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Old 27-06-2017, 11:33   #16
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Re: Adding a cutter rig / sloop to cutter conversion

xslim:

As you will have perceived, other responders have brought out the two principal considerations you have in contemplating changing your boat to a "cutter". They are: 1) "balance" when under the most common sail combination you will use. 2) Structural soundness of the rig after the change.

What you will call the boat/rig after the change is totally immaterial. The quest is for a boat than is easy to single-hand, not for one that merits any particular descriptive name.

Do yourself a favour and go through a simple. costless exercise before you start any modifications:

1: Draw a silhouette of the boat's underwater profile at some convenient scale on a piece of "bristol board" (thin cardboar) or on a sheet of thin plywood. for a thirty odd footer, I'd suggest a scale of 1:10 since you are Dutch and therefore metric. If you want to use "English" measures, then 1:8 (1 1/2 inches = 1 Foot) is good. Cut out that shape. Make a little hole at one end, say near the bow. Just exactly where is not important. Drill another small hole sort of a little aft of midships near the waterline. Then hang the cutout from a pin in the wall so it swings like a pendulum first from one hole then from the other. Each time, bring a plumb-line up to the pin and then project the line onto the cutout so there is a pencil line on the cutout. Where the two pencil lines cross on the cutout is the Centre of Lateral Plane of the "canoe body". That is your Centre of Effort through which the water acts when you push the boat "sideways" through the water and this is your datum for balancing the rig. Now you are halfway home :-)

On your drawing board draw the profile of the boat including the poles. Because you need to show the rig, you'll need a larger scale, i.e. a "smaller picture, than you used for the cutout. A scale of 1:25 would be good. Now draw in the sails that you would like to have where you can conveniently fit them on the existing poles. For each sail draw a line from the tack to the midpoint on the leach and one from the clew to the midpoint of the luff. Where the two lines cross is the CE (Centre of Effort) of THAT sail.

Then, using various sail combinations, find the CCE (COMBINED Centre of Effort) of the sail combination under consideration by drawing a line between the two CEs. Now put a mark on that line so that if the main is say, 400 SqFt (say 40 m^2) and the headsl is 200 SqFt, the mark falls two hundred "units" from the main's CE and 400 "units" from the hdsl's. There is your CCE.

Your objective is to apportion the relative areas of sail so that the CCE of ANY combination of sail gives you a lead of 12% to 15% of the LWL, i.e. that for any sail combinations the SAILS' CCE will always be 12 or 15 percent forward of the HULL's CE. If you can achieve that - which you always can by a little adroit mathematics - your plan is viable in terms of the boat's balance under all combinations of sail. Don't be too worried about the total sail area since your intention is to go deep sea, not to race. A Sail Area/Displacement ratio of 13 or 14 is going to be quite adequate. It nice to have more than that available for calms and for emergencies, but for most sailing conditions you will be reefed down to something like that.

One you've come this far, which will have cost you no money, and which will have taught you something about your boat that you might not already know, you can start to consider the structural modifications you might need to, or like to, make.

We can come back to that if your project proves viable in terms of getting the boat to balance. I see no reason that it shouldn't :-)

TrentePieds
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Old 27-06-2017, 16:13   #17
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Re: Adding a cutter rig / sloop to cutter conversion

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Originally Posted by gjordan View Post
It sounds like a Solent Rig is how it is set up now. He is talking about putting an inner forestay in the same (similar) location as a traditional cutter rig for ease of handling.
Yes, sorta ...

His inner forestay is removable, and the sail hanked-on. I'm suggesting he replace it with a furler, rather than (as he suggests) a "cutter" stay with a furler.

Advantages of the solent rig with 2 furlers over a cutter with 2 furlers:

1. avoids the issue of a permanent "cutter" stay fouling the jib on tacks -- especially if he mounts his primary working jib on the innermost of the solent stays.

2. Maintains the sail balance the boat was designed for.

3. Simplifies sail handling

4. Allows for easy double headsails downwind.

5. No need to add (and use) runners.

All that said, I have a true cutter (with the stays'l on a roller) and love it, except when I have to tack with the larger genoa in light air.
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Old 27-06-2017, 17:27   #18
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Re: Adding a cutter rig / sloop to cutter conversion

Have a read of
Convert Your Sloop to a Double-Headsail Rig - Sail Magazine
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Old 27-06-2017, 17:29   #19
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Re: Adding a cutter rig / sloop to cutter conversion

Our Taswell 43 was built as a convertable babystay/cutter rig. After several..."less than comfortable"...experiences in bigger seaways, we elected to make her a permanent cutter, and put both the genoa and the staysail on roller furlers-best decision we ever made! When the wind pipes up, we reef the genny and let out the S/S. As the winds continue to build we completely furl the headsail and rely on the S/S and a reefed M/S. We heel less, sail faster, and the boat is much better balanced. The running backs are a pain, but that--and the fact we need to almost reef the H/S to tack--are the only downsides we've found in the 10+ years since we made the change. We're not racing, we're cruising. The added power, better balance, and more comfort are well worth the little added trouble. And with all our sails on roller reefers, we rigged it so we can control everything from the cockpit-no need to go forward in a big seaway.
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Old 28-06-2017, 04:41   #20
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Re: Adding a cutter rig / sloop to cutter conversion

All this talk about sail balance -- really? Adding some sail area, as he proposes to do, right in the existing center of effort, or slightly ahead, is surely impossible to cause any ill effects. If he were moving the forestay or the mast, I would agree, but I don't think this is at all relevant here.

