backstay working load

K2MSmith

Member III
Does anyone know how I can find out the estimated working load of the backstay on an E33 ? We are replacing the high load block (we have it rigged with 1/4" dyneema).

This Harken calculator shows an "end boom" working load on the E33 of 1375 lbs (@ 35 kts) . I am not sure what "end boom" WL.

 
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frick

Member III
1.4 inch (5mm) dymena has a breaking strength of 6000 pounds.
I believe that the Boom end load is literally the load of the mainsheet if attached to the end of the boom.
 

K2MSmith

Member III
1.4 inch (5mm) dymena has a breaking strength of 6000 pounds.
I believe that the Boom end load is literally the load of the mainsheet if attached to the end of the boom.
I'm sure dyneema is fine. I'm just looking at the block.
 

K2MSmith

Member III
Check out
For cool parts designed to work with Dymena line
I am waiting for goldenstate to “beta test” the synthetic standing rigging concept :). I’m skeptical because of the stretching, but maybe it’s like guitar strings - once they settle down, it stays in tune.
 

nquigley

Member III
I am waiting for goldenstate to “beta test” the synthetic standing rigging concept :). I’m skeptical because of the stretching, but maybe it’s like guitar strings - once they settle down, it stays in tune.
Regular dyneema does stretch - I made lifelines with it and didn't make enough allowance for that stretch, so my turnbuckles ended up being max'ed, so I has to switch to lashing the eye-splices to the stanchion termini (with friction rings in the eyes to prevent wear).
But there's a (more expensive) version of dyneema (called 'heat-set', I think) that is pre-stretched - it's what standing rigging is made from.
I replaced all standing rigging last year, but wasn't willing to switch to dyneema. However, I bought a couple of these as emergency back-ups for my 19:1 ss standing rigging:
I can splice an eye in the other end at the desired length when/if needed.
 

K2MSmith

Member III
Yea the company mentioned ( link above ) provides high quality prestretched lines and connection hardware, including life line kits
I like your idea of having a dyneema emergency spare shroud, especially if you have the gear / skill / fearlessly to climb the mast . I’m pretty screwed as I have rod rigging that has rotating mast terminators. If a shroud breaks , hope that it is on the leeward side on home tack and you can depower the rig or motor home.
 

Seth

Sustaining Partner
Does anyone know how I can find out the estimated working load of the backstay on an E33 ? We are replacing the high load block (we have it rigged with 1/4" dyneema).

This Harken calculator shows an "end boom" working load on the E33 of 1375 lbs (@ 35 kts) . I am not sure what "end boom" WL.

The end boom load is used is determining loading for the mainsheet system. Is your question about load limits on the dynema or how much load you can put on the backstay?
 

K2MSmith

Member III
The end boom load is used is determining loading for the mainsheet system. Is your question about load limits on the dynema or how much load you can put on the backstay?
I was asking the question in order to select the right high load end block for the back stay . Since we are using 1/4” dyneema, we ended up using a 2” high load wire harken rated at 2000lbs working load / 4000 breaking . It’s the largest they make of that type .
 

Seth

Sustaining Partner
Should be ok, because this load is spread between the various blocks of the purchase, right? For reference, on a masthead rig for a similar boat the backstay would be loaded to close to 3000 lbs in 20+ kts going upwind. Because the E33 is fractional and the mast bends much more, the backstay loading is much less. Probably never more than around 2,000. FWIW
 

K2MSmith

Member III
Should be ok, because this load is spread between the various blocks of the purchase, right? For reference, on a masthead rig for a similar boat the backstay would be loaded to close to 3000 lbs in 20+ kts going upwind. Because the E33 is fractional and the mast bends much more, the backstay loading is much less. Probably never more than around 2,000. FWIW
This is the final block that terminates at the back stay wire , so it would take the full load . Unless the dyneema is changed out to something thicker, it’s the largest high load block that fits the line that’s available. The dyneema replaced a wire rope . I also have a secondary dyneema “preventer” attached to the block that is a backup if the line breaks or someone lets the back stay control line go .
0C2DF3A6-1502-4996-893F-EB5457B27CCA.jpeg
 

K2MSmith

Member III
I must be confused then. If u don't have a purchase how do you tension the backstay?.
There is a purchase system below deck that pulls a final wrap of dyneema around a pulley block connected to the backstay wired.05BA0D54-0C4B-4CF2-B815-FAB7A3C628DD.jpeg
 

K2MSmith

Member III
Cool mod! What is the total purchase? Is it led to the cockpit near the traveler?
It’s not really a mod . With exception of replacement of wire with dyneema and updated block , the E33 was designed that way . Here is a better photo that shows the transom .
0F1541C3-B1AE-4E13-BC52-BCE521D0070C.jpeg
 

K2MSmith

Member III
It’s not really a mod . With exception of replacement of wire with dyneema and updated block , the E33 was designed that way . Here is a better photo that shows the transom . The line goes inside the transom to a purchase system below deck. Most E33 owners I think have replaced it with an external hydraulic but I think it’s a cool idea and it’s cheap to maintain as long as you replace the dyneema periodically . The internal purchase system doesn’t get any weather so it lasts a long time. I have it backed up just in case .
View attachment 36468
 

Dave G.

1984 EY30+ Ludington, MI
I don't want to hijack your thread so let me know if I should just start a new one. You guys seem to have a handle on all this already so..
My question is 2 fold, should & how do I rig a backstay adjuster on a 30+ (split BS Fractional). I understand the principle with a split backstay but exact parts/procedure that will have enough purchase to be useful and will I need to install additional chainplates or? Any and all comments/opinions welcome.
Thanks,
Dave
 

Seth

Sustaining Partner
It is totally a mod. I worked at the factory and ran the prototype E33 race program. The optional backstay adjuster was hydraulic (not a great choice). Someone did this aftermarket
 
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