Page 1 of 2

Running Backstays with Rotating Mast

Posted: Sun Jan 07, 2007 6:39 pm
by delevi
Ok, this one is for all you :macm: owners or you :macx: owenrs who think you have the answer. I have runners installed on my boat. Recently, I discovered that due to my really tight upper shrouds, the mast gets a significant sideways bend when rotated, opposite to the side of rotateion. I will soon loosen the shroud tension to cure this. I'm not sure, however, if this problem self-corrects when the mainsail is up and loaded. I experimented with this on the trailer only. This leads me to my question. Would tensioning the windward backstay create the same effect, and if so, would the loaded mainsail correct the issue? If not, I'm thinking of installing another hound, right above the forestay/shroud hound. Then the question is whether to get the kind which is currently on the boat w/swivel to accommodate mast rotation or to get a fixed hound and criss-cross the lines for the runners. The idea is to pull the mast back to bend it and add forestay tension vs. pulling the mast sideways when rotated. Any suggestions are much appreciated.

Cheers,
L.

Posted: Sun Jan 07, 2007 6:54 pm
by Frank C
Leon,
Wouldn't this 26M backstay (Mac Mod's, Rigging) be a more straightforward solution?? M. Cantwell's approach sure is creative ... not sure if he ever posted follow up feedback.

Image

Posted: Sun Jan 07, 2007 7:45 pm
by Dimitri-2000X-Tampa
Today I was tuning my rigging and experimented with having tension on the backstay (26X). By tightening the backstay, I reduced the tension on the upper shrouds by 100#. I guess this will be good for tightening up the forestay a bit and flattening the main out more.

I only know a little bit about a 26M, but it sure seems like that backstay mod would hamper the mast from turning properly. I thought that was the main reason it was designed without a backstay (having further swept back spreaders) so that the mast could turn.

Posted: Mon Jan 08, 2007 8:24 pm
by delevi
Today I was tuning my rigging and experimented with having tension on the backstay (26X). By tightening the backstay, I reduced the tension on the upper shrouds by 100#. I guess this will be good for tightening up the forestay a bit and flattening the main out more.
I had the same situation (when my shrouds were looser) but when chatting with the dealer, he told me that the slack would be taken up by the loaded mainsail, so on the trailer, things may be misleading.
I only know a little bit about a 26M, but it sure seems like that backstay mod would hamper the mast from turning properly. I thought that was the main reason it was designed without a backstay (having further swept back spreaders) so that the mast could turn.
Since runners are always released and tensioned, it's a non issue for mast rotation. The boat certainly doesn't "need" a backstay and with all my new adjustments, I don't necessarily need to bend the mast. I can get the sail super flat w/ cunningham and now 8:1 outhaul on the loose footed main which acts like a flattening reef. The idea is to take up forestay slack to point higher. I just don't want to create sideways bend on the mast, since as it's rotated, the force from the runners is applied at about 45 degrees from the side of the mast. Not sure how much the shrouds compensate. The hound for the forestay and shrouds is on a swivel to allow the mast to rotate, so the whole deal is rather complex with respect to forces pulling in different directions. Even more challenging is observing what happens on the trailer with sail down is not necessarily what will happen on the water.

Frank,

Cantwell's mod looks interesting, but may not be practical and safe. I would be concerned to break the mast with a mast-head rigged backstay when applying a 5:1 purchase. Also, the same sideways pull problem can occur, and though it will surely bend the mast, I'm not sure it will tighten the forestay, since it sits a good 7-10 feet below the masthead.

stay tension and mast rotation.

