2020 rail uses 1010 size buttons. It is the same as putting four 1010 rails together in a square. Rail buttons aren't a limiting factor. For Unistrut you just use doorknobs.

Edward

I'm much more a fan of the 1020 rails - they are 1" wide and 2" deep. Gives you more rigidity in one direction. They also have 2020 rail that is very nice, but the key with any rail is having a good backing to keep it straight.

Edward

I like the 1020 rectangular rails, too. They even have a 1030 (1" x 3") section available, although I haven't used it. If there is any breeze when I fly off such a rail, I just rotate the rail in the pad so that the 1" face is into the wind--then the rigidity of the rectangular section resists wind movement better.

FWIW, I think it is better to buy/use the rails in 8' lengths, then use splicing plates to extend as necessary. 8020 has plates available that have sufficient length to create very strong and rigid connections. I do think that 12' to 16' is about the max length for an unsupported rail--beyond that, the rail should be secured to a rigid structure.

Putting a boom or outrigger arm at the top of the rail with guy wires could work, but you would need to be careful to apply equal tension to the wires, or you could create a bow in the rail. Which would not be conducive to straight and vertical flight. 🙂

It seems that if we acquired a length of Unistrut P-5000, which is 1 5/8" wide by 3 1/4" deep, and clamped this to the back of our 10/10 or 15/15 rail, and always kept the long side of the assembly parallel with the wind, this set-up would greatly increase the rigidity of the launch rail. With slide in couplers on both the unistrut and the aluminum rail, we could make a rail of almost any length we might desire. If we desired to strengthen this further, we would have a good foundation to work from.

Granted I have missed a few NCR launches over the last couple of years, but how much trouble have we had with rail whip on the mid power pads? It seems like most of the instability comes from the pad, not the 8' rail.

I agree that we should look at 1020 rail as an option, but when it comes to extremely high power then it is up to the flyer to make sure the right bracing is in place - i.e. the swing set, or Doug Gerard's tower.

We have such limited space in the trailer I think we need to focus on the 99% of the flights that we see and Unistrut or trusses might take up a lot of valuable space and weight in the trailer.

That being said, I encourage high power flights to be planned (by the flier) with 'enhanced' rails.

You are correct, Ed. When a project exceeds the limitation of NCR's typical equipment, it should up to the flyer to provide/procure/borrow a sufficient launch platform.

That has been the club's position since we gave the Swingset to Art. We have equipment to handle up to 100# birds with ease - Hell, we flew the Delta II project off a straight 1010 rail and as I recall flight weight was a bit north of 100#. If you're building beyond that, you better consider the launcher your responsibility as well.

Ok, let me see if I might get this back on the original track, or tack as it may be. We have been limited to 8' rails because that is the longest that will fit in the trailer and/or that is the longest that UPS will ship. I came back with two possibilities; (1) mount a protective tube on the roof of the trailer if we want to have longer; (2) get a different carrier, such as FedEx LTL to haul it, then we could get whatever size we might want. The second part of the discussion was a way to stiffen the rails, because when the wind gets up to maybe ten or twelve mph, the rods are flexing in that wind and it has been observed by some that the 8' rails whip the tail of the rocket as they come off of the rail, changing the flight dynamics. If either of these two observations would be desired to be changed, and since Ed was speaking at the meeting of replacing rails, then we might want a discussion about if we desire to have longer rails, and do we want to stiffen them, if the rail flex is a big enough of an issue. The other thing discussed at the meeting was blast deflectors, and what was suggested in another posting was triangle shaped blast deflectors and have the mounting hole near one of the three apex's. From there, bend it down at 45 degree angle and you are finished. Make it from yield signs. It was never intended for this discussion to follow a path of making new launchers and how big. If you need something special and the club does not have it, you bring your own. The club has enough for 99.9% of the launches and the current equipment does a fien job.

I've never seen rail-flex to be an issue - try just flexing a 1010 rail sometime. The problem I think you're seeing is a problem with the small pad bases. Compared to the moment-arm of leverage imposed by the length of the rail and the weight of the base, the ball joints aren't particularly rigid and the pads do rock.

Longer rails don't buy us any advantage over multiple rails joined with proper plates. If you're worried about this, fly off the red pad (usually set up with an 8' 1010) or the big pad (usually set up with 16' of 1515).

Before we worry about the length of the rails, ask what problem are we trying to solve. Managing 8' rail lengths is pretty easy. If we need anything, it may be we should start re-thinking the tripod bases we use for the lightweight pads. No one has ever hung up on a rail joint that I've seen. Now when it comes to rods, that is another thing entirely - if I had my way I'd ban rod usage for anything over 3# and G impulse. Rods over 1/4" are prehistoric technology and anyone building a project greater than 3# or G-impulse should rethink things and bring their project back to the future.

On my personal launch rail I have 3 pieces of 10/10 in 4 foot lengths, because they fit into the car easier and they pack easily. If the flex has not been observed by anyone writing in the forums, then so be it. If I think it is an issue, I can certainly take care of it myself on my own equipment. No big deal. 'Nuff said?