GBR1524 TLC and control line changes

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EdS
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Re: GBR1524 TLC and control line changes

Post by EdS » Wed Aug 28, 2013 8:16 am

So a weekend with a forecast of 15 knots and we got 20 gusting upto 28 on saturday and 5 knots to 20knots on Sunday

It was great fun though, flat water does make a huge difference, we had our first pitchpole on a 2 sail reach which was interesting, not sure we have enough foil off range at present.
The 49er nationals was also taking place which made for good crash watching and also some comparison between the two boats upwind and downwind speeds (not that we are representative of the class)

Goods news is there were no breakages, so the spreader repair and rigging replacement appears to be successful.

The spinnaker halyard take up line did not work, caused a knot on launch which was quickly followed by a swim.
now another block has been lashed at the back of the cockpit and the take up comes between those two rear blocks.

the rudder system worked although getting the foil on was more difficult than it should be. The cascade which follows the tiller adds too much friction, so the 2:1 2:1 cascade is being swapped out for a straight 4:1 which will sit further down the tiller which means it wont be dragged along the tiller surface.

How do people stop their tiller extensions going down the transom into the water?
we have the issue when we capsize because our bungee is only on the mainsheet saddle which is not tensioned then.
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Re: GBR1524 TLC and control line changes

Post by Shu » Wed Aug 28, 2013 8:53 pm

Ed,
In the attached photo (Ahhhh, Hawaii), notice the red bungee (I use (edit)1/4") going from the aft end of one rack, over the boom and down to the aft end of the other rack. That's what we use. Currently, I'm tying it to the aft top of the aft footstrap, which seems to work even better.
-Steve
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Re: GBR1524 TLC and control line changes

Post by Shu » Wed Aug 28, 2013 9:17 pm

"So a question for you all. Do i need to mount the final 4:1 purchase (of 48 total) for the shrouds exactly on the centreline?"

Ed,
I think I remember you saying somewhere in here that the final purchase was 2 cm off centerline. The shrouds appear to have an inital purchase of 3:1.Given that the shrouds themselves are about 70 cm off centerline (as measured along the angle of the purchase line), and adding another 30 cm in the initial purchase that's only about 4 percent difference in the length (taken as 100+2 cm vs. 100-2 cm).

From the photos you've posted, it appears you are using 3/16" Spectra (Dyneema), which has a breaking strength of 5,400 lbs. Typical shroud tension numbers for an I-14 are 400-800 lbs. at 3:1 those numbers are 130 - 260 lbs, or 2.5% to 5% of its ultimate strength. Spectra stretches about .5% of it's total length at a load of 10% of its breaking strength. Assuming a linear relationship, it will stretch .12% at the low tension setting and .25% at the high tension setting.

So the difference between the lowest and highest tension settings may result in about .13% difference in stretch. .13% of 102 cm is .133cm, .13% of 98 cm is 0.127 cm, a difference of 0.006 cm or 0.06 mm. That's the difference in the length of the initial 3:1 purchase line. The difference in adjustment to the length of the shrouds, from one side to another will be 0.02mm over the entire range of adjustment. If a good portion of that 70 cm from shrouds to centerline is taken up by your secondary 4:1 purchase, then the diffence will be even smaller.

I've used a lot of approximations and educated guessing here, but I think it gives you an idea about the effect of the offset, and it appears much smaller than many of the other variables in your shroud tensioning system.
-Steve
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EdS
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Re: GBR1524 TLC and control line changes

Post by EdS » Wed Sep 04, 2013 12:59 pm

Steve thanks for the pic, other than rubbing in Hawaii....

As for your math, point proven and that stops me drilling more holes :)

So for the slow response I have been sailing in Sardinia on an 82 footer who likes to think she is somewhat skiff like.


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Re: GBR1524 TLC and control line changes

Post by Shu » Thu Sep 05, 2013 5:12 pm

Talk about rubbing it in. If you have to get lead poisoning, that's sure the way to go.
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Re: GBR1524 TLC and control line changes

Post by EdS » Mon Sep 09, 2013 11:05 am

Steve, not sure it beats Hawaii......

Just got back and one or two things are on the list before 28/9 when we can next sail.

- increase forestay adjustment length (cant get the caps on easily at present)
- Two thoughts on this,
-either move the first antal ring foreward
- make the other end of the system adjustable to allow for major movements when there is no load.
- rebuild UJ mount on the tiller end to limit the range of movement
- Training main is being repaired for the winter training.
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Re: GBR1524 TLC and control line changes

Post by EdS » Mon Sep 30, 2013 8:42 am

An observation from the week when we had light winds and a question.

I have moved the caps from the cockpit floor (diamonds style) to the shroud chain plate, mainly for simplicity and also because i ripped out the cleat location on the cockpit floor.
In light airs with the crew moving from the rack to one foot on the hull forwards the trap line is interferring with the cap shroud significantly, i think we may have put a slight kink in the rod rigging.

Looking at the different configurations of the cap shrouds, what are the benefits of having them on the rack compared to the mast base.
and why would you go through both spreaders and into the mast base as some boats do (is this to help spreader stability in the vertical plane?)

Pro Rack
- on a vernier, easy to adjust no purchase system,
- Arguable the attachment on the hull gives you a shorter length of wire and a wider base so potentially stiffer (assuming you hull can take the rig tension)
- a lower proportion of the caps tension is transmitted in lateral loading at the spreader and therefore hounds

Pro Mast base
- Crew trap doesnt catch on it, hooking the mast head to windward
- Raking the rig is independant of cap caps and their tension.
- rig tension (forestay) is relatively independant of cap tension, mast bend upto the hounds being the only factor, rather than the forestay loading the caps.
- Less spreader sweep is require to get the same amount of fore and aft support (mast base being infront of the shroud, therefore inducing less prebend whilst still providing lateral support to the mast upwind.

