Doyle Universal Power Sail

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bowsprit

Postby K.C. Walker » Fri Mar 02, 2012 11:17 am

So, I dreamt how I might do a bowsprit last night. I thought I'd throw it out here for comments. For a couple of years I've been thinking about a deck mounted retractable/removable bowsprit to fly an asymmetrical spinnaker. Seldon makes one for larger boats http://www.seldenmast.com/download.cfm? ... -261-E.pdf . There are several other makers, as well. Basically they all have some kind of cradle/ring attachment at the bow and a couple of pad eyes on the deck, one for deployed and one for retracted position at the back end of the pole.

My hesitation has been how to fabricate and attach the bow mounting. And that's what I dreamt last night and I think it should work. I could make the cradle out of high density polyethylene to attach to the deck and then just lash it down with a Spectra line. I would drill a couple of holes through the lip where the hull and the deck join and that would be it. It seems so simple that I don't know why I did not think the earlier.

Now that I've ordered the UPS, I guess that's got my mind spinning. All comments welcomed!
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Postby jdoorly » Sun Mar 04, 2012 3:42 am

Hi K.C., I fly my UPS off a roller furler, about 2 feet outside of the forestay. I had trouble using the spinnaker halyard because it is too close to the forestay and the sail tended to wrap around the forestay when I furled it, so I moved the spinnaker halyard up about 30 inches and haven't had a problem since.

I think the Seldon idea a good solution and I would suggest taking it one more step and making it so you could swing it to windward to catch wind going downwind. Maybe tie the pole to a padeye on the rail?

My UPS doesn't work very well with wind between 135 and 170 degrees (wing and wing works great) and I have been looking for ways to pole it out of the mainsails shadow. I have started focusing on the idea of a spinnaker pole attached to the base of the mast but I haven't yet figuered how to reduce the number of control lines that a spinnaker needs (topping lift, foreguy, afterguy, downhaul). Maybe the Seldon deck mount with some padeyes along the rail is even better! I wouldn't have much confidence in an extendable pole and frankly don't see the need for it, but it's a good idea to get the UPS tack 2 or more feet away from the forestay so you can tack without hanging up too bad. I just roll the sail back up on the furler when I tack which works very well.
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Postby GreenLake » Sun Mar 04, 2012 5:39 am

K.C.,

I would start with the observation that the upward loads on the forward support of this extensible unicorn of yours would be tremendous. Stronger in fact than for the regular stemhead fitting, because of the leverage and larger sail area involved.

Instead of bolting through the "lip" I would rather suggest to you to duplicate the L-bracket approach that's used for securing the stemhead fitting and mount an internal bracket that's glued to and bolted to the inside of the hull and bottom of the deck. That could also be quite unobtrusive. (I'd make the L rather wide, 2-3" even).

Then you can screw your cradle through the deck into that bracket (either by tapping the holes in the bracket, or through bolting).

The pad-eye for the rear end of the pole should be fine with standard backing plates under the deck - the loads there are downwards and to the sides.

Other than that, I think your idea of a cradle with a lashing for the forward support seems elegant and avoids tedious metal fabrication. Incidentally, there's no reason why the kind of bracket I suggested couldn't be a piece of laminate. I think you'll immediately see that doing it that way would allow you to connect the two faces with a cross member, much in the way certain book-ends are constructed. With little effort this could be made almost arbitrarily strong, in fact.
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Postby K.C. Walker » Sun Mar 04, 2012 11:09 am

jdoorly,

I was hoping that you would see this thread and comment on my latest brainstorm. I'm even thinking that I will go with a roller furler, whereas before, I had just planned to attach the tack at the jib location. Now that I've decided to go out front of the fore stay it seems the proboscis keeps growing. I'm thinking that 3 feet in front of bow should not be a problem, as long as I use a bob stay down to the bow eye.

I know that you had a bit of a problem with the Harken small boat furler at first. RWO makes a small continuous line furler that I think would work and is very reasonably priced, so I think I will try that. I know that you picked 18 inches as your bowsprit length because that was as far as you want to reach out, which makes perfect sense. I'm thinking with a retractable/removable pole it doesn't matter how far out I go because it will be easy enough to rig before deploying.

So you think 30 inches above the hounds is about right for the halyard? Do you think 3 feet out for the pole is a good compromise? How far back do you have your turning blocks?

