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Hiccup installing new mainsheet block system...

PostPosted: Sun May 14, 2017 7:35 pm
by pboulanger
I'm looking to replace the old and beat-up mainsheet block and cleat system that are worn and cutting into the mainsheet (teeth on the cleat are sharp, really sticky, etc. etc.), but ran into a little hiccup - the screw holes on the new harken camcleat I purchased are about a 1/4" further away than the previous model currently screwed into the centerboard trunk. I'm concerned that the new screw holes will be too close to the previous ones if I were to just pivot the base and screw it in, sacrificing structural stability.

In order to remedy that, I was thinking that I will need to remove the old base, fill the holes with epoxy, and then install the new base. Does this sound correct? Do I need to layer a little fiberglass down for extra strength when I fill the holes, or would just filling them be fine? When I remove the old base, what exactly is it screwing into there? Is there any sort of backing, or are the screws just heading into a void?

Thanks for your help!

Re: Hiccup installing new mainsheet block system...

PostPosted: Sun May 14, 2017 10:52 pm
by TIM WEBB
Not sure which DS model you have (might not matter), but I replaced the standup mainsheet block on TRW ('79 DS2) with the Garhauer one D&R sells, and found the same hole centering mismatch, so had a machinist buddy make this adapter for me:
996
Later on I realized that since there was a metal plate glassed into the CB trunk under that base, I removed the adaptor and just tapped new holes directly into the trunk.

Hope this helps!

Re: Hiccup installing new mainsheet block system...

PostPosted: Sun May 14, 2017 11:04 pm
by pboulanger
Mine is a 1984 DSII.

So you used the smaller holes to bolt down into the pre-existing plate, and then your new block screwed into the larger holes in your adapter? Did you need any sort of backing plate, or was the strength of your adapter enough?

Re: Hiccup installing new mainsheet block system...

PostPosted: Mon May 15, 2017 1:59 am
by jeadstx
You should have a metal plate there to drill and tap. Modern hardware all has this miss alignment problem. I know a couple DS owners that have made this replacement. I've heard you can rotate the base 45 degrees also before drilling and tapping new holes. I have plans to do this on my 76 DS II as well.

John

Re: Hiccup installing new mainsheet block system...

PostPosted: Mon May 15, 2017 3:08 am
by GreenLake
Simply make a template of the new base. Rotate it 45 degrees. Drill one of the holes the proper size to be tapped, or a smaller pilot. If you hit metal, you are good, no need to add epoxy/glass to strengthen anything. Just finish drilling all holes the size you need, tap them and install your new fitting.

(I still think this assumes that the size of the glassed in metal plate is generous enough to hold a rotated pattern with wider hole spacing. On my DSI that area doesn't look very generously sized, but my original fitting is holding up nicely, so I'm not ready for an upgrade. It's the last block/cleat that's still original, except for the horn cleats, so I like to keep it around).

Re: Hiccup installing new mainsheet block system...

PostPosted: Mon May 15, 2017 10:15 am
by pboulanger
When I remove the current base, will I see the metal plate, or is it underneath the trunk?

Re: Hiccup installing new mainsheet block system...

PostPosted: Mon May 15, 2017 12:26 pm
by hsumralljr
The metal plate is covered with fiberglass you won't be able to see it when you remove the old cleat base, but it's there.

Re: Hiccup installing new mainsheet block system...

PostPosted: Mon May 15, 2017 12:40 pm
by TIM WEBB
pboulanger wrote:Mine is a 1984 DSII.

So you used the smaller holes to bolt down into the pre-existing plate, and then your new block screwed into the larger holes in your adapter? Did you need any sort of backing plate, or was the strength of your adapter enough?

Yes, the smaller holes were countersunk, and I used flush-head bolts (forget the correct term) to attach the adaptor to the existing trunk holes. The larger holes were tapped to accept the base mounting screws. The adapter was aluminum, and I didn't need any other backing plate. I later did away with the adapter and did as John and GL describe, rotating the base 45 degrees and drilling/tapping new holes. I did in fact hit metal, so at least in '79, the plate was large enough to accommodate the bigger spacing. Not sure on an '84, but you could do as GL describes and drill an "exploratory" hole. If you hit metal, great, proceed, if you don't, no real harm done, just go with an adapter.

The plate is glassed in just below the surface of the land on the trunk - if you look/shine a light down into the existing holes you should see a glint of bronze or SS or whatever it's made of.

Here's a pic of the adapter installed

995

And after I removed it

1261

Re: Hiccup installing new mainsheet block system...

PostPosted: Fri Jun 16, 2017 3:30 am
by carl10579
Looks nice, lots of leverage.

Re: Hiccup installing new mainsheet block system...

PostPosted: Mon Apr 26, 2021 8:15 am
by zeroready
So I'm in this same position and I don't know any machinists. Does anyone know where I can get a piece of aluminum that size to try and make this adapter myself? I have a drill press, if I got the right bits would I be able to drill these holes myself?

Edit - OK I found the aluminum stock on Amazon. I've tapped threads in things before, but not something this size and this many holes. Is this something I could do without spending a fortune on tools to do it? Would just a regular tap and die set and drill press be enough? Would I be better off trying to find a local machinist who could make this for me?

Re: Hiccup installing new mainsheet block system...

PostPosted: Mon Apr 26, 2021 11:30 am
by bilbo
As long as you're careful and take your time you should be able to make it. Regular bits and taps should work fine. I've made similar things before and either printed a full size layout or drawn it on graph paper, then used something like 3M Spra-Mount to stick the pattern on the metal. Then use a center punch to put a 'ding' in the metal where the holes go. It will prevent the drill bit from wanting to walk when you start the hole. After you're done the pattern and glue can be removed with alcohol. I say give it a shot, worst case you're out a little bit of metal. You could probably try three or four times and still be ahead of paying someone to do it.

Re: Hiccup installing new mainsheet block system...

PostPosted: Mon Apr 26, 2021 11:55 am
by tomodda
Ditto on the above. Aluminum is easy to work, but watch out for those wandering drill bits! Also, wear gloves and blow the work area clean frequently. Those little aluminum drill shards/splinters, whatever they're called - hurt when they get into your skin and are a pain to get out. Don't ask me how I know :)

Re: Hiccup installing new mainsheet block system...

PostPosted: Mon Apr 26, 2021 1:18 pm
by zeroready
Thanks for the advice! I called Rudy though and he said I can just drill holes into the new base to match the old holes in the boat, so there's no need to make an adapter anymore, hopefully.

Re: Hiccup installing new mainsheet block system...

PostPosted: Mon Apr 26, 2021 2:49 pm
by GreenLake
Well, what's the base made of? If stainless, make sure you get cobalt bits and use steady pressure but not too much when drilling . .

Re: Hiccup installing new mainsheet block system...

PostPosted: Mon Apr 26, 2021 3:06 pm
by zeroready
Yep it's stainless. I got one hole drilled and tapped, not too difficult. But I accidentally used a metric tap bit, the holes in the boat are for #8 screws. So I need to find my other taps. I'm not sure if I should actually tap the new holes in the base or not.