Wingmast rigs

[Bill]

After seeing Dick's post about C Class cats on the rcsailng forum, I was inspired to post the following. Since it got no response, I thought I'd try here in the hopes of getting some discussion started about these rigs. Because of the great speed potential of multihulls, I think winged rigs offer great potential for added performance. I'm surprised there hasn't been more interest in experimenting with them on a multihull platform. Sorry about the replication, but I'm not a good typist & I'm lazy ;-).

Thanks for the wonderful images of winged rigs. Is that a panel of fabric between the main wing & the flap? My personal opinion is that rotating wingmasts in combination with sail fabric will be preferable to solid wings in modeling applications, because of the need to minimize weight & reducing complexity (KISS! principle). Some excellent discussion of wingmast (& solid wing with flap) can be found at: groups.msn.com/LandsailerandIceboatdesignandconstruction/messages.msnw

Of particular interest is Tom Speer's paper about wingmast rigs using the X-Foil modeling program: www.tspeer.com/Wingmasts/teardropPaper.htm

One example of rc multihull applications had been done by Bruce Ewing in NZ radioyachting.com/multihull_photos.htm (scroll down).

Wing rigs offer several advantages where boat speed can exceed windspeed such as multihull & solid surface applications (iceboats & landyachts).
Regards,
Bill Korsgard
Madison, Wi USA
www.iceboat.org/RCBoats/rc%20boats.htm

[MultiFast Is MultiFun]

Hi Bill - thanks for your input based on your landsailing r/c racing experience. I think perhaps you are correct in your views, since we all know that a solid wing works - and probably better than a wing mast with soft trailing sail ... but the fact is that there is a lot of technical issues and details to overcome - and many are very difficult in such a small wing as compared to a full size one on a cat from18 feet up to 25 feet!

Just finding and mounting micro servos to control flap postions are a challenge in themselves - even with todays small servos. Still I think we find it much more "fun" to discuss solid wing sails, than wing masts, and more fun to discuss rotating wing masts than to discuss a "regular" mast ! ;D

Just my opinion of course, and speaking for myself, I certainly would be interested in disscussing the layup of a very lightweight, strong wingmast section. My two previous attempts using a spruce core, foam shaping with glass over just came up too heavy. They will work, but lighter weight is definitely called for.

Please feel free to post your building methods.

[Bill]

Hi Multi,
I'm not sure I agree with your heirarchy of which option is "more fun" & freely admit a preference for the wingmast/fabric rig over a solid wing (with or without flaps). My experience with full size iceboats leads me to believe that this is the way to go. Solid wings have been tried with some success, but seem to work well under a narrower range of conditions & reportedly take more time to develop speed. The dirtboat sailors out west have done more with the wings, but the fastest racing boats still go with fabric. On models, light weight & simplicity are essential as well.

As far as constuction, I built my early versions with balsa & a sitka spruce leading edge, but have since gone to glass over a foam core for lightness. The glass is vacuum bagged over the foam using techniques developed by the rc sailplane guys www.pilotsguide.com/rc/vacbag.shtml
Then I use a hot knife (sharpened soldering iron) to cut in a luff groove, into which I insert the 4 mil mylar sail fabric which is held in place with tape at the batten locations. I've used ordinary blue Dow Styrofoam,
but lately have tried Dow "Hi-load 60" which has much better compressive strength.
The foam cores can be shaped by hand carving, or using a hot wire cutter. Setting up a hot wire cutter is a whole other project, so I've been buying my foam cores from Mark Mirada who has a CNC cutter www.cncfoamfactory.com

As far as the wingmast shape, I've been using NACA 0020 thru 0022 profiles tapered from a chord of 4" at the base to 2.25" at the tip over a length of 68".
A good source for NACA airfoil shapes is at: www.pagendarm.de/trapp/programming/java/profiles/NACA4.html
You can pick the shape you want, adjust the size & print it on paper which can then be used as a pattern for shaping.

The airfoil profile of the wingmast is only one issue to consider. The overall camber of the mast plus the sail fabric determines the total airfoil at any particular location along the span of the rig. Of course, the amount of mast rotation, leach tension & twist will control spanwise variations of this profile. There's alot of variables & I'm just starting to get them figured out (I think...;-)....).

Regards,
Bill Korsgard
www.iceboat.org/RCBoats/rc%20boats.htm