It's probably no surprise to learn that we have been designing a wing sail for a moth...as we suspect a lot of other mothies have been doing. They've been around for a while on C-class cats and seem to work well. Below are a couple of notes for developing a wing rig for a moth:
Requirements
- Weight - tricky one, extra weight can be acceptable if the boat is faster around the course. consult VPP
- Watertightness - gotta be able to right it after a capsize
- Survivability - not essential but handy. if repairability is high not as important
- Repairability - if it breaks, must be easy to repair in a boat park
- Better Performance - waste of time otherwise, although it would be cool, consult VPP and mojo
- Transportability - not all of us can afford to pay ppl to look after our boat 24/7. break down to either component parts or easy to fit in a regular trailer. 2x2 piece option may work
- Cool - can't look too shabby
- Cost - preliminary costings indicate that unless it is a full carbon monolith, the cost shouldn't be too extreme compared with a traditional rig (mast, stays, sail and development of these). mods to the hull are another matter, particularly if the requirement is to switch back to conventional configuration quickly and easily.
- Arrangement - A stay-less wing rig seems like the best option on a moth. On shore handling and durability of the rig are the primary concerns with stays. This isn't locked in stone though.
- Construction - Good if it can be homebuilt without special requirements (space, tools, etc).
- full composite - likely to be too heavy and expensive
- composite and heat shrink - not a bad solution in terms of weight and cost, used by C-Class et al ie proven construction, transport is a killer
- sock over frames - with spinnaker clothe, light, cheap, not likely to be water tight and durability concerns
- styrofoam modules - cheap, heavy, don't capsize on a petrol slick, UV issues, water absorption issues.
- composite and heat shrink modules - demountable for better transport, a bit heavy, easy(ish) to build
- composite and heat shrink nested modules - easily transportable, not too heavy, but stiffness might be an issue without careful designt. Nesting refers to the open bottom which slips over the module below when rigged. All modules nest together like a russian doll for transport.
- composite and model foam nested modules - easily transportable, not too heavy, easily repairable, cheap enough, better stiffness than with heat shrink, free flooding but also free draining.
Option 5 (frames top and bottom) 
Option 6 (note open bottom, glass leading and trailing edges shown) The spar would just be a square carbon beam, nothing fancy and easy for a home builder with experience.
Note that we haven't even gone into performance and shape requirements yet, it is believed construction is the biggest hurdle to overcome.
Note that we haven't even gone into performance and shape requirements yet, it is believed construction is the biggest hurdle to overcome.
Will it be feasible? Can we be bothered to build one along with the hull and beam modifications?
You'll just have to wait and see...or do it yourself...
Sounds like it has the potential to turn the boat into a complete pain in the ass. Would be fun to see a wing win a race at Worlds though; we need a poll on whether this will occur during the next decade...
ReplyDeleteWhat does the math say the benefit is?
The performance maths has not been done yet, waiting for a working VPP from Maarkla, but he has a bit on at work (http://www.crestamotoryachts.com/). The main spar can easily be produced to a reasonable weight and structurally sound.
ReplyDeleteIf option 6 or 7 was developed to be structurally sound, then it would actually be less of a pain in the ass to rig than a conventional stayed, soft-sail rig. Put mast together, slot mast into hull, capsize, slide modules onto mast, cap the top, run mainsheet...much simpler.
how do you manage the twist with the square mast section?
ReplyDeletea_S
I don't think it would be a pain to rig as much as to get it into the water, through the surf, or up from a capsize in one piece. Say what you will about the current rig, it can take a beating in breaking surf and come through with only a broken batten or two. Being able to go sailing without worrying about the wing breaking is worth a lot to me, as I sail alone most of the time and will probably be doing more from the beach soon.
ReplyDeleteIs this a plan for a 100% wing rig or just a mast?
ReplyDeleteI see no provision for flap, camber adjustment or twist all of which are CCat features and would add considerable complexity and weight.
Phil S
this is for the first element of a 2 element rig. second element is much smaller chord, 2 piece, and hinged off the first element "frames". many ways to build the second element, EPP foam might be the best.
