Mainsheet swivel base replacement

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Mainsheet swivel base replacement

Postby oian » Wed Jul 20, 2016 5:09 pm

I have a 1978 DS with the standard 3:1 mainsheet. I'm going to replace it with a different set of blocks (see my previous post). It appears that the stock swivel base is totally riveted together and cannot be used with any replacement blocks and even if it could, swiveling is not one of it's strong points. I've seen two possibilities: Ronstan RF7 and the Harken 205. Any comments on the these? Good bad or otherwise? Any other suggestions? The standard based has 4 machine screws 1-1/16" apart that are threaded into something. Most of the replacements use a 3/4" spacing. For my 1978 version DS, what are the screws threaded into? Just the fiberglass, metal plate, imbedded nuts? What would be the most practical way to attach the replacement. Hopefully this can be done without major surgery. Does any one know the actual thickness of the top of the centerboard cap at this location, and the length of the screws that can be used without interfering with the board? I can set up the block set that I have for either 5:1 which will require the placement of a second bail on the boom, or 3:1 or 4:1 without adding the additional bail. The question is, with mid- boom sheeting, will 4:1 or 5:1 overstress the boom extrusion if used reasonably?

Digital mechanic: Thanks for the solution to my posting problems. The "insert" button had been pushed, probably by one of our cats, as they seem to think that the keyboard is a shortcut to everywhere.

Thanks, John
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Re: Mainsheet swivel base replacement

Postby GreenLake » Wed Jul 20, 2016 5:43 pm

If you dig back, you'll find a thread where somebody went through the same replacement and discussed making a shim. Basically a plate having threaded holes in the new pattern, and bolts in the old pattern.

I can't advise you on the best replacement since my original 1963 swivel still works quite well (I think it's a different design than the later ones). I do have a Harken swivel on a different boat, and that model has a limit to not allow a full 360 degrees. I find that limit irksome. May want to make sure whatever parts fits your preference.

Unless you are still pulling after the sail cloth is fully stretched the load on the boom is not determined by how hard you pull, but by how much sail force is generated by the wind. Because all you do is to counteract that force. The difference between a 3:1 or a 4:1 mostly should be about how hard it is for you to trim, not whether it's possible to reach the same trim. Also, how hard it is to hold the sheet.

The other difference, of course, is the amount of sheet you have to pull through when you make an adjustment. (And at some point, more sheet slows you down).

To ease the task of holding the sheet, the better solution is to incorporate a ratchet block. Ample discussion of those in recent and not so recent threads here as well.
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Re: Mainsheet swivel base replacement

Postby oian » Wed Jul 20, 2016 7:32 pm

The block system I'm using for a replacement does have a ratchet block. The idea of an adapter plate has some merit. A link to the post alluded to would be helpful. It likely was a piece of aluminum plate possibly about 1/4" with countersunk holes to fit the original holes with threaded holes to fit the new base. However if there is a more direct solution to the problem depending on the structure of the attachment area it would be more helpful. There seems to be quite a few people who have made this conversion, possibly without an intermediate fix.

Thanks, John
Last edited by oian on Wed Jul 20, 2016 7:51 pm, edited 1 time in total.
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Re: Mainsheet swivel base replacement

Postby klb67 » Wed Jul 20, 2016 7:50 pm

If it helps you I'm using a Harken 010 stand-up base. 4 screws went right into existing holes on my CB trunk, once I dug out whatever sealant was in them. There is a metal plate, I think, embedded in the top of the trunk. I forget the size and thread I used, 10-24 or something like that. I tried a few until I got the right one.
1976 DSII - #8039
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Re: Mainsheet swivel base replacement

Postby oian » Wed Jul 20, 2016 8:15 pm

klb67:

That's one of the ones I was looking at as it was close to the bolt spacing. It appears to be about 1/16" off which could be easily fudged. It would also use the existing cam cleat on the block set I am using. and save quite a few bucks. How is it working for you? The thread appears to be possibly a 10/32, but I' sure it is a standard thread. The way the screws came out it felt like there was some thing threaded down there. Did you use it with a block that had an attached cam cleat. Please see the photo of the block set I am looking to use. The 010 does not have a ball bearing base so it wouldn't be as easily swiveled as a full ball bearing system. How does it do as far as swiveling. It can't possibly be harder to swivel than the stock set-up. The ability to use it without major surgery to create an attachment plate would sure be a plus. I suppose you could drill and attempt to tap treads into the existing plate if necessary.
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Re: Mainsheet swivel base replacement

Postby klb67 » Wed Jul 20, 2016 10:51 pm

There is a pic in my gallery of my mainsheet set up. I forget the Harken no. but you should be able to find it. I have the cam cleat set up upside down so any pull on the sheet will ensure it is uncleated - did that as I was learning to sail it. It can be flipped right side up though. I bet the cleat on the arm may work a smidge better, but I have no complaints. It works just fine for me. I had no issues putting the screws it. I tried a few common sizes and threads and found what worked.
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Re: Mainsheet swivel base replacement

Postby DigitalMechanic » Thu Jul 21, 2016 8:58 am

Lots of questions here. I went through this modification using the Harken 205. This is probably my favorite mods I have done to the boat... It makes it soooo much more fun to sail.

