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Discussion Starter #1 (Edited)
Background:
1) The boat is a 1984 Morgan N/M 454, with a k/cb, and current rig dimensions: I=56.20, J=18.00, P=49.50, E=16.00, and currently has a 135% Genoa on the furler. Its very much an IOR design with high aspect main, and large foresail.

2) Mainsail: 440sqft, Genoa(135): 717sqft. for a total of: 1,157sqft.

3) There is a total of 8' of space from back of boom to the backstay.

4) It is a very IOR sailplan and I am trying to modernize it.

5) Its time to replace my sails is one reason I am considering this change now.

Proposal:
#1) Increase the E from 16' to 18', which would increase the Mainsail to: 495sqft, but reduce my Genoa to a 125% with a sail area of: 664sqft for a total of 1,159sqft.

#2) Increase the E from 16' to 19', which would increase the Mainsail to: 523sqft, but reduce my Genoa to a 120% with a sail area of: 637sqft for a total of 1,160sqft.


Summary:
1) In your opinion, what is the net affect of this change? More weather helm?

2) In your opinion, is it worth making this change? (ie. will this make sail handling easier? Performance increase in light air? More efficient sailplan?)

3) Is it important to keep overall sail area the same with this change?

4) Will this change the balance of the boat, and if so, how could it be re-balanced under the new sailplan? Raking mast? bending mast?

5) Any other concerns?

I appreciate any guidance you guys can offer.
 

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We've owned a very similar boat (vintage and shape, but 40') with similar rig proportions. We lived/sailed in an area with typically high winds but cruised quieter areas in summer. We rarely used a big genoa, finding the boat going well with the blade jib as long as the wind was above 8 true or so... Tacking was worlds easier and faster, and in any event we were rarely racing.

I think the mods you're thinking of will detract from the balance of the sailplan, may well cause excess weather helm (on a boat that likely already 'loads up' pretty good, I'm guessing)

New sails with maybe a 110 or 120% headsail maximum might prove to work perfectly fine on the existing rig.

I think the 'right way' to redistribute the sail area without bad effect would be to move the mast a few feet forward.. not a prospect you'd relish, I'm thinking..

Disclaimer.. I'm not a designer so take this as worth what you've paid for it! ;)
 

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grumpy old man
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Punts:
The typical old IOR hull shape had pretty balanced ends and was never known generally to have weather helm issues. You will undoubtedly need a new mainsail. I'd go with the extra 3' of "E" and a full battened main. This will help yu kep the leach from hooking and I don;lt think you are going to find any change in helm. Maybe on a hard close reach where that extra "E" is really contributing power you will feel some increase but I would thin that prudent trim and flattening measures would mitigate it.

My philosophy on changes like this is to go all the way. Don't do a half measure. With a new boom, new main and the accompanying expenses the last thing you want is to go out the first time with the new changes and say, "I think I can tell the difference."
 

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Well there you go.... what do I know :eek:

btw.. sure doesn't look like 8 feet to the backstay on the drawing above.. maybe there were variations on boom length through the production run? (or somebody already shortened the boom along the way??;)
 

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grumpy old man
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One thing you MUST keep in mind. Take the sail plan and with the added three feet of "E" draw an arc from the gooseneck to the very end of the boom. Swing the arc up towards the backstay. The boom, described by this arc MUST be able to clear the backstay. In a wild, uncontrolled jibe, vang off, you do not want the boom to hang up on the backstay.
 

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Discussion Starter #6
Thanks everyone for your guidance. I appreciate it very much. I will post update after some more analysis on the suggestions.
 

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Discussion Starter #7 (Edited)
Well there you go.... what do I know :eek:

btw.. sure doesn't look like 8 feet to the backstay on the drawing above.. maybe there were variations on boom length through the production run? (or somebody already shortened the boom along the way??;)
The line drawing you posted is actually the Catalina version of my boat, which was altered in a few ways. They moved the backstay to the end of the cockpit instead of it being half way down the transom like on the race version.

Here is the line drawing that exemplifies this and how my boat is configured:

<img src="//farm6.staticflickr.com/5476/10894468686_c7038540dc.jpg" width="700" alt="Morgan 45 R-C">
 

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Aha... well, having two different companies build the boat 'ups' the odds of changes along the way.

In retrospect you'd not likely be entertaining these changes if you already had an issue with weather helm. Our son added a foot of so to the boom of his Catalina 36 with good results.

The closer proximity to the backstay will probably mean less roach on the mainsail you buy.. excessive roach and a fixed backstay are poor playmates when gybing in light air.. BTDT... backstay 'whips' don't really work that well on single backstay masthead rigs...
 

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Discussion Starter #9
Aha... well, having two different companies build the boat 'ups' the odds of changes along the way.
Yea, when Catalina redesigned the boat in 1985 they raised the boom up, moved the backstay to the cockpit, moved the side stays outward, extended the transom and put in steps, and changed the interior as you can see in the different interior layouts presented here.

I kind of wish they just called it the Catalina 45 (or 46) or whatever as it is truly a different boat than the Morgan N/M 45. The only thing the same was the hull shape designed by N/M.
 

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Discussion Starter #10
So, I did the analysis of the (E) increased to 19' and here is what it looks like. In this diagram is the backstay, the mast, and the boom. The arc shows the clearance between the boom and the backstay as Bob suggested. It looks good to me with a little space for good measure.

<img align="center" src="//farm6.staticflickr.com/5494/11024652486_51dd4850dd.jpg" width="600" alt="Morgan454SailplanProposal">
 
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