Sail Calculations

[Pandoramark1]

Hello All,

So again I find myself out of my depth, and I have not even left the shore yet

I have been trying to work out my sail dimensions and for the most part I am cool, however trying to figure out the dimensions of the Roller Genoa, I have the Luff/leech, but am struggling with the foot and LP.

A) Is the foot the bottom of the forestay at bow to the base of mast?
Or
B) Is it bottom of the forestay at bow to the foremost fairlead position?

This then leaves me with the following

Luff – 7.3m
Leach – 6.7m
Foot – A)2.55m B)3.5m
LP – Even though I have read about this I just do not know what to do

Can someone explain to me how I calculate the LP please (and if possible show workings)

Thanks
PMK1

 

[KenMcCulloch]

LP is 'Luff Perpendicular' or the length of a line passing through the luff at 90degrees and also through the clew. The foot is the measurement of the sail from tack to clew. Note that these are measurements of the sail itself, not of the rig.

The value of LP in relation to J (which is the distance from the foot of the mast to the foot of the forestay) will obviously vary depending on how much overlap the sail is expected to have.

Do you have an existing sail you are trying to measure, or are you trying to determine the correct dimensions for a new sail? If the latter a good sailmaker should be willing to measure the boat and advise you appropriately.

 

[Pandoramark1]

are you trying to determine the correct dimensions for a new sail?

I have a project boat that i have been doing up over the winter and the final hurdle is the sails am trying to get either New (if not too expensive) though more likely to be second-hand, thus the need for as accurate measurements as possible.

Kind Regards
Jon

 

[Twister_Ken]

 

[DownWest]

If the new ones look too pricey and you can't find 2nd hand suitable (and why are they 2nd hand?) You could get 'The Sailmaker's Apprentice' and buy the fabric, Point North was my source, Kyospruce another. Cost me about 1/4 of the quote from a well know maker. See the other thread on sewing machines. It was my first try and surprising easy to make sails that set well. Encouraged a local friend to do his as well.
Hope the car injuries are not too prolonged.
Apart from anything else, the book is a good source for all sail info,such as you are asking.
A

 

[Pandoramark1]

If the new ones look too pricey and you can't find 2nd hand suitable (and why are they 2nd hand?) You could get 'The Sailmaker's Apprentice' and buy the fabric, Point North was my source, Kyospruce another. Cost me about 1/4 of the quote from a well know maker. See the other thread on sewing machines. It was my first try and surprising easy to make sails that set well. Encouraged a local friend to do his as well.
Hope the car injuries are not too prolonged.
Apart from anything else, the book is a good source for all sail info,such as you are asking.
A

Very interesting, I for some reason never though about actually making them. The reason there are no sails is as a result of this boat being a salvaged boat, so only had the hull / rigging nothing else. What book are you on about as unless I am still seeing things you forgot to give its title

Thanks again for the replies, and Twister that diagram has made it so much easier to understand now. Thank you for that too.

While I am on it do all mainsails have Luff slider holes on them to allow you to add your foot sliders?

Thanks All
PMK1

 

[DownWest]

Look at Amazon. 'The Sailmaker's Apprentice' is allover the place. Not expensive either.
Apart from the info, a good read.
A

 

[Pandoramark1]

ohh god it is not a good day today my wife has just asked my the coffee is in the freezer... thanks for not flaming me, think I will call it a day today and go to bed.

 

[DownWest]

Uh? We always keep our coffee in the freezer,, it s a USA thing. Get a grip!!

 

[Seajet]

Pandoramark1,

if you could tell us the type of boat, unless a one-off custom someone here should be able to give a few pointers; is your callsign a clue ?!

 

[Twister_Ken]

Pandoramark1,

if you could tell us the type of boat, unless a one-off custom someone here should be able to give a few pointers; is your callsign a clue ?!

SJ,

It is a Pandora, possibly a Mark 1. Or maybe he's called Mark?

 

[DownWest]

Probably just got out of the box.

 

[Seajet]

Twister Ken,

hence my question; I have learned never to assume anything - and I had the impression you're not sailing a Twister now ?

IF it's a Pandora, Mk 1 or otherwise, sailmakers should have the dimensions on file, I've found Westaways at Ivybridge, Devon very good for this, 01752 892560 ( no connection except very satisfied customer ).

 

[Pandoramark1]

Twister Ken,

hence my question; I have learned never to assume anything - and I had the impression you're not sailing a Twister now ?

IF it's a Pandora, Mk 1 or otherwise, sailmakers should have the dimensions on file, I've found Westaways at Ivybridge, Devon very good for this, 01752 892560 ( no connection except very satisfied customer ).

I have a Pandora Mark 1 Fin Keel (also in my profile) i have been in touch with Westways and Jekells who have both been so supportive and helpful, that i now not only have the correct dimensions etc, but have a sail on order from both... hip hip hooray!!!!

Thanks for everyone’s help, Twister your pic was the turning point

Happy Sailing All

PMK1

 

[VicS]

I have a Pandora Mark 1 Fin Keel (also in my profile)

You cant win can you?

If you don't put the details in your profile you are criticised.

If you do people don't read it