Mini Tempest

[Bruiser]

Back in June 2019 I designed and built the Tempest, a two stage pseudo scale Navy missile. I've flown it several times and it is a hoot to watch.

Now that I am building some 13mm rockets I decided a down scale was in order. The original was 24mm to 18 mm and while I thought about 18mm to 13mm I was afraid the fins would break off the booster so this one is 13mm to 13mm.

Here we go with my build documentation.

So it begins with the motor mounts. A BT-5 with some Estes centering rings. Both motor mounts were the same. There is a engine block in each one as well


Then I moved on to the booster. Here I show the interstage coupler being positioned


Next was adding fins to the booster. They are 1/32 bass but next time I will use something a little thicker I believe. I did taper the leading edge and yo can see where this CA was used to strengthen the sanded area.


Moving on to the sustainer, here it is with the fin jug from payloadbay.com I just print them out on paper, 3M77 them to a piece of cardboard and cut them out with a hobby knife and ruler


Decided to do the strakes next. Again, 1/32 basswood.


Can't forget the launch lug which looks huge!


Here's a view of the business end of the sustainer


Back to the booster. The original Tempest booster featured vent holes and it has worked great so far. I decided to add them to this booster also


Here's the trial fitting after primer


Here she is in full color with decals. No clear coat yet because there was a malfunction when I clear coated the decals. The can kept spraying when I released the nozzle. I tried depressing and releasing the nozzle several times, tried a different nozzle, tried tapping the can and combinations of all that to no avail. It was a new can of Krylon Crystal Clear gloss.


Here she is with the original


The primer is Rustoleum 2 in 1 filler/primer. The white is Krylon Acyrli-Quik. The red is Duplicolor Perfect Match. The decals are made by me and I got to say these went on better than any others before. There must be a learning curve

I did have a problem with the fins splaying out when I left the rocket laying on it's side for a few hours. This happened several days after I had glued them on with Elmer's Glue-All and applied the fillets with Titebond Quick and Thick. It was just a few hours after I had sprayed the fins red though. I was able to "flex" each fin back in place except one. It came loose on one side so I ended up removing it, cleaning the bonding surfaces and gluing it back on. All the fins are solid today. I'll make note if anything happens when I clear coat.

First launch would have been on the 20th but I'll be off to dogs shows so she's gonna have to wait a bit. By June, there might be another ready for a maiden also. I am thinking of building an Xtreme with a 13mm mount or building a 13mm powered D-Region Tomahawk next. I have been thinking that the nose cone of the Xtreme does look a lot like the nose cone on the upcoming So Long release. Maybe a downscale???

Thanks for reading,
-Bob

 

[mh9162013]

Looks good. You should consider doing away with launch lugs on these smaller rockets and use fly/fall away launch lugs instead. As you already observed, a launch lug on a BT-20 or similar sized rocket really stands out.

 

[BABAR]

Looks good. You should consider doing away with launch lugs on these smaller rockets and use fly/fall away launch lugs instead. As you already observed, a launch lug on a BT-20 or similar sized rocket really stands out.

Micro buttons is another option.

 

[Bruiser]

I launched the Mini Tempest on 20 May. It was a very strange launch.

I flew a A10-0T to A3-4T and it staged very quickly like pfft-pfft, maybe a nano-second between. It must have staged right off the rod as I did not even see the booster separate. The booster sustained heat damage and is a loss.


The sustainer had a normal flight. The streamer deployed at apogee and it came down at a nice descent rate but one fin did get knocked lose. I'll just flex it, clean the gap up a bit and re-glue it.

The sustainer will be a full rebuild. I think I will go 18mm this time like I originally had planned. The original Tempest is a 24mm to 18mm so going 18mm to 13mm will be more like the original. I just need to play around with the fins in OR. I'm concerned that they are a little on the small side for a nice tumble recovery.

My one experience with 13mm to 13mm has me questioning the concept. I have a Checkmate kit and I don't want the booster getting torched on it. Anybody else have extremely short boost with the A10-0T motors?

-Bob

 

[kuririn]

Sounds like you had a booster motor CATO.

 

[Bruiser]

Never had a CATO or seen one in person but now that you mentioned it I can see that's a possibility. At first I was thinking that a CATO would have blown the whole thing apart but with it being a two-stage the explosion blew the sustainer off and ignited the motor at the same time.

My eye was on the sustainer so I did not see where the booster went. I walk out after the sustainer and when I got back somebody had put the booster on a table for me.

Thanks,
-Bob

 

[kuririn]

Check your date codes:
https://www.rocketryforum.com/threads/demon-seed-estes-13mm-motors.180335/Those mini engines make for spectacular pics though


After numerous CATOs I only use my older A10s in open ended saucers and spools now.
Newer motors might be OK.

 

[Bruiser]

I just saw a message on Facebook this morning stating there is a potential motor casing issue for mini engines with a lot code that begins with H21.

