Just a guess, but adding 3½’ (or ~5’) x 20' of cabin width to the Ex40F would make rather generous accommodations? I do not have a good eye for this. What do you all think?
Mock it up from cardboard, scraps of ply, whatever and see how it feels.
Ok, back to sails.
| > | > | But rotating booms might be tough with wishbone booms.
| > | > why is it hard for the wishbone, or half wishbone to rotate around a fixed mast?
| > | Because it is usually only attached with a single string, id the mast doesn't rotate, the attachment point on the mast needs to move as the sail does. This can be arranged using a strap, but adds complexity when the sail is raised, reefed and lowered.
I wanna come back to this Rob. I skipped over stuff. What parts are more complex, just the boom strap, or other parts too?
Also, what you mean by complexity?
Is the strap more complicated to make, or operate/maintain, or what? Could you dump more detail here please?
The strap is a rope around the mast. It is all simple, but if the sail luff goes to the deck, the boom has to be unattached from the mast for the sail to go up and down or reef. A solution is to have the sail above the horizontal boom, a metre or so off the deck, with a vang from the end of the boom to the base of the mast. The sail ties to the mast are all above the boom. When you want to lower it to the deck, hook the halyard on the front of the boom, unhook the boom from the mast and lower it down. Reverse for hoisting. Unfortunately, this looks weird and reduces the sail area, although it does give vision to leeward. A variation is to have the sail down to the deck and take the reefs between the boom and the first reef point..
If a strap is more complicated, than a string, but less so than than a rotating mast/trucks, that's an important distinction. I wanna understand the options and risks. So, can your answers paint some context.
The complexity is not so much with the boom, although a boom under the sail does not need to be a wishbone so is way easier to build. The complexity is with the bearings, track and cars. The only risks are ensuring the sail is tight against the mast and that I have missed a detail (likely) and we can't figure out a solution (unlikely).
| > Is there more complexity/cost/reduced robustness/failure modes in rotating masts, or rotating booms? And/Or, what do I/We need to know about this to pick a solution for a boat?
There is much less to fail with the sail tied to the mast, but bearings, tracks and cars are usually pretty reliable, although attaching alloy tracks to carbon masts is difficult, and heavy. We have a simple carbon track which gets around this.
There are 2 issues: Cost (non rotating and strings will save a couple of grand and a lot of work) and efficiency. If the sail can be kept against the mast, keep it's shape (nearly flat, so should not be hard) and be adjustable, it will be more efficient.
| Both are pretty robust. Masts are more expensive to set up and bearing alignment is critical.
What is the expense to setting up rotating masts?
Rotating: Bearings need to be machined and fitted. They must be concentric on the mast which is fiddly. Tracks need to be made and glued/glassed on. Cars need to be bought. The mast needs a rotating skirt to keep water out.
Non rotating: The strings need to be cut and tied. A non rotating skirt needs to be fitted. The boom needs to be removable, but only when the sail is down.
How hard is it to get bearing alignment right?
Fiddly. The best way is to put them in a tube and slide them into place on the mast, then pour epoxy into them to make the inner ring. Then remove the alignment tube. Problem is, the bottom of the bearings need to be sealed so the epozy doesn't leak out. This is tricky with the alignment tube in place. On small boats, the usual fix is to locate the beaings with little wedges, apply a straight edge between them, seal the lower edge, pour the epoxy and hope for the best. A bit of sanding if they aren't quite right. A lot and another pour if they are way out of alignment. The bearings are highly loaded, but don't rotate fast, so some slack is ok.
| Tracks, cars and bearings are expensive. The main thing you/we need to know is whether the tied on sail solution is better aerodynamically, and, if it isn't, whether the lower cost is worth the lower performance.
To be clear, rotating masts, specifically, are more expensive to set up? Or are all masts?
Rotating and unstayed are more expensive to set up than fixed and unstayed. Both are way cheaper to set up than stayed and fixed, which is cheaper again than stayed and rotating.
Language question; What is a mast without expected accoutrement called vs kitted out masts? Or are they both just masts and the accessories are more about the rigging?
Bare tube and rigged tube. Apart from the mast head sheave and five lumps of epoxy for the halyard lock, downhaul attachment and boom, the unrotating mast is a bare tube.
Please clarify your recommendation of rotating booms vs non rotation booms and rotating masts. With why, also, please.
Rotating rigs (the boom is the lever that rotates the mast) are normal and guaranteed to work.
