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Why is the main sheet 75' long?

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awetmore
Master Marine Consultant

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USA
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Initially Posted - 03/24/2012 : 20:02:42

We took our Catalina 25 out today for the first time.

Why is the mainsheet 75' long? Even when we were going downwind and boom was out about as far as it goes (sail resting against shrouds) we still had miles of mainsheet hanging out in the cockpit.

It seems like a shorter sheet would be easier to handle. What's the extra length for? I'm tempted to buy a 50' line for the mainsheet, and use the 75' that I just bought to replace our genoa sheet.

We have the stock traveler and other mainsheet hardware.

Our boom vang also seems to have an incredibly long line.

Alex W
Seattle, WA
Express 37 "re-Quest"
previously owned 1984 Catalina 25 "Lutra"

Edited by - on

Dave5041
Former Mainsheet Editor

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Response Posted - 03/24/2012 : 21:18:11

A sailor once told me that he never cut line because you can always use one that is to long but never one that is to short. Maybe he once owned your boat. It may also have been part of the mast raising tackle (it is in my case,but I still don't have any extra), but I can think of no other reason to have more than 4 or 5 feet extra with the boom all the way out. Be sure the sheet is reaved properly and then cut it off. Extra line in the cockpit is hazardous.

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JeanAndre
Navigator

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Response Posted - 03/24/2012 : 22:30:26

So Dave,
as the Mainsheet Editor you are in favor of cutting some mainsheet pieces a little shorter?

( I know this is kind of a bad one, but I couldn´t resist...)

Cheers

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awetmore
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Response Posted - 03/25/2012 : 07:24:37

75' is what the parts catalog calls for, so that is what I bought when replacing the main sheet. I didn't measure the old one.

I searched some of the archived posts and it looks like 75' might have been recommended to allow for using the main sheet when lowering the mast. Since our boat isn't a trailerable model that is less of a concern, so I can run a shorter one. This thread had some useful info:
http://www.catalina-capri-25s.org/forum/topic.asp?ARCHIVE=true&TOPIC_ID=10566
as did this:
http://www.catalina-capri-25s.org/forum/topic.asp?ARCHIVE=true&TOPIC_ID=1540

I think I'll buy a 50' replacement and use the 75' line as a genoa sheet. Our current genoa sheet is 1/2" line which seems too large for the winch (I think it was a 14ST, it might have been a 16ST).

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Dave5041
Former Mainsheet Editor

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Response Posted - 03/25/2012 : 08:21:55

<blockquote id="quote">quote:<hr height="1" noshade id="quote">as the Mainsheet Editor you are in favor of cutting some mainsheet pieces a little shorter?<hr height="1" noshade id="quote"></blockquote id="quote">
Only the articles from other organizations.

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Stinkpotter
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Djibouti
9080 Posts

Response Posted - 03/25/2012 : 09:38:09

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by awetmore
 Why is the mainsheet 75' long?<hr height="1" noshade id="quote"></blockquote id="quote">Is it rigged 3:1 or 4:1? If the former, the length might be for the latter (which I considered unnecessary for a standard rig--except maybe in Kansas).

Is the vang led back to the cockpit? If not, its length might be based on doing that...

Edited by - Stinkpotter on 03/25/2012 09:42:45

Derek Crawford
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Response Posted - 03/25/2012 : 10:47:04

When the main is all the way out, the distance from end of boom to traveler is about 14.15 feet (square root of 10 squared + 10 squared)
With a 4:1 purchase this comes to 56.6', so 60' would be the minimum length required.

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Dave5041
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Response Posted - 03/25/2012 : 13:56:39

Had a little trouble with that, Derek.

I finally figured it out: square root of (10 squared+10 squared) as in "a" squared + "b" squared = "c" squared.