Guess what lot code the booster I used had?

Gonna have to contact Estes now. The message says they will replace the motors. I wonder if they'll do anything about the destroyed booster... I'll post back when I hear from them

-Bob

 

[kuririn]

I just saw a message on Facebook this morning stating there is a potential motor casing issue for mini engines with a lot code that begins with H21.

Guess what lot code the booster I used had?

Gonna have to contact Estes now. The message says they will replace the motors. I wonder if they'll do anything about the destroyed booster... I'll post back when I hear from them

-Bob

If the motor destroyed an Estes rocket, they'll replace both.
For a scratch built, probably just the motor.
Hoping they give you some kind of credit for the rocket, though.

 

[Bruiser]

I received a package yesterday from Estes. I had two packs of A10-0T motors in it to replace the recalled motors and an Epic II kit. I had explained that the rocket booster that got destroyed by the bad motor was actually a bashed Epic II and they sent me a replacement.

How awesome that is!

-Bob

 

[Bruiser]

I built a new booster for the rocket which was pretty easy. I used the fins from the original and a new piece of body tube. The engine block was actually the inter-stage coupler. Assembly was easy: glue the fins to the tube and glue in the inter-stage coupler. Took longer to paint than build but don't they always?

I sent it for it's first flight in this configuration on Saturday. 18mm C6-0 to 13mm A3-4T. With the overcast sky we lost sight of this one once the smoke trial stopped. I did hear the second stage light so we know it was up there.


We went in search of and had turned to head back in when the sustainer was spotted. We worked our way back in from there but did not find the booster. As we got fairly close someone called out to us that they found the booster. It was not to far from the launch area

I am going to redo the booster back to it's original configuration with a 13mm motor mount in it. Two stage rockets are a lot more fun when you actually see them stage and the tumble recovery booster is easier to find when it stages at a lower altitude.

-Bob

 

[neil_w]

Keep in mind you can always just put an A8-0 or B6-0 in the booster, rather than downsizing to 13mm.

 

[ep29030]

Looking at the booster damage, that was a CATO.

 

[ep29030]

FYI, one thing you can do to reduce black powder damage inside the booster is to slip in a piece of typing paper cut to fit inside. Remeber to punch a hole so the vents still function. The paper takes the heat/powder damage and is then replaced after each flight. It’s an old trick—I think G. Harry Stine was the first to write about it.

 

[Bruiser]

I did add a 13mm motor mount to the booster and it has had a successful flight of 13mm to 13mm. It was a nice flight and got high enough that we lost sight of the sustainer. Luckily one of the spectators saw it coming down when it was about 20 feet off the ground. It's got the same streamer as my mini Black Brant but for some reason you can't see the streamer with the mini Tempest. I am going to change it out for one a bit longer.

-Bob

 

[ep29030]

Use a chrome mylar streamer on sunny days—they flash in the sun and make tracking much easier. Another trick is to put chrome or gold monokote on your fins, or as a band around the airframe—the flash in the sun really helps to track the rocket.

 

[BABAR]

FYI, one thing you can do to reduce black powder damage inside the booster is to slip in a piece of typing paper cut to fit inside. Remeber to punch a hole so the vents still function. The paper takes the heat/powder damage and is then replaced after each flight. It’s an old trick—I think G. Harry Stine was the first to write about it.

This definitely is feasible Since you are doing non-minimum diameter, another option is cut a small ribbon out of an aluminum can to size and slip it in. Since there is no great force on it, and since if you cut it “round” with the can curvature, it will self expand to grip the side, white glue, ca, or epoxy will work. Epoxy is best from a structural standpoint but I don’t like to use it if I don’t have to cuz I need gloves and it stinks.

Given the very short gap between motors (well, I don’t actually see it, but given size looks like a narrow gap) I don’t know if you NEED a vent.

If you decide you WANT one, either the paper or the aluminum ribbon will block your vent holes unless you repunch them.

For non-minimum diameter long gap staged rockets, some preplanning can obviate the need for holes in body tubes for venting. If the gap between the motors is over, say one inch, extend the motor mount most of the length of the booster to about 1/8” below the launch position of the sustainer motor. You can put an aluminum can ribbon inside this extended “chimney” up to the forward end of the mount tube.

Build the mount otherwise as usual, but before installing it in the booster body tube, AFTER the centering rings are glue in, cut about 1/4 inch sections out of the centering rings, ideally lined up with each other. One in each ring should be fine, two if you want. For low power (and probably mid power) this won’t significantly affect strctural integrity. This allows a back channel vent, the gases at booster burn through will initially push forward through the motor mount tube toward the sustainer nozzle. The vents will allow the pre-existing cool gas to exit (preventing a pressure buildup that could otherwise pop the sustainer off like a cork PRIOR to arrival of the hot gases igniting the sustainer.)

This technique avoid cosmetic and possibly aerodynamic compromise of holes in the sides of the booster or sustainer.