1. The swivel on it is orbital, or a controlled circle on a fixed plane. Follows you easily no matter where you move your "self ballast" to.
2. The ball bearings in the base make it very easy/smooth to rotate.
3. I now pull down on the sheet when I want it cleated, else I pull up to hold in hand. No more auto-cleating. This is great for hiking out on the rail, and making quick adjustments without having to lean back into an over powered boat in a gust. Basically, I feel I trim the sail more quickly/efficiently and take advantage of the gust vs missing opportunity by taking to much time trying to depower or depowering too much and having to shift through to many gears again.

I will tell you for certain on my '76 DSII (near same birthday as yours) with mid boom sheeting, there is a metal plate underneath the fiberglass the mainsheet swivel base is attached to. There are no nuts, the machine screws are threaded through the plate. I am pretty sure the fiberglass on the top of the centerboard trunk is pretty thick between 1/2" - 3/4". If you want an exact measurement of the thickness of the fiberglass, you could probably take one of the machine screws you pulled out and put it back in up until it touches the metal plate. Mark it with a sharpie marker, then back the machine screw out and measure from the tip of it to the mark you created on it. None the less, if you put it through the fiberglass and the metal plate... It ain't going anywhere, lol.

The holes for the Harken 205 do not match up to the factory holes for the original swivel base. I did not want to make it where things could not be returned to "stock", so I opted to put 4 new holes offset between the original holes. Another mental note, or more like insecurity, it that I would potentially push the plate off the bottom and then have to pull the centerboard to get into there to put the plate back. Thus I removed 3 of the 4 original machine screws, and loosed the last one. Rotated the original base out of the way of the other 3 holes, and then re-instaled the 3 screws I took out. Then finally removed the last screw and the original swivel base, and then reinstalled the final screw. Basically, at this point I know when I am pushing down on that drill to make the 4 new holes, the metal plate is secured by the original 4 screws and ain't going anywhere. Not sure if the plate actually would drop from putting pressure on it, but this exercise gave me piece of mind when it came time to break the drill out. And that metal plate was a real PITA to drill through. I ruined several screws trying to tap the holes and ruined an actual hole tapper (the official tool to do the job right).

Seeing how there was a metal plate under there, I wanted to make sure that I used machine screws (the ones with the flat tip, not pointed), so that they would be nicely threaded through the tapped plate. This of course makes the thread tapping process interesting with 1/2" - 3/4" fiberglass laying on top of that plate. But it is doable. I just started with the smallest drill bit and slowly worked my way up until I got a screw to start to catch. Then I would use the tapper (until I broke it) to finish up. 3 of the 4 holes went pretty smooth. The last one is where I feel like I spent forever and a day with the drill trying to get through, and this is also the hole that destroyed the tap. I eventually got it to tap with screws but went through a lot of them. Anyway, my point is buy extra screws.

Also, getting the holes in all the perfect locations was challenging with that thick base as well. It is hard to find a pen to get through the base and mark. I actually just marked the first hole, and then drilled it and tapped it. Then I put the base on being held by the one screw and then marked the other holes with the drill bit. This made sure I got perfectly aligned holes for the base.

This is probably a a lot of information, but hopefully gets you thinking about the silly little things that will pop up before you start. The project really was not that bad. I thought it would take 30 minutes, and it probably took 2 hours, lol. None the less I would do it 10 times over again if I had to. It was really really worth it.

My parts:
Harken 205 http://www.harken.com/productdetail.aspx?sku=205
Harken Fiddle Carbo http://www.harken.com/productcategory.aspx?taxid=422
Harken 57mm Adjustable Auto Ratchet with Becket (if 3:1) http://www.harken.com/productdetail.aspx?id=4741&taxid=421

I use a 3:1 with the auto ratchet. Plenty of holding power and the sheet is very manageable. The way I look at it the auto ratchet takes care of sheeting out, making fine/small adjustments simple. The 3:1 takes care of sheeting in, giving enough resistance to allow me to not pull in to quickly (again making fine adjustments simple), but not over bearing where I cannot make a big adjustment easily if need be. I am a pretty little guy (150lbs) and left most of my muscle in high school, lol. The 3:1 with the ratchet is plenty of power for me personally.

