Trailer Design - Resources?

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Topaz

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Designing a trailerable airplane to fit a specific storage space means designing (or acquiring) a trailer to fit that specific storage space, and then the airplane fits inside of it. This is the "Russian Nesting Dolls" approach to aircraft design. ;)

I'd like to at least sketch out the sort of trailer I want for my motorglider project. If that ends up being a resource to find a trailer someone else has created and is selling, fine, but I suspect I'll end up building a custom trailer as well as a custom airplane. Two projects for the price of one. Yay. However, I'll be the first to admit that I know exactly zero about designing trailers intended for airplanes, or anything else for that matter.

Specific question: Do you know of any design resources for trailers out there in Internet land? Or Bookland? Or "I've done it myself" Land?

What are the critical parameters? What's critical to have, nice to have, who cares if you have it? What's important to avoid?

Mind you, I'm not looking for a website selling really neat airplane trailers; at least not yet. Looking for design resources only, please.
 

blane.c

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Trailer weight and trailer gross weight dictate some things, depending on where you live for instance whether or not you need electric brakes or dual axels and the tire load rating and the springs. So if you want it simple single axel and no brakes then both trailer and aircraft together have to be under legal weight. If over and you need brakes you need a brake controller on the tow rig and the tow rig has to be rated to tow the weight.

Many of the online outlets selling trailer kits and parts have guidelines for building the trailers and also outright plans that come with the kits.

It may be cheaper to build an aluminum trailer if it keeps the weight down so you don’t have to upgrade the tow rig or so you don’t have to add brakes.
 

blane.c

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So DMV website should tell you all the legal stuff about trailers and I went there first. Also say you build a trailer in one state but want to tow into another the neighboring state may have different dimensions they consider legal.
 

Vigilant1

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I have nothing definitive for you, but I've seen a lot of good ideas on the teardrop trailer discussion sites (folks who build their own very compact travel trailers.)
Also, two cheap, fast ways to a rolling chassis:
1) The Harbor Freight utility trailers. But, they max out at 8 ft long (plus the tongue).
2) A used pop up (tent) trailer. The bodywork tends to leak and get destroyed by water if stored outside, so that makes a lot of lightly used but very serviceable frames, suspension, etc. They are practically free. And you might get an A/C unit, propane stove, a tiny fridge, etc that can be sold or re-purposed.
 
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Hot Wings

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It may be cheaper to build an aluminum trailer if it keeps the weight down so you don’t have to upgrade the tow rig or so you don’t have to add brakes.
For the class of plane Topaz is thinking trailer weight may turn out to be fairly important - in that he will need some ballast. Most off the shelf trailer axle/spring kits are intended for much heavier loads. I'm guessing a torsion bar type may be the best?


Keep the wheel base as long as possible. Makes backing up easier and and moves the forces from pot holes further from the CG and hitch ball resulting in less vertical displacement of the load - smother ride.

Self contained trailer brakes with a breakaway switch for a small trailer are kind of a belt and suspenders solution for a small trailer - IMHO

Someone in an old thread used boat shrink wrap for the cover. Light, cheap and can be shrunk over shape to fit hoops to reduce side wind loads.
 
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TFF

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I have always found trailer websites pretty lacking. Every once in a while a good idea might come through.

First off, you need to know what you are towing with. No need to build a trailer that needs a diesel one ton to pull when you own a Trabant or a King Midget.

Speed and overall weight will have you choose wheel size and number of axels. Smaller the wheel, less the load, and faster the wheel bearing are spinning.

I would copy it he big guys anyway. Wouldn’t be that hard to crawl under a buddies trailer you like and take notes.
 

karmarepair

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I've recently seen something on this, but I can't remember where. It MIGHT have been in the files section of the MONI IO.Groups; It might have been in the Dick Scheder pages of the Soar Idaho website, or it might have been some branch off the Sailplane Homebuilders web site. The MONI plans include a trailer, and they are on the IO.Groups files section.

And there is this: http://www.augc.org.au/docs/73426_AUGC-TrailerDesign.pdf
And this Building the Cigar Tube Trailer

A complete Harbor Freight trailer is less money than the cheapest axle sets. I might be tempted to start there, extend the side rails and tongue either with steel or aluminum, and build truss sides out of EMT gusseted and bolted together, cover it with dacron glued down with water based contact cement and coated with house paint.
 

Topaz

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For sake of clarity, I'm going to be towing with a 2002 Toyota Tacoma V6 4WD. The truck already has a hitch, and has a maximum towing weight of about 5,000 lbs.

The airplane is about 380 lbs empty, with a maximum fuel load of about 46 lbs, for a total airplane weight on-trailer of about 430 lbs.
 

