DIY Sunfish trailer


New Member
Thought I'd post some pictures of my trailer and thoughts on it. I'm looking at building a dolly, and browsing through pictures and descriptions of what other people have done is very helpful, so I want to share some of my "build your trailer" experience. Never drew any plans for this, so I don't have them, or a specific bill of materials, just looking to share ideas in the hope that someone can make use of them.


Main trailer frame is a very ratty jet ski/small boat trailer that I got from a friend's dad when I was about 16. It had rollers on the keel and a frame over the axle with bunks (or the remains thereof) for the bottom of the hull. No good for a Sunfish and they were junk anyway, but the point being this was a "generic small boat trailer". It's a junky frame; it works for now, but I built the cradle so that I could scrap this frame and swap it for a similar one.

The cradle cost about $200 in materials. The main bunks are pressure-treated 2x12's and the rest of the frame is 2x4. A double 2x4 runs through all three roller brackets, bolted through them, and out to the stern. This is attached to the 2x12's with 2x4 joists, one pair near either end of the double 2x4, one pair in the middle, and two pairs in the middle of the "boxes" this forms. The assembly is put together with "Strong Tie" brackets and nails.

I had problems with flexing on the ends, and at a few of the joints between the joists and the 2x12's. I put more "Strong Tie" brackets on the ends with hex head "super self drilling multi thread" construction screws, and ran some of these through the 2x12's into the ends of the joists as well. This kind of screw is expensive, but work really well, and I would consider assembling the whole thing with them if I did it again. The "Strong Tie" brackets are dirt cheap, especially for what they do, and there are a bunch of varieties.

To get the profile on the 2x12's, I set one along the bottom of the hull, just inboard enough that it was completely on the hull, roughly centered on the daggerboard trunk, and parallel to the keel. I traced the hull on an offset based on the depth of the hull from this position "plus a bit". This looked right and looked like it left enough "meat" in the 2x12, so I cut it out. I used this cut piece to trace the second piece so they would be the same. I then tried to use a rasp to get the angles so the pieces sat against the hull as close as I could get it. I'm not sure this really had any effect and I probably wouldn't bother with it again.

The idea here is that the support is as far outboard as possible, near the chines where the hull is stronger, and as long as possible to spread out the load. The hull is relatively fatter ahead of the trunk, so the CG of the hull and cradle ***should*** end up forward of the trailer axle. It's stable horizontally at 55-60mph (which is as fast as I want to go on Harbor Freight tires and a janky trailer frame), and I have done a few hundred highway miles with this rig. I've never tried towing it at any real speed light, but it handles well with the boat on it.

The 2x12s are shimmed to the axle frame and tied down with pipe ties "just in case", and the shims are all secured so they won't bounce loose.

The bunks are probably my proudest moment here. These are "jumbo pool noodles", which Ocean State Job Lot (if you have one near you), in particular, sells very cheap at certain times of the year, and fairly reliably. I had tried two pieces of pipe insulation stuffed inside each other, glued to the bunks, but the adhesive came apart very quickly and they were junk after two trips and one winter. I used E6000 to stick the pieces together, and I think I stuck a piece of foam or something else soft in the noodle holes to line them up while gluing. I glued three noodles together for each side, roughly centered the pieces, and then cut them off.

The foam is held down with nylon strapping from the fabric store-- again, dirt cheap for what it can do. This is stapled into the 2x12's with 1/4" crown staples for holding power, pulling the strapping tight as you staple. I put one strap either side of each joist and one in the middle of the resulting span.

The problem with this is that the noodles are much wider than the tops of the 2x12s and the hull will try to "squeeze them out". I had no success with glues, so I made small cleats to go in between the straps. I used a piece of pine from the hardware store, maybe 2x1". I cut about 3" lengths with a bevel on one end (the pieces look "Nevada-ish but upside down" viewed along the trailer spine) attached with 1/4" crown staples, so the tops are below the centerline of the noodle hole. This should mean they never touch the hull, and if they do, it's super cheesy pine that has less chance of going through. This "cleat" method worked very well, and is simpler and easier than glue.

Lighting is run along the trailer "spine" with zip-ties ahead of the cradle, and is stapled with insulated staples to the cradle frame to the aft-most joist, where it goes through a hole in the 2x12 and out to a short 2x4 "outrigger" for the lights and plate. I used LED lights from Amazon and am quite pleased with the brightness and price, although some basic soldering and wiring is required. They're positioned so they will be outside the boat (just the transom here, so it's pretty narrow), as high as possible, and visible. I used some angle brackets here to reinforce since they might get bumped.


(pre-noodle cleats and tiedown bolts in above photo)

Strapping down is with three ratchet straps, one midships that goes to eyes on the trailer frame, plus one forward and one aft that go to the eye bolts through the 2x12s. I positioned the front eye bolts so I could catch the ratchet strap on the forward end of the halyard cleat. I use a fourth strap and bungee cords to tie the spars and mast down, with the base of the mast in the cockpit compartment on an old foam floor mat and a piece of PVC pipe (visible first photo) in the mast step and through the gooseneck to hold the spars in place. This makes a long rig, but you only have to worry about the spars moving side-to-side. I tie a bright flag (piece of an old boogie board cover) at the end of the spars.

I tie the sail up using the lines with half-hitches every so often, clove hitches and wraps at the ends (learned this at scout camp years ago) and run the main forward and the halyard aft. I clip the main into the bridle as further protection against the spars moving. The lengths work out nicely and it makes it very quick to rig when you get to your site. Unwind everything, pull the pipe out, run the halyard through the mast, drop it in, and you're rigged. Everything's right on the boat, close to where you need it. Towels and rags where you need them to keep things from scraping, and there you go.

My complaints are mainly with the trailer frame. The springs are too stiff and the frame forward of the cradle is noticeably more flexible than aft. It doesn't much like rhythmic vertical bumps at speed. I could fix this with bracing from the axle frame towards the front of the trailer if I wanted to, but taking it easy and watching for big potholes works, and I'd like to eventually get another frame anyway.

Otherwise, I'm pretty happy. Took a couple weekends and several nights after work to put together, but I feel like it takes care of my old rickety boat, it was relatively cheap, and the materials are easily available.



As for the boat, she's over 50, faded, beat up, no reason to still be sailing, but is. They don't make fire engine-red Sunfish anymore, and I personally think red and white is one of the best color schemes they did, only after the red hull/yellow deck. She still looks the part, and she will go if you ask her to.