Tri-Ceptor Scratch build

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burkefj

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I've been on a run doing RC conversion of Estes Interceptor E and Cosmic Interceptors, I got the wild ida to do a rocket only variation, use the interceptor nose cone and parts from the Cosmic Interceptor kit, and build it as an astron trident type rocket, make the fins raked forward with antennae and call it the Tri-Ceptor.....patent now pending:) One cosmic Interceptor would get the main body tubes and nose cone, you'd need to provide the cone for the rear body and the rear cone for the frontand add the side tubes (heavy foil lined 34" bt-50 from bms) and cones (two pnc 50 packs from estes) and then the fins from ply or basswood....I think it would look really good. 2" main tubes, heavy bt-50 foil lined side tubes....maybe re-use the cosmic interceptor rear end for a little detail shown in the photo....Parts now ordered....man, my mindsim has been on hyperactive this week...I need to take something to calm the heck down......


Parts and cost would be:

Cosmic Interceptor($16.99 from estes currently)
Use the motor mount unit, and the two 13.5" body tubes and the nose cone.
3 34” bt50’s for side tubes from bms(use 34" as they are available) $3 each
2 2" diameter estes nose cones $4.29 each
two Estes BT-50 nose cone packs or six bt-50 nose cones that you like..$5-$8 each

Total for the major parts $45-$50 for a pretty large model isn't bad.
 

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Got my foil lined bt-50 tubes from bms today, still waiting on the Cosmic Interceptors to arrive maybe tomorrow to get started.

Frank
 
I may put my fins ttw inbetween the connecting body tubes instead of ttw through them, otherwise it would block the ejection gas path through the tube, I don't want to do surface mount on them...I don't think it will change the look significantly.
 
Here it is with the fins rotated to allow ttw through the main tube, I'm thining I'll mostly fly F-32's, shows around 900' which is plenty for me. Fins are the same size as my RC rocket glider kit so I can use the same vinyl from stickershock on them and the body.




Frank
 

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Got my Cosmic Interceptor kits today and the nose cones, made pretty good progress.

First I wanted some bit of mechanical attachment for the tube that would carry the ejection charges because some of the bonding area would be removed for the holes, so I made some aluminum conduits that pass through both tubes and help support the glue joint. I attached those with CA to the main tubes. Next came attaching the tube bypass tube to the upper and lower tubes with epoxy. I did a quick "blow" test to make sure that I had sufficient pressure with the hole sizes I used to blow out the nose cone/laundry. I then attached one of the lower bt-50 tubes to help keep things straight.

I attached a ply disk to the upper and lower nose cones so that they would seal the motor and parachute sections off(ie no leakage of ejection gasses), added a screw eye to the forward cone to attach the recovery gear to and epoxied them both in place. I then attached the other lower bt-50 tube and added the little forward and rearward cones to both of them. Since I had two of the pnc50 sets, I was able to get a matching forward and rearward cone set for the lower tubes and then used slightly different front/back tubes for the upper bypass tube, I think it looks ok like that.

I structured it so that the top of the model with have the bypass tube and the two vertical fins will make the characteristic Interceptor V shape, the two lower bt-50 tubes will be on either side and there will be the final fin on the bottom. I then mocked up the motor mount just to see what it would look like. The one fin is a cardboard template. next up to finish the fillets on the tube to tube joints and then slot for the fins. So far it's at 15 ounces and 64" long. About three more ounces for the fins.

Frank

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Made the first fin and slotted and test fit it, it goes through to the motor tube through the main tube and coupler. I painted the motor extension flat black and the inside of the rear ring flat black and put some silver trim monokote on the outside. Sets it off nicely.

Frank

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Cut and fit the remaining fins and mounted the ply plate to the base of the cone and put the eye screw in place. I decided not to use the motor hook as I'll either tape the motor to the rear of the tube or fit a 24mm retainer.

So far from the Cosmic Interceptor kit I've used

The two main body tubes
Nose cone
The coupler/motor mount unit with decorative strakes/ring, I did substitute a piece of foil lined bt-50 for the motor tube, it wasn't required but I thought it might help longevity around the forward ejection area..

Added three 34" foil lined bt-50 tubes
Two PSII 2" estes nose cones
two packages of BT-50 cones from estes(used six of the 10)
Ply fins

Right now the weight is 18 ounces which is close to plan, the CG dry is right at the front of the rear cone tip, the CP is right in front of the fin strake so I think I won't need any nose weight..I'm going to mount the rail buttons on the bottom of the right hand lower bt-50 tube since there isn't a way to get to the main tube since I've mounted the fins onto the main tube, but there shouldn't be any problem putting them there.

