Gunboat G4 with UptiP Foils

G4

From catsailingnews: They'made the UptiP foil molds....

 

G4

Picture from facebook with Peter Johnstone on the UptiP foil:

 

G4

Nearly ready to sail:
click--

 

This is a REAL Gunboat.
Don't know why it took them so long ... playing around with earlier and ugly caravan Gunboat versions.

 

G4

I'm not quite sure what to make of this article-is the guy implying that the Oceanvolt system will allow a G4 to fly with it's auxilliary power??!
http://swizzlesportsmedia.com/gunboat-g4-is-a-fully-foiling-tesla/

 

My eyes started to glaze over when I read the term "dispruptive" but I think his point is that it has a well integrated hybrid power system.

 

I think you have gone too far with the implications.
My understanding is that the auxiliary propulsion will serve for moments when the wind goes down, to allow the boat to not stay adrift. The leg of the drive shown in the picture is also too short for foiling, if that is the drive in question.

But, apart that, if you read the tech specs of the G4 at the Gunboat's webpage: http://www.gunboat.com/series/gunboat-g4/, you'll notice that the hybrid drive is not included in the technical description of the boat. Hence, the lightweight of 2700 kg does not include the drive(s) and the batteries.

Moreover, they say this:
"2. L-FOIL DAGGERBOARDS: When you achieve a 2.7 ton displacement, lifting foils make a significant contribution to performance. The L-foil daggerboards provide lift, reduce drag, and keep things safe when pressed downwind."
and
"4. EVERY OUNCE COUNTS! At this size, weight is key to performance. The GUNBOAT G4 is ALL CARBON and ALL PRE-PREG EPOXY, post-cured in an oven for added strenth. The Nomex honeycomb core is the lightest available. Every piece of the composite platform and rig is CARBON."

What do we read here? First, they are restraining themselves and are avoiding to make too stretched claims. That's a good thing, IMO, which tells that those folks are well aware of the difficulties they might experience with the new technology they are implementing. They are not saying that the boat will be flying - what they are saying in their official page is just that foils will give "significant contribution to performance".

Next they are saying that, in order to see the foils giving a contribution to the performance, the weight is of paramount importance. Which is something we already know very well. The fact that they are mentioning 2700 kg as the target weight might implicate that the foiling calculations were made with that design weight. Hence, adding an electric drive(s) would make the boat exceed the max. allowed weight for foiling.

All of it makes me think that the electric drive is an extra feature for those who want to have the auxiliary propulsion for days with no wind. I guess they will be advised by the manufacturer that this auxiliary hybrid system will probably kill the boats' foiling characteristics, and for sure won't be able to make it fly on motors only.

Cheers

P.S.:
After I wrote the very last phrase, a thought arrived...
"for sure won't be able to make it foil on motors only" - But what about a foiling-motorsailing? Actually, I had never thought about that possibility. Now that is an idea which could be explored! :idea:

 

Slavi, in many cases too much is made of a foiler needing to be light to foil. You always have to consider power. A few years ago a well known Mothie said that there will never be a bigger sailing foiler than the Moth because they can't be built light enough.
If you have the power ,you can make a lead brick foil. Weight is critical not so much to foil but to go fast on foils.
My test model is an example: it is 21.13 lb and I was told by numerous people it would never foil at that weight. Surprise! It foiled-and it did so in a 5mph wind. 21.13 lb is the equivalent of 3.5 people on the full size boat. And it foiled with less power than my production RC foiler 15 years ago.
I don't doubt for a second that the G4 guys have included more weight than what is published in their foiling design. They advertise the boat as a cruising foiler in some recent publicity-saying it will "fly". Peter Johnstone posed on the UptiP foil molds to emphasize that(see picture below).
And I don't doubt for a second that the right amount of power would get the thing up on foils-whether sail or engine or both. When I read the article above there was too much talk of Tesla for there not to be some intent to use the power to motorfoil in very light air. I thought a lot about that last night and something is up and it could truly be mind blowing-very exciting!

Picture-1)weight is not critical to foil IF you have the power,2) Peter Johnstone on the G4 foil:
click--

 

I have made a couple of very quick calcs. Looks like it can fly on electric power, though for a rather limited time.

In order to fly that thing at 3500 kg weight (lightweight boat plus motors, batteries, controllers etc etc), looks like they would need approximately two 14-15 kW motors and two good props. That would leave some 650 kg for batteries. The question is - how much energy and power can 650-700 kg of batteries give?

The manufacturer of Tesla cars claims that their batteries give 0.6 MJ/kg. At 2x15 kW, 1 hour of ride requires roughly 140 MJ of energy (considering some allowance for Peukert effect). It means that each hour of ride requires 140/0.6= 230 kg of hi-end Li-ion batteries. So, at 3500 kg boat weight, 650 kg of batteries can give 2.8-3.0 hrs of flying in ideal conditions. Possibly less than 2.5 hrs if we consider the aerodynamic drag of the superstructure and the rig. All rough numbers, of course, but the ballpark shouldn't be too far off.

Unfortunately, can't dedicate more time to this for today, have to go now. If you want to carry on the math, you're welcome.

Cheers!

 

G4

Thanks, Slavi-very interesting! It would be fantastic to see that thing flying under power-even for one minute...I'm still not sure what their intent is-but it's very ,very intriguing.

 

The system isn't that heavy. There is only one motor. It won't fly on electric power.

 

There are some details in a brochure on Oceanvolt's site about the system. It seems to me that unless you are only overnighting you will probably still need a generator depending on accessory load and motoring distance required. I like the compactness of the electric motor and sail drive leg it looks like you could make it retractable in a case with a bit of head scratching.

http://www.oceanvolt.com/media/files/oceanvolt_multihull_small.pdf

 

Nice find. If that is the G4's drive, then 2x8.6 kW won't make it fly.

 

G4 Powerfoiler?

The more I've thought of a motorsailer that foils w/o sails or with sails the more I like it. It may or may not be the G4 this time around but it is too good an idea to just fall by the wayside.......
Thanks for the info, Corley.

 

It is a retactable unit in the G4. It can regenerate, and charged by solar panels.