Estes Blackbird - parts don't fit!

wwattles · Aug 20, 2004

Okay Rocket Scientists...

I know they're now OOP, but did anyone have a problem with one of the last runs of the Estes SR-71 Blackbird kits and the wing pieces not fitting together?

I've finally gotten a spare moment to work on one of my pile of kits, and, after just a couple steps into the directions, I'm stuck. The inner wing sections come in 3 parts that are designed to be glued together on a sheet of wax paper, then attached to the main BT. But if I do that, the edges where the engine nacelles attach don't line up. And it's not a small sanding error, either - it's about 4 or 5mm off.

I checked both sets of the stamped balsa, and they are identical - both are off by exactly the same amount. Was this a stamping problem that was in many of the kits, or did I just get a bad one?

Thanks for the help!

WW

SecretSquirrel · Aug 20, 2004

I noticed that too. I just aligned the root edges and sanded the tip edges even.

The overall length was a tad shorter than the body tube length as well, so be sure to align the front of the assembly at the FRONT of the body tube not at the rear. Otherwise, the shroud will not meet up with the nose cone properly.

wwattles · Aug 20, 2004

a-HA!

So I'm NOT losing my mind! Well, maybe I am, but not over this. Thanks for the tip on the shroud alignment. How did you make sure that the outer tube alignment was parallel to the main BT?

WW

SecretSquirrel · Aug 20, 2004

Originally posted by wwattles
How did you make sure that the outer tube alignment was parallel to the main BT?

WW

With a ruler, I just made sure the width of the assembly measured the same at various points. I can't remember the measurement off the top of my head now.

I would also suggest that you glue one of the motor mount centering rings 2.5" inside the rear of the body tube and lose the rest of the mount. Add 25 grams of additional clay in the nose and fly that baby on D12-5's.

SR-71

wwattles · Aug 20, 2004

Can-do on the measuring - real easy with a cheap pair of digital calipers I picked up on sale a while back.

As for the 24mm mod, I wasn't even planning on doing that much. My plan was to just add the nose weight, and go for friction fit on my engines so I can put whatever size in that I want, including Estes' E's and maybe even some Econojets. Gonna have to see how well the thing holds up to the initial flight testing, first though.

Thanks for the help!

WW

JStarStar · Aug 21, 2004

I built one 10 years ago, and as I recall, getting the skins glued on exactly right, with no gaps, was a headache.

I modified my kit by installing 18mm mounts in each nacelle, and installing a tail cone in the main body where the original engine mount was. (Presumably getting points for accurate operational engine configuration.)

Recovery by 12" dual chutes, one in each nacelle. Put some nose weight (forgot how much) in the main nose cone to bring the CG forward. These mods did make it a good deal heavier.

It came out looking good, and by measurement, both nacelles were perpendicular to the fuselage, and mounted straight-line, so it should have flown straight, but whenever I flew it, it corkscrewed all the way up, just twisting all the way.

Well, with all those glue joints and skin seams, etc, I probably have something at just a slight angle. enough to get it into a roll.

Wasn't a huge problem, it always flew OK. I usually flew it on 2 B4-2's. Now, it's in a box of stuff I have in storage - I don't even know where the dang thing is!