Power Foils-added power to carry sail...

Power Foils

Bistros, nice to see that you recognize the potential-thats all that could be asked in a development of this type this early on.
-Perfect conditions are not necesary-bi-foilers have proven that they are able to sail in the worst of conditions. I would expect that this system would work anytime a "normal" bi-foil arrangement does.
-Usually downwind you don't need the RM you do upwind but I imagine this boat will be sailing "upwind" anytime the conditions allow the power foils to be used on any point of sail.
-Since the power foil provides only about 34% of the RM upwind it is highly likely that a momentary loss of downforce will be able to be managed by the crew with heading changes, sheet adjustments or both. Testing is the only way to resolve this-but as you say-the potential is great that this system will work exceedingly well in most conditions.
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The small size and very low weight of this system is a pleasant surprise-my personal boat will be definitely be fitted with the system.

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There is another very exciting way to look at the potential of the power foil system. The Rave and Hobie Trifoiler are MUCH faster than a Moth if you compare topend speed but neither does well in very light air-say 5-6 knots.
A bi-foiler designed to use the power foils( using the example above) would weigh 160lb all up( 350 with 190lb crew) yet could carry 190+ square ft of SA
UPWIND. That gives a power to weight ratio way better than a Moth,Mirabaud,the RS600FF or the R Class bi-foilers. Basically, the power foil system may be able to offer better light air takeoff and speed than any of these boats while more closely approaching the top end speed of the multifoilers than any other bi-foiler. Time will tell- it is an exciting concept!

 

I can see a new business partnership....Lord & Ostlind Ltd.

If it can sail fast in say 1.5 to 2 ft waves, and can be strong enough to withstand the occasional pitchpole, I think it would be a very exciting boat. I agree with Doug that the 1st stage is to see if the thing will work. The practical details can follow. If it's dangerous, maybe the crew could wear some kind of safety harness. Power boats are dangerous too, but we still see them everywhere.

Also, I wouldn't rule out the possibility of sailing on lakes and sheltered waters.

Chris, personal projects don't need deadlines. My one took ages and it changed constantly while people were giving me lots of advice. I owe those people nothing other than respect and gratitude.

 

Doug:

This is another area where actual experience on the water in a full scale apparent wind boat is useful. Guess what direction apparent wind boats sail 95% of the time?

Upwind. At least upwind to the apparent wind. Therein lies the issue I was trying to raise. If you are going on a broad reach off the wind (which would definitely be upwind apparent wind sailing in today's foilers), and you lost the "retractable power foil", the sudden loss of RM, combined with the sudden drop in speed would certainly be a recipe for trouble.

Rig loads on apparent wind boats are very low at high speed. As soon as anything happens that drops the boat out of apparent mode, the rigs loads double and triple instantly, and swimming is imminent.

If you have spent time in a Rave, you must understand the huge difference between conventional sailing and apparent wind sailing. Your "retractable power foils" will not just be used upwind in the conventional sense - they will be used most of the time as the boat will think it is sailing upwind if it is working as intended.

If you were interested in my opinion, I think your power foils should be considered for their "real" usage i.e. most of the time sailing. If you do consider their use 90%+ of the time, then I would also think seriously about how to automate and simplify their control. Based on the results of foiling empirical data to date, this points to using wands and feedback control systems.

Something to think about.

--
Bill

 

Looks like an International Moth with training wheels.

 

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I thought I had made the point that the boat would be sailing "upwind" most of the time with this comment: "upwind"=apparent wind
"Usually downwind you don't need the RM you do upwind but I imagine this boat will be sailing "upwind" anytime the conditions allow the power foils to be used on any point of sail."
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I still believe that the power foils will not require wand based altitude control on the boat described earlier. I could be wrong but I don't think so. But using very small foils just to add RM is a concept not limited to a monohull foiler.
If the same concept was scaled up to 20' with an 18' beam with very small "amas"( about the same volume as the pods on the 16) and power foils of .5 sq.ft.(twice the size of the 16 but still very small-less than 1/2 the area of Moth main foil) a 250lb crew on a 260lb boat could carry 290 sq.ft of SA upwind in 20+ knots of wind. W/SA=1.77(Moth=2.558-smaller better)-a very good power to weight ratio for a trimaran.
And on this larger version, Bistros, you are right: wands will be the way to go

