E36RH Hydraulic Backstay Stroke

[Seth]

Needs some help

HI Mark/Vonnie,

Absolutely you are preventing the rig from bending down low. The af lower MUST be eased until you are getting a uniform bend from the deck to the top (without runners being installed). If the runner tails are tight on the lower chainplates, take them off during tuning! and make sure they are not tensioned if you are going to store them there.

BUT- before you do this, make sure you have the mast step and collar positioned per the tuning guide (meaning mast in the aft-most position on the step, and the mast blocked all the way forward in the deck cut out). The ease the aft lowers and dock tune it. You are still not done, though-you need to tune the rig under sail-you cannot really see how it looks under load by dock tuning. Dock tuning should just get you in the ballpark. You need at least 8-10 knots of wind for good tuning conditions....There are a lot of posts here about tuning under sail-check those out and let me know if you have any questions.

My guess is the bend will be close to double what you see once this is all done.

Cheers!

 

[markvone]

Thanks again (again)!

Seth,

I DO have the mast setup per the guide, step aft, all the way fwd in the partners. It wasn't until I looked at my own pictures that I realized the lower shrouds were angled slightly aft and would inhibit bend. THEN, I also realized I had the checks clipped to the lowers chainplate as well. Doooooohh! I doubt the checks were very tight - they are only a 4:1 block and tackle so it is hard to get tension (need to upgrade the checks per your previous guidance) but I do snug them to keep them from swinging around.

When I tuned the rig sailing I made sure the mids/uppers kept the rig in column with no leeward fall-off, BUT I never checked the lowers tension as the lower mast was in column. So I don't know how tight they are. I will check them next trip to the boat. We finally have snow and cold here in MD so there won't be sailing for a month or two. Meanwhile, I'll get working on the new backstay.

Thanks again,

Mark

 

[Seth]

Ok

Sounds good. I would ease them off until you get a uniform bend (you can do this at the dock). Then next season, you can go sailing and fine tune things. If the mast step is set up right, then this should solve the problem. When this is done, measure the total bend and then ask your saimaker how much luff curve is in the mainsail. Ideally it should be 80-90 percent of the max bend...meaning if you can get 10" of bend, you want 8-9" of luff curve . This way the main gets totally boarded out just before you reach max bend... Got it?

S

 

[markvone]

Determining Mainsail Luff Curve

Seth,

I assume my sailmaker can measure or eyeball the main in the loft and tell me the luff curve it was designed with?

My mainsail is a practically UNUSED 1998 full batten dacron from North, San Diego. Not exactly what I would buy now but it came with boat. I do have the original North Order Entry # for it so they might be able to look it up (although it was nearly 15 years ago!).

My sailmaker is Quantum, Annapolis. My guy, Jason Currie, a Kiwi says he remembers you from your days at Q.

Mark

 

[Seth]

Correct

With the info you have, easiest thing is to call North San Diego and ask them to look it u. Do you have the nam of the ower at the time the sail was made? That would really help, but the # should work.

Or, failing that,the next thing is your local loft.....I know Jason-I worked for Q in the early 2000's here in Chicago (but the manufacturing was in Annapolis back them)..And yes-they should be able to give you a good guess by laying the sail out at the loft.

Bon chance!

S

 

[rgraham]

Make sure there is no water in the cylinder

I have a Navtec hydraulic backstay cylinder on my backstay connected to a central panel where the pump is located. I measured the stroke at 4.5 inches. The cylinder is old and the model number is no longer readable. I had the cylinder rebuilt last year due to a top seal leak so it SHOULD be functioning correctly. The Navtec info I have found lists typical cylinders with 8, 12 and 20 inches of stroke. My cylinder stroke seems too short. Can anyone with a similar size rig (E34-2, E35-3, E36RH, E38) provide stroke info for their cylinder?

Thanks!

Mark

On my E36RH with the same backstay I had water in the cylinder where you pump it up with air for it to auto return. Depress the air valve with pressure on the backstay and see if water squirts out. If there is water in the cylinder it can't retract all the way.

Robert

 

[markvone]

Follow up on mast bend

When E36RH hull number 31 came to a boatyard near me last summer, I was able to measure her mast section outline. Her mast is significantly smaller in profile than mine. The E36RH originally was spec'd with a Kenyon 4270 mast section, the same as a J/35. My mast section measures close to a Kenyon 4477, the next larger section. I suspect my original mast was damaged and replaced with this section sometime in the past. This section has to be stiffer than the original factory spar, by how much I'm not sure, but this is the probably the reason I was never able to get as much bend as I anticipated. I'm going to check with my rigger to see if I can get some more info.

Mark

 

[Seth]

When E36RH hull number 31 came to a boatyard near me last summer, I was able to measure her mast section outline. Her mast is significantly smaller in profile than mine. The E36RH originally was spec'd with a Kenyon 4270 mast section, the same as a J/35. My mast section measures close to a Kenyon 4477, the next larger section. I suspect my original mast was damaged and replaced with this section sometime in the past. This section has to be stiffer than the original factory spar, by how much I'm not sure, but this is the probably the reason I was never able to get as much bend as I anticipated. I'm going to check with my rigger to see if I can get some more info.

Mark

Mark, the initial spars were built by Ericson' s rig shop, using Sparcraft sections, if memory serves me. I don't remember which hull number was where we switched to outsourcing the rigs to Kenyon.
That said, the bend amount is as much about mast step, partner position, and if still installed, the babystay load. You should still get a good amount of bend, but you only need as much bend as the luff curve in your mainsail needs to flatten out. If the main was designed for 12" of bend and you only can get 8" (at about 3800 lbs), have some curve removed, or better yet have a main built to match the mast. If you want to talk further, pm me or email me at sethtec@aol.com, and we can exchange contact info