E36RH Hydraulic Backstay Stroke

[markvone]

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

 

[tcooper]

Old age I Guess

Mark, I forgot to measure again tonight, good intentions abound. I'll make sure to measure and get you my cylinder size and length tomorrow night.

Old age setting in i guess

Tom

 

[markvone]

Thanks Tom!

Basically, the beginning of the threaded end of the shaft (about 2 inches of threads on the end) should be down at the seal at the top of the cylinder. If you look at the total length of the cylinder there should be plenty of room for more shaft travel into the cylinder (I'm getting about half of the shaft into the cylinder). Another possible problem may be an inaccurate pressure gauge. If so, I'm stopping at an INDICATED 3000 psi on the gauge. If it's way off low, I'm stopping BEFORE I get to full pressure. Pic of the cylinder fully released below.

My sailmaker thinks I should be getting about 4 inches (+/-) more of travel into the cylinder. I'm not getting much mast bend - which is how this situation came to light. Got a new 150 this spring, sailed around ALL summer in the Chesapeake in under 10 kts - no problem. Fall arrives with, WIND! Boat gets fully powered up at 10 kts, over powered over 13 kts. Start seriously working at depowering - what is up with that backstay? Order new #3, email EY.org for help.

Mark

 

[tcooper]

My cylinder is currently unhooked and it looks just like yours. Pin to end of cylinder is about 17". Tonight I'll hydraulically push it all the way in and out and see if it gets full cylinder throw with no load.

Tom

 

[Seth]

Much more throw

You should be getting MUCH more throw than 4-5"! The mast is designed to be bendy and if set up right you should get close to 10" of bend, which is needed to get the mainsail flat and the headstay tight in breezy conditions. If the sails are cut for less bend you can set the rig up to bend less under load from the backstay, but you will need about 3000 lbs on the gauge in over 15-18 knots of breeze (upwind of course).

S

 

[tcooper]

Mark, I measured the throw on my cylinder and it has total of 9". 24" C to C closed 33" C to C open. Wish I could just come down and help you figure out the overpower problem. Going thru sailing withdrawal already! winter wind is in the air here.

Manual says 100 psi on bottom of cylinder, but even if it lost it's pressure 3000 psi would have no problem overcoming vacuum but might be worth checking the pressure if it's not relaxing.

Good luck

Tom

 

[Seth]

Stroke

Now that I see the photo:0, there is no doubt that the exposed portion of the SS rod should compress to within an inch of the threaded portion near the turnbuckle. If you are seeing 3000 lbs with only 4" retracted something is not right. I know becuase on the factory 36 which I raced for several years we had the cylinder buried in breezy upwind conditions at 3000+ lbs, and used the same model hydraulics (Navtec, right?).

Good luck!

S

 

[markvone]

Thanks Tom and Seth!

Yes, it's the original Navtec cylinder. I have the mast setup per the tuning guide: butt all the way aft, chocked all the way fwd at the partners so I am getting mast bend started - just not nearly enough. My fore-aft static rig tension was too loose but I have about 3 inches of take-up equally split between fore and aft so this will help me get to a better starting point. I'll have to check out the backstay cylinder to see what's up with the missing travel. Also here's a better pic with her stern cleaned up.

Mark

 

[Seth]

Rig tension

You are right, the baseline fore and aft tension needs to be right to begin with. With the BS totally loose, the headstay should move in about a 6" arc when wiggled by hand (I would go looser if I were racing seriously), assuming you have 2-4" of aft rake with the rig unloaded.
It should be bone tight with the BS fully loaded-even at about 75% loaded it should be bone tight when at the dock and no sails up. I am not going into a discussion about relative headstay and backstay becuase I am assuming things are close enough and you are not doing a lot of serious racing.
If you have much more than the 6" of play, take upthe slack on the backstay turnbuckle rather than the HS-unless you have more than 4" of aft rake already.

Let me know and we can go further. If am wrong about the type of sailing you do let me know.

Nice looking boat, BTW! The 36 RH is my favorite Ericson boat (which is no slam on the wonderful BK designs-I love them too).

S

 

[tcooper]

Mast Position

Seth, what would happen with the base of mast all the way back and mast blocked forward? This is really new to me.... Would it make a neggitive effect on how the boat steers, seems like it would depower the boat at a neggitive cost of how the boat tracks?

Mark, you have orginal tunning guide from Ericson?

Tom

 

[markvone]

Mast Tuning

Tom,

I do have the (only) two tuning guides for the E36RH. The first deals with weather helm and applies to the E33RH as well. There are two #2 guides one specific for each boat. I'll send you the #2 guide direct now and dig up the #1 at home.

Seth,

I am not doing any serious racing, but I would like to get out Wed nights in Annapolis maybe next year if budget allows (this may actually qualify as serious :0). This was my first full season with the boat so I am still sorting things out like throwing away all the old, blownout, delaminating headsails.

I have 4 inches of aft rake unloaded, so I was planning on taking up equally fore and aft to keep rake at 4 inches unless you think I should reduce it for the +/1 15 kts we get in the fall. I'm curious about the reason for the extra forestay sag, jib shape adjustability, downwind?