 

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You're right-thats the point-makes it much easier to sail in seahugging mode-like sailing off or into a beach. Of course, the little foils make it much faster which could result in a boat 40%+* faster than a Moth, that takes off in lighter wind and is easier to sail.
*the man that designed the first two person bi-foiler in history estimated 46% faster than a Moth with a bit more beam and 24% faster with the beam and foil size quoted above.Thats in line with the fact that both the Rave and Hobie Trifoiler are much faster than a Moth in straightline speed at their topend. The new concept may allow the both of best worlds-very light air takeoff and very high top end speed in ideal conditions.

 

Eric Sponberg could design the mast. I would want it to be a stayless rotating wing. 37 knots doesn't seem impossible to me, but at those speeds I wouldn't want to pitchpole and land on a stay.
At 20' LOA I would consider 2 masts (one forward, one aft) like Gary Baigent's Cox's Bay Skimmer. Lots of power low down. Short masts are light.

 

Power Foils Summary

1- W/SA has nothing to do with wetted surface. It is a "quick look" ratio for preliminary comparision of foilers. The Moth is the standard at 2.558-the RS600FF, Mirabaud, the M4, aeroSKIFF1 are all very similar despite their size differences. Smaller is better.
W/ SA = W(all up weight incl crew in lb) divided by SA( sail area in sq. ft.)
16 w/o Power Foils:
1) boat weight 160lb
2) crew weight 190 lb
3) Sa= 134 sq/ft
W/SA=2.61
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16 with Power Foils:
1) boat weight 168lb(updated)
2) crew weight 190 lb
3) SA 193 sq.ft.
W/SA=1.85
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Power foil area=36sq.in=.25 sq.ft.
16 Mainfoil area= 1.75 sq.ft.
Area of Power Foil =14.3% of mainfoil area
Section of Power Foil (initial only) 63412
The Power Foil operates at a CL(lift coeficient) of .2-.6 roughly the same as the mainfoil. That range is the range of the "(low) Drag Bucket" for this foil.
The Power Foil drag is, therefore, about 14% of the mainfoil drag.
So, these figures are close to correct and the potential for the Power Foil is simply,unequivocally something around outstanding:
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Comparing identical boats the boat with power foils has:
--- a 144% increase in Sail Area
--- a 150% increase in Righting Moment
--- independent(from me) rough calculation of POTENTIAL speed increase over a Moth=24% with current(12') beam to 46% with an increase of beam to 18'.
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POWER FOILS:
a. power foil each side(only one used at a time):
---very small foils: 36 sq.in. area:2.25" chord; 16-18" span (depending on taper)
b. Max RM w/o power foil @ 20 degrees veal heel: 1475ft-lb
c. Max RM with power foil @ 20 degrees veal heel: 2225 ft-lb
d. SA w/o power foil= 134 sq.ft. W/SA= 2.61(equivalent to a Moth with 158lb crew)note: for reference Veal=154lb .
e. SA with power foil= 193 sq.ft. W/SA= 1.85(equivalent to a Moth with a 93lb crew-except the power foil provides the extra RM-in other words much more power for its weight than a Moth)

 

All other gibberish aside, I would love to see the arms on the guy who is singlehanding and hiking down an oversized Moth while trimming a sail that is 193 sq. ft.

I guarantee it is not going to be the Lord of All Ridiculous Calculations.

That's 68% larger than a Finn's sail, 29% more than an A Cat, 30% more than a Hobie 16 main, etc.

Please post the sailplan drawing of this ridiculous contraption.

 

Power Foils

And less than 50% of the upwind SA of a 21' Mini Ocean racer rountiely sailed long distances at sea singlehanded.
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17' Rave Foiler-195 sq.ft. upwind sail area-singlehanded
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Hobie Trifoiler-215 sq.ft. upwind sail area-singlehanded

 

You continue to show how out of touch with reality you are. The more you defend, the more people see how looney your ideas are. You are obviously not too bright. Gee, is anyone surprised that you did not post a sailplan drawing. Not even sail dimensions, eh?

