Micro Midger 2-Stage downscale

[Micromeister]

Last year during some of the clubs OOP motor tests I cloned an Estes Midget 2-stage to allow some of my motor box 18mm 1/2A6-0s Short motors and boosters to fly. I also built 13mm adaptors to allow the model to fly with more modern A3-0t and A10-0t boosters as well. Them model is a ton of fun so being the devoted Micro flyer I am I just had to look at down scaling this model.

I looked at 3 different combinations BT-5/T4, T4/T3 and T3/T2. After some dry fit parts testing and rough sims the middle of the road combination seemed to be the best bet for Good perfromance and recoverability. So it was full speed ahead in coreldraw to downscale everything.
As is often the case with direct proportional reductions some of the patterns didn't seem to fit up correctly. the sustainer tail cone and fin marking guides seem to large so the Marking guide will be dropped while the tail cone was completely redrawing to fit.
I'm still working on a set of decals for the model so I won't be uploading the drawings yet. But the build and flying have gone well so I thought it was worth a look.
Started in the usual way cutting motor mount tubes, and both airframe tubes to length.
Decided to use a beading wire 49strand stainless steel sockcord anchor for the sustainer along with my usual 90lb kevlar shockline.

Since the booster is T3 a T2+/T3 ring has been added to the sustainer aft end motor tube to match up the lower end of the sustainer cardstock wrap with the Booster forward end. I tiny 1/8" long piece of T2 (.246" dia tubing was used as a motor stop in both MMT's and the Booster mount has been extended 1/8" below the body to allow both internal and External taping of the motor.

 

[Micromeister]

Sustainer MMT installed in T4 tubing waiting for the glue to dry.

Cutting the 110lb cardstock Boat-tail and testing the fit the oversize error was discovered.

Redrawn and printed the new Boat-tail is fabricated dry test fit and installed on the sustainer body set aside to dry.

 

[Micromeister]

One to producing the Fin templates.
I Like to cut them out of cardstock, file folder or the like then Medium CA soak the template hardening it which allow the edges to stand up to pencil pressure better.

After cutting the fins from 1/16" basswood I stack sand them between thumb and fingers until that each 3 fin set is identical. Check progress often while sanding to ensure all remain straight and level. Round the leading and tailing edges and give the entire surface a quick smoothing with 360 grit sandpaper.

Elmer's Carpenters cement is used to attach the fins to the bodies using double glue joint technique. followed by light epoxy fillets.

 

[blackjack2564]

It's been awhile. Glad to see some posting on micros. Getting my juices going for the winter off season of high power. Have to do a little building of my own.

Would Micheal's have that or similar beading cable? And by the looks of it, you use pliers to crimp the little connector thingies?

 

[Micromeister]

It's been awhile. Glad to see some posting on micros. Getting my juices going for the winter off season of high power. Have to do a little building of my own.

Would Micheal's have that or similar beading cable? And by the looks of it, you use pliers to crimp the little connector thingies?

Jim:
Micheal's is where I picked up the Beadalon material l've been using. Heres a pic of the 49strand wire, crimp beads and crimp pliers. the Stuff isn't cheap but I can tell you i've used the 20lb 49strand .015" material in models up to 12oz. with standard 13 & 18mm motors for about a year now. So far these Shockcord ancors have shown no sign of wear or weakening. I've been very impressed with this stuff for use in Micro models with it's small diameter and coating helping Handle the very energetic ejection charges produced by some of the MMX-II motors.

 

[Micromeister]

sometimes when we get in a hurry to finish a project we short cut ourselves into a bad decision. Being a bit lazy instead of taking a little extra time to go downstairs for a proper size Launch lug I opted for a handy oversize coffee stir stick thinking it'd be fine. This particular stir stick was a good bit larger then most with an ID of almost 3/32" but it was handy and easy to cut, shape and embed in the fillet I wanted to finish "right then". So on it want.
you'll see why I consider this a mistake with the first flight pics and report.

I include this photo to show that any plastic stir stick, styrene tube or cotton swab stem should be roughed up with very course sandpaper before attempting to adhear it to the model. Here I used a 120grit glit-stik all around before embedding in the fin/body fillet.

 

[Micromeister]

Couldn't find a T4 or 10.5mm Nocecone that had anywhere close to the right profile so I turned one in one of my mini lathes from hard balsa.

Several folks have ask about how to attach Micro or downscale Balsa nosecones and leave room for adding nosewight. I've found over time it's easier to hollow out most Micro Nosecones first then add a kevlar loop which generally leaves plenty of room to add Clay, BB.s or Lead shot to adjust the CG.

I was fairly sure this model would not take much, if any at this scale but wanted to leave enough room so I started with a center drilling.

With a mill end bit and dremel enlarge the hole outward freehand using the smooth shank as a stop as I remove material deeper Through the Shoulder and into the cone itself. once I have the depth the inside wall can be adjusted carefully using the same bit to enlarge in ID.

Tie an overhand loop in a couple inches of 70-90lb kevlar, cutting the loop close to then knot.

 

[Micromeister]

Dry fit the loop in the newly cleared out NC recess making sure the loop extends beyond the bottom of the shoulder to allow ease of tying on the Shockcord a little later.