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britinusa
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Response Posted - 03/25/2012 : 14:45:05

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Lee Panza
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Response Posted - 03/25/2012 : 16:25:17

I was hoping someone else would point this out, because I don't want to be the one to call our Measurer to task ('specially if I ever intend to race in one of our Ass'n. events!!!) but if I ever get my boom out to ninety degrees off the centerline, so that Pythagoras' famous theorum would apply, I'd have lost one of my aft lower shrouds. A few extra inches on the mainsheet wouldn't matter too much to me at that point, because I'd be scrambling to keep from loosing the entire rig (if it wasn't over the side already).

Since I'm in the process of replacing all of the standing and running rigging on my formerly-neglected 1980, I too would like to know how much line to buy for my own mainsheet. The old one, with a 3:1 setup was right about 60' long (three 20' strands). I remember there being a lot left over the few times I sailed this boat before bringing the rig back to my shop.

Most of the time I don't sheet-out the boom all the way to the shrouds, because the mainsail would be doing a "Mae West" producing poor sail shape and chafe, too. But when the wind is light and more or less dead aft I guess it's nice to have the option.

As I said, my entire rig is in my shop right now, so I'm having to work with numbers instead of a tape measure. According to my CAD model, my 11'-3" boom at a 75 degree angle off center (about the farthest it could go) yields a horizontal distance of 190 inches with the traveler centered. Allowing as much as four and a half feet or so vertically between the traveler and the end of the boom (at that boom angle there would be little to gain by relaxing the vang very much) brings it up to about 196. If the traveler happened to be at the windward side, that would bring it up to about 205. Subtracting for the tang and the hardware at both ends, and adding a few inches going around each sheave brings that down to closer to 200 or so. A 3:1 tackle would need three times that, plus a little to hold and knots at both ends, which adds up to something on the order of 52 feet.

Whenever I'm working on a design where there's a degree of uncertainty and a significant downside to undermeasuring, I always tack on something to be safe. Unless the material is extremely expensive I go 10%, or even 15% when I'm working with small quantities. A few extra feet of line at this point is irrelevant to me, so I'd go 15% here. Which brings me right about up to 60 feet.

Now, I'd rather not have any excess line to have to manage, but unless someone could actually measure theirs (as Robin Williams used to say, "What a concept!") I guess Awetmore and I will have to use 60' as a starting point and trim it afterward.

Edited by - on

pastmember
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Response Posted - 03/25/2012 : 16:50:32

Good chance a PO used an old halyard for a replacement mainsheet.

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Steve Milby
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Response Posted - 03/25/2012 : 16:52:42

I'm a firm believer in not using cordage that is either too long or too thick for the purpose, but I have bought line and put it on the boat to find that it was measured a few feet too short. If you buy it in a local store, you can take it back. If you order it online, it's a hassle, so you should take that into consideration when you order online, and should probably order 4-5 extra feet. (After my experience with it, I don't buy cordage online anymore.)

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Stinkpotter
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Djibouti
9080 Posts

Response Posted - 03/25/2012 : 18:08:50

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by Derek Crawford
 When the main is all the way out, the distance from end of boom to traveler is about 14.15 feet (square root of 10 squared + 10 squared)
<hr height="1" noshade id="quote"></blockquote id="quote">If the boom length is 10' (?), the triangle is a little bigger, because the traveler looks to me at least 3' further aft of the boom end. That would add 9-10' to the sheet length with 4:1 purchase.

Edited by - Stinkpotter on 03/25/2012 18:10:07

Derek Crawford
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Response Posted - 03/25/2012 : 20:15:01

Thanks Dave. I knew I had forgotten something. So with a 3-1 purchase it comes out to 51' and with a 4:1 it becomes 68' plus whatever length you'd like laying in the cockpit.

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awetmore
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Response Posted - 03/25/2012 : 21:00:20

Fisheries Supply in Seattle had 51' of Samson XLS in 3/8" in the remnants bin for a good price, so I bought that to try as the main sheet. I'll report back when I have a chance to see if it is long enough.

My main sheet is setup 3:1.

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Stinkpotter
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Djibouti
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Response Posted - 03/26/2012 : 06:12:29

Better put a stopper-knot on it.

