Midgets Large and Small

[MarkII]

A Large Midget -- now there's a concept. Kind of like "jumbo shrimp."

In this and the following posts are some photos of two of my Midgets, all dressed up in their Sunday best. The smaller of the two (red) is my K-40 clone, replacing the original one that I only got to fly once back in 1970. The other one (blue) is my 168% Upscaled Midget. The clone has not been flown yet, but the upscale made several flights while still in primer. It uses standard 18mm motors; in fact, that was one of the reasons that I built it. I wanted to recreate my old Midget, but in a size that used a larger variety of readily-available motors and that would be easier to visually track in flight. I have launched it on B6/B6 and C6/C6 combinations and I have also launched the sustainer alone. It was actually the first one of the pair that I built.

Semroc has recently released a Retro-Repro version of the Astron Midget. These two were built with Semroc parts but both predate the release of that kit by several years.

 

[chadrog]

Those look beautiful Mark!

 

[qquake2k]

Very cool! I love upscales!

 

[MarkII]

Astron Midget clone. This one is the most recent of the three Midgets that I have built, and is the only one that hasn't been flown yet. With Estes now making A10-0T booster motors again that will change. Like the original Midget, it has 18mm diameter Series III motor mounts. (Similar to standard motors, but 1" shorter.) Due to the tube lengths, especially the booster's, it cannot accommodate standard 18mm motors. But that's not a problem, because one can reproduce the equivalent of a long OOP Series III (shorty) motor by inserting a modern-day Mini T motor into a casing from a spent standard motor that has been cut down to the correct length (1.75").

The Midget used "conventional" staging, with the booster and sustainer motors being taped together in line. For this one I intend to tape together the 18mm adapters after I have inserted the motors in them.

 

[MarkII]

For the upscale I used ST-16 for the sustainer and LT-115 for the booster body tubes. The fins are papered balsa and the sustainer boattail is cardstock, like the original.

On a B6-0/B6-4 combination it reaches something like 400 feet. On a C6-0/C6-5 combo it goes around twice as high or higher. I haven't launched with an A8-0 in the booster yet, nor have I simmed it to see if that would even be feasible. In contrast to the original and Mini-Brute Midgets, this one uses gap-staging with venting out the aft end of the booster. Another difference: the motors in both stages have old-style (C-shaped) motor clips. Since it uses gap-staging, neither clip interferes with clean staging. You can actually see jets of smoke shoot out of tail end of the booster when it stages, followed a fraction of a second later by a loud "pop" as the two sections separate. This is especially easy to see with the B motor combination.

One other thing: with the large fin area, it is rather prone to weathercocking. My theory is that this represents a rare, but foreseeable, pitfall with upscaling. The original Astron Midget needed all of that fin area for stability. Both my old one in 1970 and my Mini-Brute clone flew absolutely straight up. But on rare occasions when you upscale a design of a small rocket, the correctly-scaled fins can end up being a little bit larger than needed for that size of rocket on the motors that it uses. This seems to be the case here. At least that's my theory, anyway.

 

[T-Rex]

Beautiful!

 

[mwtoelle]

I built a K-40 clone back in 1998. Instead of messing with adapters, I installed 13mm motor mounts and a stage coupler instead. The old Beta kit used this approach when it was converted to use mini motors. Using available motors, your best motor combos are the A10-0T/¼A3-3T or the A10-0T/½A3-4T. I haven't tried an A motor in the upper stage yet. It can be hard enough to get back with the A10-0T/½A3-4T. You are right about upscale fins getting too large when you upscale the rocket.

 

[Daddyisabar]

Fantastic old school finishes!

 

[azgreg]

I dig the noce cones.

 

[MarkII]

Thanks to all for your kind comments. The finish? Gotta love that RustoLeum Painter's Touch Ultra Cover 2x. It's my go-to paint now. The nose cones are just balsa, the smaller one filled and sealed with Delta Ceramcoat All Purpose Sealer and then wet-sanded, the larger one filled and sealed with 20 Minute Finish Cure Epoxy and dry sanded, followed by priming and painting. One coat of gloss white all over, and then one coat of the accent color (Sunrise Red and Brilliant Blue).

 

[bradycros]

You've done a very nice job on both of them.