Glen L 15 with Gaff rig is possible?

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Pedro
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Glen L 15 with Gaff rig is possible?

Post by Pedro »

Dezembro 2020.jpg
Hi Everybody

Since 2013 I'm building a Glen L 15.In the blog you will find hundreds of photos with all the steps of the construction process and also almost all the errors are documented. And there were many mistakes.

https://construirumveleiro.blogs.sapo.pt

(With google translation it is understandable... I hope)

I come to this forum to ask for help. It is possible to equip the GlenL 15 with gaff rig? Keeping the sail area indicated in the project (90 sq ft), what the dimensions of the mast, boom and giff should be?

Thank you for your comments

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Roberta
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Re: Glen L 15 with Gaff rig is possible?

Post by Roberta »

Great looking boat and nice blog. Wish I understood Spanish. Gayle may be able to advise on the sail and rigging.

Roberta :D
Roberta "Queen of the Boat Builders"
Built Zip "Oliver IV", Super Spartan "Jimmy 70", and Torpedo "The Glen L".

Pedro
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Joined: Tue Aug 26, 2014 4:30 pm

Re: Glen L 15 with Gaff rig is possible?

Post by Pedro »

Roberta wrote:
Thu Dec 03, 2020 8:49 pm
Great looking boat and nice blog. Wish I understood Spanish. Gayle may be able to advise on the sail and rigging.

Roberta :D
Hi Roberta.... Is Portuguese, not Spanish :D

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Roberta
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Re: Glen L 15 with Gaff rig is possible?

Post by Roberta »

Sorry :D I have trouble with Inglesh. :lol: :lol: :lol:

Roberta :D :D :D :D
Roberta "Queen of the Boat Builders"
Built Zip "Oliver IV", Super Spartan "Jimmy 70", and Torpedo "The Glen L".

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parsj1957
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Re: Glen L 15 with Gaff rig is possible?

Post by parsj1957 »

IMG_9421.jpg
I don't claim to be an expert - but prior to my current Sweet Caroline build, I designed and built this Gaff rigged boat. In designing the sails, I used as an approximate rule of thumb the following ratios:
Ratio of the Foot to the Luff = 1.02
Ratio of the Head to the Luff = .83
Ratio of the Leech to the Luff = 1.73
I forget where I got these in my research - but they were a good guideline based on historical 'norms'

For my build, I assumed the gaff angle would be 30 degrees from vertical, and the boom would have a 5 degree angle from horizontal, and the mast rakes 4 degrees. These are important assumptions as they impact the sails angles and therefore the area.

If I use those same inputs and assume that the Length of your Foot would be roughly the same as shown on the GlenL 15 page then I get the following numbers:
Luff: 9' 4"
Foot: 9' 6" (Ratio 1.02)
Head: 7' 8" (Ratio .82)
Leech: 15' 6 1/4" (Ratio 1.66)

Main Sheet area: 90 sq ft

The result should provide for a shorter mast, and a much lower center of effort (albeit perhaps further aft also which will impact weather helm). I'd suggest playing with these numbers and see what comes out. I drew a lot of sails on graph paper and marked the CE's to visualize what I was doing before I settled on my final sail numbers. And yes I do think she sails well with these sails.

The boom and gaff are sized to allow for the length of the sail and outhauls -- likely a longer boom then the standard rig. The mast sizing in terms of diameter should be okay -- especially as it may now be shorter -- the key will be to compare the Center of Effort of the sail plan with the Center of Balance for the boat as this will impact the helm and stability of the boat.
J.

Pedro
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Re: Glen L 15 with Gaff rig is possible?

Post by Pedro »

parsj1957 wrote:
Fri Dec 04, 2020 8:33 pm
IMG_9421.jpg

I don't claim to be an expert - but prior to my current Sweet Caroline build, I designed and built this Gaff rigged boat. In designing the sails, I used as an approximate rule of thumb the following ratios:
Ratio of the Foot to the Luff = 1.02
Ratio of the Head to the Luff = .83
Ratio of the Leech to the Luff = 1.73
I forget where I got these in my research - but they were a good guideline based on historical 'norms'

For my build, I assumed the gaff angle would be 30 degrees from vertical, and the boom would have a 5 degree angle from horizontal, and the mast rakes 4 degrees. These are important assumptions as they impact the sails angles and therefore the area.

If I use those same inputs and assume that the Length of your Foot would be roughly the same as shown on the GlenL 15 page then I get the following numbers:
Luff: 9' 4"
Foot: 9' 6" (Ratio 1.02)
Head: 7' 8" (Ratio .82)
Leech: 15' 6 1/4" (Ratio 1.66)

Main Sheet area: 90 sq ft

The result should provide for a shorter mast, and a much lower center of effort (albeit perhaps further aft also which will impact weather helm). I'd suggest playing with these numbers and see what comes out. I drew a lot of sails on graph paper and marked the CE's to visualize what I was doing before I settled on my final sail numbers. And yes I do think she sails well with these sails.

