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Author Topic: Sail Plan Help needed  (Read 5670 times)

the red dragon

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Sail Plan Help needed
« on: October 25, 2010, 07:09:56 PM »

Hi,
The Yacht hull shown on the photos is my first boat, and is about 60 years old. As a project I want to re-rig it to how I remember it being, a gaff main sail and two jib sails.
The hull length is 22 1/4". the beam is 5". the max depth is 3 1/4". the w/l is 2" below the bow and 5/8" below the Stern at a weight of 3lb 12 oz ( hull, current lead and proposed radio etc).
Can anybody help with a sail plan ?.
Regards,
Geoff.
***topic name changed***






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Jimmy James

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Re: Sail Plan Help needed
« Reply #1 on: October 26, 2010, 07:47:35 PM »

Do you still have the origanal mast stepping position was it stepped on the deck or on the keel & did she have a bow spirit ? if so how long was it?  Also did she have a topsail above the gaff?
I might possibly be able to assist you
 Freebooter
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the red dragon

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Re: Sail Plan Help needed
« Reply #2 on: October 26, 2010, 11:24:00 PM »

Hi Freebooter,
Thanks for the reply and the offer of help.
The only definite things that I know are that my Dad made it for me and that a blurred photo shows a bow spirit but not a topsail.
I do not have any information on the mast position or the method of locating it, however as a guide to it's position the CLR is about 
12 1/2" from the bow. 
I would appreciate your view on which would be more in keeping with the period, the reconstructed original keel /rudder or the modification to cut back keel and a skeg rudder ?.
Regards,
Geoff.
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tigertiger

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Re: Sail Plan Help needed
« Reply #3 on: October 27, 2010, 01:47:26 AM »

A photo of the deck would help a lot. This will show where the mast is stepped. And a photo of the area in front of the mast, even if there is nothing left on it now.
Also, can you put a pencil down the hole where the mast would go? Is there a hole?

I would go with the original hull and rudder layout. By changing them you change the hydrodynamics in a lateral direction. By changing it you will negatively affect how the boats handling, and how well it turns.
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the red dragon

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Re: Sail Plan Help needed
« Reply #4 on: October 27, 2010, 09:14:31 PM »

Hi tigertiger,
Nice to see the Red Dragon flying on the model in your info box.
I have attached some more photos, but that of the deck only shows the outline as the original deck and all the other parts were removed and put in a box when I started to modify the yacht for a Bermudian rig and a vane steering gear about 1955. The box is lost and the modifications were never completed. 
So, using this new and the previously posted information, is there any chance you will be able to arrive at a suitable sail plan ?.
Regards,
Geoff.





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Boy From the Bay

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Re: Sail Plan Help needed
« Reply #5 on: October 28, 2010, 07:43:38 AM »

Removing the brown sticky take from the deck, and photo again, would help a lot.

It looks like the mast step had been covered.
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the red dragon

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Re: Sail Plan Help needed
« Reply #6 on: October 28, 2010, 11:17:05 AM »

Hi,
The tape was put on to cover where a Jib rack and a plate for the proposed Bermudian rig would have been located on the new deck, and not where the original Gaff rig was located, that has been lost. It would have confused the issue for what is in essence a start from scratch project to get a Gaff rig sail plan that will work on the hull if I had left them showing.
Regards,
Geoff.
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Boy From the Bay

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Re: Sail Plan Help needed
« Reply #7 on: October 28, 2010, 03:06:08 PM »

But does it show where the original mast was stepped?
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the red dragon

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Re: Sail Plan Help needed
« Reply #8 on: October 28, 2010, 04:32:50 PM »

Hi,
As I said, it is a new deck and does not show the original Gaff mast position. However I have just enlarged the photo of me and the yacht, and scaled from the overall length it was about 10" from the bow. I could now scale all the dimensions and make a set of sails. But, 60 and a bit years ago as a 10 year old, I has a yacht, how it sailed I do not remember and probably did not care. Now it does, I do not want to spend the time rigging it and turn up at my club with a yacht that will not sail. This is why I am looking for help. If nobody can come up with a sail plan that has more than half a chance of working, the hull goes back in the loft and I will look for another winter project.
Regards,
Geoff.
 
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Boy From the Bay

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Re: Sail Plan Help needed
« Reply #9 on: October 28, 2010, 04:59:57 PM »

Suggest you buy a book on model sail boats that covers things like lateral resistance, center of effort of sails.
Then you can devise your own sail plan. Traplet publishers do several such books and only a few bucks.

The mast position is not critical, you can get racks that allow you to change where the mast is stepped. As well as racks to adjust the shroud placement. Many of the older racing boats would change the sail plan, and mast position, season by season.

Sometimes 1 or 2 or 3 headsails. Although if gaff rigged 1 headsail was unusual.

I don't think there is an easy answer. But if you come up with a basic design, balancing center of effort with lateral resistance, and you have a rack to adjust your mast footing (for lee/weather helm), you can achieve a lot just by tuning.
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the red dragon

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Re: Sail Plan Help needed
« Reply #10 on: October 28, 2010, 06:34:41 PM »

Thanks .
I now about CLR and CP and adjusting for weather or lee helm. What I was looking for was for somebody to tell me how much sail the hull could carry in a Gaff main/ two Jibs configuration, or at least how to calculate it.
Bye. Geoff.
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Boy From the Bay

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Re: Sail Plan Help needed
« Reply #11 on: October 28, 2010, 07:01:34 PM »

There is no set answer to this question.

