make a keel

I need some thought on this,Alot of lakes I fish are electric motors only and most of them want me to take off the 9.9 when I fish them. When I'm in the front of my boat and the wind picks up a little the back end just goes all over the place.I'm thinking about making a keel to mount to the back of the boat to help this. Maybe mount it with c clamps so I can take it off when I want. I'll make it a foot longer then the back of the boat and I'm thinking foot square that would be in the water. Do you think these would help? I don't care what it looks like just trying to keep the boat straight when using the trolling motor. All thoughts are welcome please and thank you.

I fish total electric also but have my trolling motor on the transom. However there is a boat I see all the time that the owner has made what looks like a rudder on a sail boat without the tiller handle that he slides down into a mount on the transom when he puts the boat in the water. I looks like it works well for him. Sorry don't have a picture of it, but it looks like it would be really easy to make.

have you tried towing a drift sock? a 5 gallon plastic pail with holes drilled in also works.

I see I used the wrong term I guess it would be called a fixed rudder not a keel sorry about that. I didn't think I would be moving fast enough for a drift sock to open. But the bucket may work. Thanks