Author Topic: Gunnel damage from shroud plates  (Read 17862 times)

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Offline phil_kirk

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Gunnel damage from shroud plates
« on: February 14, 2008, 12:53:19 PM »
Maybee this is just a feature of the Dog design or older boats with flares.

Slippery has a continuing problem with the edge of the gunnels being crushed by the shroud plates. The more rig tension we put on the deeper the plates cut into the gunnels.  The shroud plates consist of two stainless steel strips  bolted on to the underside of the flare each side of the boat. i have locally filled and glassed over the dents but obviously need to take this a bit further.

I think I have the solution but wondered if other people have had a similar problem in the past?

I intend to cut the gunnel away for 3 inches and replace the foam with bog and cover with 2 layers of carbon.  hen repalce the plate for the lowers with a couple of layers of uni in a loop that I can attach a shackle to.  fair and fill any tight angles with bog and cover with a final layer of plain weave.  Then bolt the main shroud plate back on over the top.  I think it is as much the shape of the lower 's shoud plates as the structure of the hull.

Then I can put real rig tension on.  not had much on so far due to this problem.

Offline JimC

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Re: Gunnel damage from shroud plates
« Reply #1 on: February 17, 2008, 11:27:51 PM »
I dunno about all that bog, it sounds a bit untidy and heavy...

Here's a similar shroud attachment on my IC. There are many more than two layers of unis over the loop: I think I have about 6 pieces of the normal narrow unis, each folded in half to go through the loop, and then fanned out over about a 90 degree angle over the topside You can arrange the fold so that it unfolds andby the end of the unis its single thickness. Whilst you have a special issue with compression on the turn of the gunwhale, provided the base structure is filled back up and has a couple of layers of cloth over it to bring th strength back to what was new then I doubt you'll have an issue when all the fannned out unis are distributing load. I rebuilt the PlusPlus shroud anchors in much the same way and didn't do anything to the core, and that had just as shallow flares as your boat...


Consolidating the laminate with ply covered in parcel tape and peel ply underneath of course.


A layer of cloth on the outside over all the unis.


That's the front bulkhead now glued in against the shroud anchor...

With the vertical topside of the Canoe the unis go each side of the skin. With the PlusPlus (and of course the Dog) most need to go on the outside. I put a couple of the layers of unis over onto the inside of the skin on the PlusPlus in order to give some strength for odd eventualities, turning the boat over singlehanded by means of string to the garage roof, tying the boat down via the shrouds, other odd stuff... You don't want it to be able to just peel off if it gets a load from the wrong direction.
« Last Edit: February 17, 2008, 11:41:42 PM by JimC »

Offline phil_kirk

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Re: Gunnel damage from shroud plates
« Reply #2 on: February 18, 2008, 10:31:51 PM »
Thanks Jim,

I have succesfully uni'd rings onto the mast last year.

I am planning to retain the main shroud plates for reliability. The lower shroud plates turn tightly around the gunnel and then twist forward and it appears that the edge of the plate is cutting into the gunnel. The main shroud plates are mounted on the outside of the lower plates so the load in the main plates is transfeed to the gunnel over a small area.

By removing the lower shroud plates I hope to remove the problem.

I appreciate that the amount of fibres needed should not be underestimated.

We'll see how it goes.

Phil

ghislain_devouthon

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Re: Gunnel damage from shroud plates
« Reply #3 on: February 18, 2008, 11:53:49 PM »
I do not like UD rings as it not resistant to unexpected efforts (ie it works in traction and thats all).
I don't like either to fill with bog as it is usually the solution used when you don't have found the right solution yet.

A picture would help to appreciate the job to do.

However to keep your plates :
- you could cut into your gunnel,
- add a piece of wood,
- layer it with a fair amount of UD then plain weave carbon
- screw your plates with some epoxy

Of course this mean you can layer inside the boat.
The alternative is to cut your gunnel without removing the inside skin then glue a piece of wood with charged epoxy.

That was my to cents.

I think there are as many solution as cherub sailing  ;D ;D ;D

Offline Phil Alderson

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Re: Gunnel damage from shroud plates
« Reply #4 on: February 19, 2008, 12:49:03 PM »
If you fill the damage and put a patch of 5-6 layers tapered out from the center making sure that you fold over the edge of the gunnel you should be OK

for extra beefyness you could fit a steel plate flat would do, angle would be better just at the corner if you clamp it in place when the cloth is wet you will be sure to have a good contact.

It only needs to be slightly stronger than what was there before and lasted ten years.
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Offline phil_kirk

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Re: Gunnel damage from shroud plates
« Reply #5 on: February 27, 2008, 12:52:52 PM »
Thanks for the idea Phil.

I have gone for a 3 inch S.S. plate on underside of gunnel to spread loads from shroud plates covered by 5 layers of carbon.  I will try to take the twist out of the shroud plates and bend them so that they follow the radius of the gunnel.   

A bit of  sanding and filling and painting to do now before we are back to sailing.

Oh and I have done most of the C.board case repairs.