Adjustable boom choker on a CK; is it really necessary?

Adjustable boom choker on a CK; is it really necessary?

Postby seadago » Tue Mar 26, 2019 10:57 pm

Hi all.
I’m still somewhat baffled as to the exact function of the adjustable boom choker on a Hoyt 30 CK. Maybe it’s just my ignorance!
I have a soft choker on my booms, made of webbing. This is a throwback to the days of double-ply sails. When I changed the sails to single ply, I retained the choker concept. Not exactly the same design, but comparable. Pics attached. The choker moves freely up and down the mast with the boom.
The original rigging schedule that came with the boat called for an adjustable choker; two blocks and a line running to the cockpit. I faithfully reproduced this.
Point is, I have never used it! To adjust the camber in the sails, I play with the outhaul and the boom height. If I need a flatter sail with the outhaul fully out (rarely), I raise the boom by a foot or two, and gravity normally does the trick.
I have never adjusted the tension with the boom choker line, and I wonder if it’s really required, as opposed to a fixed length line attachment. It seems to me that the sail outhaul and the adjustable boom choker line work in direct opposition, cancelling each other.
Having this setup is not an inconvenience, but if I can simplify the bowl of spaghetti of lines which is my cockpit, it would be a welcome change.
Any insight much appreciated!
Cheers
Rafa
Attachments
Choker 2.jpg
Choker 2.jpg (34.43 KiB) Viewed 995 times
Choker 1.jpg
Choker 1.jpg (31.43 KiB) Viewed 995 times
Rafael
s/v Nausikaa
SSR 30570, sail GBR 4619L
F30 CK (Hoyt), wishbones, centreboard, G10 rig. Built by Fairways Marine, Humble, UK, '82
Beta 16 hp with two-blade prop
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Re: Adjustable boom choker on a CK; is it really necessary?

Postby cberdie » Thu Mar 28, 2019 10:48 am

Rafa;
It looks like you've got a combination plan. The boom choker is used on the nonsuches as you use your outhaul. You do need something to hold your boom forward, the boom lash works on the wrap around sails for this. It looks to me that you can eliminate either the choker or the outhaul, as long as the boom stays in place.
Carl
Running Free
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Re: Adjustable boom choker on a CK; is it really necessary?

Postby seadago » Thu Mar 28, 2019 3:13 pm

cberdie wrote:Rafa;
It looks like you've got a combination plan. The boom choker is used on the nonsuches as you use your outhaul. You do need something to hold your boom forward, the boom lash works on the wrap around sails for this. It looks to me that you can eliminate either the choker or the outhaul, as long as the boom stays in place.
Carl
Running Free

Thanks Carl. My guess exactly! I looked at pics of Nonsuch and Taunto rigs. They both use adnustable choke lines. I don't know if they both use running outhauls. Either way, glad to confrm my suspictions. Thanks again.
Rafa
Rafael
s/v Nausikaa
SSR 30570, sail GBR 4619L
F30 CK (Hoyt), wishbones, centreboard, G10 rig. Built by Fairways Marine, Humble, UK, '82
Beta 16 hp with two-blade prop
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Re: Adjustable boom choker on a CK; is it really necessary?

Postby Castaway » Tue Jun 04, 2019 4:05 pm

Rafa,

I've never seen an adjustable choker on the F35 wishbones. This is what we have:-

DSC_1393.jpg
DSC_1393.jpg (72.33 KiB) Viewed 647 times


As you can see, the harness around the mast is a different design, but it is held by lashings which we set up once per season. Sail tension is controlled by the outhaul. Excuse the grubby mizzen sail, since replaced!

However, it might be worth considering fixing the outhaul and using the choker to control the sail shape, which would mean less lines on the wishbone, but also bring the possibility of the main wishbone striking the mizzen mast when tacking/gybing with the sail flattened. That will depend on the cut of your sails, of course.

