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Sticking centreboard after beaching

 
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Sticking centreboard after beaching   Posted: Tue 31 Oct 06, 14:35    Reply with quote

[originally from: Malcolm Ratcliffe, UK, 27 Oct 2006]

In May 2003, Bill Fraser posted a message about his 920's centreboard sticking in the trunk after beaching, and asked if anyone knew what the problem was likely to be.
My DF920 did the same this year, after I dried her out on a beach gently. I managed to winch it down eventually, but only by winching very, very hard.
Anyone any ideas where the sticking is likely to be? Definitely nothing stuck up the slot;- all clean.
What did Bill Fraser find the problem to be?


Last edited by Transferer on Tue 31 Oct 06, 16:58; edited 1 time in total
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Re: Sticking centreboard after beaching   Posted: Tue 31 Oct 06, 14:36    Reply with quote

[from: Ipe Piccardt Brouwer, Netherlands, 27 Oct 2006]

I had a similar problem recently, after having run up the beach a little earlier than expected. The centreboard downhaul released automatically, but then the board jammed halfway up, leaving us stuck in the mud. After freeing the boat from the mud I managed to winch the board down. I am under the impression that the jamming was caused by slack in the centreboard uphaul line. I have now rigged a piece of shockcord to take the slack out of the line, next time the centreboard is raised involuntarily.
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Mal



Joined: 02 Nov 2006
Posts: 83
Location: Wales

Sticking Centreboard   Posted: Thu 02 Nov 06, 17:58    Reply with quote

Thanks for reply, but definitely not slack downhaul line in my case.
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Mal



Joined: 02 Nov 2006
Posts: 83
Location: Wales

Sticking 920 Centreboard   Posted: Sun 28 Jan 07, 20:44    Reply with quote

Took the table top off the centreboard case yesterday, to see if I could see the reason for the centreboard's jamming in the UP position after beaching. I can now see the reason:-

When the centreboard is pulled up by the uphaul line, the downhaul line becomes jammed between the centreboard and the case. As the centreboard comes up, the downhaul line jams in the angle formed between the aft third of the board, and the side of the case about 150mm down from the top . In other words, the horizontal downhaul line is stuck between the case and the almost fully up board. Normally, this pulls out OK when the board is next pulled down, you notice the slight 'ping' as you pull on the downhaul.

However, if after pulling the centreboard up, the line becomes trapped as described above, and then you beach the boat, the centreboad now is forced up the last few centimetres, and now the downhaul line is well and truly jammed between the board and case. This can take massive winching loads on the downhaul when you want to eventually sail off and drop the board.

This is what happens if when wanting to pull the board up, you just free the downhaul from the jam cleat on the port side, and pull on the uphaul on the starboard side. I found that if I pull lots of slack forward of the easylock on the downhaul, before pulling on the uphaul, then the jamming either does not occur, or it is minimised.

I have also thoroughly cleaned the inside top of the centreboard case where the downhaul line jams, and then sprayed the inside of the case with Teflon spray, hoping that this will encourage the line to slide rather than jam.

In future, if I know I am gong to beach the boat, I will as above make sure that the downhaul line is completely slack before pulling the centreboard fully retracted.

Incidentally;- if you do take the table-top and plate off, you will find it a nightmare job trying to undo all the screws- it is impossible to get the screwdriver on square, and stainless scews into an aluminium plate do corrode in somewhat, resulting in chewed screwheads, bruised knuckles, and bad language. Suggest you do as I did last time;- change them all to hexagon heads so that you can use a quarter-inch drive ratchet and socket. Put insulating paste on each screwthread to reduce likelihood of their' corroding in place.

Mal
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Ipe Piccardt Brouwer



Joined: 01 Nov 2006
Posts: 64
Location: Netherlands, Winkel NH

Sticking centerboard   Posted: Sun 28 Jan 07, 23:13    Reply with quote

Good work, Mal.
Preliminary conclusion to this topic: when grounding, keep your uphaul taut and downhaul slack.
Makes sense, actually.
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DF920-28 'Ngalawa', Medemblik
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Ultradry



Joined: 13 Nov 2006
Posts: 10
Location: La Trinite sur Mer/Morbihan France

Hard to downhaul centerboard   Posted: Thu 27 Jul 17, 18:56    Reply with quote

Hello, I bought recently a 920 which was birthing in mud at each tide. The board is very hard to downhaul. I thought that over time it will get better as mud inside the trunck will get cleaned away. But no improvement.
My plan to investigate the issue is to remove the table rather than dismounting the board from underneath because I suspect the problems in the upper side of the trunck.
Possibly mud dried up in the upper part of the trunck, or problem with the sheaves?
First question about "nightmare job trying to undo all the screws- it is impossible to get the screwdriver on square, and stainless screws into an aluminium plate do corrode": what is in aluminium part? Threated holes in aluminium plate?
Second question: what kind of sealent you recommend such it stay soft without gluing?
Third question: Is there any chance that the rear sheave of the downhaul line is damaged preventing a friction less operation? How is it make?
Thanks in advance;
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Christian



Joined: 13 Nov 2006
Posts: 155
Location: Sweden, Nacka

Try the bottom way   Posted: Thu 27 Jul 17, 20:50    Reply with quote

Sounds like your problem is with the sheavers turning the lines from going down from the mast foot to horisontal in the trunk.

I have opened the trunk on a DF800 - and it is not much space there. Then it was possible to see all parts. On the DF920 the lines goes another way.

I have looked down under the mast foot - and there is not much to see there. Think there are two sheavers in the bottom. The photo is taken in direction down - when the foot is removed. Look here: https://flic.kr/p/Xar2eK

Wonder if you reach these sheavers when removing the table. Maybe you can reach them if you remove the board from below.

