E36RH Rig Tune for SF Bay Spring/Summer Racing

[mgg00]

I'm looking for some advice on rig tuning for an Ericson 36RH for racing on SF Bay for the coming Spring and Summer seasons. The rig is out of the boat right now, but will be going back in next week. I've seen some recommendations from Seth on rig tune (aft in mast step, forward at partners, 3-5" of rake?) and was wondering if there are tweaks to his recommended setting for the typical 20-25+ we see most afternoons here on the bay.

Thanks!

Mark Green
E36RH #19 "Sweet Grapes"

 

[Rocinante33]

Mark,

Go to the tab for Downloads. You can download the Technical Bulletins for E-33 & E-36 owners which has a very good description of mast tuning for our fractional rigs.

 

[markvone]

Hi Mark,

A few pictures of your boat racing have been posted here on the site.

The E33-E36 Owners Bullentin #1 in the E36 Downloads section covers weather helm due to rig tuning and hull trim for BOTH the E33RH and E36RH. The second tuning guide in the E36 Downloads section (E33-E36 Owners Bulletin #2) is actually the E33 specific tuning guide for fractional rigs. I have the E36RH (specific) Owner's Bulletin #2, which deals with rig tuning the masthead rig, at home, and will send it to you if one of the the other E36RH Owners doesn't post it.

I sail on the Chesapeake, which is the opposite end of the wind spectrum from SF in the summer. I can say that the tuning guide is accurate in it's recommendations for light air. I have ~ 4" of mast rake and plan go to 6" per the tuning when I tune up the rig this spring. I sail often in 0-10 kts</SPAN></SPAN>.

Seth is a huge help, he setup and raced the factory E36RH for the Ericson factory. He will certainly be able to help tune your rig for heavy air.</SPAN>

The link below is a discussion on rig tune and mast bend for my E36RH - working to get the most wind range by setting the static rig tension and adjusting the backstay. While I am optimized for light wind, adjusting the rig tune and mast bend allow me to go up in wind speed before I have to change from my 155% genoa to my 103% #3 jib, a big job I'd like to minimize. In the Spring and Fall, I often have the #3 on the furler an need to power this sail up below it's normal wind range. This is probably something you'll need to do if your rig settings are optimized for heavy air and it gets light during a race.

http://www.ericsonyachts.org/infoexchange/showthread.php?11577-E36RH-Hydraulic-Backstay-Stroke

I'm still having issues with my hydraulic backstay adjuster and need to re-tune my rig, so I'll be adding follow-up posts to the thread above in the near term.

Mark

 

[markvone]

E36RH Owner's Bulletin #2

Here's the E36RH specific Owner's Bulletin #2 on rig tuning.

Mark

View attachment E36RH_Owners_Bulletin__2.pdf

 

[mgg00]

Reviewed the docs - have a few questions

Mark V. -

Thanks for the tuning guide and pointer to your earlier discussion - both should be very helpful. Both the tuning guide and Seth's comments seem to agree on the mast setup at the step and partners: all the way aft at the step and forward at the partners. For rake the tuning guide calls for 6" while Seth recommends 2-4". I'm currently thinking 4" given our heavier winds for the coming months, but I have some questions about how you get to this measurement:

- I am assuming that once the mast is stepped with the butt aft and then forward at the partners you will have an initial rake measurement. Do you adjust the rake at this point to get your desired measurement via a) adjusting the mast step or b) by adjusting the forestay and backstay initial settings? If b) I would think you would be inducing some level of pre-bend in the mast while this would not be the case with a). In either case I am assuming you then simply add additional forestay and backstay tension to get to your desired pre-bend, taking care not to change your rake in the process.

- I also didn't see a target measurement for pre-bend in the tuning guide or the referenced thread - I am guessing that 2-3" will be in the right ballpark, but not really sure and would love some guidance. Did I miss this info somewhere?

We are replacing the headstay anyway and need to decide the correct length for the new one - unfortunately, I don't know the rake and pre-bend we had with the old forestay - only that we were at the minimum adjustment for the turnbuckle, so not quite sure what to tell the yard.

We are also ordering a new main from North in SF - they may be the best source for recommendations on pre-bend but not sure that there is much knowledge specific to this boat up here - haven't run across any others on the bay yet.

Thanks again for your help!

Mark G.

 

[markvone]

Mark,

I would lean toward 2" of rake as a starting point for 20-25+. The balance of the boat will determine what's best. Do you have a furler on the forestay that limts adjustment or a turnbuckle with more adjustment? Do you have a hydraulic backstay adjuster? How much of the time will you need to adjust the setup to more moderate winds vs optimized for heavy air?

