OK Deck Mast Bearing

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Rich
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OK Deck Mast Bearing

Post by Rich » Sat Aug 18, 2012 1:30 pm

Hi all

Long shot but has anyone got a top bearing kicking about suitable for an old GRP OK dinghy.

I've not sailed for 2 yrs owing to broken wooden boats which I've not got round fixing but I'm keen to get back on the water again. I have the chance of picking up an old GRP OK hull up fairly cheap but it needs some work. I think I could sort most things but the top bearing is missing and making a new one would be tricky as the hole has to be machined at an angle (I assume for mast rake) and I don't have the tools to do this.

Photo of the bearing hole
Image

The two metal pieces with holes drilled in them are strengtheners which go on the underside of the two slots

Cheers
Rich

JimC
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Re: OK Deck Mast Bearing

Post by JimC » Sat Aug 18, 2012 2:03 pm

Rich wrote:making a new one would be tricky as the hole has to be machined at an angle (I assume for mast rake)
You could make the hole oversize then fill with epoxy/microfibres/silica using a suitable bit of spare tube wrapped in parcel tape as a mould...

Nigel
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Re: OK Deck Mast Bearing

Post by Nigel » Sat Aug 18, 2012 2:33 pm

Rich wrote:making a new one would be tricky as the hole has to be machined at an angle
Easy to do with a pillar drill and a cheap hole saw. Just angle the bed plate appropriately and put some sacrificial wood underneath so you cut though all the way around.

Otherwise it is possible to do it just with a hand drill.

What material would you intend to use? Nylon?

Nigel

Rich
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Re: OK Deck Mast Bearing

Post by Rich » Sat Aug 18, 2012 4:35 pm

Nigel wrote: Easy to do with a pillar drill and a cheap hole saw. Just angle the bed plate appropriately and put some sacrificial wood underneath so you cut though all the way around.

Otherwise it is possible to do it just with a hand drill.

What material would you intend to use? Nylon?

Nigel
I was hoping to find a ready made one if poss as I don't have a pillar drill ect
Rich

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PeterV
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Re: OK Deck Mast Bearing

Post by PeterV » Sat Aug 18, 2012 5:22 pm

I made a very similar one for my Finn, out of 10mm thick acetal which I bought off tinternet. I used double thickness with the two pieces bolted together. I cut out the hole with a coping saw and didn't bother trying to angle it. 5 years of use now so it can't be too wrong. If you don't want to buy a sheet of acetal(I think min size was 500 x500) then use kitchen chopping board.
PeterV
Finn K197 & GBR564
Warsash

Nigel
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Re: OK Deck Mast Bearing

Post by Nigel » Sat Aug 18, 2012 6:24 pm

Also plenty of offcuts of most materials pretty cheap on eBay.

Do you have a pattern & where are you based?

Rich
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Re: OK Deck Mast Bearing

Post by Rich » Sat Aug 18, 2012 7:09 pm

Nigel wrote:Also plenty of offcuts of most materials pretty cheap on eBay.

Do you have a pattern & where are you based?
Just been up to my local poundstretcher and and they have 6mm thick placcy chopping boards for £3.50 and so I guess 3 pieces of that glued & bolted together would do.

I'm in Newbury and the boats at Henley, but I will try & get over there tomorrow and take some measurements and see if I can find the mast. The boats in a sorry state and has been left uncovered for approx 6 years and I didn't want to buy it if I can't get it fixed up easily, as the last thing I need is a 3rd broken boat. I just wanted something GRP that I can get on the water quickly whilst I get round to repairing my main boats.
Rich

Nigel
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Re: OK Deck Mast Bearing

Post by Nigel » Sun Aug 19, 2012 7:23 am

Hi Rich,

To save the glueing and bolting, how about something like this?

http://www.ebay.co.uk/itm/NYLON6-SHEET- ... 53eac425a3

I suspect that the GRP hull will have a rectangular recess for the bearing rather than sitting on the deck as on your wooden one. It will work the same though with spacers front and back, probably all held in by a long bracket on each side to which the controls are attached

Rich
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Re: OK Deck Mast Bearing

Post by Rich » Mon Aug 20, 2012 1:18 pm

Took some measurements yesterday and the mast collar looked to be about 95-96mm diameter (hard to measure accurately) and so I guess a 100mm diameter hole will allow for a bit of clearance and mast rake.

Has anyone any experience of this type of hole saw and know if they are up to cutting hard plastic such as kitchen chopping boards

http://www.ebay.co.uk/itm/Handy-Adjusta ... 19ce3b75ea
Rich

JimC
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Re: OK Deck Mast Bearing

Post by JimC » Mon Aug 20, 2012 1:40 pm

I think you'll find you'll be better off just cutting in with a jig saw. I've always found hole saws a bit reluctant with anything but the most straightforward materials.
BTW chopping board is a bit awkward because it tends to melt round the saw and congeal after its gone past.

Rich
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Re: OK Deck Mast Bearing

Post by Rich » Mon Aug 20, 2012 2:20 pm

Thanks for that Jim, must admit I hadn't thought about the melting problem.

I think I'll give it a go manualy, I'm sure with a combination of drill, saw, file & dremel I can arrive at something roughly round which will suffice for at least the short term.

Cheers
Rich

Nigel
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Re: OK Deck Mast Bearing

Post by Nigel » Mon Aug 20, 2012 4:50 pm

Rich wrote:Thanks for that Jim, must admit I hadn't thought about the melting problem.
I do tend to run the drill at its slowest when I use one. Even with wood, it doesn't melt but you can set it on fire if you go too fast.

Doing it by hand, I would try the hole saw in a brace & bit. The only other tip I have about using one is not to go all the way through from one side. The central drill bit hole allows you to line it up from the reverse side and finish it off from there for a neater finish & no "exit wounds"

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PeterV
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Re: OK Deck Mast Bearing

Post by PeterV » Mon Aug 20, 2012 5:15 pm

A normal coping saw will cut it out fine.
PeterV
Finn K197 & GBR564
Warsash

corkman
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Re: OK Deck Mast Bearing

Post by corkman » Tue Aug 21, 2012 10:09 am

Rich, been away and just saw your post. If it's not to late I may have what you need. Old top and bottom bearings for a Boyce.
They are at the Club, not at home, so would have to wait until weekend to measure.
Perhaps you could give me a call on 01224-745491 if you are interested.
Craig :D

Rich
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Re: OK Deck Mast Bearing

Post by Rich » Tue Aug 21, 2012 9:25 pm

Hi Craig, thanks for the reply. I've already bought a plastic chopping board and so was going to have a go at a DIYing, however if you are able to measure the top bearing you have at some time then that would be great in case my effort is a dud.

Looking at the above photo in my original post, the bearing aperture (with chocks in place) is 140mm fore to aft x 148mm wide, the recess (lip) of the aperture is 18mm deep. The mast collar is approx 95-96mm and so I guess a hole diameter up to 100mm would be fine.

Cheers
Rich

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