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Hull 922 - Mast Rake

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Steve Milby
Past Commodore

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USA
5851 Posts

Response Posted - 03/16/2017 : 16:38:23

quote:
Originally posted by Stinkpotter

...as I see it, the upper shrouds and the swept-back spreaders do the bending, and hardening the lower shrouds tends to work against that.

Right Dave. Either too much or too little prebend is a bad thing. The mainsail is cut so that it is optimized at 1 1/2" prebend.

When tuning the mast, you create the prebend by increasing the tension on the upper shroud. That causes the midsection of the mast to bow forward. If the lowers are too taut while you're tightening the uppers, the lowers won't allow the midsection of the mast to thrust forward. But, after the correct amount of prebend has been established, then the lowers should be snugged up. They shouldn't be as taut as the uppers, but they shouldn't be slack at all. They should be snug. If they are left loose, the midsection of the mast can bend even more under load. The purpose of the lowers is to hold the midsection rigid, at precisely 1 1/2" prebend, and no more.

Steve Milby J/24 "Captiva Wind"
previously C&C 35, Cal 25, C25 TR/FK, C22
Past Commodore

Carl in LA
Captain

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USA
284 Posts

Response Posted - 03/17/2017 : 16:18:39

Carefully reading each post I hit it again today - especially with a clue from HappyNow...

(disregard that killer black carbon fiber mast on the Farr 40 next to me in the slips - that boat is just so awesome)

Started with turning loose the backstay 100% - laying in the cockpit...

Next, turned both the upper and lower stays loose to the ends of the threads in the turnbuckle.

Next, used the HappyNow clue and strapped on the hoisting strap and ran a line to a block at the stem and back to a winch - and winched it until I forces a bend - which means the previously loose upper stays were now tight holding back the top of the mast...

Then I started tightening the upper stay turnbuckles - I turned them in 13 turns - at the end of my comfort zone - worried about stripped threads, pulling out the compression fitting, snapping an end, etc.

With the upper stays at tight as I was comfortable tightening them - then I let off the line to the strap - and of course the mast relaxed back to a slight forward pre-bend.

Wow... Reconnected the backstay and that is where she sits at this time.

Catalina 250 - Pretty Good Boat

Edited by - Carl in LA on 03/17/2017 16:28:04

TakeFive
Master Marine Consultant

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2269 Posts

Response Posted - 03/17/2017 : 17:03:56

Did you check boat resting on her lines and adjust rake to 4" before tensioning the stays and shrouds?

Rick S., Swarthmore, PA
PO of Take Five, 1998 Catalina 250WK #348 (relocated to Baltimore's Inner Harbor)
New owner of 2001 Catalina 34MkII #1535 Breakin' Away (at Rock Hall Landing Marina)

Carl in LA
Captain

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284 Posts

Response Posted - 03/17/2017 : 17:10:51

quote:
Originally posted by TakeFive

Did you check boat resting on her lines and adjust rake to 4" before tensioning the stays and shrouds?

No - I did not test the mast rake aspect - the fight for the pre-bend was enough for the last few days.

Glancing at the boot stripe - I have the same stern-heavy situation reported by others at this moment...

Appreciate the speedy note...

Carl

Catalina 250 - Pretty Good Boat

islander
Master Marine Consultant

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USA
3992 Posts

Response Posted - 03/17/2017 : 17:33:04

Carl, I think your over tightening things and making large adjustments at one time. Rig adjustments need to be done in small adjustments. 1/2 turns, 1/4 turns.Nothing should be bow tight.

Scott-"IMPULSE"87'C25/SR/WK/Din.#5688
Sailing out of Glen Cove,L.I Sound

Carl in LA
Captain

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284 Posts

Response Posted - 03/17/2017 : 17:49:03

quote:
Originally posted by islander

Carl, I think your over tightening things and making large adjustments at one time. Rig adjustments need to be done in small adjustments. 1/2 turns, 1/4 turns.Nothing should be bow tight.

Thanks Islander... one would presume you are right.

I left out of the report that I tested the relief at several instances of tightening the uppers. I did 10 turns at first, released the strap, and, the mast popped back straight to slightly negative, then added turns one at a time to the maximum of 13 where I stopped.

Does the amount of threads exposed on the inside of the turnbuckle look normal?

Also, rereading my report - its a bit confusing about the uppers getting tighter upon pulling the pre-bend into the mast with the strap... you would think that pulling the middle of the mast forward would shorten the dimension along the upper stay - but as the back stay was not connected - the uppers were still pulled tighter as the mast swept forward by the strap.

