So back when I threw a tower on my old ski nautique. My fair skinned self needed some shade. In my mind the price of a Bimini was outrageous.
so I went about making one. Materials needed: sunbrella fabric of your color choice, grommets (1/4" silver ordered on amazon. Still got about a billion left over) double sided seam tape, paracord, Emt conduit I used 1/2", 4 conduit corners, hand full of stainless bolts, washers and nylon nuts. 4 exhaust clamps I found stainless on line. Used standard junk temporarily and it rusted relatively quick. Rubber washers or unused rubber from tower clamps
Start by by determining how large you want the Bimini frame to be. Measure inside the tower legs. And leave some clearance, maybe 1/2"-1" per side. Then decide how long you want it. I went a little longer front to back then side by side. Cut the conduit pieces to length and width and build the frame using the corners. They use a slip joint with set screw to secure.
I did this part first because I didn't exactly know what I was doing. Now that the frame is assembled take your sunbrella material and lay it out. I'll throw some random numbers out here. Let's say 60" long by 55" wide is the frame demensions. The idea was to have the fabric smaller then the frame for mine. My finished fake size would have been 58" long by 53" wide. That's an inch all the way around between the frame and fabric. But you also need material for the grommets to grab, I left 2" all the way around to fold under. So my cuts for the fake demensions would have been 64" by 59"
Lay out the material flat and get the double sided seam tape. I used a pencil or something to mark off my 2" mark. Place that tape down and fold over to your marks. Repeat on all sides.
I measured and decided to put my grommets relatively close. Maybe 3-4" apart, on both layers of material. An inch or so from the edge. On all 4 sides.
The grommets were snug for a finished end of the paracord. But it works, start on an end with a small quality cinching knot (double overhand) around the frame, spiral it around the frame and through all the grommets on that side. I used a clove hitch and an overhand knot to terminate the run. The 2nd knot is easily adjustable but won't let go unless you want it to.
Now after all 4 sides are done I got some extra hands from the wife, she held it up in place while I measured. Made a "y" shaped leg for each side on the rear and a straight leg for the front. For the legs the attachment on the tower was an exhaust clamp, I used trimmed down rubber from an actual tower clamp to protect the tower. One bolt installed like normal, the other captured an end of the leg.
Making the legs: measure from clamp to desired location on the frame. Cut conduit to length. Hammer ends flat and drill the holes. I Used my angle grinder to shape the ends round. Bolt them up. I cut rubber washers out of the spare clamp rubber I had.
The "y" leg is necessary to keep it in place and the process was the same as above.
The top top held up fine for well over a season, I did bend it the one time we traveled to a different lake. Our normal spot is 20 minutes out. Max speed is about 55 on the street. I got up toward 70 on the interstate and bent it. Since it's always deployed. I replaced the two bent bars and added a center support. But kept the speeds down.
We found out we were pregnant so I went ahead and purchased a collapsable over the tower top so I can hang a toddler swing from the tower.
The top ended up looking good and actually getting many compliments. Improvements could have been stainless frame, and sewed seams but it did the trick. I'll post a pic of the inspiration as well