open 20 footer

[usa2]

the sailing here is great-except for in the summer when the fog rolls in and for at least 3 weeks there is no wind whatsoever.

[usa2]

another reason a foiler might not be good locally here is the ledges

Foilers don't have to have a fixed draft; they can be sailed at different altitudes with different foils or by having two position foils.
The max draft off the foils is not likely to be more than a "normal" dinghy of whatever size.

[usa2]

true, but if you hit a ledge in a foiler, you will most likely be going faster than a normal dinghy, unless you are truly flying and therefore drawing about 0 inches of water

[Paul B]

Originally Posted by CT 249

The Moth is defined by its ISAF rules as having an LOA of 11'. The normal measurement of LOA by IRC, ISAF and other rules does not include the rudder. Even fishing boats do not include outboard brackets and outboards and rudders in their LOA measurement. The outboard powerboat case is a classic one, because they need their outboards much more than a Moth foiler needs its rudder foil. The powerboat can't even move without its engines yet they and their mounts are not measured in LOA, the Moth can sail quite happily without its rudder foil.

So either EVERYONE ELSE in the world is wrong, or you are. Take a pick.

Hmmm...

Someone is claiming Moths are 12+ feet long. Same individual is claiming to be inventing a 12 foot foiling boat...

Watch for it.

[Paul B]

Originally Posted by usa2

that still doesnt imply who is doing it. Also, now you're just saying that they "believe it is an important part of the future of offshore sailing". That says they believe its important, but does that mean they are doing any R & D on this? And from what you said, you are convinced that some people you know believe it is important for future offshore sailing. i believe that statement, because obviously some people think that is important for future offshore racing boats. The question here is, of the people who believe it is important for offshore racing in the future, are any of them designers and /or other people who are working toward actually building an offshore foiler? and if they are, who is doing it. Most designers, if they have a website, would have some information available, unless this is a top secret project.

Read back re: other claims by this individual about boats that were "under development". Never any pics, sketches, or technical info.

[CT 249]

Doug, if you don't want people to read you as talking about BRYC as being like Bass Strait or the Southern Ocean, maybe you shouldn't cite the Moths there when replying to USA2's query "Say that you are designing a foiler for the sydney-hobart race."

LOA doesn't really worry me, it's just amusing to hear people singlehandedly re-define accepted terms. It's sort of like those marketing guys who call overweight, underpowered sailboats "skiffs" just in a lame effort to catch some of the limelight of the real skiffs.

By the way, I didn't realise the conditions USA2 had to sail in. Skiffs (here) are mainly creatures of the warmer, flatter waters (Brisbane, Belmont, Sydney) where clubhouse poker machines support the cost of the boats. Even the designer of the current League 18s, who comes from New England, believes that they are not really suitable for most sailors from that area. He doesn't say that guys there are not hot sailors, they just tend to live away from the water, work longer hours than Aussies, Kiwis, Brits and Euros, and have a short season on cold water. Therefore they don't get normally get to spend the time on the water skiffies reckon they need.

While I'm certainly no skiff expert, I agree a blown-up 18 would be a major problem in USA2's big waves. How a 20' foiler would handle them I have no idea but all the current Moth foilers are sailed by guys who can already handle what is perhaps the world's trickiest boat, aren't they? That alone takes some trying.

(Actually, perhaps the current narrow Moth is the world's second hardest boat, the older fat skiffs where the most difficult boat to sail I can remember).

[usa2]

when the waves around here are small, as they are for most of the morning, then a skiff type boat would be fine. However, i then would need to be able to get back into the bay. Narrow deep boats optimzed for upwind work seem to work best around where i am

[Paul B]

Originally Posted by Paul B

You are in the ball park, but just a bit off. Of course the lug above the keel pivot can be quite short, so through a large range of motion it can stay inside the boat. As the length of the lug get shorter compared to the length of the fin the forces go up.

To see the real problem lay out the canting mechanism and run check the kinematics. As the ram pushes the lug away from the cylinder the included angle gets smaller and smaller.

As you can see from the attached image, once you get over to 55 degrees you are using more force trying to tear the lug off the top of the keel than you are actually canting the keel.

OK, now for some fun. On a big canting keel yacht I would think you would want the mechanism to be as "locked in" as possible. When canted to any angle I would want the system to be rigid. Or at least as rigid as a hydraulic system will allow.