Thanks!

Mark

 

[Seth]

Mast set up

The setings for the mast step and partners have zero impact on "tracking" or how the boat steers. The purpose of this setup (which I agree with for the RH 36 based on mast characteristics) is to induce some prebend, and as result the mast will take on a more uniform bend profile as you add backstay tension. This is desireable becuase as you bend the mast (which does depower the boat by flattening the mainsail) you want the sail to change shape over the entire luff length, and to do so in a uniform manner.

What DOES affect steering qualities is the amount of mast rake-the more aft rake you have, the greater the tendency to have weather helm. You need a little aft rake, or the boat won't want to point as well as it was designed to. Too little rake and the boat will not point as well, but will have less weather helm which will improve downwind and reaching performance at the expense of upwind performance, and vice versa.

"Tracking" is not affected by rake or prebend-this has more to do with the location of the keel in the fore and aft plane, and also rudder shape, size and location-all of which are correct on this design.

For example, if you set up the rig so that there were no prebend, the mast would bend much more at the top than at the bottom, with the result that only the top portion of the sail would flatten as you add backstay tension, while the lower portion would change much less. This will result in a sail which is flatter at the top than the bottom and this is not the objective.

The mast has a total bend potential of about 10" when using a bckstay adjuster. The sail should be designed so that it is relatively full with no backstay load, and become very flat at about 80-90% of the available bend. This way you have a full range of adjustment to match the conditions.

If you do not use an adjuster, then the mast will not be able to be controlled in terms of bend, and the sailmaker MUST take this into account and begin with a flatter sail shape (since it cannot be adjusted except for outhaul, cunningham and vang). You would still want some prebend (but the sailmaker must know how much prebend has been induced) so that you get at least SOME uniform bend as you add vang tension. Prebend also helps prevent the mast from inverting (bending forward) in heavy seas.

Sail design must take into account the bend characteristics of the mast, and the available adjustment.

Hope this helps answer you question.

S

 

[Seth]

More...........

[Seth,

I am not doing any serious racing, but I would like to get out Wed nights in Annapolis maybe next year if budget allows (this may actually qualify as serious :0). This was my first full season with the boat so I am still sorting things out like throwing away all the old, blownout, delaminating headsails.

I have 4 inches of aft rake unloaded, so I was planning on taking up equally fore and aft to keep rake at 4 inches unless you think I should reduce it for the +/1 15 kts we get in the fall. I'm curious about the reason for the extra forestay sag, jib shape adjustability, downwind?

Thanks!

Mark[/QUOTE]

SO...........the 4" is good for your area, and I agree to take up equally front and back. In light air a saggy forestay will make the genoa deeper with a rounder entry which will improve power (and hence speed) and pointing (rounder entry allows a wider groove to keep consistent flow all along the luff of the genoa). In under 5-6 knots of breeze you want the HS to sag as much as possible without it bouncing around more than and inch or so (this will detach the flow each time it bounces). If you have the HS sagged way off (good in light air upwind), but see it bouncing more than an inch or so, take up just enough backstay to settle it down. As the breeze comes up, the genoa will become too full (under load) and sag will become excessive, so you add backstay tension to reshape the depth and entry of the genoa to match the conditions. Reaching in light to moderate air is the same-keep the sail as full as possible but don't let it bounce around too much.

Downwind, having the backstay eased will allow the top of the mast to go as far forward as possible, which reduces weather helm, and since you are not holding as much rudder angle to go straight (drag), you will go faster.

The mainsail benefits at the same time; the eased backstay in light air allows for a fuller, more powerful shape, and as the breeze comes up, adding backstay will flatten the sail by bending the mast-so it all works together.


What else?

S

 

[markvone]

Thanks Seth! (Again)

Seth,

You have confirmed what I have been experiencing most of the summer. My rig seemed really loose (fore - aft only) but the new 150 (Quantum Fusion M 4000) was easy to trim and powered the boat up nicely in +/- 5 kts and started to hit max heel at 10-12 kts. We rarely see 10+ kts from June - Aug and the Bay is FLAT, so I did not get bouncing except from random power boat wakes. The loose setting seems to be a nice setting for summer here so I will probably tightened up now and go back loose after Spring for the summer.

Mark

 

[Seth]

Rig tune redux

Mark,

I think it might be OK to leave things as they are for summer sailing (hard to really tell without seeing the rig), but I hope you are using the backstay some whenever you get more than 5 knots or so. Without doubt you need more rig tension in 6 knots that 4, and more in 8, etc.

The loads increase in a non-linear fashion as the breeze builds-the shape that is good in 4-5 knots is too full in 8-10, so adjustments should be made if sailing the boat to its' potential is the objective. This applies to genoa and mainsail.

BTW- has the babystay been removed on your boat? This does help induce bend without adding backstay tension (just as running backs can remove bend without losing backstay tension), BUT-I ended up removing the babystay as the benefits were offset by the interference when tacking and dealing with the spinnaker pole-especially around the buoys. I did keep runners ready to use, and in 12+ they were very handy to fine tune mainsail shape..

10-4?

