Variable Drag Project

[Rocketjunkie]

The Estes altimeter needs pretty good sized static ports in the model to work consistently. In that chunk of BT-60 you are using as a payload bay I’d put three 3/32 inch diameter holes (at least).

That said, you’ll find the FireFlys to be easier to deal with if a little harder to actually read.

I have 3 1/8" holes. If I cover 2 holes and suck on the other one, I consistently get good readings, but out on the field if I do exactly the same thing none of them work. (I have 4.) The Fireflys flash the same sequence as the Strattologger beeps so I have no difficulty interpreting the flashes
I intend to give the Estes ones "free to good homes" like kittens for kids.

 

[BEC]

wow, cool to hear that someone figured out how to make an estes altimeter work.. no one i know ever did

The strange thing is that when I set out to intentionally make one fail, I couldn't do it. Even with a nearly sealed small payload compartment, it read a plausible value, and when flown with a FireFly alongside, reported VERY similar results. Truly mysterious.

 

[BEC]

I have 3 1/8" holes. If I cover 2 holes and suck on the other one, I consistently get good readings, but out on the field if I do exactly the same thing none of them work. (I have 4.)

That doesn't make any sense. What else is different between the two situations besides, I'd guess, the temperature? There must be something.

 

[Rocketjunkie]

That doesn't make any sense. What else is different between the two situations besides, I'd guess, the temperature? There must be something.

Temperature and there is some wind on the field, none in the motel room. I did try waiting various amounts of time between turning the altimeter on and potting it into the payload section.

 

[BEC]

Temperature and there is some wind on the field, none in the motel room. I did try waiting various amounts of time between turning the altimeter on and potting it into the payload section.

The Estes Altimeter has no “installation delay”. It starts looking for the pressure change (amount unknown) and, I think, rate of pressure change (again, amount unknown) to trigger it’s “I’m flying” logic. So waiting times should not matter. It’s hard for me to imagine that winds blowing into/across static ports would fool it into not thinking it is flying.

Note, by the way, that the apogee is NOT locked in and pulling the nose cone off the payload section with the static ports blocked will change the result it reports.

All this is really more argument to use the FireFly. Lighter, less expensive and much more consistently reliable. And if you can manage to catch the Firefly Field Data Display in stock on perfectflitedirect.com then you can just plug it in and read altitude, max speed, flight time, and descent rate from the display.

 

[Rocketjunkie]

The Estes altimeters never show a liftoff detect. They still read 0 on recovery. I'm moving to the 4", it will recover dual deploy with the Strattologger CF and so doesn't need a second altimeter.

 

[Rocketjunkie]

Received the box of LOC parts today. Will be referred to as TV400. Enough parts for 2 boosters, 4 payload bays, and 1 set of 6 plates.

This is the first time in over 30 years I've gotten LOC nose cones that weren't white The white one is the nose cone from my original (1989) EZI, the only part of the rocket I still have. Also parts to repair You Gotta Be Nuts! that was damaged by a J99 cato.

 

[Rocketjunkie]

The plates on this one will be slightly smaller than the direct scale of the TV60, 7" instead of 7.31" giving a triangle size of 10.39". Tube fins will be 1/6 of a 34" tube (5-5/8"), main body will be 1 34" tube, and main chute bay will be 1/2 of a 34" tube.
I also mixed up 4 2 grain 54mm J220s (700 N-s). Planning a set of flights at the April ICBM launch.

 

[BABAR]

Does airflow over the vent holes distort the measured altitude?

 

[Nytrunner]

Older altimeters could be spooked by turbulence at mach. Then youd have to set a mach delay period so it wouldnt deploy before then.

These days the altimeter is pretty good about ignoring the fluctuations through boost/coast and reading the final altitude in "still" air.

 

[Rocketjunkie]

Start construction with avbays. Started with 1/2" OD, .120 wall aluminum tubing. ID of .260" is just right for 5/16" UNC threads, so cut to 5-5/8" long and tap both ends. Enlarge center hole of bulkheads to 5/16".

Picture shows all 4 rods with 5/16" eye bolts along with centering ringsand bulkheads.
Next picture shows dry fit of altimeter bay, then with altimeter. All my rockets have this style altimeter bay so I can use any altimeter in any rocket.

Altimeter bay fitted in coupler, rear, inside, and front.

 

[Rocketjunkie]

Couplers cut for the other 3 bays

Epoxy the bulkheads and threads on the forward end of the center rod.

Repeat 3 more times for the other 3 bays.

 

[Rocketjunkie]

Add 50" chutes, main recovery harness, and nose cones to payload bays.

17 and 18 shows how I add eye bolt to nose cone. Forged are not necessary here as they only need to withstand the weight of the nose cone.
Begin work on thrust plates and booster bodies.
Thrust plates with template I used to mark the plywood. The line from the round portion to directly out is 7".

Thrust plates with 4" long couplers

Stop and prep other rockets for this weekend's ROSCO launch near Camden, SC

High Tech H45 on CTI H54, Motoreater on J460 and 2 H97, Deuce on 2 J150, and 3" Tuber on I59.

 

[Buckeye]

Why are 4 rockets needed? Can you make the modular drag plates removeable/configurable on just one rocket?

 

[GlenP]

Why, so you can have a DRAG RACE, of course!

 

[Rocketjunkie]

Why are 4 rockets needed? Can you make the modular drag plates removeable/configurable on just one rocket?

