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rfjustin

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Ok I was thinking that even for a 54 min. dia. rocket 2oz is a little thin. So do you just wet out the airframe and fins, lay the glass on, brush the epoxy in, and call it good? If the finish is decent I will probably go with that.
That's pretty much all I do. I would recommend 4 oz for fin to fin on a 54mm bird. Its really not needed on a Mach 2 though. If the fins are straight, and you have beefy fillets, you should be good to go.
 

Rocketman_dan

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That's pretty much all I do. I would recommend 4 oz for fin to fin on a 54mm bird. Its really not needed on a Mach 2 though. If the fins are straight, and you have beefy fillets, you should be good to go.
Ya I know that it definitely doesn't need it but I want to learn. Good to know I can get a decent finish without peel ply.
 

Rocketman_dan

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That's pretty much all I do. I would recommend 4 oz for fin to fin on a 54mm bird. Its really not needed on a Mach 2 though. If the fins are straight, and you have beefy fillets, you should be good to go.
Do you use any sort of peel ply when doing tip to tip like this?
 

CPUTommy

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Justin , just awesome clean clean work. I Have a similar rocket and will be using this thread to build it.

What do you think will be the highest altitude you could reach ?

Tom
 

Rocketman_dan

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Justin , just awesome clean clean work. I Have a similar rocket and will be using this thread to build it.

What do you think will be the highest altitude you could reach ?

Tom
I am no expert but I believe you could get 50K on a 75mm motor in a single stage configuration. Two stage is where you can really get serious altitude. I run a rocketry program, soon to be class, at my high school and we are going to build and modify a Wildman falcon 98 and send it up to around 50,000 with an N motor. I believe if it is HIGH ALTITUDE you want you might want to move up to a 98 mm tube. The configuration you are using being similar to a mach 3 I bet that you would have NO issues getting it to right around 40K if built properly.
 

plugger

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I am no expert but I believe you could get 50K on a 75mm motor in a single stage configuration.
Maybe at Black Rock on a good day but I it would be tight (I suspect). Both Nic Lottering and Curt von Delius have broken 45k ft with a 75mm M motors but unless you're swapping the aluminum motor casing for a CF one my suspicion is that 50k+ is a very hard target.
 

MichiganJohn

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Justin this a great thread, thank you for sharing. I've been studying it to prepare for my first minimum diameter build.

Couple questions:

1) Did you route a pocket into the root edge of the fin, is that what this is? Is the purpose to hold epoxy and provide more bonding surface area?

1613748007175.png


2) Once the drogue anchor/ engine retention plate is is epoxied in, what is your method of connecting the motor casing? It appears that the hardware was not set when you epoxied it in place - do you drop your bolt in through the top and hold the head with a socket extension to tighten up the case?

1613748457855.png
 

rfjustin

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Justin this a great thread, thank you for sharing. I've been studying it to prepare for my first minimum diameter build.

Couple questions:

1) Did you route a pocket into the root edge of the fin, is that what this is? Is the purpose to hold epoxy and provide more bonding surface area?

View attachment 451346

2) Once the drogue anchor/ engine retention plate is is epoxied in, what is your method of connecting the motor casing? It appears that the hardware was not set when you epoxied it in place - do you drop your bolt in through the top and hold the head with a socket extension to tighten up the case?

View attachment 451347
1. No, I simply scuffed the root edge of the fin with 80 grit, and what you are looking at it a healthy bead of 5 minute epoxy. Notice the "dry" area at the front and back of the fin where there is no 5 minute epoxy, this is intentional. Once the fin is on the airframe and confirmed to be straight and true, hit the front and back of the fin with some thin CA to lock it down quickly.

2. The motor would have a 3/8" threaded rod bolted into the forward closure, which passes through the center hole. I drop a washer, lock washer, then a stop nut, and yes a socket extension is used to reach down into the cavity and tighten it up. Don't over torque locking the motor in place. If you do, you risk popping the plate loose.

Best,
 

MichiganJohn

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1. No, I simply scuffed the root edge of the fin with 80 grit, and what you are looking at it a healthy bead of 5 minute epoxy. Notice the "dry" area at the front and back of the fin where there is no 5 minute epoxy, this is intentional. Once the fin is on the airframe and confirmed to be straight and true, hit the front and back of the fin with some thin CA to lock it down quickly.
That makes sense, good idea - I noticed the CA at the front tip in another pic. (for some reason my brain saw that line of 5-min as a pocket, maybe the thin white line of reflection along the top section tricked my eyes). Thanks for the tip on the motor retention too.
 
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