Answer b) You lengthen forestay/shorten backstay to increase rake, then tension each equally to add more pre-bend. The mast butt aft and partners fwd guidance gets the mast slightly out of column and started to bend so that additional backstay tension will compress the mast and continue the bending. Since the E36RH geometry is already maxed out (butt aft/partners fwd) there's no more messing with it after setting.

You need just enough pre-bend to keep the mast stable and prevent pumping but enough remaining bend to depower the sail over the remaining bend range. I would think 1-2" of pre-bend would be the target. Seems logical to me that the farther into the total range of bending available you start with your pre-bend setting, the less bending remains for flattening the main. Seth can add much more specific detail on rake and pre-bend for the E36RH when he checks in.

I will be up the mast several times in the next few weeks adding instruments and replacing the backstay, so I will have the opportunity to measure my forestay length. With this and the measured rake, it should give you an idea what forestay length you need. My current wire backstay is too long to get adequate tension with 4" of rake. Also the hydraulic cylinder is shot. FWIW, my rigger recommended using rod for the backstay for better sail shape control when it's windy. Cost is about $100 more than wire. My forestay is rod but the backstay was switched to wire when SSB insulators were added in the past.

Let me know if you need anything else.

Mark

 

[mgg00]

Thanks, Mark!

We have an older Harken furler which limits us to about 3" of forestay adjustment. If we get the forestay length right, this should be more then enough to allow the rake to be adjusted from 0-6" (if my calculations are correct it only takes about 5/16" of forestay length change per 1" of rake). When I calculate the nominal no rake forestay length from the I-J measurements, I get 49' 10.8". My yard says the current effective forestay length is 49' 9.5" with the minimum adjustment on the furler. The mast was previously set with the mast butt aft with the mast close to centered at the partners, so I expect even less initial rake with the new mast placement.

We have a Navtec backstay adjuster - we had previously been getting about 4" of throw on the adjuster at 3000 pounds of backstay tension - haven't tried going farther then this. Sounds like we need to be able to pull quite a bit more backstay to get the full range of mast bend. We are currently in the transition period where we get some moderate days but by May we are typically seeing 20+ 8 out of 10 days. We do frequently start in lighter air, but rarely finish in lighter conditions. Most of our weekend races start right during the time frame where the wind switches on, so being able to maximize our flexibility is critical for us.

The rig is going in before the weekend, so we will be tuning Saturday morning if the weather permits. Thanks again for all your help!

Mark G.

 

[markvone]

Mark,

I have the same Harken furler/Navtec 9" stroke hydraulic cylinder as you.

I have not been able to get helpers to haul me up the mast yet so I don't have my forestay length measured for comparison. I will say that my forestay is probably factory original and that length combined with the 3" of adjustment from the furler will easily allow rake adjustment from 0-6", probably more like 8" max. The 49' 10.8" nominal FS length value is what I get also. Your current length should allow plenty of rake adjustment from vertical.

I was getting the same +/- 4" of stroke at 3000 psi on my cylinder when I started the older thread in the link. You can pump it up to 4000 psi without issues, it just gets harder to pump and by 4000 psi you get no reaction. Factory relief setting is 4000 psi.

After experimenting this week with really loose HS/BS tension (12" of HS swing) and my rebuilt hyd cylinder, I got 7.5" of stroke at 4000 psi but the same mast bend profile seen in the pictures in post #20 of the old thread. That was with the rig set as tight as I could get it! This tells me two things. The rebuilt hyd cylinder is working fine, but it is only able to supply so much load. Since most of the bend is above the lower spreaders and not down low, this means I am NOT inducing enough pre-bend in my lower mast section with the butt all the way aft and the position at the partners all the way forward. This could be particular to my boat: the mast base is more forward on the keel, the partner hole in the deck is slightly more aft, or both. But without starting the bend down low with the butt aft/partners fwd position of the mast, the hydaulic backstay just pulls the tip of the mast aft putting most of the bend into the top half of the mast. The cylinder can only pull so hard until it equals the load of the stiffness of the mast. I don't know if there's anything else I can do with my mast/step/partner geometry. I still have my babystay hardware, so I may experiment with a removeable babystay to get lower bend when it's windy.

The good news is the BS cylinder will take up all the slack from a loose setting to a pretty tight higher wind setting. For your situation, I would set up the rig rake and tension so that it was good at full hyd BS pressure at your typical max wind. Then with minimum BS pressure, you will get more HS sag, less mast bend and more powerful sail shape. I power up my #3 this way during the spring and fall to avoid using a #2 that I don't have and to avoid underway changes to my #1 which is a huge PITA.

Mark