Fixed masts with the sail tied to lee are lighter, cheaper, less to go wrong and theoretically more efficient. But untested because yours truly is too busy playing with other experiments.
I would build the latter. Worse case scenario is it doesn't work and you have to add the track, cars and bearings (maybe make the mast hole oversize, just in case), and get the sail recut. The last one is the only extra expense vs building a rotating rig
| All the evidence is that it is better, but there have been no full size tests apart from the ones on Bucket List which were promising, but with nothing to compare against, not much help.
| Most/all the potential problems with handling the tied on sail have been sorted, but again, not all have been tested full size.
I recognize it is an experimental rig. Of line you and I have talked about this rig. I am in. I want to help figgure this out.
Cool. As long as you are aware that you are experimenting.
My thinking is, if the aerodynamic performance is not great, but the sail area is cheap and can be voluminous, then, unless educated otherwise, I think I would choose that. Why shouldn't I?
The savings are in the hardware, not the sail. The sail may not be cheap. It still needs to not stretch and has some shape (not much, but the cost of some vs plenty is negligible). There may be a recut required as well.
If, it might have poorish performance, but it may be great performance, I think I want to fiddle with it, under your advisement, to figure it out/help refine it.
Ace. Lets do it. The other requirement is a simpatico sailmaker. These are not common, and those who are, are usually inundated with yachties with dopey/untested ideas. Start looking. Be aware that they have a living to make. Probably the best way to start the conversation is to look at an Optimist sail. These are tied to the mast. Not much in common after that, but it gets you on the same page. Really cool would be to fit an Opti mast with a sail track and a sail with a sleeve and compare them to the standard. This would be a rare case of the new idea (tied on sails) being the optimised solution vs the added on, no optimised, heavier comparison. Normally, it is the other way round.
If it turns out great, then great! Right? Or did I miss something?
No. Pretty much sums it up.
I mean I was looking at a junk rig anyway, simply for the value of the sail...
It will perform better than a junk rig, cost and weigh less.
| > If you think it interesting, I would love to know more about how this all works.
| >
| Easiest is if you ask questions, which I will answer.
This assumes I know anything about masts and sails!
Well perhaps a learned reader will jump in, and help me ask smart questions...
You aren't doing bad so far. As always, the devil is in the detail. A test bed is a good idea so you can work out the details quickly and simply. The E25 should be fine for this. Maybe have one rotating and one not, compare the speeds on different shunts.
| The fundamental point is that the turbulence behind a mast/sail is far worse on the lee side than the windward one. So a sail against the lee side of the mast works better. Attaching it is the problem. A track on the lee side of the mast works, until you are caught aback, when it gets ripped off. Strings work, if they are tight. Hoops are easier, but not tight, particularly on a tapered mast. A string on them will pull them tight, but needs to be accurately tied, and changed when you reef.
| An endless line tieing the sails to the masts gets messy when the sail is lowered and the sail tends to blow away when lowered. So individual ties are required, with some means of tightening them, which is not difficult.
So, are you saying you think you got a good set of solutions for holding the sail against the lee of the mast?
Yes. It is in the same category as rudders. Each new one is better, but we are not at 'perfect' yet.
And it can flip 'from aide to side', when you shunt, for example?
So tight that it won't flip, is a good problem to have. Means it is aerodynamically right. Worst case would be having to ease the halyard, but wind pressure should be enough. Certainly less effort than trying to get the battens across on a a roachy, full battened main in light air.
And it is easy to tighten/loosen, and plays well when disassembled/re-assembled?
Yes and yes, There is some work (unattaching the boom) required between disassembled and reassembled.
| The next issue is attaching the halyard, downhaul and boom so the sail can be raised and lowered. Ideally with a simple, fail safe halyard lock so the luff tension does not change when the mast bends. We have solutions for these, but I suspect there are others.
Ok, so you are reasonably confident you got a plan for your super cheap sails to work, and you think they will also be good performing.
yes, but see above about cheap sails.
I am in. I wish I knew enough about sails to engage you further. I don't.
Nor does anyone else. All most people know about tied on tight rigs on tapered masts is that they don't work. Because if they did, everyone would have them. Grab a 2" diameter piece of pipe, some string and a piece of sailcloth with eyelets along one edge and put them together, you will be one of the most experienced people on the planet
I think there was a video of a halyard lock by Mr Aitken. Is that similar to your idea Rob?
No. I can't find the video and can't remember the details, but do recall it was a cooler solution than the commercial ones. Mine is only cool because it is simple and has a failsafe mode so the sail can always be got down. Mine would not work on his rig.