Going to 4:1 or 5:1, I would not worry about stressing the boom, as the sheet just pulls the boom in. On the water, doing that is just going to make the boat heel. I would think the worry would be about overpowering your trim and losing the ability to make subtle/fine adjustments.

2185
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Re: Mainsheet swivel base replacement

Postby Zinger88 » Tue Nov 29, 2016 5:30 pm

I really like the upgrade DigitalMechanic did and thinking about doing the same. Also appreciate the detailed info on the "silly things" within the process....always nice getting a heads up on potential issues to be aware of. Would it be possible to get the exact Harken Fiddle Carbo you used? The link you provided doesn't narrow it down the the exact product...



Thanks in advance!
Jim H
'76 Daysailer II, Sail #7920, Windsong
Burton, TX
~~ _/) ~
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Re: Mainsheet swivel base replacement

Postby DigitalMechanic » Tue Nov 29, 2016 6:12 pm

No problem. The site must have changed the URL or something?

http://www.harken.com/productdetail.aspx?id=4729&taxid=422

It is the harken #2621 (57mm becket-less fiddle carbo). That with the becket ratchet will allow you to to get the 3:1 purchase.
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Re: Mainsheet swivel base replacement

Postby Zinger88 » Tue Nov 29, 2016 6:29 pm

Thanks for the quick reply. Now I just need to wait for my bride to ask me what I want for Christmas and hand her the order form.... :D
Jim H
'76 Daysailer II, Sail #7920, Windsong
Burton, TX
~~ _/) ~
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Re: Mainsheet swivel base replacement

Postby DigitalMechanic » Tue Nov 29, 2016 9:53 pm

Yikes! I remember that being an expensive upgrade. Good luck my friend, I hope you get it :)
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Re: Mainsheet swivel base replacement

Postby jeadstx » Wed Nov 30, 2016 4:51 am

I suggested these parts to a friend on Canyon Lake for his main sheet upgrade. They are from Stuart Marine that are the current maker of the Rhodes 19 and Mariner (originally built by O'Day). When O'Day built the Rhodes 19, they used the same hardware for the main sheet as they used for the Day Sailer. The boom is the same on both boats. The parts shown are Stuarts center boom upgrade. My friend is very happy with his upgrade. I will be upgrading mine this way at some point.

Swivel Cam: https://stuartmarine.squarespace.com/mi ... eler-w-cam
Main Sheet Boom Block: https://stuartmarine.squarespace.com/mi ... boom-block
Main Sheet Swiveler Block (rachet block): https://stuartmarine.squarespace.com/mi ... eler-block

As I recall it is all Harken hardware.

John
1976 Day Sailer II, #8075 - Completed the 2011, 2012, and 2013 Texas 200
1952 Beetle Boat Swan Catboat
Early Rhodes 19
1973 Mariner 2+2, #2607 - Completed 2014, 2015 and 2016 Texas 200
1969 Day Sailer I, #3229
Fleet 135; Canyon Lake, Texas
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Re: Mainsheet swivel base replacement

Postby DigitalMechanic » Wed Nov 30, 2016 9:01 am

That looks like a nice way to setup a 4:1. A little extra pulling power than my 3:1. When using a ratchet, which was a must have for my project, I was not sure how to go to 4:1 with the mid boom sheeting. Once I set it all up though, I don't think 4:1 is needed (but may have made it a little easier to "sheet in" in heavier winds). I like how I can now make very small adjustments to the sheet easily with the ratchet block on, or hold the sheet in hand if I like. Well worth the trade off for 3:1 vs 4:1.
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Re: Mainsheet swivel base replacement

Postby Zinger88 » Wed Nov 30, 2016 6:26 pm

John,

I'm assuming your friend has a DS? Do you know if the holes for the swivel base from Stuart Marine matched up with the your friends stock swivel base? Obviously that would certainly make it a lot easier and one less step of having to drill & tap new holes as DigitalMechanic had to do.
Jim H
'76 Daysailer II, Sail #7920, Windsong
Burton, TX
~~ _/) ~
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Re: Mainsheet swivel base replacement

Postby jeadstx » Thu Dec 01, 2016 5:22 am

I believe he had to tap new holes. I'll send you his e-mail address and you can check with him. I have found no hardware that matches up with the hardware O'Day used.

John
1976 Day Sailer II, #8075 - Completed the 2011, 2012, and 2013 Texas 200
1952 Beetle Boat Swan Catboat
Early Rhodes 19
1973 Mariner 2+2, #2607 - Completed 2014, 2015 and 2016 Texas 200
1969 Day Sailer I, #3229
Fleet 135; Canyon Lake, Texas
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