boat some other way! However, after 9 years work, close to full time, he did end up with a very nice cruising multihull, but not without problems along the way. This was the cylinder mold technique, whereas you are interested in the 'constant camber' technique, but to my mind the two methods seem rather similar, the difference being that one uses a mold with a double curvature surface and the other a mold with only a single curvature surface.

Simon's boat started off as a Kurt Huges design but departed from Kurt Hugh's drawings in order to improve the accomodation in the bridgedeck area and to have a different bow profile. The panels for the hulls were made up from thin plywood vacuum formed over a mould and from what I remember from Simon's presentation there were considerable difficulties avoiding voids between layers of plywood. Then, when the plywood shapes had been formed they were so large (full length of the 10m hull) that there was difficulty manipulating them off the mold and forming the hulls working with only 2 persons. Another problem was that Simon particularly wished to avoid having internal stringers within the hulls as specified on the plans. He consulted Kurt Hughes who sugested that he could leave out the stringers if he stiffened the hulls by adding a substantial thickness layer (I think it was something like 30mm) of structural foam inside the hull skins, then laminating internally over this foam with GRP. A bizarre way to proceed to my mind, but Simon went ahead and completed the boat that way, ending up with a very strong structure, but a huge amount of extra work basically building another boat within the boat. I cannot help but think that Simon would have done better to accept the stringers, but having seen the finished boat I can say that it is a beautiful job and this summer Simon and Andy did a circumnavigation of the UK with it.

Re: Constant Camber (tm)

Posted: Mon Nov 19, 2018 10:39 pm
by dave367
From Robert Biegler ยป Sat Nov 10, 2018 8:32 pm

There is some information in this book: http://outrigmedia.com/outrig/wp-conten ... me-two.pdf It's not a manual, though. The patent is here: https://patents.google.com/patent/US4471710


Thank you Robert, I'm aware of both, though didn't know Brown book included info on Constant Camber--thanks! Happily, I just downloaded the book on Kindle Unlimited, so the author gets his royalty and I still get to read for free. I love the internet. I have spoken with John Marples a time or two, and I understand there are now 3 similar methods; Constant Camber by Brown and Marples, Cylindrical molding by Hughes and this "toroid sectioned" shape as well.

I found what looks like the exact same idea, only using a female mold, patented in 1997: http://www.freepatentsonline.com/6021732.pdf

This one allows more refined shapes than cylinder molding does (as does C-C), and likely it allows more refining than C-C as well (Marples and Brown either have or are contemplating suing this patenter--too similar) The thing I really want is how to design to the technique. More "recipe" and less "high concept"! C-C is brilliantly simple--for lots of small boat shapes, not just multihulls, but it apparently did not prove viable as a commercial venture, and the inventors/designers are understandably reluctant to teach me what they do for a living. Perhaps I should have asked John, not "how" but rather encourage him to write a book on designing to the concept then sell that book. :-)

There is a 12 page manual for the cylinder mold construction method: file:///C:/temp/Cylinder%20Mold%20Construction%20Manual.pdf It mentions a manual on video or DVD.

I think I have this--it's included as an appendix to his catalogue/portfolio--ar at least it did in 1998 which is the date on my copty! Designing for cylinder molding is a bit more intuitive than CC or Toroid molding

I have wondered whether it would make sense to combine cylinder molding with Rob Denney's intelligent infusion by using curved, female mold laminating surfaces.

It almost certainly would, but Rob's designs require a high degree of precision so they'll "fold" into the completed shape with minimal joins and re-working. C-C hulls have quite a lot of tolerance and both halves (or both or all three hulls) are not very near spec or even each other. My level of OCD is OK with that, but many aren't. :-)

Cheers,

Dave Culp

Re: Constant Camber (tm)

Posted: Tue Dec 04, 2018 6:56 pm
by Robert Biegler
dave367 wrote:The thing I really want is how to design to the technique. More "recipe" and less "high concept"!

As I understand it, the panels you can make are cuts through the torus. That sounds like a job for a 3D rendering programme. That wouldn't tell you how to combine panels if you want more than one panel for each side of the hull, though.

If there is anything for tiling 3D shapes, that would give you the common shape to which you cut all your planks or veneers.