For the 4", I'm building 2 rockets. I prefer to preprep the rockets at home so that's why I have 4 payload sections. There was not much difference in cost between 1 booster section and 2 so I went ahead and got enough parts for 2 boosters. The drag plates are removable and can be moved from 1 rocket to another. The 7.5" version will be only 1 rocket.

 

[Rocketjunkie]

The Camden launch scheduled for this weekend was cancelled . Standing water on the field, Looks like Sunday would have been perfect, sunny, high low 60s, and light wind never going above 4 mph.
So, back to work on the TV400s.
Cut tube fins and seal the edges with CA

Align with bulkhead, coupler, and tube fin then wood glue the bulkhead to drag plate. Wood glue the coupler next. Once the wood glue dries, use epoxy to fillet the bulkhead-coupler joint.

Repeat for the other 5 drag plate assemblies They're on the TV60s flown on D and E motors.

 

[beeblebrox]

The Camden launch scheduled for this weekend was cancelled . Standing water on the field, Looks like Sunday would have been perfect, sunny, high low 60s, and light wind never going above 4 mph.
So, back to work on the TV400s.
Cut tube fins and seal the edges with CA
View attachment 408514
Align with bulkhead, coupler, and tube fin then wood glue the bulkhead to drag plate. Wood glue the coupler next. Once the wood glue dries, use epoxy to fillet the bulkhead-coupler joint.
View attachment 408515 View attachment 408516 View attachment 408517 View attachment 408519
Repeat for the other 5 drag plate assemblies They're on the TV60s flown on D and E motors.
View attachment 408518

Where is the Camden you reference? If you mean Camden NJ, give me club contact info for future reference!

 

[Rocketjunkie]

Where is the Camden you reference? If you mean Camden NJ, give me club contact info for future reference!

Camden, SC. About 1/2 hour east of Columbia. Home of ICBM and ROSCO clubs. Info in the group rocketrysouthcarolina on Facebook, some info at rocketrysouthcarolina.org

 

[Rocketjunkie]

Continuing the build.
54 mm motor mounts, 12" long
Attach tube fins to booster section.
Then install motor mount
I did install the nuts that came with the CRs but they will need longer screws to clear the motor tube. I just tape in the motor.
Shock cord mount, a length of shock cord and a blob of epoxy. This is like the old style LOC string mount but far less likely to zipper.
Apogee harnesses. About 40ft. long. The regular quick link fits on the booster shock cord mount, the longer one is needed to fit over the 5/16" eye bolt on the altimeter bay. View with booster sections
Also mixed up 4 2 grain 54 mm white J220s. About 700 N-s. They use the small hole closure and 29 mm nozzle. Lots cheaper than a 54 mm nozzle.

 

[Rocketjunkie]

Next, I sanded the oversize from the drag plates until they fit.
TV400-6
TV400-4 TV400-2 TV400-0
Both boosters,one with all 6 plates, the other with none.
All that's needed are rail buttons in tube 6 for when not flying all 6 plates. If all 6 are used it will fly off a 1/2" rod between the tube fins. The rail buttons will be surface mounted, 1 inside tube fin and 1 above it. See next post coming within a few days.

 

[Rocketjunkie]

(TV400 47, 50) Glue on nuts with rail buttons on them.
(TV400 52, 53) Bend flanges to fit 1 for outside of BT, the other for inside of fin.
(TV400 54, 55, 56) Nuts installed on 1 booster. Repeat for the second.
(TV400 57, 58, 59) Roll launch lug 9/16" ID, 4 layers thick from gummed paper tape. Last picture shows a 1/2" threaded rod in launch rod configuration.

 

[Rocketjunkie]

Finishing up the TV400 build.

Apply 2 coats of filler primer to drag plates, sanding 220 then 400 grit after each coat.

A single plastic rivet prevents the drag plates from rotating when using less than 6. You can see the other booster with rivet holes in the background.
This completes construction of these test vehicles.

 

[Nytrunner]

I missed it apparently, how do you secure the plates to the rocket so they don't get blown out the back?

 

[Rocketjunkie]

I missed it apparently, how do you secure the plates to the rocket so they don't get blown out the back?

The plates have a 4" section of coupler that fits into the tube fin. See the plate construction in post #47. The loads are asymmetric, so the load tends to jam the coupler. In addition, there is a rivet, that in addition to preventing rotation, also prevents the coupler from slipping out. In the TV60, I just used a small piece of masking tape to make sure the coupler stayed in. These rockets are NOT designed to go any where near supersonic!

 

[Nytrunner]

Doh, the rivets!

Hopefully that'll keep things nice and secure, and the scale up of the area won't turn into killer drag on the plates

 

[Rocketjunkie]

4" TV400 rockets ready to fly. Project on hold until HPR launches resume.

 

[Rocketjunkie]

Finally got to fly at the October launch. I used CTI J244 motors.
TV400-2 728'
TV400-4 515'
TV400-6 460'
I did not fly the TV400-0 due to winds aloft. My Nuts rocket, the same size and less than 1 lb. heavier, goes 2300' on a J275.
The TV400-4 scorched the main harness and it failed. Nose cone recovered on the main chute. The rest fell without chute and landed directly on the irrigation pipe breaking it.

 

[Rocketjunkie]

Flew the TV400-0 on a J275 to 2900 feet.
Last weekend I flew the set on Rx J220's (700 N-s)
TV400-0 2481'
TV400-2 582'
TV400-4 464'
TV400-6 cato on pad
All 4 launches in this video

 

[cwbullet]

Sad ending. This has been a greta project to follow and a good concept to keep rockets on a smaller field. You can test a higher flying motor without a trip to the trees.