If you continue to use the outhaul, then it might be useful to keep your current choker, but make it off at the foot of the mast, or at any rate, forward of the cockpit. Adjustment of the boom would be much easier, even if infrequently needed.

Hope your sailing is getting well underway!

Regards,

Gerald.
Gerald Freshwater,
s/y 'Castaway', (UK F35 cat ketch, centreboard, 1987)
Lerwick Boating Club
Shetland Isles, Scotland
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Re: Adjustable boom choker on a CK; is it really necessary?

Postby seadago » Tue Jun 04, 2019 10:06 pm

Thanks Gerald. Same to you! Almost there.... replacing now the lining on the cabin roof. A proverbial pain in the back. Literally! One more week of work, and I'll be ready as I will ever be :lol:
Re the choker lines, I have them tied up to the block shackle on the boom, so they are more or less permanently fixed in length. Not pretty, but it works.
Rafael
s/v Nausikaa
SSR 30570, sail GBR 4619L
F30 CK (Hoyt), wishbones, centreboard, G10 rig. Built by Fairways Marine, Humble, UK, '82
Beta 16 hp with two-blade prop
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Re: Adjustable boom choker on a CK; is it really necessary?

Postby andygc » Wed Jun 05, 2019 6:14 am

The original setup on the 28/30 CK, as far as I can make out, was just a length of 12mm rope round the mast with a loop tied in the middle. The loop provides the attachment for the boom halyard, limit strop and reefing tackle. I've gone for the slightly posher addition of a stainless steel ring hitched into the middle of the yoke for the other thing to be tied and shackled to. It's just then a case of adjusting the length of the yoke rope to hold the wishbone about 6 inches forward of the mast. Having an adjustable choker would seem to add complication - I don't see how you could do away with the outhaul.
Feronia
(UK Freedom 30 cat ketch, build number 107)
River Exe, Devon
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Re: Adjustable boom choker on a CK; is it really necessary?

Postby seadago » Wed Jun 05, 2019 8:22 am

andygc wrote:The original setup on the 28/30 CK, as far as I can make out, was just a length of 12mm rope round the mast with a loop tied in the middle. The loop provides the attachment for the boom halyard, limit strop and reefing tackle. I've gone for the slightly posher addition of a stainless steel ring hitched into the middle of the yoke for the other thing to be tied and shackled to. It's just then a case of adjusting the length of the yoke rope to hold the wishbone about 6 inches forward of the mast. Having an adjustable choker would seem to add complication - I don't see how you could do away with the outhaul.


Hi Andy. Thanks for your insight. I guess flexibility is the wonderful thing about these rigs; there are so many ways to adjust and fine tune. Like you, I use the outhaul to trim the sails. Even so, I have relatively little play with the outhaul; about a foot or so between the sail's clew and the aft end of the boom with the sail slack. This is just a function of my sails geometry. When I need to further flatten the sails, I raise the boom. Gravity tends to push the boom aft relative to the mast, providing additional tension on the clew (and at a better angle IMO).
However, in other comparable rigs (e.g. Nonsuch, Tauton also, I believe), the sail's clew is fixed to the end of the boom. Trimming is done by tightening or loosening the choke line. Tightening moves the boom aft relative to the mast, achieving the same result. I know of a couple of members in the forum that have done this conversion in their own Freedoms. I toyed with this idea at the beginning, but sine my booms' halyard is attached to the top of the mast (not to an eye plate on the mast itself), I have considerable room to raise the forward end of the boom to any required angle. Then let gravity do the rest.
I haven't been caught in very bad weather yet (the time will come... :shock: ) so I don't know how this setup will behave under stress, but so far, so good!
Cheers
Rafa
Rafael
s/v Nausikaa
SSR 30570, sail GBR 4619L
F30 CK (Hoyt), wishbones, centreboard, G10 rig. Built by Fairways Marine, Humble, UK, '82
Beta 16 hp with two-blade prop
User avatar
seadago
 
Posts: 69
Joined: Sun Jun 03, 2012 8:42 am
Location: Lowestoft, England


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