Has anyone built a wing mast for a marblehead yacht? I been thinking about this for awhile, the mast would be round sect where it goes into the hull and have chord of 10 to 15 mm with a bolt track for the soft sail. I envisage a servo below deck to control the mast rotation.
It’s probably been done, but the chances of finding that person on this forum are surely just above zero.
If you have any wacky ideas in the Marblehead Class, you’re best bet is to just do it.
Maybe it will work. Maybe it won’t but you will have learnt something.
Check with the 10 Rater guys. Since these may be off-shoots with the Marblehead class (depending on formula) it is possible someone may have used a 10 Rater mast on a M Class boat.
Mark Gee would be the logical contact point. He used to be class secretary (position is now open) so email the 10 Rater class at: 10r@theAMYA.org and ask to have it forwarded to Mark. He did an article on wing MASTS for the AMYA magazine a few years ago, but I can’t find the issue.
Good luck. Dick
Waliki masts are all nice carbon wing masts. They are set up to auto rotate by having a pin on the front at the bottom and the shroud/back stay attachments rotate. You can splice in a carbon tube if you want a round section where it goes into the deck. The other option is to build your own.
Hi Lordy,
the rotating mast is one of my desires, I made several samples to check the feasibility. Some ideas borrowed from Land RC sailing models.
I will present my work with images. Never finished one !!! busy in doing a lot of other things.
The Modern Marblehead Rules alias Class M do not allow Rotating Masts if I remember well, only sleeve sail not wider then 40mm at the top.
Once I was thinking a main with sleeve and a small jib acting as a slat, see picture below.
Here the images
ClaudioD
few images more :
One important point is that the Forestay attachment shall be positioned exactly on the rotating axis
ClaudioD
Thanks for all the replies gents, you have given plenty of ideas to get started.
Mmmm… Geoff and me were talking about this idea in another thread, but better move the discussion here, as it looks other people have though a lot more on how to build this…
Some of our thoughs follow:
Rigid wings are allowed in RG65’s, but their whole lateral area is to be counted as sail area. The 12mm diameter rule applies to the mast when it’s not counted as part of the sail area… If I use a 30mm chord wing-mast, and count it’s area towards total sail area, then it’s not illegal… Just read about this!
Not a bad idea at all! May be tricky to get it to move freely around the mast when wind is pressing the sail… worth a second though. Oh, 12mm. dia is the maximum allowed. Typical RG65,s masts are 6mm dia.
Today you can buy a stiff 6mm dia. carbon fiber tube. I’ve never seen a different shape. A non rotating 12mm chord airfoil was what I was thinking of in the first place… 
Thanks for the pointers!
I built one years ago for a Ten Rater. I used wooden molding from Bunnings Warehouse. It was a near tear drop shape about 50mmx25mm. I just covered the section with packaging and laid up the carbon. Once I popped off the section I capped both ends and the forestay exit point with wooden plugs and glued in square balsa up the back edge. I just used stainless staples in the back edge and tied on the sail to the staples.
Keep your deck fitting as close to the front of the spar as you can to allow it to pivot. If you have to use side stays set them up at the fore stay attachment point. A simple mast spanner from the mast to the boom to set rotation works good.
You will need to be extra careful about lay up as its easy to get over weight.
Should read packaging “tape”.
mmm… received a PM from Jim, so it looks my rationale needs more elaboration… Here it goes… any ideas are very appreciated!
The other day I was looking at my RG65’s swingrig, and thought the 6mm diameter mast is a part of the design that can be improved. Main issue I think is turbulence created on/behind main sail. So I started to think restrictions and options. One restriction is the 12mm max diameter imposed by the RG65 rules on spars. Other restriction is weight (current carbon mast weights just 40gr). So I started thinking on two lines:
- Use a better shape for mast than a circle, keep it inside the 12mm rule. Looks difficult to achieve, impossible without shrouds.
- RG65 12mm diameter rule applies to spars. Is a rigid wingsail a spar? What about a hybrid sail (half rigid-half cloth) - is the rigid part a mast or a sail? So I started ask around interpretations of the rule. If these are allowed, then I may use a setup like the ones seen here: http://www.rcsailing.net/forum1/showthread.php?7039-Wingmast-for-Marblehead If not, go back to number 1.
In both cases the mast/wingsail must be allowed to rotate freely do align with wind… which adds to rig complexity, and possible weight… but solutions for these are already available I think.
These are my thougths so far… Help on the rule interpretation is appreciated! Thanks a lot for your interest!
Regards,
Thomas Armstrong
One possible try is the use of a semirigid carbon foil or similar, see pictures. Myself I have laminated it and cut in slices wider then on pictures.
Each slice should be around 5cm height and separated from the adjacents ones of about 2mm.
A bonded pin with some longitudinal tollerances to allow main to change form when backstay is adjusted.
Care shall be taken to create local “windows” for the Stay and Shrouds.
Once ready the full wing composed of hard and soft material, shall be slided into the mast and free rotation checked beore asembbly the spreaders and fixation of stay and shrouds.
CD
Shrouds and Spreaders can be deleted if a larger mast tube is used !
Of course from 8+6mm mast tube to 12+10mm, the extra weight is about +27g
but shrouds and spreaders are not needed.
CD