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PostPosted: Thu Jan 10, 2008 2:23 pm 
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I use the 'normal' Hobie sailkit on my AI hull (as a kayak) using an adapter I have made for the mast base to allow the roller reefing facility of the AI to be used on the smaller sail.

I have also started using a jib which I set 'flying' using a halyard running through a micro block attached to the top of the sail that I store inside the rolled up sail and a downhaul that I run through a micro block installed on a padeye just forward of the front hatch.

The jib creates too much bend in the mast for upwind sailing and the mast bend, which is inherent in an unstayed mast, means that very little luff tension can be achieved in the jib so the sail shape can be pretty poor - and again, this is not good for upwind sailing, or sailing at all really.

So to get better upwind performance, to be able to use the jib in higher wind strengths and to be able to get more luff tension in the jib I want to try to stay the mast and I am looking for input & ideas as to how best this can be achieved... !

My proposed 'chain plates' or lateral/aft deck-level staying points for the backstays are the holes at the ends of the forward aka bars where the AI aka extensions attach (I could also use the aft aka bars with running backstays, but I think there would be very little lateral tension applied by the stay to the mast from this point and therefore it may be difficult to prevent the mast from falling off to leeward from here). The forestay point would be the front padeye - easy enough. For simplicity I plan to use spectra for the stays but thin wire is a possible alternative.

I think it would be relatively easy to stay the mast if the roller-reefing facility of the mast is dispensed with, but this would mean always having the main sail up and deployed which is not ideal, so I am trying to develop a solution which still allows the main to roller reef....

This seems to imply that the stays would have to be connected at the top of the mast to some kind of cap or insert with a bearing system which will allow the mast to roll under the stays whilst still maintaining enough tension in the stays.

I have performed a simple trial which encouraged me to continue. This involved
1. putting an insert in the top of the mast (and through a hole punched through the strop tape at the top of the sail) to which the stays were attached.
2. hauling on the roller reefing line to see if the mast would still rotate.
The results were that the rotation was not trifically smooth and there was a tendency for the sail batten-end to get caught up on the backstays (until enough of the sail had been rolled away for it to clear them) but mast rotation could still be achieved.

Re the interefence between stays and batten-end: I have thought about a system of 'craning' out the stays at the top of the mast to hold the stays out from the mast so as to provide clearance for the batten end while rolling up the sail. A similar thing is available for the Blokart land yacht (www.blokart.co.nz) but this would have to be modified for this application. A different non-catching batten end could be used.

I have now bought another complete sailkit mast and all to use as a development test-bed (got it cheap !)

When I started using the sailkit in my AI roller-reefing adapter I had to cut about 6" off the top of the mast to make the sail set lower down because the mast in the adapter sits higher than in the normal mast base. With my new mast, rather than chopping the mast down, I plan to use the extra mast length to provide clearance for the batten end by sewing a longer strop into the top of the sail so as to lower the sail down the mast. I don't yet know if it will afford enough clearance but hopefully it may. A different strop arrangement at the sail top should allow me to incorporate some kind of cap or insert for the top of the mast. The strop of the sail will then be attached to the cap/insert and the cap/insert would need to be designed to feature a bearing to which the stays are attached (still with cranes if needs be) to allow the mast to rotate freely underneath the stays.

So my challenge is how to design the mast cap, bearing, mast-top staying system (I think the nautical term for the attachment of the top of the stays to the mast is the 'hounds') including cranes if needed and also where to get suitable components/raw materials.

If there's anyone out there who can follow this description of my challenge and would like to offer some I would be delighted to receive suggestions...

"You must be barmy..." is a perfectly acceptable one, but "It'll never work..." is not, by the way !


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PostPosted: Thu Jan 10, 2008 10:11 pm 
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Looks like a fun project! As you probably know, the Hobie inflatables use a stayed mast, but without the furling feature. Also, the mast sits in a pocket allowing it to raked as desired.

