Hi Jolly,
If you took all the presently available US built boardless beach cats in the 16ft, 17ft and 18ft length range and measured their bow heights and then took them out and made them pitchpole using the same sailing technique, you will find that the taller bow height boats are harder to pitchpole than the shorter bow height boats.
The imiginary boat you described with the torpedo hull shape underwater has no pitchpole resistance because there is no reserve bouyancy at the bow. It is the reserve bouyancy, the freeboard, in the forward end of the hull that when pushed underwater makes the center of bouyancy migrate forward in the hull and this creats "restoring moment" which opposes the pitching moment from the sails and stops the boat from "pitchpoling". When the foredeck finally goes underwater, there is no further increase in restoring moment so the boat frequently "pitchpoles".
The craft you have configured with the Torpedo foredeck/hull shape that sails underwater has no additional or further increase in restoring moment as the bow is pushed further underwater. As I understand your configuration, it would pitchpole quite easily.
Think about the modification done to Playstation to improve its "pitchpole characteristic". How was that boat changed? The bows were extended 20ft and made much taller. These changes created more "reserve bouyancy" further forward and resulted in a major increase in restoring moment for Platstation which allowed the boat to be driven harder and faster than the original design.
sailing rules, meet Mr. Bernoulli
Bill,

>>If you took all the presently available US built boardless beach cats in the 16ft, 17ft and 18ft length range and measured

Well the list that results from this condition is not really big is it ?

Hobie gateway
G-cat 5.0
Arc-17
Hobie 16
Nacra 5.0


All others like Mystere 5.0 are of course canadian. Other hobie products like the Pacific are European build. Isotopes and such are of course american build aren't boardless. I don't understand what boarded or boardless is imporant with respect to pitchpoling Than the Nacra 5.7 is longer than either 16ft. 17ft. or 18 ft. And so on and so on.

So what bill is saying out of the list of 5 boats, as given above, the "higher bow - higher pitchpole resistance" is valid.

Of course in general this is not always the case although it is often unlikely that taller bow boat is worse than a shorter bowed boat.

The counter example is of coure the difference between 90's generations A-cats and the new Flyer A-cat shapes. Here the smaller bowed hull has more dive resistance because of other aspects that were changed. However these don't fall under the definition as given because these boats have boards or are often produced outside the US. The A2 is of course US build but not available yet.

Wouter

Wouter,
You could add P16 and 18 to your list.
Check the man's first post. The man asked about the SC17 relative to Hobies and Nacras. He is not a racer and wants a boat for daysailing and he is considering the SC17. He asked if it was more pitchpole resistant than Hobies and Nacras. I was trying to give him a simple way to compare boats of the same size/type rather than just say, "yes, the SC17 is more pitchpole resistant".
Bill
PS If you want to go off on a tangent, get into a discussion with the guy purposing Torpedo shaped submarine hulls for a catamaran sailboat.

Remeber that the extra bouyancy should not be used during normal sailing, it is just as an safety margin when you sail the boat bad! Using the extra bouyancy gives you loads of drag compared to using the normal water line.

The new A-cat shape requires that you sail the boat correctly. You have a designed water line, sail the boat that way. If you get the bow to much down, move back and depower the top of the sail and get the boat back to normal position. No one sail the A-cat bow down when going downwind! You might need the non existing extra bouyancy in some extreme conditions, but how often does that occur? The A-cat is a racer and is designed for upwind-down wind racing during "normal" conditions.

Weight
Is a heavier boat is more resistant to pitch poling than a heavier one?!
Take an M20 sailing downwind, add 80 kg in the middle of the tramp or maybe a bit above to compensate for a heavier mast and rig. Is that better or not?
The righting torque for pitch poling divided by total weigh of the boat including crew is always better in a lighter boat.

/hakan

Wouter,
I have seen some of these 90s design boats with the downward sloping foredecks pitchpole when no other boats in the race pitchpoled. I guess someone needs to tell the builders of some of these new boats about the "other aspects".
Bill

I have to argue for the carbon mast on the T. Like someone said on that thread (no, I have not read it in a while), instead of buying several extrusions and testing them to find the best/most suitable, have a mast built like you want/need and be done with it. A team can have a mast(s) tailored to suit their needs and the bend characteristics and quality can be more tightly controlled.

As far as narrower and lighter goes... If you build a lighter boat, then less hull volume is required b/c the weight of the whole package goes down and requires less displacement. So, if you keep a similar volume, more of it will be in reserve for when you need it. Also, with a lighter boat, the crew then becomes a greater percentage of the total package weight and has more control and effect over the center of gravity. On the con side, weight aloft becomes more of an issue too (pitching). As you go to the heavier wider boats, it's not just the volume in the hulls that is keeping them up. Since you have more beam, the crew can get further away from the bow and has more leverage (fore and aft) against the platform to keep the bow up.

