Build of Inexpensive Ultralight Trailer

I lost the storage where I had been storing and tinkering with my old Rans S-4 ultralight. I temporarily had it in a carport tent on my driveway, but with winter coming I needed a better solution. The dang squirrels were storing walnuts in it.

Mission parameters for the build: big enough for my little plane, light enough to tow with my minivan, cheap (money for trailer comes out of plane budget), relatively weatherproof, life span at least a few years with easy repairs if needed.

I broke this out of another thread (Shrink Wrap Wings), didn't want to interfere with that one.

I started with a boat trailer. I found one that had 2 frame rails all the way to the front, was heavy duty (for stiffness more than weight capacity),and most important had the frame tops all in the same flat plane. Paid a whole $120 off a Craigslist ad. And it's even got decent tires and bearing buddies.

If you want to build a trailer like this,I'd look for this type of trailer. It's an Evinrude Fathom Master from the 70s. They seem pretty common, usually found with a nasty old fiberglass trihull boat on them, which gets cut up and dumped.

 

First step, remove all those rollers and brackets with a sawzall. Along with the front to rear walkway.

I left the rearmost brackets on, I think they will come in handy for attaching the rear loading ramp.

After removing the brackets, I framed out the floor. A few sketches determined I need about 72" of width, so I made it 78" just to be safe. Framing is 2x4's on approx. 24" centers.





I didn't want to drill the top edge of the frame and create stress risers when attaching the floor, so I notched some 2x4s to allow me to sandwich the trailer frames between the floor joists and the bottom 2x4s. These are placed such that the floor cannot slide in any direction side to side or fore and aft.

This framing is fastened with 3" and 3.5" construction screws.

 

I'll get some more pics shortly. Unfortunately I didn't really take any more during the building process so you will see a nearly finished trailer.

I finished out side rails for the floor just shy of the winch mount in front, and extending about 4' past the end of the trailer in the back. I ended up taking out the 8' rear side rails shown in the photos and replacing them with 12' so there wasn't a joint here. You'll see why later on. The portion over the trailer was then decked with 1/2" 4 ply BC plywood and screwed in place. I trimmed the outer edges with a router so there were no overhangs to interfere with the walls.

The next step was to saw a bunch of good 2x4's into 1"x1.5" actual size boards 8' long. These were fastened to the outer edge of the frame 24" OC using 3" screws. To avoid splitting them I predrilled and countersunk the holes. Next , these were made perpendicular to the floor using a framing square and locked in place with a diagonal brace at the bottom.

Once the wall studs were in place, the top plates were added. These were again 1x1.5 pine, 8' long with a doubler at the joints.

The roof was a bit more complex, I would have liked to use a flat roof for simplicity, but we get a bunch of snow some times, and flat roofs always leak eventually. So the roof has a peak about 1' higher than the edges, about a 15 degree angle. I'll try and get some pics tonight and finish this write up pretty soon.

 

I hope you used treated wood. Otherwise the bottom pieces will be rotting out in 3-4 years.

There is available rubberized material that would work for the roof covering. Never leak, and sun resistant.

Richard

 

Me too...I was just about to say the same thing.

 

No treated wood, it's usually heavy and terribly warped from the treatment process. At least the stuff I see around here is. I'll probably be coating the underside with either paint, varnish, deck stain, or something similar when it gets warm out next spring. Until then it's not going to get wet so it should be just fine. Planes aren't made of treated wood and they last rather a long time with a good coating of varnish.

That rubberized roof coating requires a plywood deck beneath-I considered it but the cost and weight were high (5 sheets of ply plus the roofing membrane and adhesive) was in the area of 250 pounds and $250. Too heavy and expensive for what I am trying to accomplish here.

Here is the rest of the build process, then some pics. It's mostly assembled now and I didn't take pics while building it (done mostly in the dark with a couple work lights so pics wouldn't have turned out well.