Posted: Wed Jan 24, 2007 6:04 pm
by charlesvanmidd
I picked up my Mac 26M late in the season last year so I am still experimenting with the standing rigging tension. Some of the guys in other slips at the marina helped me tighten the side stays almost were you can pluck them and hear middle "C". With the stays this tight I have trouble manually turning the mast. My question is: which of the side stays would I loosen in order to enable the mast to turn properly. I will appreciate any help I can get on this topic.:macm: CVM

Posted: Wed Jan 24, 2007 6:11 pm
by delevi
Start with the uppers, which should usually be tighter than the lowers. Make sure to make identical changes on each side. Site up your mast to make sure it's straight, otherwise compensate by loosening the shroud on the side where the tip of the mast points. A good setup is when you see a very small backwards bend in the mast. If it won't rotate freely, the shrouds are too tight. You certainly don't want them too loose, though. Frequently check the mast for straightness, sighting up the sail track. Taking a lot of load off the uppers will probably add more load on the lowers... they sort of work in opposite directions. Don't worry too much about keeping the holes on either side in the same place. The cables will stretch differently. You can also go to http://bwyachts.com They have a link to rig tuning which is excellent.

Leon

Posted: Thu Jan 25, 2007 5:07 am
by baldbaby2000
Some of the guys in other slips at the marina helped me tighten the side stays almost were you can pluck them and hear middle "C". With the stays this tight I have trouble manually turning the mast.
I think you have them way too tight, I'd loosen them ASAP. You can get a gauge to check them and remove all doubt. A little teflon spray will help mast rotation.

BB

Posted: Thu Jan 25, 2007 6:39 am
by beene
Sure sounds too tight to me. If yours sounds like a C mine is an Eflat. :D

Posted: Thu Jan 25, 2007 8:10 pm
by James V
I was talking to Bill at the factory and he said that it could be done easily but did not go into details. Has anybody asked him about running backstays?

Posted: Thu Jan 25, 2007 10:11 pm
by delevi
I haven't asked Bill, though talked to him several times about other things. Jeff at Arena Yachts (my dealer) encouraged me to install them. All you need is 1/4" line, about 80 feet, a couple of snap shackles and some blocks. Here is how mine is set up:

Lines tied at the hound where the jib/spinnaker halyard attaches, just above where the forestay & upper shrouds attach. The lines should be long enough to reach about 1 foot aft of where the cabin lifeline pelican hooks attach. Attach snap shackles at the end of each of the running backstay lines. Get some Harken mini blocks. Snainless fiddle block with becket & v-jam & a double block (2 sets of each) Attach the fiddle blocks to the base of the stanchions furthest aft, the ones near the helmsman seat. The double blocks clip on to the snap shackles. Use 1/4" line to connect the blocks, thus makinga 4:1 purchase. The working (windward) stay will be connected and loaded. The leeward stay will be disconnected form the 4:1 tackle via the snap shackle. Snap the shackel to the lifeline forward of the pelican hook, and it will just ride forward. When tacking, make sure to release and disconnect the backstay. Once youre set on your next tack, bring the new windward stay back, hook up and crank it down with your 4:1 tackle. You may need to use your boat hook/pole to grab the stay. Simple and efficient and really increases performance upwind. Just make sure you don't forget to disconnect when tacking. I have a couple of times and almost got myself in trouble. All that said, the :macx: boat with its permanent backstay has no need for these, but a great mod for the :macm:

Leon

Posted: Thu Jan 25, 2007 10:47 pm
by eric3a
..

Posted: Thu Jan 25, 2007 11:25 pm
by James V
delevi - Cool,
a great mod for the :macm:
Please post mod with some pic's.

Thanks James V

Posted: Thu Jan 25, 2007 11:29 pm
by delevi
Next time I'm at the boat, I'll do a photo shoot of all my mods and post some pics. I know I promissed to do this a while back, but keep forgetting to bring the camera along.

Posted: Fri Jan 26, 2007 12:49 pm
by baldbaby2000
Leon,

That sounds similar to what I did but I'd like to see photos. I have bungees on a cheap carabiner clipped to each line that pulls it forward when that stay is released so the boom doesn't catch it when sheeting in the main after it's been out. I don't disconnect anything when changing tacks.

Daniel

Posted: Thu Feb 01, 2007 1:51 am
by delevi
Don't quite understand your setup Daniel. How do you keep the main from being stopped by the leeward stay if you don't disconnect? Do you just let out a whole bunch of line? Not quite picturing the bungee setup.. :?: