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Old 17-12-2013, 15:01   #1
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Suggestions for things to Test with a Load Cell?

I had a load cell some years ago, broke it (anchoring test), just today ordered a new one . . . 10,000lbs capability (which can double to 20,000 or more with a tackle). It also produces 10hz (10 points per second) data thru a cable stored to excel

So my question is does anyone have anything in particular they want to see load tested?

I have a bit of a list from my life line and rigging papers. on breaking strengths of various knots, splices and bend radius's on various types of line.

And I am a bit curious on the loads on my dyneema innerstay.

I also want to update the dynamic loading data (this unit is a faster data rate than my old one and should better catch the peak loads) I have with Hawk on anchor and on a mooring ball, and I might try anchoring by the stern (suppose to reduce peak loads but I have never measured it).

Anyone else have anything they are interested in seeing tested/broken.
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Old 17-12-2013, 17:58   #2
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Re: suggestions for things to test with a load cell?

Oh you just made a mistake with this I have been tempted to grab one for years... I just couldn't justify it.

1) number of designs for soft shackles
2) ring hitch MBL
3) splices around different sized bars (sail rings, lifeline tubes, grommets, ect...)
4) dock lines (would also love frequency of loads)
5) anchor line (and frequency)
6) jib, main, and spinnaker loads


I may need to think about this some.
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Old 17-12-2013, 18:37   #3
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Re: suggestions for things to test with a load cell?

Friend of mine had one permanently mounted on the inboard end of his anchor snubber, he used it to back down on the anchor and then set an alarm on rising chain tension.
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Old 17-12-2013, 19:05   #4
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Re: suggestions for things to test with a load cell?

Just an FYI, I think it was Practical Boat Owner, the UK mag, that did breaking strength tests on a number of common marine knots this year. I probably should have bought that issue...
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Old 17-12-2013, 19:14   #5
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Re: suggestions for things to test with a load cell?

Quote:
Originally Posted by Stumble View Post
Oh you just made a mistake with this I have been tempted to grab one for years... I just couldn't justify it.

1) number of designs for soft shackles
2) ring hitch MBL
3) splices around different sized bars (sail rings, lifeline tubes, grommets, ect...)
4) dock lines (would also love frequency of loads)
5) anchor line (and frequency)
6) jib, main, and spinnaker loads


I may need to think about this some.
Great . . . If you want to think about it . . . Give me a suggested list of knots, and soft shackle designs, to test. I will do each knot in Dacron and in dyneema. There is an endless list of possible knots . . . Let's try to keep an initial list to say 10. I only use two different soft shackle designs (one where the two strands are mostly seperate and the other where one strand is mostly buried) and my suspicion is they will both test the same (and break near the diamond knot). So, I am interested if you have other fundamentally different designs.

The only major limitation is 10,000 lbs is not all that much when considering high modulus breaking strengths. But I don't really want to be involved in breaking forces much higher than that . . . Too much risk. So I will only be looking at smaller line sizes.

Yes, dock lines, anchor rodes and sheets will all be easy. I hope that 10 hz will be fine enough to capture the transient loads. I am sure it will be for Dacron and nylon, but not completely sure with dyneema and vectran.

Quote:
Originally Posted by sy_gilana View Post
Friend of mine had one permanently mounted on the inboard end of his anchor snubber, he used it to back down on the anchor and then set an alarm on rising chain tension.
Yes, we have debated "bollard pull" loads vs Wind loads, and how much wind backing down is equivalent to. I have a guess, but have never known. That will be easy to look at.
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Old 17-12-2013, 20:13   #6
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Re: suggestions for things to test with a load cell?

At first my thought was to test everything, but then I figured it really would be better to prioritize things by what has the least good data already available. Off hand I think that means things like sheet loads and dock line loads before breaking stuff.

