Hi Bill.
I am using 1.6mm s/s wire ,thats 1/16th in your terms.
The wire twists with torsion,this is the single most important part of the rig.
You can tune the ammount of torsion in the wire with the ammount of thread or
carbon used to wrap the boom in place.
There are other tricks to vary the stiffness as well which will become obvious once you start playing around.
I wouldnāt use anything smaller than the 1/16th wire,perhaps a little bigger would be better even but I have used what I have got and also the weight saving with the lighter wire is quite a bit.
I managed to obtain the carbon tubes and rods in a hobby shop here in NZ,we are not known for our well stocked hobby stores so I donāt expect you guys will find it differcult locating this stuff.
This design is not much different in practice to the version you built earlier Bill,the bendy boom is the only real difference.
Bill, my wire is about the same as Brett`s.
I have built another with something a little thicker to try as well.
I like the idea of bicycle spokes mentioned previously and shall be investigating these next week.
I made a few sails today including a B rig.
It is so quick to do that I can see that having a whole wardrobe of different cloths will be the go.
The angle of rake of that front upright is the most critical component of these rigs and can be used to tune the twist to be optimum.
Have you considered using a bent or curved mast? having a bend in the mast should allow one to keep the sail area low or change the proportions of the fore- and aft- sections. Possibly even to control the amout of lift from the sail or the vortices flowing around the luff.
Curved masts are a pain to get the sail attached and setting right.
With a straight mast you can build a pocket luff sail in about 3 minutes and it sets beautifully. (If it aint broke don`t fix it )
Tomo,
Since you like to contribute so many suggestions & comments, how about showing us something youāve actually built. That way weāll know youāre a ādoerā & not just a ātalkerā. Not just kiddingā¦
Bill, you forget the most important thingā¦ Any thing you do is 90% inspiration or ideas, and 10% labor. Also, I set my priorities differently than you or anybody else. When & if I get time to do any boat stuff, I will do so. Besides, this information system was created for just that reason.
Instead of offereing rhetoric, why not offer help?
If Mr. McCormack can churn out his ideas en mass, thatās his deal, and he seems quite happy in his role. I do my stuff for enjoyment, and statisfying your ( or anyone elseās) predilection for constant production or improvements has no affect on me.
Hereās a few pix of the new āequilibrium rigā I put together tonight. Very simple & fast. I basically copied what Brett & Ian have done, with the exception that the luff sleave was done with stiffer material (4 mil Mylar).
This was done in the hope of creating a better wing shape. Since the material was stiffer than usual, it needed to be thermoformed around an airfoil shaped aluminum extrusion in order to create a tighter radius on the leading edge.
Wire shaped with boom glued & bound. Wire is 3/32" ss piano wire, boom is 2.5 mm carbon rod. Mast is 4 mm cf tube which fits snugly around the wire, but is still free to rotate.
2)Overall shot of spars.
Luff sleave draped over the extrusion prior to heating. Clamps & clothespins will provide enough weight to pull it down when the Mylar softens.
4)Heating with heat gun. Move smoothly & rapidly a couple inches above,
watching closely for softening.
Photos of the finished rig will be shown on the next post
The stripes are just drawn on with a marker in order to make sail shape more obvious. The 3 mil Mylar is stiff enough to get a decent shape without battens. I looked for some 2 mil or 1.5 oz Trispi, but couldnāt find it. lighter is probably better. The amount of draft can be controlled by the attachment point of the clew (done with tape which can be adjusted).
6)Size/shape comparison with existing rig.
Total weight of the rig is 24 g. Is this heavy? Amount of flex feels ok, but may changed based on experience. One of the nice things about this concept is that itās really easy to change out components. Sorry, I donāt have the Footy emblem on yet, Iāll have to get that done before Sheboygan.
Looks real good Bill,
Yes 24g is heavier than mine,but all my components were smaller diameter etc.
Your rig should be stiffer than mine,which can be good or bad depending on what you want.
My next version to try will be slightly stiffer and hence heavier.
In saying that 24g is still a very lightweight rig.
I like your planform for the sail and your method of āshapingā the pocket luff.
I just make a very hard crease line down the front to get the shape in.But I can see how forming the mylar around a tube could result in a better leading edge.
It is vital at this size to reduce all parasitic drag in the rigā¦this concept does it very well indeed I belive.
So simple,so light,so much less dragā¦seems win win.
edit,
A airfoil shaped foam wingmast could be used instead of the carbon tube,a peice of high density foam shaped and then the mylar sail made around it would make a very accurate and lightweight leading edge.
Bob,
It could be, but not without significant reinforcement to resist the bending moment at the lower end. Iām not sure if itās really worth the weight penalty or complexity of construction (see the foam wingmast thread in the āhow to?ā section), especially if a decent airfoil shaped leading edge can be obtained with a luff sleave. Remember the KISS concept.
Anyway, since Brettās āequilibrium rigā offers a major benefit in itās ability to flex to absorb gust energy, I thought Iād measure how much weight it took to deflect the mast down 2". The idea is to get a quantifiable basis of comparison between different rigs. This was done with 3 masts, all 460mm long & supported horizontally on a benchtop vice clamped 3/4" down on the pivot. Scraps of wood were placed on the head of the rig until it bent down the 2", then weighed on a digital scale. A photo of the setup can be seen below.
RIG; original wooden spar & boom with 2 mil mylar sail
Total Weight of rig: 35g
Deflection to 2": 45g
RIG; 2.5 mm piano wire with 4mm cf spar & 3 mil mylar sail
Total Weight of rig: 24g
Deflection to 2": 27g
RIG; 2mm piano wire with same mast & sail as #2
Total Weight of rig: 22g
Deflection to 2": 21g
Now the next thing to do is get it in the water & see how the differing amounts of flex effect boat handling. This will be most useful when comparing #2 & #3 since the sail rigs will be identical
BillāHow long is your forward tubeāor mast? also is your rake of the mast in line with the pivot post on the deckāie top of mast to pivot point? thanks Bill.
Bill,
I pretty much copied Ianās number of 460mm. Yes, rake it back so it is in line with the axis of the pivot below. None of this is carved in stone & in fact one would probably end up with at least 2 or 3 sizes of rigs, along with different shapes.
This eveningās project was to build a lighter, more flexible rig using 1.6mm (1/16") wire & spinnaker cloth. The total weight comes in at 17g & the 2" deflection dropped down to only 9g !! Iām thinking this is the least stiffness desirable, but weāll see. The mast spar was also lighter at 3.2mm, but the biggest weight savings was the sailcloth. The cloth was salvaged from the āBā rig from my old Fairwind (which has since found a home on the bottom of a local lake.) It will be very bendy, should be fun to watch it āworkā.
Below are the finished rig being deflected & a closeup shot of the clear mast sleave. I found that uniformity of heat & clamping is the key to getting a smooth leading edge shape.
Iām interested in experimenting with a scaled up version of this on my Micro Magic (sorry if thatās blasphemy round here). Should be very simple to set up if I can get enough area far enough forward to maintain the balance.
Brett, how does the area of one of these rigs compare to the equivelant / standard bermuda rig? Somehow I imagine being able to carry more canvas like thisā¦
It strikes me that one of the very few illogicalities of Brettās design is the use of carbon for the boom. By and large, we use carbon for stiffness, but the essence of the system is that the boom bends. Of course, we can use lighter carbon but at some financial expense and logistical inconvenience. The other problem with carbon is that it is difficult to customise its bend characteristics by very much. I am therefore contemplating a laminated wooden boom using hot glue, which is highly flexible per se and which can be adjusted with a sharp pen-knife.