An articulating pole could be fun but I think I won't go there. It does seem like it would be easy enough to have a pad-eye on each rail but then you'd have to go on deck to change it. If you put a goose neck on the bow you could attach your pole there and control it with adjustable whisker stays and bob stay. It would be a little complicated but maybe worth it. It would all be available hardware, though. Apparently another advantage to an articulating pole is that you can get a tighter up wind angle by moving it to leeward.

Thanks for your thoughts!
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Postby K.C. Walker » Sun Mar 04, 2012 11:35 am

Green Lake,

Thanks for weighing in with your thoughts. I was hoping you would brainstorm a bit with me on this one. I think your idea of reinforcing from the inside makes good sense. I keep wandering out to the boat and looking and trying to visualize. I keep trying to avoid getting up into the pointy end to do any kind of work.

It's amazing how physically handling a mockup and holding it to the boat brings things into my mind. I took a piece of PVC out there and plunked it on to the deck. With that, 3 feet out didn't look like a problem and here is my latest idea for lashing it down. I make the cradle U-shaped tall enough to definitely hold the pole, side to side. I hold it down by simply using a 2:1 bob stay. I attach some spectra line at the end of the pole down to the bow eye back up to the pole approximately midway, through a strap eye, and back to a v-cleat. It should be really quick to rig and no modification necessary for structure. At the back end I can simply lash it to the deck cleat that's already there. No added hardware except the cradle.

I'm thinking this is enough to get me started and I can refine the aft attachment point, maybe another cradle? It seems like the bow eye should be strong enough to handle the tension. The pole would mostly be under compression load for halyard tension. I guess the question is how big a pole to use for handling sideways force.
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Postby GreenLake » Sun Mar 04, 2012 7:04 pm

K.C.,

I'm always in favor of this kind of jury-rig so one can try out new stuff without immediately committing to permanent alteration.

So, let's see. If your pole extends 3feet out and 3 feet along the deck, the forces at the forward support (midpoint of the pole) should be precisely double the forces that the sail exerts (those are both the upward and sideways forces).

I could be persuaded to believe that the bow-eye would be a sufficient strong-point to handle the upwards loads. If your pole was strong enough, you could tie it down at mid-point, otherwise your bob-stay idea will trade some bending loads for compression loads. (On the bow-eye, you would trade some shearing loads for "pulling" loads, but given that these eyes can hold forces generated by a trailer winch I'm not necessarily concerned).

Because you're doubling your line, you know that whatever material (and diameter) you are using for the halyard would work, ditto for the cleat.

Leaves the sideways force at the U bracket. These are also double from what the stemhead would hold if you flew the sail from there. Wedging the fitting against the stemhead on one side, and form fitting the base so it goes against the "lip" of the deck might work - if the bobstay can reliably hold the pole down.

In your design there are no bending stresses from the upward pull, only from the sideways pull (equivalent to supporting the ends and loading the middle with twice the sideways load).

I think the compression loads are probably comparable to what you'd put on a spinnaker pole, but the bending loads would likely be a bit higher.

I've seen people here beef up spinnaker poles by inserting a second, tight fitting, aluminum tube. Or you could use a standard 1" section and add laminate reinforcement on the outside. Some of your leftover carbon, perhaps?

I wouldn't know how to estimate the forces involved reliably enough to make a difference, so some trial an error with a beefed up pole would be what I would go for in such a situation. (My own spinnaker pole is bamboo with just a bit of glass cover - works, but not something I'd set forth as an example to emulate).
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Postby jdoorly » Mon Mar 05, 2012 3:03 am

KC, if you go out 3 feet from the forestay tack with a pole I don't think you will need the 30" beyond the forestay tang with the spinnaker halyard. I think 18 to 24" would be fine. As you attach the spinnaker halyard up and away from the 'hounds' (where the shrouds attach) you put more forward pull on the mast since there is no backstay to equalize the force. So there is no good reason to go higher than necessary. You might even attach the spinnaker halyard block temporarily to test and see where the problem of entanglement does and doesn't occur. In general, the farther away the UPS is from the forestay the better (if your flying it outside the forestay). If you fly it from inside of the foretriangle you also need to keep the sail away from the forestay but I haven't done that so I cannot guide you.

I continue to agree that the Seldon pole looks like a great solution, but for myself I plan to build a fixed length pole (for strength, stiffness, and simplicity) with 2 snap shackes at inboard end and middle, that attach to eyes on centerline or a second, possibly third pair of eyes athwartships on the foredeck's toe-rails for broad reaching.