My advice for the OP would be to GO FOR IT. I think his plan is absolutely solid. A staysail on an inner forestay is a fantastic addition to the sail plan. Whether it makes the boat a "cutter" or a "proper cutter" or not -- who cares. The staysail low down and back against the mast will never upset sail plan balance (if that even matters on his boat -- doesn't on mine), and will give him a built-in always ready storm jib in the right place for one, and will give him a small area headsail to use in strong wind. We can't say for sure how well it will work with the principle headsail -- he'll have to try and find out -- but used alone, if the sail is cut right, and he rigs sheet leads to provide the correct sheeting angle, there is no reason for the staysail to not work very well going upwind, as my staysail does.

If he arranges proper running backs as he proposes, and uses them, and gets the new inner forestay attached properly, then no harm will come to the mast. The trickiest part will be the chainplate -- often an anchor locker bulkhead can be used for this, or it can be supported under the deck with a big enough backing plate.


I don't think he needs an engineer at all. He needs a good shipwright to work out the chainplate, and a good rigger to work out the rest, to the extent he's not able to do it himself.

The staysail should be extra heavy and should be cut pretty flat, to be good as a storm jib as well as heavy weather working headsail. If it works well together with another headsail, then that's just a bonus. A furler is not really essential, as the staysail will never be reefed, but makes it easy to deploy quickly in case of need. Sheet leads can be tracks or twings.

Another piece of advice for the OP: Keep the jib and removable stay, or obtain a nice 95% jib for the forestay furler. 150% genoa is a rather specialized sail which is not good for going upwind, and has a limited upper wind range. We were discussing this very topic on another thread recently, IIRC.

I have 120% yankee and 95% jib on my boat, and use the jib probably 80% of the time.
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Old 28-06-2017, 04:52   #21
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Re: Adding a cutter rig / sloop to cutter conversion

Quote:
Originally Posted by jamhass View Post
Yes, sorta ...

His inner forestay is removable, and the sail hanked-on. I'm suggesting he replace it with a furler, rather than (as he suggests) a "cutter" stay with a furler.

Advantages of the solent rig with 2 furlers over a cutter with 2 furlers:

1. avoids the issue of a permanent "cutter" stay fouling the jib on tacks -- especially if he mounts his primary working jib on the innermost of the solent stays.

2. Maintains the sail balance the boat was designed for.

3. Simplifies sail handling

4. Allows for easy double headsails downwind.

5. No need to add (and use) runners.

All that said, I have a true cutter (with the stays'l on a roller) and love it, except when I have to tack with the larger genoa in light air.
Your staysail is on a furler? If so, then the next time you replace the sun strip on it, ask the sailmaker for an extra slippery material (I forgot what it's called). The friction or lack of friction between the staysail sunstrip and the genoa is what makes it easy or hard to tack it ahead of the inner forestay.

On my boat, it's NO problem. In fact she is the easiest boat to tack I've ever had, because she carries momentum so well through the tack. I easily short-tack single handed.

Concerning the Solent stay -- the purpose is a little different from what the OP has in mind, I think. The Solent stay is usually used around here (in the Solent ) to make it possible to have both a jib and light overlapping headsail at the ready all the time. The downside is WINDAGE, and some trickiness getting the balance of tension right between the Solent stay and the regular forestay. But the windage would be a killer for me.

Most Discoverys come rigged with Solent stays which work like that. But I would not put up with the windage -- I would prefer to change sails on the regular forestay, and to have a cruising Code O on rope furler on a sprit. You can rig and leave that up when you know you will be using it a lot, but when you have upwind work to do, or heavier weather, you can strike it down on deck and get it out of the airstream.
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Old 28-06-2017, 05:59   #22
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Re: Adding a cutter rig / sloop to cutter conversion

So currently, my 150% Genny is on furler. It does not have a sunstrip - it has a separate sun cover that I pull up on it.
The 100% Jib is quite heavy, hanked on. (with possibility to reef - it has reinforced reef points)
Because the boat is aluminium, I have no problem putting/welding the chainplates.
What I'm trying to figure out is how to attach all this to the mast (new forestay and running backstays).
As I understand, welding to a mast is not the best idea, so I ned to bolt the fittings to it.
What fittings should I use?
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Old 28-06-2017, 06:14   #23
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Re: Adding a cutter rig / sloop to cutter conversion