S

 

[markvone]

Seth,

Yes, I am adding backstay pressure quite quickly as the wind builds between 5 - 10 kts. With a properly functioning cylinder with full stroke, I MAY be able to use the looser rig settings in more wind OR a slightly tighter setting all year.

I still have the runners and have used them a couple of times when I had mast pumping.

I still have the mast t-ball fitting and the deck hardware for the babystay (see pic). I had thought about re-installing the babystay to get more mast bend, but only if I could leave it detached and out of the way at the mast when I don't need it.

How much more bend might I expect from the babystay? I ask because I would love to minimize the wind range gap between my new #1 and new #3 and skip a #2. Both sails were built with this as the goal, but it will require pushing the #1 higher in wind range.

Mark

 

[Seth]

Seth,

Yes, I am adding backstay pressure quite quickly as the wind builds between 5 - 10 kts. With a properly functioning cylinder with full stroke, I MAY be able to use the looser rig settings in more wind OR a slightly tighter setting all year.

I still have the runners and have used them a couple of times when I had mast pumping.

I still have the mast t-ball fitting and the deck hardware for the babystay (see pic). I had thought about re-installing the babystay to get more mast bend, but only if I could leave it detached and out of the way at the mast when I don't need it.

How much more bend might I expect from the babystay? I ask because I would love to minimize the wind range gap between my new #1 and new #3 and skip a #2. Both sails were built with this as the goal, but it will require pushing the #1 higher in wind range.

Mark
View attachment 11898

Runners can certainly help steady the rig-you will see it pumping more often when you have disconnected the baby stay and are in waves, BUT-this is not the primary function of runners on a rig like the 36 has. The benefit is that in conditions where you may want a tight headstay, but need the mainsail powered up (such as sailing near the bottom end of the Heavy #1, #2, #3 or #4 genoas), you can add tension on the runners to remove the bend induced by having a tight backstay (which tightens the headstay and reduces sag). It is a great way to modulate mainsail power while keeping a consistent amount of tension of the headstay. And, let's say you have the #3 up at the low end of that headsail, and have the main powered up using the runners to offet the bend from the tight headstay, and the breeze comes up another 5 knots. You will now be overpowered because the main is too full..just ease the runners until the main gets sufficiently flat. Easy!

The baby stay can induce up to about 4" of bend independent of the backstay or runners, and most of this is down low. One of the big reasons we suggest setting the rig up aft at the step and fwd at the partners is the induce low bend without having to use the baby stay. Around the time the 36 came out, baby stays were beginning to fall out of favor since we found we could accomplish the same thing with mast step/partner position and proper use of backstay and runners..In fact, if it were me, I would remove the baby stay from the mast entirely for buoy racing and local sailing, and maybe install it for an offshore passage or long offshore race(where tacks and gybes will be less frequent) and use it to give the ultimate in adjustability. The benefits when buoy racing are offset by the hassle of slower tacks and added difficulty handling the spinnaker pole on the foredeck.

So, the pumping issue is really secondary to optimizing sail shape.

Does this answer your questions sufficiently? If not, come on back and we will keep at it!

Cheers,
S

 

[markvone]

Thanks Seth,

I'll get to work on the missing backstay throw and then see what degree of bend I can get with it and maybe a tighter static setting before I re-create the babystay. I've got plenty of projects ahead before I'll be ready for offshore and the need for the babystay. I'll post the results of the backstay investigation.

Mark

 

[Seth]

Babystay

Thanks Seth,

I'll get to work on the missing backstay throw and then see what degree of bend I can get with it and maybe a tighter static setting before I re-create the babystay. I've got plenty of projects ahead before I'll be ready for offshore and the need for the babystay. I'll post the results of the backstay investigation.

Mark

Sounds like a plan...Just so we are clear, IF I were to use the babystay, it would only be for longer offshore cruising or racing. However, in my opnion, the use or non-use of this really depends on how you sail and how you use the other tools (backstay, runners, and mast step and partners positioning), and how the mainsail was designed and built. This is just my opinion, but I believe you can control the mast (both for safety and performance) sufficiently without it if you are aware of the proper use of the other tools at your disposal. 2 cents paid:nerd:

Hasta,

S

 

[markvone]

Follow-up on backstay work

I completed the following check out steps since the last post:

Pumped hydraulic cylinder up to 4000 psi (factory relief setting).
Further pumping produced no more travel
Got 7.5 inches of travel
Checked air (return) side of cylinder for oil which would indicate an internal seal leak none found
Recharged air side to factory setting (100 psi)
I tried to take up the available 3 inches of thread equally between fore and back stays but could not easily adjust the furler or backstay threads under load
The pics show the unloaded straight mast and 4000 psi bend. The halyard tack and sheeve offset is 2 inches in the unloaded picture.

I am getting a couple of inches of bend which is not bad considering how loose the rig is at the starting point.

I am wondering if the lowers (which are slightly aft of the uppers/intermediates) and/or the checkstays (which were stored attached to the lowers chainplates - not sure how tight they were) are slightly inhibiting bend down low?

I plan to replace the backstay to eliminate two old SSB insulators and I will add a turnbuckle to the new backstay to get more initial tension and to more easily adjust amount of fore-aft tension.

Mark