But I would really like to see some data on the effects on dyneema when attached where thimbles aren't possible. Say an eye splice onto a sail ring. It's done regularly, and I have no idea how to quantify the strength loss when splicing an eye onto a 1/4" stainless ring, versus using a ring hitch, versus using a soft shackle, versus an integral shackle ( Integral Halyard Soft Shackle ).
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Old 18-12-2013, 06:35   #7
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Re: suggestions for things to test with a load cell?

Quote:
Originally Posted by Stumble View Post
At first my thought was to test everything, but then I figured it really would be better to prioritize things by what has the least good data already available. Off hand I think that means things like sheet loads and dock line loads before breaking stuff.

But I would really like to see some data on the effects on dyneema when attached where thimbles aren't possible. Say an eye splice onto a sail ring. It's done regularly, and I have no idea how to quantify the strength loss when splicing an eye onto a 1/4" stainless ring, versus using a ring hitch, versus using a soft shackle, versus an integral shackle ( Integral Halyard Soft Shackle ).
Well, I will test/break a lot if stuff over time . . . But I need to sequence it. So you priority question is dyneema small bend radius attachments? That is fortunately a quite easy one to test.. . . And one directly relevant to my life line project. I recommended thimbles but neither ISAF nor USSailing have added that as either a recommendation or requirement.
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Old 18-12-2013, 07:32   #8
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Re: suggestions for things to test with a load cell?

-The actual loads on genoa sheets, possibly by sail square footage in several wind speeds to see the actual load curve.
- The breaking loads on a given size genoa sheet in Dacron. With new being compared to a weathered line of a known vintage. To see how much strength they lose over time, use and UV exposure.

That would help in judging when they really should be replaced.
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Old 18-12-2013, 09:08   #9
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Re: suggestions for things to test with a load cell?

Would really like to see the forces on series drogues ?!

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Old 18-12-2013, 09:49   #10
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Re: suggestions for things to test with a load cell?

Quote:
Originally Posted by lifeofreilly57 View Post
-The actual loads on genoa sheets, possibly by sail square footage in several wind speeds to see the actual load curve.

The breaking loads on a given size genoa sheet in Dacron. With new being compared to a weathered line of a known vintage. To see how much strength they lose over time, use and UV exposure.
The sheet loads is easy and I plan to do it on Hawk. BUT . . . it will depend on the boat righting moment in addition to area and wind speed, and so not completely accurately generalizable. There are some web calculators for sheet load, and I am curious to check their accuracy.

UV is very interesting, but much tougher, because you need 'aged' line. If I can collect aged line of truly know heritage (and with breaking strengths under 10,000lbs) from other people I can easily test them. Or I can hang some line out the window and report back in say 10 years . Hawk's sheets/lines are pretty much all way too strong to break with this load cell.

Quote:
Originally Posted by goboatingnow View Post
Would really like to see the forces on series drogues ?!
I can and will measure drogue loads in a gale, the next time I get one... but I can guarantee the load swill be relatively small (I have measured them before). . . and we don't get even severe storm conditions very often and I am honestly not sure how eager I am going to be to mess with a load cell if I get in one. The last time I was in one, and launched the drogue, I had placed two measured marks on the dacron bridle and was able to make an estimate of load from stretch length.
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Old 19-12-2013, 08:30   #11
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Re: suggestions for things to test with a load cell?

Not sure if I'd exactly be looking to put myself into a situation requiring a drogue just to do some load testing, however if the situation did arise.....
Good luck and thanks for the offer to test any of the equipment people have requested.
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Old 19-12-2013, 08:46   #12
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Quote:
Originally Posted by estarzinger View Post
I had a load cell some years ago, broke it (anchoring test), just today ordered a new one . . . 10,000lbs capability (which can double to 20,000 or more with a tackle). It also produces 10hz (10 points per second) data thru a cable stored to excel

....
I'm interested in your previous, or new, anchor testing data. I've always suspected that some of the existing theoretical tables were high.
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Old 19-12-2013, 09:01   #13
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Re: suggestions for things to test with a load cell?