I don't like the uncertainty of this situation.

Catalina 250 - Pretty Good Boat

Edited by - Carl in LA on 03/17/2017 17:51:00

Steve Milby
Past Commodore

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5851 Posts

Response Posted - 03/17/2017 : 18:26:47

You should set the rake before you set the prebend. If you don't, then when you adjust the rake, you will have to set the prebend again, because setting the rake will require that you completely change the adjustments to the uppers and lowers. It has to be done in the correct sequence.

Steve Milby J/24 "Captiva Wind"
previously C&C 35, Cal 25, C25 TR/FK, C22
Past Commodore

Carl in LA
Captain

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USA
284 Posts

Response Posted - 03/17/2017 : 18:55:26

quote:
Originally posted by Steve Milby

You should set the rake before you set the prebend. If you don't, then when you adjust the rake, you will have to set the prebend again, because setting the rake will require that you completely change the adjustments to the uppers and lowers. It has to be done in the correct sequence.

Noted Steve...

Several posters noted that the boat has to be on its lines to establish rake.

I've only been in the water a week and I have yet to sail the boat...

Island Dreams appears to float stern down as several others report. Until I sort out stowage (which is just a couple tool kits and galley gear) it won't be known as to the amount of ballast needed in the bow to get level in the water. Right now I'm liking the plastic bags of pebbles idea for ballast.

The boat on the trailer was allegedly level... the sole of the cabin was level which another poster reported as matching the waterline. On the trailer, even sucking up an extra inch on the forestay, left the halyard hanging a foot behind the mast... I may have reported that above - and it was advised that wait for further adjustments until in the water - then that dang pre-bend thing popped up.

So, I don't like being lost in this situation... and I don't like having an over tight rig either.

But I do like the assistance...

Catalina 250 - Pretty Good Boat

Stinkpotter
Master Marine Consultant

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Djibouti
9013 Posts

Response Posted - 03/18/2017 : 10:01:28

With a mast-head rig, the principle to remember is that the forestay and backstay don't impart the bend--the upper shrouds do by pushing the midsection forward via the swept-back spreaders. That will have little or no effect on the position of the mast-head if the fore- and backstays are set--they might need a little tightening after the bend. So as Steve says, get the rake right, and then gradually put the bend in. Leave the lower shrouds to last (and least), since they will pull back against the bend.

Finally, I don't know what Catalina recommends for the C-250, but in general a mast-head rig is not designed to create as much bend as a fractional rig where fore- and backstay contribute to the bending. Don't try to make her look like a J-24 (or that Farr). The normal tightening of the upper shrouds should give you the prescribed bend.

Dave Bristle
Association "Port Captain" for Mystic/Stonington CT
PO of 1985 C-25 SR/FK #5032 Passage, USCG "sixpack" (expired),
Now on Eastern 27 $+!nkp*+ Sarge

Edited by - Stinkpotter on 03/18/2017 10:09:31

HappyNow
1st Mate

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USA
99 Posts

Response Posted - 08/13/2017 : 21:48:08

Carl-- I know you've just been dying to revisit this topic so I might have a little more to add if you never got the prebend correct. When I rerigged the boat in May, I looked at the CDI furler and the white hockey puck was totally jammed inside the boot, so I replaced it with a roller bearing puck from CDI which made a world of difference in the furling. Since I had been pulling so hard on it to furl, it looked like a couple of strands on the forestay were tweaked so I decided to replace that as well since I didn't know it's age either. The forestay was as loose as it could go, but a real struggle to put back on the fitting when raising the mast, and the turnbuckles were already at their loosest. I had the new forestay made 1 and 1/2 inches longer than the old one. Bingo. No more trouble raising the mast, and no more trouble getting prebend. No longer necessary to use my raising strap to start the prebend. So if you're still having a problem, that might be the next thing to look at. Also, don't order your new forestay from Catalina Direct if you have a CDI furler. The fitting they supply doesn't work with CDI furlers.

Michael Levin
Sailin' on Sunshine
C250 #402 WK
Lake Tahoe

Steve Milby
Past Commodore

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USA
5851 Posts

Response Posted - 08/14/2017 : 05:35:43

Instead of having a non-standard forestay made, you can buy ss extenders very inexpensively. If you decide you don't like the extension, you can remove it. The length of the forestay is prescribed for the boat by the marine architect, and it's intended to establish the mast's rake with enough adjustability in the turnbuckles to allow for fine tuning. If you have the forestay made longer, it can't be easily shortened.