After the walls were up and the top plates on, I checked them for square at the top and put in diagonal braces to keep them square. Ran rafters across the 2 walls every 4' to keep the walls from bowing out when the roof is added. Then built the roof frames with the ends cut at about a 15 degree angle to match the wall and to meet in the middle. That allowed me to just cut all the studs with 90 degree ends for speed of manufacture. The roof studs are on 20" centers, I thought 24 might be a little too wide for the snow load I might get here in Wisconsin. These were built indoors in 8' sections and then assembled on to the trailer. After that, I put some center supports from the rafters to the roof peak.

The rear walls overhang the trailer by about 4' with no floor. The reason for this- I only needed about 15' of floor to support the plane. Adding additional floor would complicate construction and add weight since I'd have to add to the trailer frame to support it, more 2x4 joists, more plywood decking, etc. To keep those straight and stiff, I added an 8' plywood panel about 8-9" high on each side, then screwed that to the bottom 2x4 to create a beam about 12" high. It's very stiff in the vertical plane. The overall structure is surprisingly rigid.

Then I sanded the exterior of the framing wherever there was a sharp edge. Just used a 6" RO sander and 24 grit paper, no need to get fancy, this is just to keep from cutting the exterior wrap.

The exterior is wrapped in 7 mil marine shrink wrap. I got a roll 16' wide, started wrapping at the wall/roof junction and down one wall. Then at the opposite wall/roof junction and down the other wall, so I have a double layer on the roof. I followed the instructions for wrapping a boat, check out Dr Shrink on youtube. Found a good deal on a propane heat gun used, and shrunk it all down. Burned through a few places and had to patch it, but came out good enough in the end. Taped all the seams on the outside. I would have preferred white rather than blue wrap, but I got a deal on the blue locally, shipping in white would have added about $100.

My plane loads super easily, I made a lightweight pair of ramps 8' long. I can set the tail up on the floor, then push the front wheels up the ramps. Fits right in. Installed some blocks to keep the front wheels in place. Still need to build the wing racks along each side (that's why the trailer is longer than the plan, to give room for the wings). Currently have the wing braces bungeed to the rafters, I'll add some hooks for those.

Total investment approx. 120 for trailer, 126 for wrap, 150 for wood for a total of just under $400 so far. I might have $50 more in finishing the rear doors and floor, then $50 for LED lights so I can tow it legally, so around $500 all in. A whole lot less than buying one, and an order of magnitude lighter.

 

Overall exterior view. Wrap looks pretty good from a distance but not so much from real close. But I was a lot better at it by the end of the project. The winch is still installed, but my plane is so llight I won't need it. I'll pull it off later, save 15-20 pounds.


Rear wall support beam where there's no floor


Interior roof framing. Sorry the color is odd on all these, but that's what it looks like inside the trailer. Certainly ain't going to be doing any painting in there.


Detail of roof peak support


Wall/roof junction


More wall/roof junction


Wall framing

 

It ain't high tech, but it does what it needs to at minimum cost and weight. I'll update when I get the rear floor filler panel and rear doors in.

Hopefully this can serve as inspiration for others in need of a low cost way to store a little plane. If ya'll are in my neighborhood, I'd be glad to let you walk through and check it out in person if that's helpful.

 

I would include some ply corner gussets to guard against the joints breaking loose. If the structure folds, it will take your plane with it.

 

Might do that, first need to see if it would interfere with storing the wings, or cause a sharp corner that could abrade them. Or contribute to splitting of the studs since it would introduce additional holes near the ends. It's pretty dang strong as is, I can hang on the walls.

 

Yeah, but it's easy to underestimate the force of the wind (from driving) on such a broad surface. I'd definitely do some dry runs on a long unused road before putting your plane in it.

 

May I throw another opinion into the discussion, even though the OP's trailer is finished?

Look into using the fiberglass or lexan/vinyl/plastic corrugated roofing panels instead of the tarp.

You guys in Wisconsin have a little more weather to deal with than we do here in CA. (matter of fact, the temperature here in LA plummeted to below +60 F yesterday, the Governor is expected to call for a state of emergency and request federal funds for insulated Bikinis for the working girls on Hollywood Bl.)

Weather, rain, wind, etc. has a habit of shredding those cheap blue tarps, long before the sunshine goes through the fabric.

