Some Questions About the CFX Six Footer

[goldlizard]

I have a few more questions about the Sunward CFX Six Footer.
1). Are the paper fin fillets worth using or would I be better off just using glue fillets?
2). Would using nylon nuts and screws to hold the body tubes together in the middle, melt during ejection charge?
3). If so what would be a better way to join the BT's together for flight?
4). I am using an ejection baffle in the upper section, would I need to lower it to protect the nylon screws?

 

[samb]

I don't have a Six footer but I can show you how I modded the tube joints of my Mean Machine. I think the specs on the two are similar enough for comparison. The Six Footer is 78 inches long with a 1.35 (BT-56) inches diameter airframe. Four fins and a 24mm motor mount at the business end. The Mean Machine is 79 inches long with a BT-60 (1.64 inch) body tube.

After reading some flight reports on www.rocketrviews.com and hearing stories from the local rocket crew, I decided that the longevity of this one would be increased by lengthening the tube couplers. This would provide two benefits: during construction the length added guidence to get a straight join. Second, the strengthened airframe integrity during launch and recovery should increase the survivability.

So you can buy some tube coupler material from one of our fine vendors or make your own. I made mine from paper towel cores, printer paper, and white glue. Through trial and error, I found that the core and two sheets of paper (20 lbs, Walmart, recycle printer paper) provided the right fit. The first layer of paper gets a good soaking of glue, like paper mache. The second layer goes on top and really dries up nice and stiff. I used about a four inch length for each tube connection and figured about a 6 gram weight penalty per coupler. I've been very happy the results, flying on D12-3 and Aerotech E11 and E18. Hope this helps.

Here's some pictures of my creation next to the kit supplied 1 1/2 inch coupler and the final result.

 

[samb]

1). Are the paper fin fillets worth using or would I be better off just using glue fillets?

Reinforcing the fin/body joint with paper is an old school but still valid technique. I say yes. Search "tip to tip" to see what the high power guys do with fiberglass layups on fins.

2). Would using nylon nuts and screws to hold the body tubes together in the middle, melt during ejection charge?

Don't have any experience with them. They'd be a couple of feet up from the motor right ?

3). If so what would be a better way to join the BT's together for flight?

Longer couplers like I described oint:

4). I am using an ejection baffle in the upper section, would I need to lower it to protect the nylon screws?

Not quite following that, if the baffle's in the upper section where's the chute compartment ? I take it the baffle is aftermarket ?

 

[goldlizard]

Reinforcing the fin/body joint with paper is an old school but still valid technique. I say yes. Search "tip to tip" to see what the high power guys do with fiberglass layups on fins.

Thinking glue fillets will be fine.

Don't have any experience with them. They'd be a couple of feet up from the motor right ?

Three feet

Longer couplers like I described oint:

Ok

Not quite following that, if the baffle's in the upper section where's the chute compartment ? I take it the baffle is aftermarket ?

I was going to put the baffle in the top tube about 6"-8" below the NC

 

[samb]

Ok, I gotcha. I'd modify it to break in the middle. One of the rocketreviews guys did that and Tim VanMilligan recommends it on the Apogee site.

https://www.rocketreviews.com/sunward-aerospace-cfx-six-footer--by-glenn-little.html
If you haven't already, you should read the build reviews here on this model. At one guy was kinda down on the fin reinforcement method.

https://www.apogeerockets.com/Rocket_Kits/Skill_Level_2_Kits/CFX-Six_Footer

Neither one shows the details but I think it would look like an anti-zipper design:

https://www.info-central.org/?article=132