20" is the minimum clearance you need for a swing kiel when trailering my sailboat - Catalina 25' 1979. Kiel is literally just about barely touching on the metal. (That 20" measurement is from the top of the bunk that boat sits on to the metal bars of the trailer that would block kiel.)
In mid August I was looking for a hefty trailer because the one I had was not sufficient. The few good deals I found would have to be modified but disappeared fast as I guess many other sailors were planning the same. Thus by October, I desperately settled on modifying the insufficient trailer instead. In my research I found this site topic/question and I found that wikipedia had basic info on this like the draft with keel extended - 5.00 ft (1.52 m) and 2.66 ft (0.81 m) with the keel retracted into the keel slot. Unfortunately I couldn't get the info from Catalina itself as they said they do not sell trailers nor manufacture any for the Catalinas was their statement. As this trailer was for a NW sailboat (which I couldn't find any info on by the way) that was wider but smaller by about 3 feet, I was literally guessing and planned on at least 2 attempts to get my cat out before the crazy November NW WA storms hit. I'm experiencing one while I write this in my cozy office. My guess was amazingly right on - correct - but the center of gravity was not. So on my failed first attempt, my engineer sailor friend gave me very good advice: "move axle further back and winch assembly further front", not too difficult being they were held by U-clamps. I had already replaced the 10' bunks with 12' bunks. Therefore on my 2nd attempt it was a success. Now if that wasn't brazen enough, the trailer is only rated for 3200 lbs but the cat weighs 4200 lbs! Nevertheless, it has held it well. I know from 25 years of experience in pulling boats that trailers will hold a lot more weight than they list, especially if they are in good shape. A good piece of advice: you can use your truck step if you have pipe style type, to gain leverage when using the forestay to lower the mast and definitely use 10 foot 2x4s with grooves to catch the mast.
Finally in getting, slowly and carefully, it out I noticed the tires were really low and when I pulled into a local marine parts place, they said the tires are car tires and they were already at 50 psi, 10 psi greater than car tires should be, to my surprise. In fact the port side tire even had cracks if that wasn't bad enough. The NW project sailboat had been sitting on this trailer for many years. As it was getting dark, I had no choice than to get it as close to my place as possible. Amazingly, I made it 8 miles up hills to the foothills of Lake Whatcom at my place. Anyway I hope I've provided my fellow sailors with some good information and warnings - make sure your tires are trailer tires, LoL. As I'm planning to pick up some good ones, believe it or not, they are still holding up almost a week later! Let me know if I can be of any more help to any of you.