Consider the attached quick sketch. If we mount the cyliner (gray box) rigidly, so it is always in the same place with the same angle things get interesting, and not in a good way. I am assuming you don't want this to toggle, although it could.

So let's mount the cylinder rigidly, with the shaft (blue) horizontal when the keel in in nominal position (centered). Line up the wrist pin in the keel lug so it is at the same level as the end of the shaft. Pin it all together.

Now push the top of the keel away from the cylinder. As the keel rotates around the pivot pin (which we'll also assume is fixed) the horizontal CL of the wrist pin gets lower. It is carving an arc and getting closer to the horizontal CL of the pivot pin. At 90 degrees they would be collinear. But at 45 degrees the distance would only be half of the original delta between the wrist pin and the pivot pin. This delta is even worse as the height of the lug increases.

So how can this happen? If the clyinder and cylinder shaft are fixed then the cylinder shaft cannot move down to stay with the wrist pin. Obviously the keel pivot is not going to move upward. We need some freedom in the system.

This could be accomplished with a slot in the keel lug for the wrist pin to slide in. But this would result in a non-rigid system.

We could have the cylinder toggle a few degrees, but again the system is not rigid when in position.

Does anyone know a simple solution for this problem?

[Skippy]

You don't want to prevent the cylinder from rotating. The system is still rigid because it only has one degree of freedom, even though it's a little complicated, and the cylinder is controlling it.

[Paul B]

Originally Posted by Skippy

You don't want to prevent the cylinder from rotating. The system is still rigid because it only has one degree of freedom, even though it's a little complicated, and the cylinder is controlling it.

Thanks for that. Triangles are great things. I had it stuck in my mind with the toggle in the cylinder AND a slot in the lug. That simply wasn't working. Sometimes can't see the forest for the trees.

Looks like the guys who do it for real really do toggle the cylinders:

www.cariboni-italy.com

[gybeset]

re "NOT in the case of the Moth foiler where sailing length is from the bow to the trailing edge of the rudder hydrofoil when the boat is on foils."

the sailing length when foiling is obviously not from the BOW. idjit

its sailing length footprint would be from its Cboard foil to its rudder foil, which btw would be a @#$% sight shorter than 11'

[Andy P]

[quote=gybeset]re "NOT in the case of the Moth foiler where sailing length is from the bow to the trailing edge of the rudder hydrofoil when the boat is on foils."

the sailing length when foiling is obviously - the length ( chord ) of the main foil which is about 120mm!!
The rudder is normally excluded from measured boat lengths. ( any dinghy, open 60 etc, even on extensions like i14, 12 14 16 18 skiff)

The int moth when sailing has a 'design waterline' length of 120mm ( with long overhangs)
If measured at rest, then the waterline length does measure 11 feet.

Since even the Moth class is discussing this on their forum I find it interesting.
As best I can tell the sailing length of a Moth (OR ANY FOILER)is from the bow to the trailing edge of the rudder foil regardless if it is on foils or not.If it's on foils the bow still comes into play and it is actually sailing on the rudder foil.
If it's not on foils then the overall length is again, the sailing length.
The foil footprint, in my opinion ,is from the trailing edge of the aft foil to the forward edge of the main foil.
Because of convention the sailing length was always regarded as the hull LOA-11' in the Moth case because back when these conventions came about speed was related to that sailing length-it isn't any longer.
Foils change everything and I think a modern definition of sailing length should reflect the two types of sailing that the boat does so a convenient-and accurate- definiton of sailing length(of a foiler) seems to me to include the overall length.

See the Moth Class discussion; click on "message board",then on "Rules and Regulations"; then click on "rudder gantries"
http://www.moth.asn.au

[usa2]

The Moths seem to have several different lengths depending on who you are and your perspective. Some people say thay are 11 feet, some say 12.75, and others say that they are just the length of the foils. If the boat is really flying off the rudder, than that wouldnt count in the sailing length, as Andy P said. Thats why Moths are called 11 feet, rather than 12 feet 9 inches. The only boat i have ever heard the rudder being counted was when Britton Chance hung the 12 metre Intrepid's rudder farther back of the underside of the transom and connected it to the keel using fairing strips. The Aussies protested this(successfully) even though it wasnt measured in the boats waterline. Nobody has complained about moths being a foot and 3/4s longer than listed, so i dont think foiling off the rudder is a problem really.