Not sure if this is a testable small radius bend, where the line bends around the bail, but I am interested to know your thoughts on this arrangement. Adding a thimble and a shackle for this connection just didn't make any sense to me.

I also am interested in adding a gate to my lifelines and there again, why do I want to add shackles and thimbles to rope to make a connection? Why not a knot? So I was wondering about a gate set up where the inboard end terminated in rings that couldn't pull through the stanchions when the gate was open. Closing the gate means an eye splice to the ring on one side and a knot through the ring on the other side.

Well that's a couple small radius bends right there. Upsize the line? I currently have 1/4" but it looks like I could go up to 3/8" and still fit through the holes in my stanchions. Am I missing something here?

I try to keep it simple whenever I can, I mean I have thimbles in the after ends of my lifelines and lash them around the pushpit tubing, but why use a shackle when you can use a knot?
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Old 19-12-2013, 10:08   #14
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Re: suggestions for things to test with a load cell?

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Originally Posted by belizesailor View Post
I'm interested in your previous, or new, anchor testing data. I've always suspected that some of the existing theoretical tables were high.
My prior test suggested the ABYC tables were approximately 4x high at 30kts and 2x high at 60kts. HOWEVER, the ABYC tables have a note saying they have (somehow, I am not sure how) "included the effects of current and wave action". My testing was with small fetch (so very little waves) and zero current. I think they have just added a fudge safety factor in, which accounts for quite a bit of this difference.

I don't go looking for lousy anchorages with big fetch, but I do occasionally end up in one, and I will try to get measurements when I do. But what I think I can say from my prior testing is that just the wind load (in a small fetch harbor) is way lower than the ABYC table.

Quote:
Originally Posted by Delancey View Post
Not sure if this is a testable small radius bend, where the line bends around the bail, but I am interested to know your thoughts on this arrangement. Adding a thimble and a shackle for this connection just didn't make any sense to me.

I also am interested in adding a gate to my lifelines and there again, why do I want to add shackles and thimbles to rope to make a connection? Why not a knot? So I was wondering about a gate set up where the inboard end terminated in rings that couldn't pull through the stanchions when the gate was open. Closing the gate means an eye splice to the ring on one side and a knot through the ring on the other side.

Well that's a couple small radius bends right there. Upsize the line? I currently have 1/4" but it looks like I could go up to 3/8" and still fit through the holes in my stanchions. Am I missing something here?

I try to keep it simple whenever I can, I mean I have thimbles in the after ends of my lifelines and lash them around the pushpit tubing, but why use a shackle when you can use a knot?
What you have here is considered completely acceptable. It sounds like you know this, and do it at the aft ends . . .but the 'best practice' way to do that pulpit attachment is have a thimble in a spliced loop in the dyneema lifeline, which stops about 3" from the pulpit tube. and then a lashing around the thimble and tube. This is slightly better for three reasons. (1) the lashing is of smaller diameter cord, and usually lower modulus, so is less sensitive to bend radius, and (2) if you need to get a MOB back on board, you can cut the lashing to drop the life line, and you have not destroyed the lifeline and re-lash it quickly, and (3) the lashing gives you a good tool for tensionning (and retensionning) the lifeline.

(1) and (2) are still good reasons to have the lashing at the front end, even if you have a lashing at the aft end to do (3).

This is not a perfect example, but shows the general principle:

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You do want to avoid knots in the primary lifeline. They do weaken the dyneema significantly. (here is a climbing article that does some knot testing in dyneema and other materials) If you need something that opens, I would suggest a soft shackle rather than a knot. The better technical solution is to splice in a trigger shackle (like a tylaska) that hooks to a spliced in ring. That would be full strength and easily openable and closable even under decent tension. But it does add cost/complexity.
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Old 19-12-2013, 10:26   #15
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Re: suggestions for things to test with a load cell?

I've always wondered what the UTS of a Wetzel's pepperoni pretzel is???? Cyclic loading is unimportant.... Do you have linear strain gauges so we can determine elastic modulus???
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