# Trailer Design - Resources?

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#### Vigilant1

##### Well-Known Member
That all looks fine.
Another plus of larger wheels/tires: Less jarring of the trailer in potholes, cracks, etc.

My inclination would be to consider an end loading design that was still big enough to allow a human to comfortably get in with the airplane for attending to small tasks, fetching things, checking on a connection, etc. Yes, this will increase issues with crosswinds on the road (will I likely be taking the plane to and fro when the Santa Ana winds are blasting through?). I'd think this would still fit largely within the presented frontal area of your Tacoma or most other likely tow vehicles. The alternative is to remove the plane from the trailer if you need to touch or look at any part of the plane for any reason.
Also, a trailer slightly bigger than a glove-tight fit can more likely accommodate your next design.

#### TFF

##### Well-Known Member
So, which is more complicated? Design of the plane or trailer?

#### Topaz

##### Super Moderator
Staff member
Log Member
... The alternative is to remove the plane from the trailer if you need to touch or look at any part of the plane for any reason.
I'm actually okay with that. I learned long ago that, when you have the option of working on something in a confined space or taking it out, take it out. Your knuckles, shins, forehead, and sanity will thank you.

Also, a trailer slightly bigger than a glove-tight fit can more likely accommodate your next design.
Ooooooooooo!!!!

So, which is more complicated? Design of the plane or trailer?

I'll let you know when I get them both done!

#### Matt G.

##### Well-Known Member
Thoughts on a few of your thoughts:

• A "tube" trailer (that is to say, without a lift-up lid) is the way to go for simplicity of construction and operations on breezy days. The key to this is a good dolly system inside to extract the glider fuselage and wings. I need to research those further later, when it comes time for detail design of a trailer.
• Getting the proper tongue weight and CG position are critical to stability. I have calculators for those now, thank you!
• For structure, a welded steel perimeter frame with cross-bracing for the bottom platform, then square aluminum tubing "hoops" and pop-riveted aluminum skin seems to be common, provided I provide mitigation for galvanic corrosion at the contact points between aluminum and steel, as always. Anyone have any objection to gusset-and-tube pop-rivet fastening for the upper-cover structure? Sealed, of course.
• Sailplane-trailer-conventional solar-powered vents (probably 2?) will give enough ventilation for my needs, as the trailer will have long-term storage indoors itself.
I spent a LOT of time researching wing dollies, talking to various people, etc. and ended up using a modified version of a design from a friend's Zuni trailer. Out of all of the glider trailers he has had, he said they were the best design. They are captive in the trailer and as such will keep the wind from blowing the wing over when it is being pulled out of the trailer. If I didn't throw enough details on that webpage, let me know and I can get you some more info at some point.

Make sure to check the CG of the trailer both empty and loaded. It was suggested to me that the tongue weight should be 10% of the weight of the trailer, and I ended up at 10-13% empty depending on whether the rigging equipment was in the back of my truck or at the front of the trailer, and 9-11% loaded. I think in reality it is a bit higher loaded, as my CG estimate for the glider fuselage was a bit off.

The clamshell top of my trailer is gusseted and riveted aluminum square tubing. I also put adhesive between the gussets and tubes. I put sealant between all of the skins and tubes, and wet-installed the sealed rivets.

I have one solar vent at the top of the trailer, and two static vents, one on either side at the lower aft corners. Even on extremely hot days, this is enough to keep the temperature in the trailer at ambient, and I have never had issues with condensation inside.

I'd encourage you to look at torsion axles (local place by me sells Lippert and Dexter. Can't remember which one I went with), and not bother with trying to kludge a car suspension under one of these. As long as the loaded weight of the trailer is very near the axle capacity, it will ride fine. 99% of glider trailers have trailer axles, and they are not beating the gliders to pieces. The one anecdote shared earlier in this thread is not representative, in my opinion.

#### Pilot-34

##### Well-Known Member
Thoughts on a few of your thoughts:

It was suggested to me that the tongue weight should be 10% of the weight of the trailer, and I ended up at 10-13% empty depending on whether the rigging equipment was in the back of my truck or at the front of the trailer, and 9-11% loaded.
Remember that 10% is a minimum. The lowest acceptable value.

#### TFF

##### Well-Known Member
This is one of those times that as close to minimum will be best as it will be hand moved just as much as pulled behind something. Parking in storage will probably be about getting close and then pushing the rest.

