Gunboat G4 with UptiP Foils

G4 on foils

Video from onboard during initial testing:
https://vimeo.com/124671522

 

Ah yes , carbon fiber make a good bell although the foils vibrating at that freq. worry's me about their longevity!

 

G4 Timbalero Flying!!!

Extraordinary video of Timbalero-the first production cruiser-racer foiler in the history of the world:
https://vimeo.com/124676763

 

Amazing. The next few years are going to be very interesting indeed.

 

An album of photos on Facebook from Gunboat of the G4's first racing outing at Day 1 of Les Voiles de St. Barth: https://www.facebook.com/gunboatcatamarans/posts/10153179790408490

 

Pictures of the G4 in the Les Voiles de St Barth 2015 by Jesus Renado:
click for best view-

 

From catsailingnews.com :
"It’s really fun to be the last group starting, because its a blast passing TP52’s and the other big boats. We felt confident enough in the boat to pull off the port start, which we felt was the best point of attack. Most importantly, the boat behaved like a dream in the waves, we were very excited to see how well the foils calmed the sea state. The guys were in great spirits, everyone stayed motivated to push hard through the long course and we finished the day with huge smiles and high fives all around." -- Mischa Heemskerk after the first day of racing aboard the new GUNBOAT G4.

 

A couple of questions

I have done some searching but can't find why the Gunboat people have gone U tip instead of wand or active system. I know Tom Speer said you couldn't use active on a heavy boat but I do know that Jumbo jets seem to use active controls and they weigh lots only hang gliders don't use active control in aircraft. Tom knows more than me so there must be some good reasons - any good guides out there? Carbonic boats use active controls on their A class cats and there are no rules stipulating you can't use active systems like in the last AC for the Gunboat. Is it because of simplicity with no wands but then you get the added hassle of trimming the board case?

Also what about the cross over where drag is reduced by foiling. What is the typical speed to length ratio (or similar) where you get less drag by foiling. Obviously there is a point where it is less drag to float on the boat's bottom but cats with their very low drag shapes have low drag so the need to fly should be pushed back to higher speeds compared to a short fat boat like the Moth. Again any good reads out there on speeds required on cat shapes? IN one article Morelli from Proboat - https://www.proboat.com/daggerboard-debate.html - says the last AC cats had their crossover point at 25 knots. That seems awfully fast for big cats but they were 72 ft long. It would be nice to know how far down the chain foiling could come but would heavy normal cats benefit at all from foiling or are they just too slow and fat for it to ever work? I would love to see how someone calculates the foil type, area and worth of a foil configuration.

cheers

Phil

 

The UptiP foil is a major breakthru in foil design because it is the only foil with no moving parts that has intrinsic altitude control and allows a catamaran foiler to sail with a single main foil in the water. Since 34 boats like the GC32, Flying Phantom and Nacra fcs have been designed with uptip foils that need very little ,if any adjustment underway. My test model uses UptiP ama foils that have required zero adjustment under sail while controlling altitude with very different speed and load cases.
The foils can be designed for what you want the boat to do-in the case of the G4 they want foils that are forgiving in heavy seas-you can learn a bit more in the G4 thread on multihullsSA(see link below). In the case of of a small trimaran, you might want to ensure that the boat flies in light air (5knot wind)-it's relatively simple to design the uptip ama foils to handle that.
See the picture below of Dr. Bradfields 40' wand controlled foiler SKAT. The problem with a wand based foiler using TWO main foils is the limited altitude before the main hull bottoms out which can be designed out by allowing a foiler design that can heel. And/or: there is no reason a wand system couldn't be used on just a single main foil if you can simply retract the windward wand+ foil. But the wand system is more complicated than using a refined version of an UptiP foil.
The same leeway coupling principle that makes these foils work is now being used on Open60 monohulls for foil assist. You can read Tom Speers technical description of leeway coupling in "Sailing Foiler Design" here: http://www.boatdesign.net/forums/hy...r-design-foil-assist-full-flying-40894-4.html

Also more here: http://www.cupinfo.com/en/featuresindex.php "foils that shaped the Americas Cup part 1&2".
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If you're willing to pick thru the typical SA junk this thread has some technical nuggets about the G4 design: http://forums.sailinganarchy.com/index.php?showtopic=157244&page=2
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Pictures,L to R-1) 40' SKAT with wand controlled foils, 2) Pictures A &B show UptiP ama foils maintaining the same ama altitude in two different speed and load cases. The test model is designed to sail at a 10 degree angle of heel keeping the windward ama foil clear. Initially, the main wand controlled foil lifts the whole boat but gradually unloads until the leeward ama foil lifts the majority of the load-automatically, 3) Pictures 4 & 5 show boards utilizing the same "leeway coupling" principle first used on AC 72's on Open 60's just launched:
click for best view--

 

Thanks Doug - great links

I am always interested in things more cruising and where the foilers will meet more normal boats. It seems as though a good foil is hyper critical and very expensive - Morelli says they are almost pure high grade carbon and the most well made thing on the AC cats. Maybe some parts will trickle down in the future.

So the Gunboat uses U tips to fully fly downwind but does not fully fly upwind. Do you know if they set the foils to any AOA upwind to reduce drag overall or is it better to trim the boards to neutral pitch and just float upwind? I wouldn't want to have the foils pitched up in light winds when there is no possibility of foiling. Whereas Oracle was trimming the pitch all the time on the Gunboat is it set and forget once you work out the best trim for a particular condition?

Thanks for the tutorial

Phil

 

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I think the Gunboat is at least as "set it and forget it" as are the Phantom and GC32. You set the foils for the conditions and how you want to sail-the vertical lifting portion of the foil can be set to zero degrees(no lift) to even slightly negative to help stabilize the motion in non foiling conditions. The real design achievement of the G4, among other significant firsts, is the rough water capability of the foils. I do think that the Gunboat will foil upwind in the right conditions....
From a design standpoint when using UptiP foils it pays to read Toms correction of my using the term "like a surface piercing foiler" and then look at the pictures of boats like the GC32 Phantom and Nacra and G4. Tom specifically says that the fastest way to sail these foils is with the "up -tip" fully submerged though almost none of these boats do that on a regular basis. I think the boats that have the least required adjustment allow the uptip portion of the foil to break the surface on a reqular basis and I think Martin Fischer has even remarked along those lines for the GC 32 foils.
You can't beat these foils for ama foils on a trimaran-particularly if you have a bi-foiler arrangement on the main hull!
Below is a render of a 19' trimaran that should have been ready before now but may still be under development in France. It uses UptiP foils on each ama with rudder t-foils on each ama. I don't think that is the best tri configuration but I'd like to see it sail.

Pictures Exocet 19 and notice the inboard foil tips on the G4, Phantom and GC 32:

 

G4 over!

No story yet: (pictures by Sharon Green)

 

Ooops!!

 

G4 over!

Rumor that wind was around 10-12 with chop and ocean swells. If thats true it means the capsize did not occur with the boat on foils. Boat has been righted:
click-

 

The starboard foil is visibly extended in the pictures. Which might indicate that they were foiling on the port tack prior to capsizing.