This is not possible using your mast sleeve arrangement. More importantly, you have to be careful not to accidentally warp the mast with uneven stay tension. This would require fairly loose stays that would limit rather than prevent mast bending. The other advantage of employing your stays this way is that it would not bind the mast when furling.

I agree that your best solution to the batton problem is to effectively extend the length of the mast past the sail head enough to clear the furling batton.

One possible way to re-mount the sail might be to weld or pin a large washer just below the mast top. You can sew the head of the sail sleeve to a grommet large enough to slip over the mast top and rest on this large washer.

Were you thinking of using eye-bolts through the aka mounting holes for the sidestays? This would allow quick and easy fine tuning. By mounting the eyebolts upside down, this would discourage them from rattling around under load, wearing against the softer aluminum. At the same time, you could gain a slightly more advantageous position routing your stays around the aft side of the bracket. 8)


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PostPosted: Fri Jan 11, 2008 2:12 pm 
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RR, thanks for your response.

I am very interested in the staying arrangement at the 'hounds' for the inflatables - do you have any pictures ?.

Yes I envisage stays that limit the mast from moving out of alignment and therefore relatively loose, however if I have a tripod of stays, I will be able to vary the tension by having one of the stays as a running stay (a pull or release on this one will tenson or release the other 2) and this is what I am planning; probably a running forestay to the bow padeye withe the line returning to the cockpit via the AI sheet cleat and a different arrangement for leading/cleating the small sail sheet (which I set up & used very effectively on my Adventure).

I didn't plan eyebolts in the Aka ends at this stage - I want something that is demountable and cheap enough to experiment with. I am also wary about galvanic corrosion between steel (presumably) eyebolts and alu aka bars. I planned to fit the deck-level ends of the stays with small hooks which would be hooked through a loop of heavier line inserted into the aka holes from the bottom so that the loop protrudes at the top and the knot in the loop stops the loop pulling thru the hole (dead simple). I don't believe the stresses in the set up will necessitate anything more robust than a bit of cordage. As I have indicated slack can be taken up via a single running stay.

I have also now worked out the arrangement I am going to use; it is like this:
1. similar to your suggestion I am going to open up the strop at the top of the sail to allow the sail to slip all the way down the mast. Then by sewing some kind of rope arrangement into the sail top and using a fitting (a simple s/s hoseclamp would do in the short term - not stylish but effective !) on the mast I will be able to secure the sail to the mast at any desired level below the masthead.
2. this simplifies the arrangement at the masthead as there is no longer the compexity of having to both attach the sail and the stays at the mast top. So the mast head can carry either a cap that sits over or a plug that sits in the mast end that carries a freely rotating attachment for the stays. Which I use will depend on what components I can most easily find/make. At this stage I am undecided but one arrangement could be a nylon bushing plug with a screw hole drilled centrally in the top, the plug to be inserted into the mast end. A screw/bolt screwed into the hole in the bushing so as to retain a s/s disk ( like a large, thick washer with a small hole in the middle) with 3 holes drilled near its edges to attach the stays. If the nylon to s/s bearing is not slippy enough for easy mast rotation a corrosion-proof thrust bearing could be inserted between the washer and the bushing plug.

That is as far as I have got to date...


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PostPosted: Sun Jan 13, 2008 12:34 am 
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stobbo wrote:
I am very interested in the staying arrangement at the 'hounds' for the inflatables - do you have any pictures ?


Here's the only picture I have showing the hounds. Note the stays are all sewn directly on the sail!
Image

Here are some other pics of the stayed sail and mast for the Inflatable.

Triangulation
Image

Mast step
Image

Slack stay (Inflatable flex or line stretch?) causes no problems at all, and is unavoidable in this case.
Image

Downwind sail position
Image


There are some differences in the mast you might want to know about.

It comes in 3 bungeed pieces
Image

It is a little shorter than the standard mast because it doesn't use a sleeve
Image

Image
by about 19 (?) cm.

Much of this wouldn't apply to your project, but it gives you some ideas about how Hobie approaches the stayed sail and how it works underway.

