Bill, you forget the most important thing… 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, that’s his deal, and he seems quite happy in his role. I do my stuff for enjoyment, and statisfying your ( or anyone else’s) predilection for constant production or improvements has no affect on me.
Here’s a few pix of the new “equilibrium rig” 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 couldn’t 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 it’s really easy to change out components. Sorry, I don’t have the Footy emblem on yet, I’ll 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 “shaping” 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 rig…this concept does it very well indeed I belive.
So simple,so light,so much less drag…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. I’m not sure if it’s really worth the weight penalty or complexity of construction (see the foam wingmast thread in the “how to?” section), especially if a decent airfoil shaped leading edge can be obtained with a luff sleave. Remember the KISS concept.
Anyway, since Brett’s “equilibrium rig” offers a major benefit in it’s ability to flex to absorb gust energy, I thought I’d 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
Bill—How long is your forward tube–or mast? also is your rake of the mast in line with the pivot post on the deck–ie top of mast to pivot point? thanks Bill.
Bill,
I pretty much copied Ian’s 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 evening’s 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 !! I’m thinking this is the least stiffness desirable, but we’ll see. The mast spar was also lighter at 3.2mm, but the biggest weight savings was the sailcloth. The cloth was salvaged from the “B” 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 “work”.
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.
I’m interested in experimenting with a scaled up version of this on my Micro Magic (sorry if that’s 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 this…
It strikes me that one of the very few illogicalities of Brett’s 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.
MeGrimm, if you simply measure the length of your jib foot and use that as the distance from the pivot to the front upright and the main foot as the distance from the pivot to the clew point you should be about right. Add another 20mm for the length of the boom.
As the forward part of the new sailplan goes higher than your existing jib it will compensate for the lack of the slot distance.
If you start with a similar height as your existing rig you will be able to tell us of the differences between the MacRig and the standard one.
The angle of your mast should put the top of the mast over the pivot point.
Please report your findings as a number of us are considering using this rig for other larger craft and little is yet known of the intricacies of the concept.
Angus,
Yes, there is potential for upward bend at the aft (CF) end of the boom to open up the leach & increase sail twist. But as I see it, the crucial feature is the torsional twisting of the horizontal wire portion of the boom, which allows the entire rig to “slop” off to the side as a means of spilling air & absorbing gusts. For this reason, I have chosen to not attach the CF boom along the entire length of the wire in order to allow unencumbered twist. The CF rod I’ve been using for the boom is quite stiff & at some point I may play around with thinner material, but for now I’m more interested in the flexure offered by the wire alone.
You are entirely correct on this point.The beauty of wood is it’s ability to be easily shaped as you suggest. In fact, that’s why I prefer laminated wood for the planks of my iceboat/landyacht platforms: if it’s too stiff, a session on the sander is an easy repair. There’s no reason the entire rig can’t be built out of wood, in fact the early ones were (see below). It’s just that the wire method is very quick & easy to build & less prone to failure by shear along the grainline if one seeks more extreme twisting.
McGrimm & Ian,
Good point. Actually, I have been contemplating this for some time myself for use on my landyacht rigs. The foam core composite wingmasts are nice, but alot of work. I would probably incorporate a wire or CF “gaff” at the head in order to maintain strong leach tension. I’m talking about something 68" (173cm) tall, with a thermoformed mylar luff sleave over a tapered carbon rod.
Thanks IanHB i’ll give it a try. Any idea what size of wire I’d need on a rig that size (as a starting point)? I’m hoping to use a bicycle spoke if I can get one of suitable dia. I’m guessing that 2mm will do…
Also, I guess that a backward sweep (rake?) of the pivot in the hull will result in the centre of area being affected when sheeted the sail is out, but at the expense of the whole rig being raked backwards. Maybe a way to adjust balance downwind?? So many things to try!
Tomo is correct, except that the key is that the pivot must be exactly vertical. Otherwise, mean ol’ Mr. Gravity will do nasty things to keep the rig from swinging one way or the other.
Not only that, Doug, but if the pivot isn’t square to the deck, one end of the boom will hit the deck on either tack, and you won’t get much swing either way. If it’s not square, elevating it will only give you a little more swing before it hits. I think that the wind would have more of an effect on swinging the boom over than gravity, unless it’s a very calm day.
TomoHawk, in this case I doubt that’ll be a problem. The raised hatch means that I can’t put the boom too close to the deck and the (relatively) narrow beam means that everything should clear ok. I’m more likely to have problems with the clew dragging in the water.
I got my stainless bicycle spokes today (one plain and one butted so I have slightly different thicknesses of wire to try) and I have a bit of carbon tube sitting about so I hope to have a go soon…