Screwing or nailing the fiberglass panels around the wood framing not only prevents the shredding, it also makes the trailer more solid and stiffens/braces the wood framing.

These panels cost more than the tarps, no question. But I believe it is very worthwhile both in the short run and the long run.

If you're not going to use treated wood then I'd sure as heck Thompson's Water Seal the bejeesus out of it.

Basically I'm saying that with the addition of only a little bit more money in the right place you can make the quick/dirty/short-term trailer into almost a permanent one.

 

After building a backyard shed I had a bunch of 89 cent 2x4s left over. I made a picnic table out of them, finished it with one coat of red deck stain, it sat out in the weather for 17 years and was just about as solid then as when I put it together.

 

Thanks for the feedback, Victor. It's not tarp, I agree with you, those suck. It's boat shrink wrap. UV treated, should be good for 2-3 years. I've got enough left over from the roll to wrap it another time, maybe twice. It actually puts a great deal of tension on the frame when shrunk, sounds like a drum when you tap it. The whole wrap weighs about 25-30 pounds, it's amazingly light.

Fiberglass panels would have been nice, but I'd rather spend the money on flying lessons and ultralight parts. The classic economic problem of unlimited wants and limited resources. Trying to put resources where they return the highest fun per dollar. Also sealing the edges of corrugated panels to keep hornets out is a pain in the backside.

Hopefully by the time this is no longer usable I'll be done with my PPL and flying something that lives in a hangar.

While I plan to seal the exposed wood underneath, I think all y'all might be overestimating the environmental degradation of wood. The exposed studs in my unheated garage are perfectly serviceable and over 50 years old. The wood in the trailer should be exposed to the same conditions (temperature, humidity, limited UV, kept out of direct water, etc). It's going to be parked except on nice days suitable for ultralight flying so I don't foresee trailering in inclement weather much if at all. It's quite possible I've overlooked some factor here, I'm a pretty clever hillbilly but I don't know everything. Is there a specific concern?

 

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You would have been better off just putting side/back/front Siding panels on the Car Port, throw some moth balls/crystals around the edges, squirrels, rats, mice, etc., don't like the smell. Use a small LP Heater inside, and you could still work on it over the winter, but a light weight transport trailer is nice to haul it.

 

My glider trailer is wood. It is varnished on the inside, and the outside was covered in vinylester resin and fiberglass cloth, then painted with good quality exterior latex paint, including the underside. It sits around for all but a few days of the year, and does not get towed in the rain because I don't fly on rainy days. In spite of this, it seems like all I do is chase wood rot problems all over. The paint cracks as the wood expands and contracts, water gets in, and it rots. Water splashes onto the underside of the trailer when it is just sitting there. The way you have the plastic wrapped around the bottom, water will splash up onto the bottom of the trailer and run down inside of the upturned edge of the plastic in the area shown in your 2nd picture. Yes, you can varnish it, but you're not going to be able to get it perfectly everywhere in that structure unless you had varnished the individual pieces before assembly, and water will find a way in somewhere and cause it to rot.

I'd also be concerned about the plastic vibrating in the wake of the tow vehicle and wearing holes through it where it passes over sharp edges. I'll echo bcmj's concerns about how that will hold up to being towed. Try it empty before you put your plane in it.

 

I would guess that a good thought experiment would be to look at your structure and judge if you could manually push or pull on the boards or joints and tear them apart. If you think there is any chance that you could break it with brut force, keep in mind that the wind forces will be much greater than what you could impose by muscle alone.

 

I have a trailer that has a plywood floor, 1/2" thick I think with 3/8" sides with a box in the front. No top, no back, just floor, sides and front. (used to haul snowmobiles around with it.)

I have had about the same results as Dana in the lasting property's of the plywood being exposed to the weather year round.

I have found that two coats of oil based paint on the parts before being assembled into a trailer helps slow down the rotting. But only oil based paint. Water based, (latex) will not cut it. And to pieces have to be painted before assembly otherwise you are putting wood against metal and water will just sit there and rot the wood and rust the metal.

Richard

 

Had a high wind advisory last night, for around 8 hours. 30mph steady winds with gust up to 50. Came through it perfect with no damage.