TFF

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I would personally not buy a Harbor Freight trailer. I have a welder sitting on one. It’s ok but being bolt together and bent metal, it is flexible. I saw one, albeit overloaded, disintegrate in front of me when the tung channel folded in a turn. Pretty spectacular.

I would probably build a aircraft only trailer in an inverted A frame truss. Main span out of 2x3 square tube with the rest 2x2. Probably sprung like a pop up camper. Deck depends on cash flow. I would probably try and find marine ply varnished but aluminum diamond plate is nice. Tilt could eliminate ramps but you also don’t want it to tilt at the wrong time.

Is the plan to be inclosed? If not, I think I would want the wings caged. Maybe a hot wired leading edge cradle and maybe even trailing edge locked so it can’t move.
 

Victor Bravo

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I strongly agree with Hot Wings, get RID of the heavy-rated leaf springs and put a proper SOFT suspension on it. A long-travel coil-over shock or McPherson deal or whatever, or the torsion bar, or the rubber block axle stub gadget.

Definitely NOT a Harbor Freight trailer, nowhere near enough "meat" or quality. A small boat trailer would be a much better starting point.

The 1-26 association website has links to a page with a bunch of 1-26 trailer pictures. Not much of a design resource but a reference.
 

Dillpickle

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I've built a few trailers over the years. First thing to know is the 60/40 rule--you want approximately 60% of the load ahead of the Axle . Aft CG on a trailer is just as dangerous as aft CG on a plane. Forward CG is better, to a point where the tow vehicle isn't compromised. Easiest way to do that in a box trailer hauling crap is place the axle at the sixty percent distance of the box. The length of the tongue doesn't figure into that 60%, the load determines that. But as mentioned before, longer is a bit smoother. California is a remarkably EASY place to register a homebuilt trailer. So....to give you advice on length, width, axel size, etc, we'd need to know the size of the box or platform, the weight of the aircraft and everything else you want to haul on the trailer, and whether you want the heavy bits (engine, fuel, etc) towards the front or rear of the trailer.
 

Matt G.

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In 2018 I built a new trailer for my glider from scratch. A guy named Luebke made plans for homebuilt glider trailers (he is now deceased; I am unsure of current availability of his plans), and I acquired a partial set of his plans and loosely based mine on them. IMO, his design was not strong enough at the tongue attachment, and carried a lot of excess weight in some other areas. But, it was good for overall layout and sizing and determining parts suppliers for some of the hardware.

I spent about 2 years designing it, then about 10 months building it. Overall I am very pleased with it- it tows rock solid at 80 mph. I documented the build process here. Feel free to ask questions. Hopefully I still remember most of what I did. IMG_9471 (Large).JPG
 

Hot Wings

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You put the wheels in the right place to get the tongue loading.
My remark about ballast is not about tongue weight or the 60/40 rule.
Finding springs for a trailer that is only going to haul #500 (maybe #800 gross?) that won't beat an aircraft apart over our deteriorating roads is a challenge. A couple of hundred pounds of concrete poured in a box over the wheels is a cheap way to 'smooth' the ride.

The AV-36 has been permanently grounded in Germany due to a couple of inflight breakups - partially attributed to ground transport on a poorly designed trailer.
 

Hephaestus

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The biggest part is getting the axle located correctly & tongue weight right. Having helped at times with some off airport glider recoveries - some of the factory trailers are really poorly done too. Don't follow the path of dropped floor; you're probably going to want it taller - ever seen an RV trailer getting dragged on the jack/bumper with wheels in the air coming/going from parking lots?

Your local spring company can assuredly build you a set of leaf springs for any weight needed. Just because you don't see one on amazon / rockauto doesn't mean you can't get it. Just means it's not popular option - if you look around almost assuredly there's a local spring manufacturer who probably has the ability to build a set to your needs (in my neck of the woods that's standen's).

Just like glider design - it's all about the details - but there's tons out there on how to figure it. Like was mentioned - the tnttt & michenkell forums have some long ass discussions & feedback on theories (they're also really good on knowing the details on springing for super light weight trailers) and a couple of the suppliers of the bits and pieces are trying to help you design it right too:

But before you start - check your local dmv/registry/whatever your licensing agency is - a lot of the times the harbor freight becomes the 'basis' because of the data plate; throw everything else associated away, but having that certificate & VIN becomes the quickest way to not have a headache.
 

Dantilla

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Even though you will be very light, you do NOT want 12" wheels.
Ever notice the trailers stuck on the side of the road usually have small-diameter tires?
They are spinning so fast to keep up with the tow vehicle the bearings overheat.

While you want 15" wheels, you do not want the stiff springs that usually accompany them.
Soft springs will give the aircraft a soft ride.
You want the airplane to fly by itself.
No reason to launch the trailer into the air when driving over a bump.
 
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