My turning blocks are outboard and a few inches forward of the mainsheet. I use the sail in all light air conditions, and when I had the blocks back near the transom the long catenary of spinnaker sheet kept weighing down the clew. I tried 1/8" sheets but didn't like using them or having to keep them aboard, so I moved the blocks as far forward as possible and still retain a good fairlead.

I'm glad to hear your going with a furler, I feel that all of the 'spinnaker headaches' are addressed positively with a furler.

There is a technique that old timie NA's used to calculate bowsprit forces. I won't bore you with it but will tell you that given a 1200 pound forestay breaking strength (3/32" dia 1x19 wire) that the bobstay breaking strength should be 2400 pounds (use 5/32" wire 3300lbs or 1/4" doublebraid). The max compression felt by the pole = 2550 lbs.

Perhaps a DS class spinnaker pole would work OK!

Lastly, I never thought of flying the spinnaker pole to leeward, I'll have to try it sometime.
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Postby K.C. Walker » Mon Mar 05, 2012 5:31 pm

jdoorly,

I called Annapolis Performance Sailing today to ask about the RWO furler and talk a little bit about rigging. The guy I talked to was very interested and thought it was a pretty cool project.

Do you use the telltales on the sail? The pattern that I first planned to go with is alternating blue and white panels. I think it might be difficult to see telltales. I was thinking more in terms of a spinnaker, I guess.

If I go up 1 foot above the hounds and go with a 2.5 foot bowsprit the UPS is a 155% approximately. I figured this would give me a triangle of a little over 100 ft.² not counting the extra roach. This seems like approximately the right size as the class spinnaker is 95 ft.².
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Postby jdoorly » Mon Mar 05, 2012 11:36 pm

KC, The RWO furler looks to me to be a cheaper and less jam-able mechinism than my Harken drum furler. But you have to keep tension on the line like a reef-able furler. Hmmm...

Strangely enough I never even thought about telltales for the UPS before this moment. I guess I never needed them. The luff curls so predictably thats all I need. You can take it to weather just like a jib without needing telltales. Except in rivers with steep banks. For the life of me I can't figuer rivers out! However, if your designing the sail's color pattern using the app on the Doyle website, please understand that the UPS for the DS (i.e. specifying a 15 foot luff and a 9 foot foot) is much smaller than their regular customers request and contains less verticle panels so the pattern you think your perfecting will have a few missing pixels when you see it.

I wouldn't get only 1 foot above the forestay tang, 18 inches or 24 if your reducing the sprit from 36" to 30". I'm not sure what your saying is 155%- if your talking about LP overlap, thats measured from the forestay back, so a sail out on a pole would be out of context. If you mounted the UPS in the fore-triangle, in place of the jib the LP would be close to 150% since the foot is 9 feet compaired to the jib with 7 feet (115%). However, the UPS is not a legal class sail and you can specify any size you desire to Doyle. Had I thought of this before I ordered mine I may have gotten a slightly bigger one, Tho I'm very happy with the one I got. The size I got, specifying a 15 foot luff and 9 foot foot was 72 square feet. If you add more luff though you should think about how to counter the new mast bending forces. The class spinnaker is 95 square feet, but I believe that's much more of a downwind sail than the UPS (though I hope to find a 'poled' position where I can use mine past a broad reach.
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Postby K.C. Walker » Tue Mar 06, 2012 10:17 am

jdoorly,

Thank you very much for this ongoing discussion. I have to admit that I am totally in new territory. I have never flown a spinnaker on my own and have never been in a boat using an asymmetrical spinnaker. So, all I know is from observing other boats and what I've read, mostly from searching the web. So, I guess I will get all of my "practical" experience experimenting on my own boat.

I'm thinking I will lead the RWO continuous line through a double block on the inboard end of the bowsprit pole, from there I'll lead it along the side of the cuddy to a snap shackle that is tensioned by a bungee. Right now I'm envisioning that the bungee will be secured somewhere inside of the cuddy and that the continuous line will be clipped somewhere close to the back edge of the cuddy at deck level. I'm thinking if there's enough length in the bungee I would be able to pull the clip and line up on top of the cuddy to do the furling and then flip it back down to the deck as the "parked" position. Does this sound reasonable to you?

