Enrico -
a couple of thoughts for your consideration … determine “what” you want the wing to do. Start by using a leading edge wing portion and a single flap. Obviously both must be symmetrical foil shapes and designed for low speed performance. We started our landyacht by using an indoor/park flyer and simply made back to back wing foil sections glued together. You need to only control 4 basic adjustments
No camber - No angle of attack
No camber - adjust angle of attack
add camber - no change in angle of attack
add camber AND change angle of attack
Originally we tried using a double arm servo - but could not adjust independently - so needed to use a double servo - one for wing angle and one for flap camber/angle. Add more flaps on trailing edge - you get/have to add more servos to control each flap separate from the others. It “could” be done using cascading pulleys/lines, but was a pain to adjust as they were inside the wing. Try (as Disabled suggested) just using a simple set of minimal elements to start. You can get progessively more sophisticated later and start adding other controls. My first wing-plus-flap had camber adjusted on shore - just like a softsail using an “outhaul” type of manually set line controls. As you would expect, once on the water (just like a soft sail) there was no easy way to make adjustments… but that can come later. I’m not sure who posted earlier, but there is always a problem in adjusting sail trim when you aren’t on board - and like a multihull - you can only react to what you see is happening - often too late to recover.
If you want to start with a quick, easy build wing “MAST” - you can use one of these methods - all you need to do is connect two of them together for wing with flap.
I’ve also quickly “raided” my photo stash of wing mast stuff from a variety of sources - some showing single element wings, some showing mast build ideas, and there is one of a 2 Meter with a single wing/no flap. The fullsize wing catamaran photos are of “WILD TURKEY” from back in the early 1980’s and one can easily see the power generated by a wing that is less than 10 meters tall an a 5.5 meter hull !
Perhaps some of these may cause braincells to work to come up with innovative alternatives.
Dick, thank you so much for the information, it sure is valuable. I been reading the German website forum and that seems quite complex. Unfortunately with mono hulls, racing allows only 2 servos so control will be limited. Maybe for a class or off class that allows multiple servos, the task could be simplified. My plan is to eventually put a wing sail on my RG -65 Round Rangers and/or Cobra 5. Don’t have anyone to race against here, but maybe it could be that some eye brows get raised and we start a class. Oh, well, back to the building board. Didn’t manage to get anything accomplished this morning, so hopefully I’ll be able to play around with the concept for a bit. OK, i’ll sign out for a bit to work on the rg-65s I have to build, and experiment while the glue dries!! I’ll be checking the forum in case more progress or ideas come through.
Thanks again!
Enrico
Just a thought, forget the servo rule. Just to see if the wing sail on a monohull would be faster than a soft sail. I think that’s the question. Keep everything else the same, hull dimensions, sail area, etc. Just use a computer radio with a slider to control the camber.
Hey GUZZ,
would you be so kind to give me/us the links,
where I/we can find more about Dr. Mark Drela, XFOIL and XFLR?
Or, as you appearently have the program(s) would you be willing to give me more datas for a four parted wing of 100cm width at the bottom and 50 cm at the top - 276cm high?
My idea is to basically follow the datas and technology the german gent uses for his mini40 wing,
but start with the big thing - as I got thick and clumsy fingers.
Dimensions:
Each element is 69cm high (4x = 276cm)
The lowest element is 100cm/100cm wide.
2nd element 100/91.666cm wide.
3rd element 91.666/75cm wide.
4th element 75/50 cm wide.
Makes 2.3575m2 overall.
Forward profile is for now 50% of the overall cord - 50/25cm wide - NACA 20%.
Aftward profile is for now 50% of the overall cord - 50/25cm wide - NACA 12%.
Is there any way for you to verify the efficiency of/for these profiles and/or
a way to show me/us that other profiles would be better for the given Reynold´s numbers?
Below is a rough first scetch of the wing I intend to build for my 2M catamaran.
Carbon, Epoxy,peelply, vaccuumbagging and so forth aren´t the problem.
The forward 34% of each profile (the “nose” of it) will be laminated over a male plug.
Possibly 2x 160 gr. carbon. Main shear web 3x 160gr.
But this could also be built lighter/thinner.
In order to be able to do this, the main shear web needs to be straight all the length up to the top.
This is shown in the right scetch posted above.
As the forward (main) profile may be a NACA 20% of 50cm at the bottom,
the shear web would be 10cm wide.
With 25 cm at the top it is still 5cm wide.
( And with that size/thickness it´s no problem to install servos for twist and cambercontrol inside the wing!
One servo for each element. -
Which is one reason, why I want to build in that size.)
The aftward (flap) profile may be a NACA 12% of 50cm,
it´s shear web would be 6cm wide at the bottom and 3cm wide at the top.
If there is a way for ANY person of this forum,
to make an (educated) suggestion about this project, please tell me.
FYI - Xfoil is somewhat difficult to use, as it’s text based. XFLR is a bit easier, as it uses the Xfoil code inside a graphical interface. But both require work to learn. I’ve only barely touched on their capabilities.
The airfoil investigation database has the polar graphs for various airfoils for the low range of Reynolds numbers, which is what XFOIL or XFLR generate, which quickens the search/elimination process. But then you really need to take the airfoils you like, the put them into XFLR, generate the polars for the Re range you want, then build the wing in the software and look how it behaves.
Which NACA 12% are you looking at? NACA 0012-34, NACA 0012-64, etc.? They are all 12% thickness airfoils, but of varying shape, and different CD, CL, CM.
A really good, but really in depth, tutorial for the process of using XFLR is in RC Soaring digest Feb-2008 (It is really in depth, and sometimes hard to follow, but it is really good).
Also, you can read the thread from RCGroups, Experiment 1 - my attempt to learn design in the Hand launch forum to see someone going through the learning process of using XFLR. (It inspired me to learn it, since my other love is Discuss Launch Gliders, but I’m still a newbe working with it).