So you have three options.
1) Cleaning from below. Remove knot and try to dive and clean - if the knot is removed then will a 1/3 of the slid be accessible. Maybe with high pressure water you can clean the sheavers diving below the boat

2) Remove table - a lot of screws.

3) Lift boat and remove board - that is easy if you got the boat hanging or on a trailer over a pit. (Done it on both a 800 and a 920)

Post some photos of your progress! Interested to know how it looks down there. / Christian
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Ultradry



Joined: 13 Nov 2006
Posts: 10
Location: La Trinite sur Mer/Morbihan France

Hard to downhaul centerboard- Dismounting the table   Posted: Fri 28 Jul 17, 23:00    Reply with quote

Thanks Christian for the recommendations.
1- The plate on top of the trunk is in Stanless steel and not aluminium on my 2006 Extreme. The srews have been very easy to remove and reinstall. To ease the job I used a 300 mm long screwdriver, which help. (see pictures)
2- There is no sealent but a multi lip rubber seal, which make the operation confortable.
3- The sheaves are in good shape, especially the wide rear diabolo.

Observations and tests with the table partially open. Partially because the mastic between the middle of the table and the wall is acting as an hinge.

The trunck seemed clean from what I could see from the top.
No trapped line to start with.

The problem is that the board is too thick in some place or the trunck too narrow in those places.
To get clearer: the board is moving freely in upper position as well as in lower position. However while trying to take the board down, after about 15° of rotation, the board gets harder and harder to move due to lack of clearance between the board and the trunck. All lines are clear.

If the dowhaul line is pulled slowly until the low clearance position is reached, the line between the rear sheave and the eye is not yet strait. If you pull the line hard (winch) at that time, the line will find his way between the trunck and the board and all system is blocked by the trapped line. The more you pull the downhaul line the more this line get squeezed and the more the board get blocked.

In such case, the best way is to return in upper position. But you need to pull really hard (winch) on the uphaul line and to keep some tension on the downhaul line to untrap the dowhaul line and to clear that mist!!!

Up to now, I used to release the downhaul line at once and the board would go back in upper position in one move due to its buoyancy (remember it is an Extrem, i.e. foam core instead of wood). However I tried to release slowly the downhaul line. Such way the board get stuck after about 45° rotation and don't get in upper position. All lines are clear. You need to use the winch again to get the board up, which confirm the lack of clearance.

By trials and errors I found that it was possible to pass the hard angle positions by pulling strongly and quickly the downhaul line right away from the upper position. Such way, the board gets some momentum which allows it to pass the critical stage and reach an angle where the dowhaul line is strait between the rear sheave and the eye, such way no more risk to trap the line.

I repeat the process many times and it seemed that the board is sticking less. I got the impression that a quick move of the board inside the trunck is helping getting more clearance. Maybe some barnacle which are difficult to remove without energic scrapping ?
I will try again tomorrow.

I knew that the previous owner needed to repair the board due to delamination. From the small improvement I hope that I can forget about a swelling of the board due to delamination again. Maybe, after the repair the board is slightly thicker than originaly which make it more sensible to any deposit in the trunck?
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Jacob Blom



Joined: 05 Nov 2006
Posts: 15
Location: The Netherlands, Harlingen

board downhaul   Posted: Sat 29 Jul 17, 10:37    Reply with quote

Our boat had the same problem after we repainted the board and replaced it in a perfectly clean trunk. We discovered that the problem was caused by the part of the downhaulline that is in the top of the trunk when the board is in the up position. There was not enough space for this line between the board and the side of the trunk. We solved this, easy and definitely, by removing the board when the boat was in the crane. We mounted a new dyneema downhaule line from which we stripped the braided cover from the part of the line that’s always in the trunk. In this thin end (braided core) we spliced an eye that is stropped on the eyebolt on the board. The result is a thin, strong line in the trunk and a part with the original diameter on deck. Use the original downhaul to pull the new one up from bottom to deck (by sewing them together). Bring the board in the trunk again and place the security bolt.
Jacob Blom
DF 920 # 134 Gúzjen!
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Bo Wetzel
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Joined: 01 Jan 1970
Posts: 150
Location: UK, Penzance & France, Flayosc

Photos for topic "Hard to downhaul centerboard"   Posted: Sat 29 Jul 17, 11:01    Reply with quote

For a reason I don't understand at the moment I cannot add the photos to the posting of Ultradry.
Hence they're here :

Please click on any of the photos to see them enlarged!


Steel plate:

Long screw driver:

Partially open:

Mastic hinge:

Rear sheave rubber seal:

Downhaul line not yet strait going to be trapped:

All-lines-clear:

Trapped:

Downhaul line strait clear:
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Ultradry



Joined: 13 Nov 2006
Posts: 10
Location: La Trinite sur Mer/Morbihan France

New layout of the lines   Posted: Wed 02 Aug 17, 15:14    Reply with quote

Coming back to my previous posts.
Issue is that the board is thicker than the trunck in some location, making it difficult to move, such way that the downhaul line get trapped and squeezed between the board and the trunck. Under such condition there is no more chance to get the board up or down even by winching very hard.


Please click on any of the photos to see them enlarged!

I have developed a new layout of the lines to be seen in the animation.
To avoid the downhaul line to be trapped, I have split the uphaul line in two by taking the core out of the cover and I install the downhaul between those two.

Video animation: VID_20170731_155519.mp4

Now I can get the board down or up, even it remains hard. But no more blocking.
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Christian



Joined: 13 Nov 2006
Posts: 155
Location: Sweden, Nacka

Cool!   Posted: Thu 03 Aug 17, 8:29    Reply with quote

Love your prototype! That is really a danish way of thinking
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