The reason I ask about the telltales is that the Doyle website says that they are included with the UPS and they show on their drawings. River sailing, it's like sailing in the lee of something all the time!

Back to unknown territory: when I've been talking to Doyle sail makers and salesmen they refer to the UPS as being between 150 and 165%, so that's where that came from. The measurements that they wanted to know, to fit the sail, were the I & J. Chris sent me his specification sheet which was for I = 15 feet & J = 5.4 feet. Surprisingly, the price quote for those measurements was exactly the same as two years ago.

In doing some research I figured out that the "I" measurement is from the deck not from the top of the cuddy, hopefully that is correct. That would make the "I" 16 feet for the spin figured go up 1 foot to get a new I = 17 feet and bowsprit of 2.5 feet gives the new J = 7.6 feet which I assumed (and we know what that means) the new LP = 11.8 feet. This gives a 101 ft.² sail. Do you think this would be too large a sail?

I am going to call the guy a Doyle today and talk about this a little more. Hopefully, he won't be sick of my questions and indecision yet. I will be able to experiment with bowsprit length easily as at first I will just lash it down. Experimenting with the block height might involve a few extra holes, though.

Thanks again for your thoughts!
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Postby jdoorly » Sat Mar 10, 2012 11:32 pm

Hi KC, You got me thinking about a special spinnaker pole to fly a UPS upwind as well as getting the sail out of the mainsail shadow going downwind. Perhaps You will be interested in my result.

[thumb=1226]

The equipment on the deck is qty 2 1.25"x1.25"x 9" aluminum angles with 3'8" holes every 1" and 2 through-bolts into the deck backed with a backing plate (position A & C). Also there are padeyes at position B & D.

The spinnaker pole is about 7.5 feet. with a shackle at the inboard end (Position A or C, and an angle like the others at position B. These offsets allow some flexibility in fastening locations.

Here's how you might use it.
The air is light so you put up the UPS and close reach on starboard. The pole inboard end is shackled to the starboard angle Position A, and the deck padeye at B is shackled to the angle on mid-pole The wind changes putting you on a beam reach so you move the inboard end of the pole to position C. leaving the mid pole at position B. Later the wind changes putting you on a run so you shackle the mid-pole connection (9" angle) to position D.

I didn't want to make the explanation too lengthy so I excluded sailing on Port Tack. So there are a total of 3 angles and 4 padeyes, 4 shackels

Sorry about the degraded color, it looked great at 1284x1074!

If you don't understand my explanation you're not the only one :oops:
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Postby K.C. Walker » Mon Mar 12, 2012 10:53 am

jdoorly,

I think your explanation is clear of how you would use it. I'm assuming that all the angles other than AB would be for extremely light air. And then you would put it in the AB position, connect the bobstay, crank up the halyard tension to furl the sail?
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Postby jdoorly » Mon Mar 12, 2012 3:19 pm

No, not at all! The bobstay is a separate issue and has everything to do with preventing separation of the hull and deck. Given adequate structural integrity of the hull to deck joint all that is needed for the spinnaker pole is backing plates and through bolts.

Now the UPS is a light air sail and the closer the reach the lighter the air should be, but I regularly fly it in 10kn at 35 degrees apparent.
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New UPS!

Postby K.C. Walker » Thu Apr 26, 2012 4:46 pm

My UPS arrived this week! I am pretty excited about trying it out. I did go a little larger with a 17 foot luff and a 13 foot LP.

I haven't ordered any of the rigging parts yet so it's time to get on with that. Josh from Doyle Sails suggested that 6 mm sheets should be fine. He said the sheet load really won't be that much. I was thinking about trying something like New England ropes flightline. I suppose that I could go with tapered and get something more hand friendly. Chris or jdoorly, have you any thoughts on the sheets you've been using? Or of course, anyone have any ideas about spinnaker sheets? I would expect the loads on the sheets to be about the same as the class spinnaker.
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Postby ChrisB » Mon Apr 30, 2012 9:50 am

I use 1/4" New England Ropes Yacht Braid on mine. It runs through a turning block about 3.5' aft of the jib track and then across the cockpit to a clam cleat. When reaching in a good breeze, the 1/4" is hard to hold and I have to wrap it around my glove. In lighter air and off the wind it's fine. You would not want heavy line anyway as it will weigh down the clew of the UPS in light wind.
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