The boom and gaff are sized to allow for the length of the sail and outhauls -- likely a longer boom then the standard rig. The mast sizing in terms of diameter should be okay -- especially as it may now be shorter -- the key will be to compare the Center of Effort of the sail plan with the Center of Balance for the boat as this will impact the helm and stability of the boat.
Thanks for the fantastic help. I will follow the same process and draw the CE on Bermuda and gaff versions on graph paper. I think that this way it will be possible to have a helm behavior similar to that of the original project. Once I get results, I share.
I had a doubt about the mast rake. You assume 4 degrees, which is a big difference to the Bermuda version (1.2º). Is this a feature of the gaff rig? And thanks again

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parsj1957
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Re: Glen L 15 with Gaff rig is possible?

Post by parsj1957 »

I don't think there's any gaff rig feature -- I was designing my boat but with several old (1890 - 1920's) gaffers as analogs -- my teacher's approach was to have you research traditional craft which had the sailing characteristics you wanted -- then design your boat and if you were too far away in style and approach from the analog's - likely you needed to rethink your design. So my analog's raked their masts from about 1.5 degrees to close to 5 degrees.
My final call of four degrees balanced a 10% lead between CE and CB. The 5% upward angle on the boom was to create head clearance for me when at the helm - I'm 6' 3" so I wanted the boom to be higher as it went aft.

I'm not sure how the mast step is done on the Glen-l 15 so if you can get the balance okay without further tilt I'd stay with the original mast step design and tilt.
J.

Pedro
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Re: Glen L 15 with Gaff rig is possible?

Post by Pedro »

After the excellent suggestions from Parsj, I made some drawings on graph paper that helped me to understand how changing the sail rig can have an impact on the behavior of Glen L 15. In total I did 10 tests, and the result that seems to me more interesting is to follow Parsj suggestion:
- Upward Angle of the boom - 5º
- Mast rake - 3º
- Luff - 9 '4' '
- Foot - 9 '6' '
- Leech - 15 '6 1/4' '
- Head - 7 '8' '
the position of the global CE go back 3.3% compared to the original project. I hope that the behavior of the sailboat slightly increases the weather helm, but after testing it will still be possible to adjust the mast tilt slightly.

Who has built the Glen L 15 what balance experience do you have? Is the lee helm too sharp?

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parsj1957
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Re: Glen L 15 with Gaff rig is possible?

Post by parsj1957 »

I have a spreadsheet which I used to do all my angle/area calculations. If you use Excel or can read excel files PM me and I can email the file for your use.

When I punched in your numbers my sheet calculates the Leech -- with a 30 degree gaff angle it come up with a Leech of 15' 8"

And to get a Leech of 15' 6 1/4" I had to assume a gaff angle of 31.475 degrees -- minor I know but will matter when you go to order sails...

But numbers look good otherwise --

good luck

J.
J.

Pedro
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Re: Glen L 15 with Gaff rig is possible?

Post by Pedro »

I built my own spreadsheet. It was a good exercise to remember trignometry that was a little bit forgotten. Here is a picture with one of the results (metric units).

Foot - 290 cm - 9' 6 1/8''
Head - 231 cm - 7' 7''
Leech - 481 cm - 15' 9 1/4
Luff - 280 cm - 9' 2 1/4''

Foot / Luff - 1,04
Head / Luff - 0,82
Leech / Luff - 1,72

Boom angle (degree) 4,00
Mast Rake (degree) 2,00
Gaff Angle (degree) 32,27

Main Sail Area (m2) 8,36 - 90 sq ft
gaff rig.jpg
I will now send this data to the sail manufacturer for comments.

Thanks for your support, Parsj. Can I use your Photo in my blog to illustrate the post about gaff rig?


PGR

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steveh41
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Re: Glen L 15 with Gaff rig is possible?

Post by steveh41 »

This thread is a very informative discussion of sail design (even for a non-sailor!) and a great example of the wealth of information and expertise available on this forum... worthy of some serious study! Spreadsheet looks good...

P.S. J., is that Sausalito in the background of your gaff rig? Awesome boat!

Regards,

Steve
The longest journey begins with a single step… then repeat as necessary!

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parsj1957
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Re: Glen L 15 with Gaff rig is possible?

Post by parsj1957 »

Pedro - happy to have you use my photo -- and you can call me J. Parsj is a email/login handle from my early computer days -- first four letters of last name (Parsons) and first letter of first name -- J. (James formally) which is also what I've used as my first name my whole life...
And looks like you've got all the calc's nailed down tight! -- I was a math major so also enjoyed re-working some old brain cells to do the calculations.

Steve -- Thanks - yep that is Sausalito - that was the inaugural sail -- we only had about 4 knots of wind that day and as a full keel gaffer I was concerned about getting stuck in irons on any tack -- but she sailed sweet and true so made me very happy.

Happy New Year all! J.
J.

Pedro
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Re: Glen L 15 with Gaff rig is possible?

Post by Pedro »

Last Sunday, Glen L 15, for the first time left the workshop. I took the opportunity to rig the sail. Some details are still missing and the boom is too high. But the option for the Gaff rig seems right to me, especially since the mast is 16 ft instead of the 22 ft of the Bermuda version. I have exactly the same sail area indicated in the original project, and CE go back 2 ". Now I’m impatient to do the flotation tests.
Maio 2021 5.jpg
;
Maio 2021 4.jpg
;

Pedro

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