#### Vigilant1

##### Well-Known Member
I learned long ago that, when you have the option of working on something in a confined space or taking it out, take it out. Your knuckles, shins, forehead, and sanity will thank you.
See, I just keep making that mistake. Subconsciously, I must be afraid that they will take away my diploma if I stop making those ongoing tuition payments to the School of Hard Knocks.

Okay, another thing: I'd include an access hatch or two to allow floor space to be used near the front of the trailer. In addition to the obvious handy spot to store stuff with the plane and out of the elements, it provides a place to add ballast if you have a temporary weight addition at the back of the trailer (gonna be moving fuel to feed this airplane?). If you plan on a foldable tongue, it probably won't be convenient to keep a weatherproof locker there.

#### Victor Bravo

##### Well-Known Member
HBA Supporter
I have a rather unfortunate amount of experience with using (well-designed European) glider trailers to disassemble gliders after landing out in ridiculous places. What I can say is that the Europeans have figured this out rather well. As as much of their configurations and ways of doing things that you can steal and design into your system as you can... steal it and incorporate it. The German trailers (Komet, Cobra brands) that I have experience with really really work well. The American Schweizer system and many self-designed systems work, but not as well.

If it is at all possible, just outright steal their overlapping wing spar and large shear pin design, and steal as much of their control hookup stuff as you can as well.

The European system is of course designed for rapid and frequent disassembly, which you may not need nearly as often with the engine on the glider... after all you will be 'making it back' far more often. But you may want to put the glider in the box every day or weekend regardless, for glider longevity and security. So either way, IMHO the speed, smoothness, and reduction in the number of people required will be worth having no matter how often you use it.

One good example (of several) is the European style fuselage "cradle dolly" and jacked-up dual-ramp system. It certainly cost them more time/money/weight to build, but every good European trailer has it... why???

Because it solves several problems and prevents damage. It allows one person to get the fuselage in and out with zero risk of it tipping over. It quickly puts the fuselage at the right height, WITHOUT tilting the whole trailer, and regardless of what type of surface the trailer is parked on. The little scissor jack can be used before or during assembly to raise and lower the fuselage easily, and it keeps the fuselage level unless you rotate the fuselage intentionally. When it's all done, it slides into the trailer and it engages little slots or hooks to keep it from bouncing around.

So regardless of whether you use a toy box, a clamshell, a tube, or a converted school bus, My strong suggestion is that (assuming you are using a 'glider' type mono-wheel) this ramp/cradle in your trailer. If your glider is going to be a two or three wheel "airplane" style landing gear, then you can eliminate the cradle and scissor jack, but I still recommend the "U-shape" ramp to roll it on and off the trailer without having to tilt the whole thing.

Tilting the trailer means that you are fighting the uphill/downhill battle with the wings, every time, with all the risk that involves. Tilting the entire trailer will probably prevent you from ever having a safe, working "one man rig" system.

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#### Topaz

##### Super Moderator
Staff member
Log Member
I have a rather unfortunate amount of experience with using (well-designed European) glider trailers to disassemble gliders after landing out in ridiculous places. What I can say is that the Europeans have figured this out rather well. As as much of their configurations and ways of doing things that you can steal and design into your system as you can... steal it and incorporate it. The German trailers (Komet, Cobra brands) that I have experience with really really work well....
Thanks for the suggestions. I'll go a-looking for good images of the dollies in those trailers.

If it is at all possible, just outright steal their overlapping wing spar and large shear pin design, and steal as much of their control hookup stuff as you can as well.
Oh, I've already stolen all of that!

The European system is of course designed for rapid and frequent disassembly, which Topaz may not need nearly as often with the engine on the glider... after all you will be 'making it back' far more often. But you may want to put the glider in the box every day or weekend regardless, for glider longevity and security. So either way, IMHO the speed, smoothness, and reduction in the number of people required will be worth having no matter how often you use it.
Yes, the plan is to trailer the glider every day it's flown. If it's a particularly good season, I may spring for a tie-down at the gliderport for a few weeks, but the airplane will live in the trailer at the gliderport, too. Irrational or not, I don't want the craft of my hands out exposed to the dirt, dust, direct sunlight and, unfortunately, rare vandalism at the gliderport.

Ideally, this is a one-person operation for extraction, set-up, tear-down, and re-packaging in the trailer. If other gliders can do that, so can mine.

One good example (of several) is the European style fuselage "cradle dolly" and jacked-up dual-ramp system. It certainly cost them more time/money/weight to build (compared to Schweizer), but every good European trailer has it... why???