W

You of all people Bill should know that to say that "a higher bow has a lesser tendency to pitchpole" is way too simplistic.
Darryl

Will,
I think this post belongs in the Tornado mast thread. But anyway, picking out an aluminum mast to suit a team's wants/needs, assuming such a mast exists, is a matter of going to the boat source and testing several masts from the mast storage rack. You do not have to buy several masts to pick out a stiffer one or a softer one to suit your wants/needs.
Your next comment about the carbon mast confuses me. You start off saying a team can have a carbon mast built like you want/need. Then you go on to say its quality can be tightly controlled. If a carbon mast is built to each customers needs, every mast is a different composite layup. On the other hand if the quality is tightly controlled, all masts are identical in layup, weight, section, bend characteristic, CG location,etc..
The other part of your post has to do with narrower and lighter which I think is a spin off from the SC17 pitchpole question. I'm lost.
Your comment about, "on lighter weight boats the crew becomes a greater percentage of the total package weight and has more control" over everything, total sailing weight and max righting moment, is very true. Boat weight plus crew weight equals total weight. Total weight is the prime driver of hull drag. Lighter weight boats become righting moment limited in less wind strength and require crews to trapeze sooner. Max righting moment determines max sail thrust sailing upwind especially. The two most important drivers of the speed of a particular sailboat design are HULL DRAG and SAIL THRUST. On a lighter weight sailing system the crew weight affects both hull drag and the sail thrust to a greater percentage than on a heavier boat. The lighter weight sailing system will be more sensitive to variations in crew weight than a heavier weight boat. This is an inherent undesireable characteristic of lighter weight boats/platforms.
Bill

Bill,

You're confusing "quality" with "consistancy". Quality of carbon masts can be tightly controlled even though the consistancy can be varied. You can order a high-quality stiff mast, or a high-quality flexible mast. They can lay up the same amount of cloth, but change the fiber orientation to change it's characteristics.

With the aluminum masts, they try to make them all as similar as possible, and simply allow the differences that occur "naturally" in the tapering process to change the characteristic of each mast.

Basically- using aluminum, they build the mast and then figure out how stiff it is. Using carbon they determine how stiff they want it and then build the mast to suit.

Also- how is the lighter weight boat being more sensitive to crew position an undesirable characteristic? A good crew can change their position to tune the boat to the conditions. Also- a lighter weight boat with the same hull section as it's heavier counterpart won't be that much more sensitive as the crew will still be placing their weight over the same section of bouyancy.
However- I entirely agree that a lighter boat would need a correspondingly lighter rig. The A-cats have been known to capsize to windward if the crew allows themselves to get teabagged when a gust dies out.

Yes, I was commenting on quality and not consistancy. The quantity and layup of the carbon can me more widly adjusted than a aluminum mast can. The quantity or resin can also be tightly controlled. You all were talking a/b one designs and masts earlier, so I figured it did belong here. The A cats are one design, but different masts for different people. Stiffer sections for heavier skippers....etc

I think it's kinda nice to be able to see more change when shifting weight. Increased sensetivity to weight is just one more thing to consider when sailing a high performance boat. You don't see F1 drivers running around the course and never braking or shifting.

On a side note, what good is a high tech fast/efficent design if you can't push it hard? I would rank sailability high on the list of speed producing factors.

>>I have seen some of these 90s design boats with the downward sloping foredecks pitchpole when no other boats in the race pitchpoled. I guess someone needs to tell the builders of some of these new boats about the "other aspects".


Of course you did as at least one builder made a huge mistake while trying to copy the flyer design. He even called it an improved setup, but was wrong. HOWEVER, this doesn't means that the Flyer itself is less dive resistant than the 90's generation A-cats which had taller bows. Because the Flyer is regarded as more dive resistant.

By the way; the downward sloping deck is not the goal of the flyer design but a result of other factors. The working core of the design is the redistribution of the volume. Some is taken away from the top and put near the keelline.

But like I said in my other mail ; The rule that taller bows are better with regard to dive resistance than shorter bows holds in many cases despite the fact that exception are known.

Wouter

Bill,

>>You could add P16 and 18 to your list.

Haven't they have been discontinued and therfor they there not available in the US. At least that is what I was told.

Wouter

PS If you want to go off on a tangent, get into a discussion with the guy purposing Torpedo shaped submarine hulls for a catamaran sailboat.

Well that boat would be a pitchpole waiting to happen.

Wouter

Why do you think that? to my mind the thing that prevents pitchpolling is more volume in the bows, and a low drag bow regardless of the trim of the boat.

If you take Hakans view to the extreme, that any volume above the water line is wasted, then a torpedo would be a good shape if not the best.

Gareth

Hi Will,
Consistency is a part of quality. I too wish the T clas would go for three different stiffness masts but I do not think that is in their plan. "One size fits all". It is a good thing the rules makers don't think like that in Olympic track events and make everybody wear the same size track shoe because that is more "ONE DESIGN".
The outcome of an Olympic caliber catamaran race is much more highly affected the normal variation in crew weight than in the location of crew weight along the hull to minimize the inertia of the sailing system. The rest has all been said before so I am not going to say it again. Some day the rules makers will finally get it right.
Bill

>>It is a good thing the rules makers don't think like that in Olympic track events and make everybody wear the same size track shoe because that is more "ONE DESIGN.

You hit the nail on the head here Bill.

A good one.

I picked up a 1982 SC17 for $2500 this past summer to sail the windy afternoons at Cowichan Lake on Vancouver Island. I am really a novice sailor with good fundamentals - read a lot in preparation for cat sailing. I can tell you that the SC17 is a blast, a rocket flying a hull on the edge of thrill and terror; but thankfully no pitch poling in heavy wind and water. Several times I buried the bow, eased the sail ever so slightly and the bow came up like a surfacing sub. Quite easily clocking 25 knots and unbeaten against a Nacra 6.0 and a 5.5, and numerous Hobies. The others look at my 25 year old SC17 in amazement! I can't wait for next summer, so much so I think I'll do some winter sailing off Victoria BC. THanks Bill Roberts!!!