About the running forestay, I'm not sure you would need it (depending on how you set this up). If you could avoid it, it would keep your cockpit cleaner. 8)


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PostPosted: Sun Jan 13, 2008 12:56 am 
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Here's another thought -- If you're going to stay the mast, you don't really need the small sail adapter any more --- you could simply step the mast directly into the bottom of the cup.

If so, you no longer have to worry about flexing at the sleeve. Also, you could then rake the mast for better positioning. With the Inflatable, this made a big difference in helm balance. Finally, this would eliminate the possible need for a running forestay.

You could simply mount a spool on the mast below the sail for reefing.

The mast base might need a small adaptation to fit the cup detent, but that shouldn't be too difficult. 8)


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PostPosted: Sun Jan 13, 2008 1:05 am 
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Another way to do this might be to slip the mast in to a small sail sleeve with the spool mounted on the sleeve, and the sleeve anchored only at the mast cup base. The advantage to this is being able to use the sail on other applications without having to customize the mast directly. This still allows you to rake the mast and avoid mounting stress at the aka bracket bezel. 8)


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PostPosted: Sun Jan 13, 2008 2:55 pm 
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RR, firstly, thank you for your excellent input ! Appreciated.

Lots of stuff to cover.

Thanks for the photos of the inflatable set up. I think what they have developed is pretty much the only way to do it on the bendy inflatable hull & it would seem to work pretty well in practise too. In relation to my wee project it gives some useful pointers.

I am really keen to keep the roller reefing capability on the main and therefore couldn't attach stays to the sail.

I could do away with the adapter but I don't really see the point now. Having got this far with it it would seem simpler to retain it, though there's no doubt that with stays the mast could be stepped directly into the AI mast cup. If I fail in my experiments I will probably need to come back t this option.

I think that in my proposed set up it will be desirable (though possibly not absolutely imperative) to ensure that the mast is more or less upright in the base. I note that the unstayed mast flexes from the base anyway, so I guess a small amount of mast bend won't adversely affect the roller reefing action... ?! I am hoping that the Spectra I plan to use for the stays will be pretty much no-stretch under the loads to which it will be subject and I hope, via some fine tuning to be able to set the system up so that the mast can be held almost perfectly vertically in the base with a bit of a tweak on the forestay.

As to the running forestay idea: for safety I want to be able to step and unstep the mast while at sea so I need to have at least one leg of the tripod of stays demountable. Given that I need a forestay whether running or not, there will be a line from bow to cockpit when the mast is unstepped. As far as I can see 'one line part of the time' is almost as bad as 'one line all of the time & 2 part of the time' and/but the ability to fine tune the tension in the stays (as well as unstep the mast) is worth having. A running forestay/un-steppable mast also removes the neccessity of having to fine tune the stay length perfectly from the outset. You are right, though, that the cockpit will get cluttered... you should see the amount of line I have swilling about in there when I am using my jib: jib halyard, jib downhaul, jib sheet, roller reefing and mainsheet ! Adding a jib forestay to that list probably isn't going to change matters significantly but one of the things I am ultimately going to have to do is install some line-organisation perhaps like those bags they have on larger sailboats.

Over the WE I managed to come up with an 'almost' solution for the hounds. This consists of a stainless-steel rod welded to the centre of a s/s disk in a configuration like the base of a standard lamp that I picked up for a nominal sum at our local boat-breaker. With a s/s bushing/sleeve inserted into the top of the mast this lamp-base thingy can be inverted & inserted into the top of the mast (in the sleeve to provide a non-binding bearing surface) and sitting there it rotates quite nicely. The disk is wider than the circumference of the mast & is already drilled with holes which will accept the hooks I plan to use for my stays. I reckon that with a bit of cunning I might even be able to adapt this system to use with a bearing for very little more than the price of a few washers... So for $5 I have got my hands on the bones of a design without having to do much more than show up at the shop :D I also acquired a s/s pipe clamp for holding the head of the sail to the mast.... I will try to photograph all this today & post picture tomorrow.
All I need now is the sail which I am going to pick up this week.
I will keep you posted.


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