@Lester

Great minds and all that.

Maybe a few beers will help me get the full picture although I can' help thinking that to improve on my suggestion must involve more beer than I'm used to.

Re: No beer necessary

Does the rod need to go through the wing? Can the plane just sit on the rods, sandwiched between the bottom of the truss and the rods? If the rods are close enough to the fuselage, that should be enough to hold the plane straight and square as the motor fires.

Interesting either way!

Cheers!

Matto :)

Re: No beer necessary

One rod.

@Matto in AUS

>Does the rod need to go through the wing?

Not being privvy to the craft design the only other thing I can think of is if a hole through the wing would subtantially weaken its structural integrity then use tubes or eyelets fixed flush to the wing or possibly along the fuselage. Assuming the wings will be curved then the fuselage/tube or wing/eyelets seem more likely options.

Re: two parallel rods

Ever since I saw the initial design with two parallel rods I have been wondering if that isn't a high risk launch option. There are several factors that could result in those rods not staying parallel during the course of ascent.

The rods being mounted on different parts of the platform structure 'could' result in either a convergence or divergence of the rods due to thermal changes and loading stress in the platform structure as it ascends into the colder regions of our atmosphere. This would effectively 'clamp' the craft between the rails during launch and wreaking havoc on the whole platform when the engine is ignited.

My suggestion would be to use a single rod and 'hang' the craft upside down on that rod. There is no up or down in space so the launch orientation is irrelevant.

Would hate to see this fail because it got stuck on the launch rails.

@Reginald Gerard

The problem with one rod is that the craft might spin and the wing drag along the truss potentially causing damage. Another possibility is that during the ascent the wing remains in contact with the truss and freezes to it. Or if you really want to consider other possiblities there is nothing to say that the rod won't warp towards the truss and have the craft launch into it. This is still a possibility with a two rod solution however two rods require a shorter length than for one rod and so any warping will be less.

Furthermore I assume that the materials for the rods will be tested to ensure they don't warp too much at low temperature or if they did they would still be flexible enough that upon launch the guides would pull them back parallel.

Re: Exxxxxcellent news smithers

That's a great question - one other...

When will we get to see video of LOHAN and a donkey?

Shes obviously to young to have worn a pipe notch yet.

Don't be tempted to cheat by applying Dremmel to the teeth..

*Too

Re: Boffinry

I understand that the boffinry qualification test in the rocketry department has to include hydrogen peroxide and cardigans, Bonus points for Morris Dancing.

Re: Launch gubbins

"some (longish) rails under each wing should hold her securely through the buffetting of the ascent, but provide little resistance when the rocket kicks in."

You'd be surprised how these things can work fine on the ground, but not at altitude.The launch rails will be subject to icing and possibly thermal effects, so may not be exactly parallel at launch altitude.

To retain the rocket on a single rail I'd suggest a loop of fine fishing line through two small holes (pinholes really) in the exhaust tube; the line will have plenty of strength to hold the rocket in place but the engine will burn it away on ignition leaving the rocket free to launch.

Re: Balsa Launcher Out Weighs Just Ordinary Balloons

No, of course not - just as in real life (tm) they're bound to use straps.

ttfn

Real life? It'll never catch on.