Its got to be here somewhere - a thread about an adjustable backstay by way of a servo - yet I can’t find it in searching the site. Hope you all can help.
Fitting my ketch with a servo that will tension or ease two backstays. As read elsewhere; to move mast foreward when running and to twist off sails when pointing but overpowered.
Would appreciate reading success or failure stories associated with this set up.
When you say two backstays, do you mean one for the main and one for the mizzen or twin backstays for the main?
I suspect there is little point in twealing a mizen backstay very much: the big effect (full size at any rate) is on forestay tension. If you are talking about twin backstays for the mainmast, much the same effect can be achieved with only one adjustment point by bifurcating the lower part of a single backstay. The lower bifurcated part is a separate wire that runs through a block at the bottom of the upper (single) part. Saves weight and windage too.
Thanks Angus. Yes,a backstay for main and mizzen. The mizzen mast and sail are as big as the main (as in Mari Chi style), so do you think an adjustable backstay would be necessary on it?
Historically (at full size) I don’t think anyone has ever used much in the way of rake adjustment on mizens unless a high-aspect mizen genoa was used - and there have been some very high tech big ketches.
Another intriguing possibility that worked but was then banned by the rule was to use hydraulic rams on the mizzen shrouds to cant the mizen to windward out of the downwash of the main (Britton Chance, Equation, c. 1974).
Just a thought
Many, if not most AC class (Model America’s Cup) boats use an adjustable backstay. Although not a ketch, you still might mine some info at their website, http://www.orgsites.com/mi/model-ac-class/ or at least make some inquiries there.
There was a thread somewhere a few years ago with images showing a regular servo being used as a 2 position sort of cleat. There was a ball that clicked in or out of a hole. In the hole tight - out of the hole loose. (I believe) So it did not burn any juice except when working to put the ball in the hole or out of it. It might have been being used for a backstay. I wonder if anyone remembers that and where it was. Sounds like a Steve Andre innovation but maybe not.
I use a slightly more powerful servo (than what comes with the standard radio these days) when adjusting backstay on the medium sized models such as the Santa Barbara. Typically they are setup to take advantage of the Landing gear type switch on the transmitter in that they are either slack or tight (up or down position switch) By setting up in basically a two position arrangement, I can come around the weather mark and slack the backstay with the flip of one switch. The same holds true at the bottom of the course coming back to weather, flip the switch and the backstay tightens back to it’s original postition and requires no trimming or even attention.
I have variable adjustments on 3 of my J’s but I find that trying to dial them in is ok near the dock but out on the course it’s just too hard to see (even on a 10’ mast)
Something akin to the Futaba 3801 gives good service for this, more powerful and yet not overly expensive and easy to find. I would recommend running the adjustment line through some blocks or other plumbing to take the direct load off the winch itself. This can also make the adjustments smaller and more suited to what you are trying to accomplish.
Log in to Windpower discussion group - rcsailtalk.com. I reposted the images smaller and rotated so they would post. Topic is backstay lock or backstay cleat. Short memory.
You can always find everything on Windpower by doing a search.