The previous owner of my Cal 25 added an extension to the forestay and had the backstay shortened. The result was that the tiller pressure made me arm weary to steer it, it couldn't point and it was slow to windward in a blow. To make it right I had to remove the forestay extension and add an extension to the backstay.

Steve Milby J/24 "Captiva Wind"
previously C&C 35, Cal 25, C25 TR/FK, C22
Past Commodore

HappyNow
1st Mate

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USA
99 Posts

Response Posted - 08/14/2017 : 11:02:22

Good to know about the extensions. Makes sense. I needed a new forestay anyway, didn't trust the old one. Might be the solution for Carl though. Worth a try. Does the extension go at the masthead or under the furler?

Michael Levin
Sailin' on Sunshine
C250 #402 WK
Lake Tahoe

Steve Milby
Past Commodore

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USA
5851 Posts

Response Posted - 08/14/2017 : 11:24:28

quote:
Originally posted by HappyNow

Good to know about the extensions. Makes sense. I needed a new forestay anyway, didn't trust the old one. Might be the solution for Carl though. Worth a try. Does the extension go at the masthead or under the furler?

If it will fit under the furler, that's where I'd put it, because, if you decide to remove it later you can do so without lowering the mast. If it won't fit there, I think (not sure) you could put it at the masthead.

Steve Milby J/24 "Captiva Wind"
previously C&C 35, Cal 25, C25 TR/FK, C22
Past Commodore

Carl in LA
Captain

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USA
284 Posts

Response Posted - 08/14/2017 : 20:54:14

Michael and Steve...

Appreciate the tip about a slighty longer forestay.

I did achieve pre bend but only with the upper stays hihly tensioned - which I was uncomfortable with. I backed off the upper stays and lost the pre bend and have simply lived with the consequences. Im a cruiser and can live with the performance.

If I did lengthen the forestay I would also have to change the backstay.

I had jokingly told myself the next time I have the mast down I would lay it on a couple of saw horses and pile a couple of bags of cement on it to force a little pre bend into it.

P.S. Im using the CDI bearing also... pricy but helpful mod.

Catalina 250 - Pretty Good Boat

HappyNow
1st Mate

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USA
99 Posts

Response Posted - 08/14/2017 : 21:35:16

I was fortunate that my split backstay had plenty of room left in the turnbuckles. Yes pricey about $200 for the new bearing furler but I would highly recommend it if anyone is having trouble turning their furler. At times I would have to go up on the bow to turn it by hand, no fun when it's blowing 20 and unsafe as well.

It might be cheaper and easier to run the masthead into a bridge to get prebend rather than use the cement bags. You won't hurt your back lifting them.

Michael Levin
Sailin' on Sunshine
C250 #402 WK
Lake Tahoe

bushav
Deckhand

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USA
20 Posts

Response Posted - 08/31/2017 : 10:19:46

Gentlemen,

My new trailer has arrived. I would like to confirm something with you guys.

The manual indicates I do not need to loosen upper and lower shrouds before lowering mast. I would like to confirm this with you guys.

One of the above posts mentions damaging the mast if those shrouds are not loosened. However the manual does not seem to support this statement. We will be lowering the mast on Monday.

Thanks,
Lane

Lane

TakeFive
Master Marine Consultant

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2269 Posts

Response Posted - 08/31/2017 : 10:42:12

I think it is very important to loosen the upper shrouds before dropping the mast. The forces created by the swept back spreaders actually contribute to holding the mast forward, and lowering the mast without loosening them could cause damage to the shrouds, swage fittings, or chain plates. You may also find it nearly impossible to detach the forestay without loosening the uppers, lowers, and backstay to allow the masthead to come forward a bit.

quote:
Originally posted by bushav

Gentlemen,

My new trailer has arrived. I would like to confirm something with you guys.

The manual indicates I do not need to loosen upper and lower shrouds before lowering mast. I would like to confirm this with you guys.

One of the above posts mentions damaging the mast if those shrouds are not loosened. However the manual does not seem to support this statement. We will be lowering the mast on Monday.

Thanks,
Lane

Rick S., Swarthmore, PA
PO of Take Five, 1998 Catalina 250WK #348 (relocated to Baltimore's Inner Harbor)
New owner of 2001 Catalina 34MkII #1535 Breakin' Away (at Rock Hall Landing Marina)

Edited by - TakeFive on 08/31/2017 10:43:54

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