Carefully add a Few drops of CA to the recess to capture the loop knot and let dry.
Once the CA has set use a tooth pic to completely embed the knot end of the kevlar loop in 5-minute epoxy. When dry tie the Shockline the the Loop with 2-Half hitches or your favorite terminal knot.

Add a butterfly knot about 1/3 of the way between the NC an body for attachment of a 3/4" x 12" piece of Teflon Plumbers tape or other Streamer of your choice. Remember however if using any material other then teflon tape you'll also need PF Wadding in the sustainer before installing the streamer. Teflon tape serves both as PF wadding and streamer. Saves a little extra weight

 

[Micromeister]

One photo I forgot to take was tying a butterfly knot about 1/3 of the way between the NC and sustainer body for attachment of a 3/4" x 12" Teflon Streeamer. If your not using Teflon tape for your streamer then you'll also need to install a few 1/4 squares of PF wadding before packing the streamer in the model. Teflon tape serves as both PF wadding and streamer saving a few extra grams.

The unfinished Booster came in a 2.4grams, The Sustainer with 3/4" x 12" Military grade orange teflon streamer 4.3grams. Combined less motors 6.6grams. and the view of the rough completed combination before a little tweek sanding to seat the sustainer squarely on the booster.

 

[Micromeister]

I generally try to pre-flight prep most of the models I plan to fly the night before the launch.
3 pics showing the motor internal/external taping on the booster and interal tape friction fit only for the sustainer. unfinished LOWt. 8.8grams.

 

[chuckpo]

This build is looking great! You see lots of people upscaling rockets, but few downscaling. I like it!

 

[Micromeister]

This build is looking great! You see lots of people upscaling rockets, but few downscaling. I like it!

Thanks: this one should be fun flying. I have about 130 some different Micro downscales in the current fleet. Many of the builds have been posted, most are still available in the TRF 1.0 file. If you looking for something specific you might try the files section of the MicroMaxRocket yahoo group where I most of the one page plans posted.

 

[Micromeister]

a couple weekends ago, I flew the unfinished Micro Midget 2-stage. as this was a club launch I wanted to be sure if it did not stage it would be lawn darting well away from the others on the field so I angles the launcher a good bit away down the hill.

Also since this is staged I decided to use a longer 16" launch rod to allow the model to get up to speed before leaving the rod. As I soon found out that was something I really didn't have to worry about. the oversized Launch lug was now concerning me however As it seems to give the model way to much wobble on the .049" diameter rod. At ignition the model jumped off the pad but the combination of tilt, loose Launch lug and longer rod the model tipped off much more then wanted. Up she went and then the .85 second wait for staging. which went all but as she staged the sustainer took off on an arc going up the hill ending up almost horizontal at ejection. No damage but if it hadn't been for a couple young folks up in that area the sustainer would almost surely have been lost.

I'm going to alter the LL in one of two ways...perhaps both. add or alter the existing oversize LL with an additional section of better fitting tubing. either a dollar store Q-tip stem or my normal 1/16" plastistruct tubing drilled out to .052". the other option being contemplated is to add a very small piece of correct size LL a but further forward on the model. I've already decided seeing you quickly the booster lifted the stack I can safely revert to my standard 12" launch rod. I'm confident these changes will correct the tip off problem and allow Micro Midget to fly was well as it's BT-50 size big brother. I tried to catch the liftoff with my digital camera but as happens more often then not all I got was the smoke trail
Now it's time to start finishing the model. I'm thinking of a white/yellow and white/orange combination to help with tracking. As with most micro model this little bugger is very quick! I'll try to upload the PDF 1-page plan if any of you would like to try building this one. I'll update this thread after some priming and painting





View attachment MM 362c2_T4-T3 Midget 2-Stage_09-11-09.pdf

 

[blackjack2564]

Jim:
Micheal's is where I picked up the Beadalon material l've been using. Heres a pic of the 49strand wire, crimp beads and crimp pliers. the Stuff isn't cheap but I can tell you i've used the 20lb 49strand .015" material in models up to 12oz. with standard 13 & 18mm motors for about a year now. .

Thanks for the tip. I finally found a store with it on stroke of luck. While on the road passed a craft shop called "Pat Catan's". Evidently a chain, though I never heard of it. Very similar to Micheals , but everyday everything 40% off.

They had the 30ft rolls for 15.00 but also smaller ones ...I got 9ft just to try it for 2.79. figured I could,t go wrong. Looks like some awfully tuff stuff!

How far up the airframe are you running it ? Or all the way out so you can re-attach a burnt sc?

 

[Micromeister]

Generally the anchors are located Motor mount to about 1/2"-3/4" below the forward end of the tube so I can replace the kevlar or elastic when needed by pulling the beading wire loop back through the motor mount with a hooking tool from the aft end.

Not sure if these pics make the process any clearer but they show the Anchor line run out the aft end of the motor mount for both motor mount installation or replacement/attachment of the Kevlar or Kevlar/elastic shockline parts.

 

[blackjack2564]

Crystal clear. Thanks!