Quote:
Originally Posted by xslim View Post
So currently, my 150% Genny is on furler. It does not have a sunstrip - it has a separate sun cover that I pull up on it.
The 100% Jib is quite heavy, hanked on. (with possibility to reef - it has reinforced reef points)
Because the boat is aluminium, I have no problem putting/welding the chainplates.
What I'm trying to figure out is how to attach all this to the mast (new forestay and running backstays).
As I understand, welding to a mast is not the best idea, so I ned to bolt the fittings to it.
What fittings should I use?
Simples. Wichard make an excellent fitting:

https://www.bluemarinestore.com/wich...-mast-fitting/

And there are others. You are lucky to have a metal boat, in this question! This will also greatly simplify arranging sheet leads. This will be an easy job for you.
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Old 28-06-2017, 06:29   #24
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Re: Adding a cutter rig / sloop to cutter conversion

Interesting, is there any mast fitting that "clamps" around a mast and provide fitting for both a stay and back runners ?

What about dyneema loop around mast few times over the spreaders?
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Old 28-06-2017, 07:13   #25
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Re: Adding a cutter rig / sloop to cutter conversion

Why not use this excuse as an opportunity to get a new boat? The one you really want and can manage easily?
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Old 28-06-2017, 07:21   #26
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Re: Adding a cutter rig / sloop to cutter conversion

Quote:
Originally Posted by xslim View Post
Interesting, is there any mast fitting that "clamps" around a mast and provide fitting for both a stay and back runners ?

What about dyneema loop around mast few times over the spreaders?
I've never seen a "clamp" on fitting. That doesn't mean it doesn't exist, however, but I've never heard of it.

I think you should do it right and just rivet on tangs. This is neither expensive nor difficult to do. Just be careful with the unlike metal issues using stainless on alu and take all proper precautions -- duralac, isolation, etc.
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Old 28-06-2017, 07:27   #27
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Re: Adding a cutter rig / sloop to cutter conversion

I would assume that making a sloop into a cutter by adding a fore-stay is unlikely to be a good thing unless blessed by a good marine designer. However, the thread brings up a thought I have had for a while. My roller reefed jib makes a poor storm sail. I have thought about mounting a removable wire fore-stay and halyard a foot or two below the fore-stay so that in storm conditions I could mount and tension the stay and hoist a small storm sail. Has anybody tried a rig like this?
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Old 28-06-2017, 07:49   #28
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Re: Adding a cutter rig / sloop to cutter conversion

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Originally Posted by Dave22q View Post
I would assume that making a sloop into a cutter by adding a fore-stay is unlikely to be a good thing unless blessed by a good marine designer.
It never hurts to consult a designer, but I can say now that adding an inner forestay is not rocket science, should not affect sail balance, should not be beyond the skill of any decent rigger or boat owner to engineer in a structurally sound way.




Quote:
Originally Posted by Dave22q View Post
However, the thread brings up a thought I have had for a while. My roller reefed jib makes a poor storm sail. I have thought about mounting a removable wire fore-stay and halyard a foot or two below the fore-stay so that in storm conditions I could mount and tension the stay and hoist a small storm sail. Has anybody tried a rig like this?

Use a Highfield lever. Extremely common arrangement, almost universal in the UK among sloop rigged boats used for any serious offshore sailing. You would want the removable inner forestay to be more than a foot or two below the masthead, however, in order to get the center of effort of the storm jib down and back. Put it where the normal inner forestay would go -- that is, opposite where the head of the mainsail is when it is reefed to its deepest position. That way the removable inner forestay will also help balance the loads from the deeply reefed mainsail, in a blow.

If you want to really do it right, add running backstays, but I have seen lots of boats, including several Oysters, which were rigged like that from the factory, with no runners.
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Old 28-06-2017, 15:08   #29
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Re: Adding a cutter rig / sloop to cutter conversion

Call any major rigging shop and ask about HOUNDS for a staysail. They will know what you are talking about. Since your boat is a double spreader rig, the inner forestay would typically attach at the upper spreaders, so you might have some of the hardware already, but any good rigging shop will have , or order what you need. Even with a metal boat you should reinforce the deck or do the attachment at a bulkhead or some other hard point. Many people run a wire and turnbuckle from the lower side of the deck/chainplate to the stem, so that the deck is not holding any of the upward force. Talk to a rigging shop. ____Grant.
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Old 28-06-2017, 15:11   #30
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Re: Adding a cutter rig / sloop to cutter conversion

Quote:
Originally Posted by xslim View Post
Interesting, is there any mast fitting that "clamps" around a mast and provide fitting for both a stay and back runners ?

What about dyneema loop around mast few times over the spreaders?
How do you hoist the main past a loop around the mast?
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