Nose weight for 4xE9 Phoenix cluster?

[pdooley]

I wanted to give my Phoenix some extra kick, so I ordered a BT50 cluster center ring kit from Thrustline.

The kit allows flight on 2 or 4 E9's.

Unfortunately, from what I have heard, the Phoenix is not a stable flyer. Some extra nose weight is in order.
I was thinking of weighting 2 different cones for 2x or 4x launches.

I don't have rocsim, so am kinda lost now.
With all the extra motor weight, how much nose weight would I need for each configuration?

 

[wwattles]

For 4 E's, you'll need about 6 1/2 oz of nose weight. The thing flies beautifully on about 7, but you'll also want to consider the strengthening the heat-resistance of the fin can.

The proximity of the exhaust nozzles to the side of the BT, plus the depth inside generates a LOT of heat on the inside of the tube, and unless you line it with either a layer of epoxy (unreliable) or some foil tape, you'll burn through your fin can in a single flight!
Also make sure you have a stand-off from your blast deflector or the back of your fins will get badly scorched.

These pieces of advice are from the voice of experience with my FrankenPhoenix.

WW

 

[wwattles]

By the way, you'll want a 7-second delay... anything shorter and you'll destroy your chute and zipper your BT!

WW

 

[Ryan S.]

I have heard of people who cut soda cans and then stuck them inside the tubes.

 

[pdooley]

My Phoenix kit is still in the bag, but I was thinking about mounting the motor can flush with the end of body tube. The rear centering ring would be at the end of the body tube, the motors would stick out approx 1/2 inch.

I don't know if this would make the rocket unstable, I assume the original kit mounts the motor further inside the tube to help the CP/CG relationship.
I would be willing to add a little more nose weight to mount the motor can further back. I really haven't looked at the thing too much, I might be all wet.

Any thoughts, ideas, suggestions?

 

[wwattles]

I played with that idea a bit too, but doing so means adding a LOT of noseweight. All that fin area means the CP is very far forward, and the whole reason Estes put their mount so far inside is to make the thing stable with a minimal amount of noseweight added.

WW

 

[pdooley]

So the answer looks like foil tape or a soda can.
That's cool. I would hate to have to rebuild the thing after one flight.:kill:

Maybe some thin CA, or is that for strength only?

 

[RocketSmokEater]

i just recently finished my stock-built Estes Phoenix, but with a small color scheme twist as you'll notice in the pix. a color inversal if you will. i like this deviation much better than the white!

regarding strengthening the aft-end fin can of the rocket [supposedly in order to prevent those rear fins from snapping off on hard landings], what i did was just take some light/mid cardstock and cut it at the exact circumference and depth dimensions of the fin can. the formula i used to cut the exact size needed was as follows:

simple circle circumference formula: c = 2(pi)r, where "r" is the radius and "(pi)" is 3.14 of the diameter of the BT (in the Estes Phoenix's case, 2.6"). and of course the "c" is circumference. my results were a cardstock length of 8.164" by approx. 3.5" BT depth from the aft end lip to the rear CR. remember to test fit it first and lightly trim just to make it a perfect fit.

using a nice even layer of wood glue around the entire inner fin can structure, i just carefully slipped in the piece i cut and secured it all around. after a few hours the wood glue dried and i coated the entire inner surface of the fin can with water-thin CyA followed by light sanding with a #400 grit sheet. the whole fin can now is nearly rock solid! i only added 1oz. of the suplied clay (2 bars) in the NC for weight. no further balancing/adjustments needed - i even verified it with someone who has RockSim. by the way, the cardstock i used was the backing paper that Epson puts in with it's photo-quality ink jet papers - some may know what i'm talking about. i kept some of those sheets for random uses such as this.

pics included.
RSE

 

[RocketSmokEater]

and here she is, in full view on my deck.

 

[pdooley]

sweet. nice color/paint/decals..

 

[wwattles]

Here's the aft view of my phoenix's motor mounts, after 3 D's (the fourth failed to ignite). The lining was a foil tape. Note that the edge where the tape didn't cover fully got completely scorched.

WW

 

[wwattles]

This is the forward end of the motor mount. That thread sling is 80 lb kevlar. Just to give you an idea of the power of what goes on inside your rockets when the ejection charges fire!

WW

 

[wwattles]

By the way, Pdooley,

As for the nose cones with different weighting, I solved the problem by putting strips of industrial strength velcro into a hollow nosecone (the standard-issue stock one in the packaging worked well), and got some pinewood car weights from my local hobby shop. I just velcro in the right amount of weight and let 'er fly!

WW

 

[pdooley]

I called Christine at Estes and got 4 nose cones out of her, $4 bucks each. She threw in one for free
Sooo, I have plenty of NC's to experiment with..

I like the epoxy/BB method, and after seeing that cooked fin can, I may just move my motors back and load the NC up with weight.

We can do a "dueling banjo" thing, see how each model flies and holds up over time.