There is a connection to the righting moment, that you can calculate. And then look at the CP and the heeling forces that it creates. But other than that there are only variables. The biggest being wind force.

You can keep increasing sail area relative to boat size. Extreme cases would be the Balmain bug and the J Class boats. In the end the Js only sailed in fair weather, but the sail areas had increased by about 80% over time.

Think about 1m boats with 3 sets of sails for light, medium, and strong winds.
Think about a full size boats that may carry jib, genoa, genoaca, headsails, etc. And may just as easily reef in stronger winds.

If it were me. I would rough design to sort out the CP and CLR to give me what I want regards weather helm. This can be roughed on a drawing board. And is easier to adjust if the mast footing is changeable.

Righting moments can be ballasted out. Or if you have fixed ballast and she is being knocked over I would cut from the foot of the sail. Although I don't see much of a problem without a topsail.

There is a lot of theory in the book Racing Sail Boats from Traplet. You may also find some info on sail design on the AMYA Website. Although this is for Bermuda rigs the principles will be the same.

There is also room for some trail and error.
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Jimmy James

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Re: Sail Plan Help needed
« Reply #12 on: October 28, 2010, 08:40:58 PM »

Give me 2 or 3 days and I should be able to draw you a set of plans of a gaff rig of the 20's /30's with a small bow sprit . This will be a usable rig but because of the scetchy infomation it will be a general rig and sail plan
Freebooter
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the red dragon

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Re: Sail Plan Help needed
« Reply #13 on: October 28, 2010, 09:08:21 PM »

Hi,
Thank you boy from the bay for your input, it has been appreciated, and jimmy james for your offer to develop a set of sails. I may at last be nearing the time when my old yacht is back on the water with a set of sails similar to those that were on it originally. I have in the meantime made a set of Bermudian sails for it, but to fit them would be giving up on a "want to".
Regards,
Geoff.
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Jimmy James

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Re: Sail Plan Help needed
« Reply #14 on: October 28, 2010, 10:18:03 PM »

Geoff
You should be able to make a set of sails these drawings . I've based this on a 24" mast , an 8" Gaff ,a 14" main boom , a 6 3/4" staysail boom and a 5" (from the stem post) bow sprit
 The scale is 1" =  10mm [1 cm} the drewing is to scale
 Hope this helps you out
FREEBOOTER



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the red dragon

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Re: Sail Plan Help needed
« Reply #15 on: October 28, 2010, 10:42:58 PM »

Hi Jimmy James,

My most sincere thanks to you. These will go into production this weekend with the hope that it will be on the water before the weather beaks, giving me time for a paint job over the winter.
Which would you recommend using, the original keel with attached rudder ( for period looks ) or the cut away keel and skeg rudder (supposedly gives better performance ) ?.
I will, if I may, keep you posted on progress via your private E-Mail.

Regards,

Geoff.
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Jimmy James

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Re: Sail Plan Help needed
« Reply #16 on: October 28, 2010, 11:12:59 PM »

I think with the keel it is a case of suck it and see
 You can e-mail me at any time if you need help  but do try to keep the thread up dated as well
 Photo's are allways welcome
Jimmy
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Boy From the Bay

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Re: Sail Plan Help needed
« Reply #17 on: October 29, 2010, 12:49:52 AM »

Your choice of keel will determine the CLR.
Once chosen you can decide on the rig placement.

The more traditional look keel will shift the CLR back a bit.
Loosing the rudder at the stern will shift the CLR forward.

Overall effect may be close to neutral.
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Jimmy James

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Re: Sail Plan Help needed
« Reply #18 on: October 30, 2010, 07:43:24 PM »

Just a rough sketch for adding belly to a sail



 I normally cut belly into my sails, it makes them look and draw better and for period vessels it is historical correct... the added triangle can be adjusted to allow more or less  depth of belly
 as I said this is an old sail makers trick  and has been used for hundreds of years
 Jimmy
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the red dragon

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Re: Sail Plan Help needed
« Reply #19 on: June 07, 2011, 03:26:30 PM »

Hi.
After a number of delays the rebuild of my first yacht is completed, and it is now on the water.
Setting it up and understanding how to sail it took some time as the characteristics of a Gaff Rig are not the same as the Bermudian Rig I am used to. However all is now sorted and it sails so well it may replace my R36 as my preferred yacht.
Once again thanks to all who contributed to the project.
Geoff Jones. 









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Jimmy James

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Re: Sail Plan Help needed
« Reply #20 on: June 07, 2011, 06:00:59 PM »

Geoff
 Glad I could be of some assistance, Did the rough sketches I made help
 Jimmy
De Freebooter
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the red dragon

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Re: Sail Plan Help needed
« Reply #21 on: June 07, 2011, 06:32:15 PM »

Hi Jimmy,
They certainly were, as was all the other information you gave me. Without them the Yacht would probably be back in the attic or be sporting a Bermudian rig.
Geoff.
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Jimmy James

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Re: Sail Plan Help needed
« Reply #22 on: June 09, 2011, 08:54:19 PM »

As I said before ,,,Glad I could be of assistence
Jimmy
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