I saw a Boyer A cat for sale that had canted hulls listed as an upgrade? I did a quick search but didn't get a answer. Do they tip the hulls toward center? Does this make them better while flying the other hull?
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John
Nacra 5.0
CT
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What are canted hulls?
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Posted: May 02, 2018 - 09:20 AM
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Posted: May 02, 2018 - 11:06 AM
Yea, angled in, so when you are at the optimal angle of heel the leeward hull is level in the water and a little more efficient. The windward hull is more or less out of the water so is unaffected from an efficiency point of view. -
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Posted: May 02, 2018 - 11:17 AM
Thanks. Is this a mod that anyone outside A class is doing? It sounds like it could be done by shimming the beam connection. A rudder remount would be in order too?
I would do it just for fun.
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John
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Posted: May 02, 2018 - 12:20 PM
here is an older discussion with tons of data about the topic and canted foils
https://www.catsailor.com…bb=showflat&Number=28737 -
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Posted: May 02, 2018 - 01:23 PM
Nah I dont think they remount the rudders. Still stays inline with the hulls I'd assume -
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Posted: May 02, 2018 - 01:55 PM
according to this post - EU Inter17's canted 6*
"If it is an Inter 17; it may be canted; all EU spec boats were canted at 6 degrees."
http://forums.sailinganar…pic/111535-canted-hulls/ -
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Posted: May 02, 2018 - 02:30 PM
They are canted out - bottoms are further outboard than the tops. This keeps the rudder and boards in a more vertical position when flying a hull.
The new foiling boats do not have canted hulls or foils. The object on them is to lift the hulls and sail them as flat as possible, sharing the lifting forces between all four foils. Or in the case of some of the new prototypes, the leeward foils are lifting, and the windward foils are pulling down, resulting in a level boat. -
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Posted: May 02, 2018 - 03:24 PM
Prototype ...
beachcats?
AC75?
Mono's? -
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Posted: May 02, 2018 - 03:33 PM
Hobie Trifoiler used sensors to do level, which generally meant lee-lift, windward-low... my test ride was much fun, and the thing cornered like it was on RAILS... quite the G-force.
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Posted: May 02, 2018 - 04:12 PM
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Posted: May 02, 2018 - 04:26 PM
Going off of memory here, I think you’d be looking at somewhere around 15 or so degrees of cant. Basically figure out where the waterline of the leeward hull is and then how many degrees (minimum) you need to rotate the hull to get that plane below the plane of the bottom of the opposite hull. Bottom line, we’re not talking about canting one or two degrees here. You would have to place a significant shim under the beam for the cant to be anywhere near effective and that starts to have the potential to effect the structure/racking of the hull platform. There are probably many better things to spend time tinkering with that would have a much more significant speed impact (carbon mast, improved foils, spinnaker kit, lifting foils....).
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Posted: May 02, 2018 - 04:51 PM
He said for fun, not for performance.. -
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Posted: May 02, 2018 - 04:53 PM
Don’t forget to adjust the trailer.. -
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Posted: May 02, 2018 - 06:18 PM
So it’s fun to spend hours working on boat projects that will likely have no perceptible performance benefit and which could potentially negatively impact the structure of your boat? Okey dokey.
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Posted: May 03, 2018 - 11:00 AM
Ha, ha, I see what you did there. Unfortunately I have seen many examples of people spending massive amounts of time, money, and effort on boat projects that had marginal impact on actual performance and some even caused fundamental structural problems. Like a friend that recently modified a Hobie 18 with T rudders and C boards to make a foiling Hobie 18 without doing any sort of reinforcement of dagger trunks or transoms. Never even got up on foils before it ripped out one of the dagger trunks.
Edited by bradinjax on May 03, 2018 - 11:08 AM. -
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Posted: May 11, 2018 - 07:34 AM
Did this to a H-18 many years ago. I used a few stainless washers as shims on the inside bolts and bedded the beams to the saddles with epoxy. That is an important step if you do this and will yield the most benefit especially on older boats. I would also argue that canting will increase righting moment as your moving the bottom of the hull outwards.
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Have Fun,
Mike
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Posted: May 11, 2018 - 01:26 PM
A profound waste of time.
Well designed non-foiling cats are at their intended optimal angle when being sailed with the windward hull just skimming the water.
Canting alters the intended structure and would only improve a poorly designed cat.
Any time you alter the bedding of the crossbars to the hulls you are planning a structural failure.
I hope no one gets hurt.
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Bob
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Prindle 18-2 #244 "Wakizashi"
Prindle 16 #3690 "Pegasus" Sold (sigh)
AZ Multihull Fleet 42 member
(Way) Past Commodore of Prindle Fleet 14
Arizona, USA
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Posted: May 11, 2018 - 02:05 PM
Meh, the ideal angle of the windward hull just skimming the surface is based on reducing the wetting surface in the water, not based on the hydrodynamics of the leeward hull going through the water. You gain more in lost drag than you lose from the inefficiency of an angled hull in the water. That's where canted hulls came from. So that you not only reduce the wetting surface of the windward hull but also keep the leeward one level when you heel the boat. -
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Posted: May 11, 2018 - 04:34 PM
Not really sure how bedding the beams would alter the structure. Canting aside, the fact is, you sail a boat with horrible beam/seat tolerances. Most older boat saddles are horrible. In fact, one of the best things you can do to stiffen a boat like yours is bed the beams. If you doubt me pull one of the beams and look at the wear points. You will find that hardly any of the beam touches the saddle.
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Mike
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Posted: May 11, 2018 - 06:01 PM
This is incorrect.
Look at the early Prindles for example. The 16 and 18 hulls have their decks at a significant angle because they were designed to be sailed with one hull out of the water. The factory- based Prindle Class Association published articles about this in the 1970's. The asymmetrical hulls provided the best lift to the windward mark when sailed in exactly this manner.
Here is a view of how far down the decks come inboard:
https://www.thebeachcats.…8b930dcc1ba2aca612cbca64
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Sheet In!
Bob
_/)_____/)_/)____/)____/)_____/)/)__________/)__
Prindle 18-2 #244 "Wakizashi"
Prindle 16 #3690 "Pegasus" Sold (sigh)
AZ Multihull Fleet 42 member
(Way) Past Commodore of Prindle Fleet 14
Arizona, USA
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