Actually, your sail area is about 75% of the mainsail area of a Mini. On a Mini you are not hiking, you can use your legs and back to help trim the main.

You don't sail either a Rave or a TriFoiler like a Moth. More dis-information from the Lord of BS.

On a Hobie 16 some of the less powerful people really need to use their legs while trapping to get the main sheeted.


While "moth hiking" you will be depending on arm strength, with a lot of sheet ON/OFF to keep the thing in the correct attitude. You are just nutty if you think many people will be able to do that.

But we knew that about you long ago.

 

Power Foils

You don't sail a boat equipped with Power Foils like a Moth.

 

Your crazy talk is catching up with you..again. I hope you spend your last dime trying to patent this. That is if you even have a last dime, which is doubtful.

By the way, why haven't you been truthful about the area of the mainsail of the Rave?

Can't you get someone else to draw the sailplan of your contraption for you? I doubt anyone with real skills is willing to help you anymore. You are a laughingstock.

 

Power Foils

More info-post from SA(corrected):

1) Foil configurations have nothing to do with the relevance of W/SA. This ratio is a quick look comparison with a bias toward light air/early lift off. Since the Power foils are not used in conditions under about 15-20 knots of boat speed the comparison is valid.But just for the heck of it hereis the comparision at various beams including the download from the Power Foil as weight:
a. 12' beam, no power foil: SA 134sq.ft. ,All up weight (160-boat +190 crew)= 350lb; W/SA=2.61( Moth is standard=2.558-smaller better)

b. 12 beam +power foil: SA 194sq.ft. (168boat,190 crew,100 power foil download)=458lb; W/SA=2.37

c. 16' beam + power foil SA 215 sq.ft ( 172 boat, 190 crew, 100 power foil download)=462lb; W/SA=2.14

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NOTE: power foil is only used at boat speeds above, approximately, 20knots
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And here are the figures for the 16 in conditions up to about 20 knots boatspeed
a. 12' beam, no power foil: SA 134sq.ft. ,All up weight (160-boat +190 crew)= 350lb; W/SA=2.61 ( Moth is standard=2.558-smaller better)


b.12 beam, no power foil deployed SA 194sq.ft. (168boat,190 crew,)=358lb; W/SA=1.85


c.16' beam, no power foil deployed SA 215 sq.ft ( 172 boat, 190 crew, )=362lb; W/SA=1.68
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2)& 3) Drag breakdown:
a. boat w/o power foils-350lb; drag est @ 18/1 L/D ratio(total drag)= 19lb (SA=134sq.ft. RM=1475ft.lb.)

b. boat with power foils-358lbs; load due to power foil=100lb( boat speeds ofapprox. 22 knots and above-between 15k boat speed and 22 drag is much less); 358+100=462 load; drag @ 18/1 L/D =25.6lb (SA 193sq.ft RM=2225ft.lb.) + 100/18=5.6lb Total drag w/power foil=31.2lb

c. Max drag increase with Power Foil=64.2%( boat speeds of approx. 22k and above)
Sail Area increase with Power Foil=44%(12' beam)
RM increase with Power Foil= 50% (12' beam)

d. At 16' beam xtra foil drag remains zero to around 15k boat speed ,low to 22k and as before after that. Max drag increase=64.2%
Sail Area increase with extra beam + Power Foil=60% (16' beam)
RM increase with extra beam+ Power Foil=67% (16' beam)

e. Potential speed increase(of 16 using Power Foils) over Moth @12' beam=24%

f. " " " " " @16' beam=39%

g. " " " " " @18' beam= 46%
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Note: since boat is sailed with 20 degrees veal heel there is some vertical lift from the sail that is not included here. It would be a drag reducing/speed increasing factor.

 

Doug at less than 20kts you might not use the power foil - how do you balance the boat during this time? Through sheeting and weight adjustment like a moth?