Rc sailrocket

I have the floats and foil set at 30 degrees relative to the fuselage when looking from above. So in theory wind resistance is at its lowest with an apparent wind of 30 degrees relative to the direction of travel. 0 degrees relative to the fuselage. Let's assume true wind is 30kmh
If we aim to keep the apparent wind at 30 degrees we can bear away as we accelerate .
The highest appartment wind speed (and therefore power?) achievable is 60kmh with the boat travelling at 240 degrees relative to the wind while moving through the water at 50kmh.

For a sail area of 0.9 m²
Air velocity of 16.667 m/s
Air density of 1.225kg/m³
And coefficient lift of 1

We get
1×0.6125×277.77×0.9= 153

153 newtons from the sail compaired to the 152 newtons previously calculated for the carbon foil . I reckon that is definitely ball park.

 

Hi Glueandcoffee,

Thanks, but no need to explain the rear foil as Alexander did it, just after the post you refer to.

About CL2(two dimensional) and CL3(three dimensional) Alexander gave a good explanation where he uses cl and CL instead of my CL2 and CL3.

Use CL2=cl when setting incidence, use CL3=CL when calculating lift.


"The carbon fiber one is 180mm radius to tip. Radius chord 80mm. Tip chord 65mm. Estimated profile naca2315. Has ventilation fence."

Must ask, as I get 0,013sqm whereas you use 0,00774sqm in your calculation? Mean value of chord 0,0725*0,18=0.0130sqm, AR=2,5.

If using Alexanders formula foil CL*foilarea=(sail CL*sailarea)/800 I get foil CL=0,087 when using area 0,013sqm, corresponding to cl=0,18 and incidence in the ballpark of -0,5 degrees.
The alternative is to use foil CL=0,15 that gives an foil area of 0,oo75sqm. This is not far from the area you used in your latest calculation.

Some of the guys sailing RC-foilers use helicopter rotors for foils. Got the idea they would fit as a larger span and shorter chord, ie larger AR usually is beneficial.

If we assume your present foil probably being less efficient, the figures are good enough for testing, looking forward to your first IRL tests. Weather in Cork seems to be less promising at the moment.

 

Oh. Thanks for the explaination of that. Thanks for pointing that out. Definitely did something wrong on the calculator. I don't think I could have gotten so close with the error I got if I tried. But I'll keep crunching and see if I'm understanding the cl/CL.
I know someone who would definitely have large rc helicopter blades . But I think the problem with those is making an L foil. I can imagine it being quite difficult to get good strength at the intersection. And cavitation is more likely on a sharp intersection instead of a let's say 1 inch radius .
The weather is is rarely promising in Ireland. We do have 15 knots forecast for tomorrow evening. I'll play it by ear , see if I can test it.

 

I still have to paint the name on it . I was thinking Awegon . Its a running joke between a few buddies and I . When something disappears or breaks disastrously someone says "awegon" like it's all gone said like a toddler stating the obvious. Hopefully when I get around to testing its controllable and doesn't crash too bad or sail off into the sunset. I'd hate for it to be named ironically.
Anyone have other name suggestions?

 

It is difficult to find good names. But necessary. Most of my sailboats have lacked names. That's probably the reason I have not been as successful in yacht-racing as I have in skate-sailing. Some 40 years ago a friend of mine christened my OK-dinghy "Ormboet" (the snakes' nest) because all automatic trim-functions I had (outhaul, kick and cunningham changed automatically as a function of the boom-angle) I think that was the last of my sailboats I have won any race with.

 

I have long thought that a suitable name for an experimental craft would be What Could Possibly Go Wrong? It should be accompanied by the chase boats Oh, Dear! and I Told You So!

 

Like the spaceX drone ships , Just Read The Instructions and Of Course I Still Love You , for landing the spent Falcon 9 boosters on after re-entry.