I'm thinking it will be white with the us air force and stars/bars on the forward section, red stripes down the sides of each connecting tube, the tail markings from the normal interceptor..put the FU-803 number on the rear body tube section.

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I'm not quite sure what to do, there aren't any wings or foam on this model....I feel helpless....:)

I added the kevlar line and nomex and chute and put a reinforcing ring at the top to help prevent zipper, used a double thickness of the extra tube that comes in the kit for the intake scoop. 22 oz, so probably 26 finished less motor.

Frank
 
Did the primer and sanding last night, then a couple of coats of tamiya white laquer rattle can. Got the stickershock markings for my IntR/Ceptor kit in the mail, did a few modifications and added a few red/blue strips and some black/silver accents and then used a sharpie in the panel lines for the nose cone. 24 ounces less motor. Came out not too badly, need to pick up some F-32's now.

Frank

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Perfect flight today on an F-35 at the Tri-cities rocketeers launch site!

[video=youtube_share;tP_bXxbMJdk]https://youtu.be/tP_bXxbMJdk[/video]
 
Flew my tri-ceptor this weekend on the softest but biggest 24mm G motor from cti I could find, a G-65, flew great to 1800', it did not pause at all, just boom, off the pad....

[video=youtube;v5OiL0rZj7s]https://www.youtube.com/watch?v=v5OiL0rZj7s[/video]
 
Got in three more flights this weekend.

First flight, the cti motor did not eject the chute, however fortunately the rocket stabilized completely horizontally spinning with about a 10 fps decent rate and landed in a small patch of the only soft weedy area in our field for a no damage recovery. Everyone was amazed that a long rocket like this that is over stable stabilized horizontally, must be due to the wind going through the triple tubes and the fin shape.... Turns out the cti g65 motor delay did burn but there was a rubbery material blocking the ejection charge hole, the powder was fine.

Second flight I removed the ejection charge cap and charge and used a small flat screwdriver to ream out the hole slightly to make sure there was nothing blocking, added new powder and flew it to a nominal flight, only problem was that one shroud line caught on a rail button so the chute was partially deflated, again no damge.

Third flight was perfect with perfect recovery, except on retreival we found the motor casing had ejected along with the chute, but we tracked back to around the ejection point over the field, and Gary Fillible, Glenda and my wife walked a line and my wife found the case within about 5 minutes! I left an extension on the motor tube and had been using masking tape retention and not had any issue, however I may have to break down and fit a 24mm motor retainer since due to the porting of the gasses there is significant back pressure not existing on a normal open stuffer tube design.

I like the burn characteristics of this motor, but I'm not real happy with the cleanup, even with greasing liberally, the 24mm moon burner burned through the liner every time, about 2/3 of the liner length leaving a very rubbery deposit on the inside of the casing that was only removed with scraping with a hard chopstick or aluminum rod with a sharp end, which took about 15 minutes each time. So much for cti reloads being load and remove, easy peasy....ready to fly immediately:) However they are currently the only maker of a G class 24mm motor so what are you gonna do...

I got lots of nice comments on the design and look though and it flew nicely to around 1800' each time nice and straight.

Frank
 
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It was great to see this flying this weekend, Frank. I didn't see you after the second flight, saw it come in under a fouled chute and am glad there was no damage on that landing.
 
Thanks Ryan, was great to see you and Jim come down from Washington. I just broke down and ordered an aeropack retainer for the larger l2 tubing and a 3 grain case from appogee since I do have a 24mm F-30 reload which should put it up at around 1000'
 
Well to be fair, it goes 3.5x higher than my gliders:)

Here's the video of the tumble recovery:

[video=youtube;vb7W70jDERs]https://www.youtube.com/watch?v=vb7W70jDERs&feature=youtu.be[/video]
 
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Well to be fair, it goes 3.5x higher than my gliders:)

Here's the video of the tumble recovery:

[video=youtube;vb7W70jDERs]https://www.youtube.com/watch?v=vb7W70jDERs&feature=youtu.be[/video]

That recovery throws me. How does a rocket which is stable on boost, after burning off all the propellant ( which if anything should make it MORE stable/nose heavy) transition to horizontal spin recovery? It obviously DID happen, and given such a nice rocket I am glad as I am sure you are that it happpened, but I don't understand it. Did the motor mount shift back?
 
I have no idea, motor didn't move, rocket is at least 2 diameters stable at launch, so closer to 3 at burnout, I assume the spinning of the fins and the flow through side tubes have some effect..

Frank
 
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