Because it solves several problems and prevents damage. It allows one person to get the fuselage in and out with zero risk of it tipping over. It quickly puts the fuselage at the right height, WITHOUT tilting the whole trailer, and regardless of what type of surface the trailer is parked on. The little scissor jack can be used before or during assembly to raise and lower the fuselage easily, and it keeps the fuselage level unless you rotate the fuselage intentionally. When it's all done, it slides into the trailer and it engages little slots or hooks to keep it from bouncing around.
A picture is worth a thousand words. A video is worth a thousand pictures. Just sayin'.

So regardless of whether you use a toy box, a clamshell, a tube, or a converted school bus, My strong suggestion is that (assuming you are using a 'glider' type mono-wheel) this ramp/cradle in your trailer. ...
That is a correct assumption. While it has evolved, the airplane is still very much in the ballpark of this earlier version. Mono-wheel main gear, steerable tailwheel, plug-in outriggers. The outriggers plug in for "touring" ops where I'll want to taxi around at an airport, and then they can be removed at a gliderport where I have a wing-runner (or am willing to do a wing-down takeoff, as is common at my own gliderport) and want to focus on soaring with minimum drag.

#### Vigilant1

##### Well-Known Member
Trailer suspension: Leaf springs vs torsion axles.
-- Torsion axles use an elastomeric ("rubber," but not really) element inside the axle tube to provide the tire travel and damping, so they aren't like a metal torsion bar in a car (or armored vehicle) suspension. Over time, especially if the trailer is near the max allowable weight for the axle, the elastomeric element degrades and sags. This is a well known phenomenon in the RV community, and owners who have a trailer with torsion axles generally know to take the weight off the wheels (with jackstands attached to the trailer frame) during storage. (See sites for owners of Scamp or Casita trailers for more stories. Unlike a typical utility trailer and like the use case we are discussing, these trailers keep the trailers loaded constantly to near the max weight of allowed by the axles). So, if you go with torsion axles, consider adding screw jacks at the corners of your trailer to accomplish this easily (the ones that can be turned with a cordless drill are fast and convenient).

Leaf springs also sag under load, but my impression is that the problem isn't as large and the cost of rectifying the problem isn't as high.

Not directly related to the above: A web site with some comparisons of the pros-cons of the two suspension types.
Leaf springs vs torsion axles

#### Topaz

##### Super Moderator
Staff member
Log Member
Trailer suspension: Leaf springs vs torsion axles.
-- Torsion axles use an elastomeric ("rubber," but not really) element inside the axle tube to provide the tire travel and damping, so they aren't like a metal torsion bar in a car (or armored vehicle) suspension. Over time, especially if the trailer is near the max allowable weight for the axle, the elastomeric element degrades and sags. This is a well known phenomenon in the RV community, and owners who have a trailer with torsion axles generally know to take the weight off the wheels (with jackstands attached to the trailer frame) during storage. So, if you go with torsion axles, consider adding screw jacks at the corners of your trailer to accomplish this easily (the ones that can be turned with a cordless drill are fast and convenient).

Leaf springs also sag under load, but my impression is that the problem isn't as large and the cost of rectifying the problem isn't as high.

Not directly related to the above: A web site with some comparisons of the pros-cons of the two suspension types.
Leaf springs vs torsion axles
Thanks! More information to study, which is exactly what I wanted when I started this thread so, awesome.

The source Hot Wings gave me has a wide variety of types. I'm sure I'll be able to find something suitable.

#### Victor Bravo

##### Well-Known Member
HBA Supporter
What if the elastomer rubber was removed from the "torsion axles", and a simple OTS shock absorber was put in between the trailing arm and the trailer frame? This would give you independent suspension (reduce trailer rock n' roll), longer travel (less impact damage) , and damping (less bounce).

#### blane.c

##### Well-Known Member
HBA Supporter
You may want to paint, especially the steel. Painting stuff like this often takes a backseat but is easier if planned in the building process.

#### Topaz

##### Super Moderator
Staff member
Log Member
What if the elastomer rubber was removed from the "torsion axles", and a simple OTS shock absorber was put in between the trailing arm and the trailer frame? This would give you independent suspension (reduce trailer rock n' roll), longer travel (less impact damage) , and damping (less bounce).
Does anyone make something like that that's "bolt-on", that I can buy outright rather than fabricate?