TMF versus CBTF

[Paul B]

Originally Posted by Lorsail

Yeah "Paul B", you must be right- after all, who would want to spend the big bucks to use such an unproven system on a race boat especially since as "2" points out the system has a built in brake when surfing in offshore conditions! Astute observations such as yours and "2"'s contribute mightily to the greater understanding of this obviously defective technology-too bad I didn't read all this first-live and learn ,I guess........

Of course you don't answer the questions, since you haven't a clue.

Bruce Farr designs have won all the recent Whitbread/Volvo Round the World races, including ALL the races in the Volvo 60 class and the final 3 installments of the IOR Maxi class. Nearly every team has gone with a Farr design the past two Volvo races. His team uses the best weather routing information possible, as well as some of the most sophisticated design tools in the business. So it seems he and his team might have a good plan for winning it again in the new Volvo 70 class.

So how many of the Farr teams do you think will use CBTF? If any of the teams don't (like the one already launched) why not? Are they "nuts"?

I think there are a lot of reasons an organization might not use CBTF-the biggest one in my opinion, is cost. None of the BTP(beat the patent) boats that are depending on sponsorship can afford not to consider things like the patent fee. And it is definite that some forms of ocean racing -Vendee, for instance, may not lend themselves to CBTF. But the criticisms made earlier are just nonsense: "suckng down the bow wave instead of rising up over it", "the forward foil is a brake in surfing conditions".
If you go to the Volvo 70 thread you'll see an interestng post by Nico where his analysis determined that CBTF would be faster in the Volvo-just a little bit- but still faster. He also thought that with a little more analysis he might find a daggerboard system better.
So with careful analysis related to a particular offshore race one system or the other may prove superior but I believe that if the call is a close one especially in a race like the Volvo-then the extra 5% per boat cost from the patent fee may be the deciding factor.
Another major factor mitigating against CBTF in the Volvo is the 40° limitation on canting the keel. Most CBTF designs use a 50 or 55° cant angle which can allow a more easily driven hull than the hull that has to live with 40° cant angle. The high cant angles of CBTF boats are critical to the performance of these boats allowing a lighter boat for the same RM and reduced wetted surface for the same length.
One problem that has surfaced with BTP(beat the patent) canting systems using a fixed daggerboard in my numerous experiments using extremely technically detailed RC models is that the BTP will develop excess weather helm as the keel is canted whereas on my CBTF models made with direct assistance from Bill Burns and Bruce Sutphen of CBTFco that is not the case-the balance of the boat does not change. This problem with fixed daggerboards and canting keels has led designers of such boats as "Full Pelt" and the Stimson 65 performance cruiser to put the daggerboard behind the canting keel so that the shift in the CLR as the keel cants keeps the boat in balance as the wind picks up. The BTP's utilizing trim tabs on the forward"canard" or twin asymetrical daggerboards mitigate this problem somewhat but I'd bet in equal boats designed with a high max cant angle(around 55°) that CBTF would always win out.
Boats designed to race to a rule that limits the effective use of a canting keel( 10° static heel or 30/40° max cant) AND that are designed to the specific requirements of a particular race
may ,in some cases, be less advantaged using CBTF then they would be otherwise.
And coupling that with the chance to save 5% of a million five or so could -and does-lead to various BTP solutions.
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Volvo 70 page 2 under "boat design"; Nico's post 17 and subsequent...

[usa2]

VO 70 canting limit is 40 degrees, not 30. It is interesting to note that while the CBTF system allows the "narrower more easily driven hull", only one CBTF boat- Genuine Risk- actually has an exceptionally narrow hull. The two TMF boats-Nicorette and Skandia- are both narrower for their length than the Z86s. It is also interesting that both Skandia and Nicorette can cant their keels well past the 10 degree static heel limit-which is why they were fitted with devices that limited the cant angle in the Sydney to Hobat. Your fixed daggerboard models, while interesting, have nothing do to with this because the TMF boats have RETRACTABLE daggerboards with trim tabs.
The MaxZ86s couldnt race the Hobart because of the rating limit, and now it looks like they are going to be completely outclassed by the new boats which are the 90' Nicorette and the rest are 98'+.
About the "brake". The forward foil is sucking the bow wave down, the CBTF website even has a diagram showing it.

[Paul B]

Originally Posted by Lorsail

I think there are a lot of reasons an organization might not use CBTF-the biggest one in my opinion, is cost. None of the BTP(beat the patent) boats that are depending on sponsorship can afford not to consider things like the patent fee... And coupling that with the chance to save 5% of a million five or so could -and does-lead to various BTP solutions.

Nice job of showing how little you know. These professional programs spend the money on the things that will bear fruit. They pay Bruce Farr's design fees, when they could save a lot by going to a less proven office. The successful programs hit the water early and spend a fortune on training and sail development. They hire the best professional sailors, at very high salaries. They build the boats from the highest tech, most costly materials and processes that are allowed under the rule. Last time around Assa Abloy built high tech female molds so they could save the weight of filler in the hull fairing and put those few kilos into the bulbs. That was a much greater expense than the cost of getting the CBTF license would be.

Your opinion that it is a money-driven call is ridiculous.

Originally Posted by Lorsail

If you go to the Volvo 70 thread you'll see an interestng post by Nico where his analysis determined that CBTF would be faster in the Volvo-just a little bit- but still faster. He also thought that with a little more analysis he might find a daggerboard system better.

No disrespect for Nico, his work is really something great for a student, but surely you are not going to compare his result with someone like Bruce Farr? We have no idea if Nico is a competent person at all (again, no disrespect for Nico). But because his result agrees with yours you refer to it.

Originally Posted by Lorsail

One problem that has surfaced with BTP(beat the patent) canting systems using a fixed daggerboard in my numerous experiments using extremely technically detailed RC models is that the BTP will develop excess weather helm as the keel is canted

It seems your models may not be as technically correct as they should be. Maybe you have no idea, but there are canting keel boats out there that do not have the problems you attribute to all.

[usa2]

the rc boats with fixed daggerboards are not accurate in any case, as no current big boat has a fixed daggerboard being used with a canting keel.

[usa2]

VO-70 Telefonica 529 miles in 24 hours. Top speed off the wind 36 knots. This boat uses 2 daggerboards. What happens to the CBTF forward foil when you are going 36 knots? As far as i know, none of those boats(MaxZ86s, Genuine Risk) have come remotely close to that speed. Nor are they expected to.