Balanced Lug Sail Shape?

Hello everyone, I am here to ask a question that I can't really solve on my own.
I wanted to rig my 10ft dinghy with a sail to have some fun with it, and based also on space constraint I was looking to fit a balanced lug sail on it.
A friend gifted me with an old (and already repaired twice) MK1 laser sail, the foot is 2,5 meters so I guess it's perfect on that regard. Since it is too tall to be used as is, I wanted to cut it out a little at the top, I guess it's ok since I already wanted a balanced lug but now I'm torn on the sail shape I should go for.
The "common" balanced lug is usually depicted as "shape A" on the picture, and I do see some "shape B" ones on google but they are not as common. My question is: does it really matter how pointy a balanced lug is, if performance is not my main issue?

The question is obviously based on what I already have to work with, the laser sail is taller than my planned mast, but I would love to be able to get as much sailing area as possible from this piece of cloth

 

Helle @Headfirst !
Here is a link with images of the Laser sails, I think a foot of 2,5m is a 4.7 sail:
Laser Sailboat Sail and Rig Sizes | West Coast Sailing https://westcoastsailing.net/guides-advice/laser-sail-and-rig-sizes-explained
It might be worth doing a sketch of existing and proposed to scale and see how they look one on top of the other.

 

What Tops said, sketch it and see. You will have a much shorter head and yard anyway.

You may need other modifications to the sail besides cutting off a bit at the top. The sail is cut to have a convex luff, from mast bend. A lug sail is likely to have a concave luff, because pressure on the sail will pull the luff back. (Doesn't apply to sails that are full enough, such as spinnakers.) You might end up with a very baggy sail. Or perhaps the luff will just fold back and what remains will have a decent shape. I don't know. Try it, and be prepared for some extra work.

 

Thank you all for your kind replies, I managed to photoshop the sail I have (which is indeed that 4.7) onto the desired shape I wanted it to be cut as, and this is interesting because I did not realize I miss some material on the leech to really get that trapezoid look.
I also feel like that Shape B is not really that much different from shape A, so I added shape C to better visualize what I had in mind. My guess is that in order to get a balanced lug out of this sail I could go with shape C, but will a balanced lug with such high peak work or should I reconsider my rig and go for a different design such as gunther?

 

I decided to go this route as picture attached, the green line is around 150cm (the mast is double that measure) and the red ones are around 250cm. This should get me both a balanced lug main and a triangular jib, while keeping the total sail area around 4,5 square meters.

Wish me luck, and if you think I'm wrong on something please let me know, I am in no rush to cut this sail at the moment as I still have to buy and shape the mast, for which I am planning an octagonal section with a square base.

 

Molto bene! I think it will be a good experiment and use of an old sail.
The double-sided basting tape 'Seamstick' is nice for getting slippery fabrics to stay aligned and go through smaller or non-walking foot sewing machines.

 

Hi Headfirst, I have made a couple of balanced lug sails cheap. Check out > Forums (list) - down the bottom > All things boats and boating > 'DIY sail making', by me - Seasquirt. Instead of ruining a sail already made, get some cheap 50/50 % cotton/polyester sheet to ruin, from a local home fabric store. Then you can make your sail to an optimum size and shape without compromising due to using a small sail to start with. On some of my posts (Seasquirt) I have gone into details to make it easy for anyone to make a cheap but effective balanced lug sail at home. Mine are still in good condition after over a year of use and abuse. Larger is better, with reefing points; lightweight high pointing yard is best; good downhaul at the luff of the boom is best. Plenty of internet lug sail sites to look up for help and tips. Good luck and have fun.