Where to put sail on dinghy?

Long story short I am attempting to make a 7.5 in Portuguese style dinghy that I found free whole designs for online called the farra belle. I asked a person who sells sails which one I should get but they said that what I should be focused on is where it is I need to mount the sale and whether or not it's balanced. something about the center of something? Like where the sail I think would have the greatest maneuverability? How do I figure that out? Like how do I do the math there? Also, I was going to essentially put a piece of wood straight down the center to make a keel the length of the dinghy that's about 6" total the whole length. Would a dagerboard be better for stability? Like just one center of piece of wood mounted on the center? Sorry idk what I'm really doing here with some of this.

 

I have been where you are at ,wanting a small, cheap sailboat. I chose some free plans that were a disaster. Not all free plans are bad but many of them are. Beware.
The center of lateral resistance (CLR) and center of effort (CE) balance needs to be planned by someone with training and experience. The structure of a sailboat is more stressed than a rowboat. Slapping a keel, rudder and sail on a little dinghy is not that simple.
Do yourself a favor and find plans for a sailing dinghy. Your chances of success will be much better.
As far as sails, commercially made ones are quite expensive. You can find instructions online to make small sails from poly tarps and duct tape.

 

Do you have any examples of a simple ish 7-10' dinghy with a sail? You may be right, I just assumed it would be fairly simple. The lake I want to take it on doesn't allow for motors, even electric ones. So my solution was basically "what if I stick a sail on it?" Lol.

 

A 7' dinghy is tiny, an extra 2-3 feet will feel like luxury in comparison.

 

Okay which plans would you suggest for someone new at building boats?

 

It doesn't get much easier than this. The $40 plan cost will save you a lot more money by not making mistakes
OZ Racer Plans - family sailboats - Two versions and one kit https://www.storerboatplans.com/boatplans/oz-racers-two-versions-and-one-kit-of-this-simple-to-build-8ft-boat/

 

Umm. Their closing duck works today...

 

Not forever, and that s not the only place. You can also Email Micheal Storer from this website

 

Ok so I emailed him and can buy it. Sweet. It's funny AF its basically a box lol.

 

I think your best option is an Optimist. There are hundreds of thousands of them, which makes it easy to find used masts and sails.

 

I have built a side airbox 'Duck' (Puddle Duck Racer) with a Michalek rudder and a polytarp sail and am working on a Portuguese dinghy currently.

Puddle Duck Racer - Easiest Sailboat to Build and Race https://www.pdracer.com/

Portuguese Style Dinghy | Free Boat Plans https://hvartial.kapsi.fi/dinghy1/simboii.htm

I did not go the route of paying someone to explain someone else's free designs to me with another set of plans.

The Duck was fun, I did not use marine ply, nor stored it well, nor painted it ...and it succumbed to the elements.

The dinghy is more of a wrestling match bending things in place. I would skip brad nails and screws and do most of the plywood alignment with stitch wires except keep the stem screwed per plan. Having an able-bodied helper to attach the stern (transom to sides) and gunnels would be a big help. It's going to be painted!

The advice from@Milehog for a few more feet would be worth it in the end, I don't see this dinghy having enough room for sailing gear, but I am not using it to sail.

The advice from@gonzo to start with an easy to find commercial boat is good too, I keep a Sunfish around for those days I don't want to work on a boat...

 

The crude looking Puddle Duck, Oz Racer, Oz Goose boats are actually pretty decent sailors. I am skeptical of their rowing abilities though.
I myself would not build one but that is purely a shallow, vanity driven decision.
Had my first build been one of them it would not have been the disaster it turned out to be.