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awetmore
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Response Posted - 03/26/2012 : 06:30:19

always

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dmpilc
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Response Posted - 03/26/2012 : 10:31:49

Here's a way to shorten the needed mainsheet length. Remove the block on the end of the boom and attach it to a 3 ft. piece of quality low-stretch 5/16" or 3/8" line. Tie the line to the boom where the block was attached, or use a shackle to reduce chafe. Adjust as necessary so the block is just above the fiddle block on the traveler when the boom is centered over the cockpit. you've just eliminated approximately 9 ft. of the necessary mainsheet length.
Also, that is approximately 9 ft. you no longer have to sheet in after sailing down wind or let out again after gybing. It does work.

When I took this pic, the knot at the bottom was temporary, but you get the idea.

Edited by - dmpilc on 03/26/2012 10:35:51

Dave5041
Former Mainsheet Editor

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Response Posted - 03/26/2012 : 15:08:24

Glad you covered that. I was going to mention it but couldn't think of a concise way to explain it without a photo and hoped somebody else would.

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awetmore
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Response Posted - 03/26/2012 : 16:11:19

Nice idea, I'll give that a try when I'm down at the boat later on today.

On a sort of related note, I'm thinking about putting a proper outhaul on my boat. I've looked at the kit from Catalina Direct and it looks like they use self tapping sheet metal screws to a block and a cleat to the boom. Is this the normal way of doing it? It seems like through bolting or tapping and using machine screws in the boom would be better, but I also don't have any context for the wall thickness of the boom or what aluminum alloy is used.

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awetmore
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Response Posted - 03/26/2012 : 17:21:53

With a 51' mainsheet my boom can rest against the rear shroud and I still have 6' dangling in the cockpit. I'm going to do the modification recommended here and it will be even shorter.

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Lee Panza
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Response Posted - 03/26/2012 : 20:56:42

Thanks, awetmore. You just saved me that extra 8' I was going to add on for safety margin.

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dmpilc
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Response Posted - 03/26/2012 : 20:57:12

The picture doesn't show it, but I recommend using a caribiner with an eye at the small end to attach the line to the tang on the end of the boom. The tang could cut into the line over time, so the caribiner reduces that risk.

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awetmore
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Response Posted - 03/27/2012 : 09:40:34

I used a large shackle, but a caribiner seems like a better idea and less likely to come undone. I'll pick one up next time I'm at Fisheries Supply. With the 30-36" of fixed line my 51' sheet is more than long enough, it can reach from the transom back to the mast support post inside the cabin. With my 6' long measuring tape that looked to be about 13-14' of excess.

I also saw that the boom is about 2.5mm thick, which is too thin to safely thread. However the block and eye that I need to add for an outhaul are near the back of the boom, so if I pull off the tail I can run nuts inside on machine screws.

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Lee Panza
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Response Posted - 03/27/2012 : 22:10:30

David, that's a nice trick; but in thinking about it, mightn't that upper fiddleblock get slung around in the vicinity of your noggin on an accidental gybe? I've been slapped by the mainsheet on smaller boats, and I'm wondering if that hardware might possibly present an additional hazard (if the boom doesn't get you, that is).

Edited by - Lee Panza on 03/28/2012 02:13:12

dmpilc
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Response Posted - 03/29/2012 : 11:49:20

I use a single block with becket (and the mainsheet starts there for a 3:1 purchase), not a fiddle block. I've been slapped by the lines a time or two, but never by the block itself. The block tends to come across behind me, perhaps because I'm rarely sitting at the stern, mostly about at the end of the tiller. It really does work quite well.

Regarding the outhaul, I have a small single block with becket attached to the clew and a small double block (see pic) attached to the boom. The line runs forward along the port side of the boom to a jam cleat, the kind that hold the line when it's loose:

For the cleat, I used self-tapping screws, but destroyed one screw in the process. Better to drill and tap the holes.

Edited by - dmpilc on 03/29/2012 12:08:33

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