Not sure if much of the above is valid, but just wondered about people thoughts and if anyone else has the same issue with lightwind trapping.
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Re: GBR1524 TLC and control line changes

Post by gbr1442 » Mon Sep 30, 2013 1:04 pm

hay ed

sorry missed you call friday my phone is playing up. on the light wind front move the crew trapeze so that its in front of the cap that way it wont pull on it when one footing the foredeck. id never seen this before till new boat and thats what sam and alex have done for that reason but also leave it like that when windy as puts a bit more tension in them when at the back of the bus. def not slowed them down having it like that nice easy bimble two no tools needed! :D


im on duty saturday at weston and now i'm not teaching every weekend i'll have a chance of bring the boat back from weymouth and sailing again!
Tom
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EdS
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Re: GBR1524 TLC and control line changes

Post by EdS » Tue Oct 01, 2013 9:31 am

Hi Tom,

Thanks for that, i will try it out next weekend.
So the Monkey is yours now, when do you think it will be at Weston.
Are you planning to do the Weymouth Events?

Any other comments from people about the performance benefits of the caps configurations?
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Re: GBR1524 TLC and control line changes

Post by gbr1442 » Tue Oct 01, 2013 11:30 am

hay ed

hopefully sumtime in the next week i'll have sum time to go get in maybe sunday. yea i'm planing on doing the won at the end of this month as well as the one in november and december. not sure how many will go as to this one as it is double booked with the autumn pint at itchenor but i don't want to run the boat aground in my first event with it so will be doing weymouth should see how many weston boats we could get to go hear mark has rhino up and running again to.

the caps configuration id almost say is a fashion thing i've seen so many boats move them in and out then in again then out again. I would of thort if you have them out you get more support and stop the mast pulling sidewards more. Im sure this is more apparent on the older softer rigs like yours or my old rig. with my old rig there were in but i had them go throu the very ends of the bottom spreader which made a huge difference on that rig to when they just came straight down from the top spreader to the bottom on the mast on say like dave's rig.
Tom
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Re: GBR1524 TLC and control line changes

Post by Shu » Tue Oct 01, 2013 6:14 pm

Ed,
I think you've summarized the pros and cons with respect to cap shroud termination very well. As for the hull being able to support the loads, it really doesn't matter. If you take the caps to the mast base, then all the load on mast tip is transferred to the primary shrouds. So either way, the load is transferred to the hull (or rack struts if thats where you terminate your shrouds).
-Steve
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Re: GBR1524 TLC and control line changes

Post by Shu » Tue Oct 01, 2013 11:16 pm

Correction: I use 1/4" bungee from the aft end of the racks over the boom to stop the tiller extensions from trailing aft. 3/16" is not firm enough.
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EdS
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Re: GBR1524 TLC and control line changes

Post by EdS » Mon Oct 14, 2013 9:36 am

Steve,
thanks for that. I tried it, but the bungee is either too tight to allow the boom out of too loose. I have tied it to the racks, maybe that is the issue.

On a different note, there is nothing like taking your novice girlfriend sailing to test your new additions.

Lets just say it was Steph 1 : Tiller extension UJ's (both of them) 0

So this has encouraged me to improve the mounting design so that the flip flip blocks cannot hyper extend and self destruct.
There was a lot of friction from going around the tiller, so i will be mounting the blocks offset just below the tiller to remove this friction.

I am halfway temped to give up and mount cleats on the side of the boat, but i will keep going a little more, the pushrod on the biscuit makes life hard because as i increase the angle i lose around 1/3 of the moment due to the pushrod design. The is something for later this week to fix.
Once the new mount in in place and the biscuit pushrod done it is make or scrap for this idea.

I made a model out plasticine (yes i am a monkey) and a piece of L shaped carbon which got cut down into pieces.
The plasticine has recessed to accept some G10 which are going to be backing plates.
photo (33).JPG
the patten
The plasticine was wrapped in light weight carbon, the G10 put in place and the L shaped slid into position. Extra plasticine was used to encourage the carbon to follow the mould.
photo (34).JPG
curing
Pictures of the results to follow. the G10 plates didn't stay in the right place but the rest is a success.

Lets just say it is stiff and will work, but not the pretties thing.

I have got some chemical release agent, what a difference.
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photo (35).JPG
cable ties are the new locating method
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Re: GBR1524 TLC and control line changes

Post by EdS » Fri Oct 18, 2013 11:21 pm

Some bog for initial attachment a bit of sanding followed by a layer of light carbon
and we have the finished item, needing some sanding, 5 holes and clear coat
photo (36).JPG
photo (37).JPG
photo (43).JPG
rudder finished and restrung.
Last edited by EdS on Tue Oct 29, 2013 10:18 am, edited 1 time in total.
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Re: GBR1524 TLC and control line changes

Post by EdS » Mon Oct 21, 2013 12:06 pm

Does anyone have a copy of the plans for the B5 which has the location of the X frame at the base of the mast.

I want to replace my mast base which is corroded and so i need to work out where the centre of the X is (mast base... maybe it is that obvious) and also the angles of the bulkheads so that the new base spreads the load effectively.

Thanks,

Ed
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