ReplyDeleteapparently single element wing rigs are no good for sailing. camber control is required. The bottom module sits on a "boom" which includes camber control, this is not lead up the mast, relying instead on the torsional stiffness of the mast, modules and flap. no specific twist control. with the square mast, the frames are fixed in rotation (excluding torque in the mast). this could be changed with the socket shape, no reason the modules can't rotate relative to each other independently. alternatively the mast sections could rotate relative to each other.
twist in the flap is dependent on size and material, etc, and whether the flap elements are designed to rotate relative to each other (ie top rotating more than bottom) again no specific flap twist control.
I wouldn't want to run any controls up the mast, it would just be a pain to rig.
hey nick, very much anticipating the VPP stuf. will a wing make a moth go faster is the big question right? thoughts:
ReplyDeletewhat about a mylar sock over carbon frames? that would be watertight and tough. slightly heavier but the frames can be very light.
instead of being self flooding/draining, i reckon you could quite easily do a valve across the whole bottom like a flap that lets water out but not in. so like presses up against the bottom frame when theres pressure against it.
If you fix the top frame to the mast, and allow all the others to rotate freely, you can control twist by rotating the mast. this could be done using a spanner off the mast, paralell to the boom. downhaul on the skin controls how the wing twists, whether it falls off sharply at the base or evenly.
the carbon ribs provide good places to attach the hinge for the second element, corresponding ribs on the aft element.
the aft element could be the same construction with a central spar or foam composite as inversion 6 or 7.
i think its safe to say that if the front element twists the back element will follow. better to have a straight hinge like our foil hinges, unlike the BMWO wing that needed heaps of flaps.
anyway point is, don't write off the sock thing i reckon it could go well.
A mylar sock would be close to twice the weight of an existing sail. If you got a hole in it, you'd never right the boat. These are my biggest concerns with the sock.
ReplyDeleteLaunching through surf is a tricky design requirement that I might try to avoid for now.
You back in town flutter?
ReplyDeletenup, barcelona. will be back by august probably.
ReplyDeletehey what about putting a bladder like the bladerider tramp ones in the top of the spinnaker cloth wing? like a big floatie!
could a foam/composite wing be comporable weight to our existing rigs?
One thing that is in my mind always is that the skins need to be atleast half the weight per square metre of the existing sail material to get even close to a reasonable weight. This is because there are now two skins. A spinnaker cloth wing with a bladder is an option, but would need to be pretty light. Might be possible with the latest kite tech...
ReplyDeleteAges away, there's a fair bit of activity in SE QLD now, you're missing out. Although it is a fair bit colder this year than last.
Hey there,
ReplyDeleteI had a nice prototype wing rig on a small model back when n4rkla was doing the mini 40 multi's. Then I saw an article on sailing anarchy of some huge yacht using the same concept a few months back - just after the AC.
Basically you have a mast and a whole heap of stiff battens going through a rectangular-ish shaped sail that gets wrapped around the mast and zips or velcros together at the leech (like 125 jibs used to - or maybe still do, I haven't seen one for a while). There's some spacers from the mast to the battens on runners a bit like camber inducers to give the correct thickness and chord shape, and there's still a boom, outhaul and mainsheet, but you can get a nice smooth assymetric shape with adjustable camber pretty easily. Twist control is as per a normal vang setup.
It does fill with water when it goes over, but on my model this drained pretty quickly out of the bottom... might be a bit hard to right though. Total weight is only double a normal sail plus a few additional batten weights, mast is the same and boom is a bit shorter.
Anyway, it's an easy concept to prototype, the main drawback being that the mast is at the maximum camber point, so the CE will be a bit far forward for a retro-fit.
global twist for the wing would be achieved in a similar fashion to the gybing centreboards.
ReplyDeleteI just found this blog. I thought you may be interested in the work we are doing. We have a wing with variable thickness and camber. Made from mylar skins supported by battens. Each skin is a bit more than half the weight of a conventional sail. Drainage is no problem as skins are essentially separate so can drain along entire length of the leech and foot. Uses a conventional mast. No modifications to the boat. Easy to rig. Our prototype is a little heavier than we wanted due to making a few modifications so material distribution is not optimal. The target weight for the production rig is 9kg (sails, battens, mast, boom). We could reduce this by using carbon battens and different sail membranes but believe that the 9kg is an acceptable weight and the mods would drive the cost up.
ReplyDeleteHave a look at www.facebook.com/advancedwingsystems or www.advancedwingsystems.com