Did I screw up my zephyr by using 15 minute epoxy?

[samb]

@overklock the best way to feed your ocd is to start or post to a glue thread. I’ll add to the chorus: “No worries with 15 minute.”
Happy New Year and happy cert flight!

[edit] p.s. the stock chute is good enough.

 

[overklock]

@overklock the best way to feed your ocd is to start or post to a glue thread. I’ll add to the chorus: “No worries with 15 minute.”
Happy New Year and happy cert flight!

[edit] p.s. the stock chute is good enough.

lol yeah, I realized a little too late that glue threads are quite the hotly debated topic around here. Happy new years to you as well!

 

[mtnmanak]

Interesting. So since they have a high Cd, one could use a smaller chute?

Since I've got you on the line here and you have some experience with the zephyrs. Have you ever used a 29mm motor with adapter on them? I'm curious if the ejection charge on a standard G76 RMS is enough to pop the top during ejection.

You absolutely can use a smaller chute if it has a higher Cd - it is the main reason the (eye wateringly expensive) Iris Ultra Compact line of chutes exists. I don't always use the Iris line - on larger diameter rockets you can get by with a larger and cheaper parachute. But the 3" diameter and 4" diameter fiberglass rockets (in my opinion) are exactly where you end up with a perfect storm of size to weight problems. The payload bays start to get really small really fast with larger parachutes. This is a scenario (along with minimum diameter rockets) where the Iris Ultra Compact line really shines.

You absolutely do not need a Fruity Chute for a Zephyr, but a nice Rocketman or Top Flight chute would be a great upgrade at a price that doesn't break the bank.

I have used 29mm motors in Zephyrs, many times. For the most part, when I use motor eject these days, I just add more FFFFg black powder and fill the charge well up on the forward closure of the motor. You don't have a back up, so blow it out or blow it up!

 

[mtnmanak]

BTW - the Fruity Chutes descent rate calculator is fantastic for chutes from many manufacturers:

https://fruitychutes.com/help_for_parachutes/parachute-descent-rate-calculator.htm

 

[overklock]

You absolutely can use a smaller chute if it has a higher Cd - it is the main reason the (eye wateringly expensive) Iris Ultra Compact line of chutes exists. I don't always use the Iris line - on larger diameter rockets you can get by with a larger and cheaper parachute. But the 3" diameter and 4" diameter fiberglass rockets (in my opinion) are exactly where you end up with a perfect storm of size to weight problems. The payload bays start to get really small really fast with larger parachutes. This is a scenario (along with minimum diameter rockets) where the Iris Ultra Compact line really shines.

You absolutely do not need a Fruity Chute for a Zephyr, but a nice Rocketman or Top Flight chute would be a great upgrade at a price that doesn't break the bank.

I have used 29mm motors in Zephyrs, many times. For the most part, when I use motor eject these days, I just add more FFFFg black powder and fill the charge well up on the forward closure of the motor. You don't have a back up, so blow it out or blow it up!

Cd is definitely new for me but this is extremely good to know!

I definitely need to find a source for 4F powder. All I can find in my area is the knock off stuff. Apparently doesn’t pressurize as well.

 

[overklock]

BTW - the Fruity Chutes descent rate calculator is fantastic for chutes from many manufacturers:

https://fruitychutes.com/help_for_parachutes/parachute-descent-rate-calculator.htm

Interesting. So I should be able to match my current descent rate to that of one of their smaller chutes. Thanks!

 

[mtnmanak]

I definitely need to find a source for 4F powder. All I can find in my area is the knock off stuff. Apparently doesn’t pressurize as well.

I have ordered from Buffalo Arms before - very reliable:

https://www.buffaloarms.com/black-powder.html

 

[overklock]

I have ordered from Buffalo Arms before - very reliable:

https://www.buffaloarms.com/black-powder.html

Five lb minimum eh? Definitely going to wind up on a list lol. Maybe I should get my level 1 first before ordering.

 

[samb]

…

I definitely need to find a source for 4F powder. All I can find in my area is the knock off stuff. Apparently doesn’t pressurize as well.

One option, Aerotech ejection charge kits:

https://aerotech-rocketry.com/products/product_16004c76-1095-4679-7c10-8e599082ca2a

Another, ask the locals ( you’re in Cali, right?)

 

[overklock]

One option, Aerotech ejection charge kits:

https://aerotech-rocketry.com/products/product_16004c76-1095-4679-7c10-8e599082ca2a

Another, ask the locals ( you’re in Cali, right?)

Yes sir, California. Pretty much everything is regulated here so I'm always a bit on the paranoid side. Not even sure I can have bulk BP shipped here.

This looks like a great option though. A little expensive, but not a bad choice.

 

[bobbyg23]

Good to hear, main concern was the heat breaking down the bond between the fin and the motor mount/canister. If that' of no concern than great!



I'm using through the wall fins, with the fins epoxied to the motor mount/canister, is it the same in your scenario? If so, great!

1. This was my plan from the start. Almost never attach the parachute to the nose cone, especially those with a plastic loop.
2. Now this is new. Why exactly would I place nomex blanket so much further up, let alone near the parachute? Generally speaking, you want the nose cone to pull the parachute OUT of the nomex blanket, no? If it's that close, I could see a scenario in which the parachute gets stuck in the blanket.
3. I may need some visual representation for that. Normally I just wrap my lines around the folded parachute.



Interesting. I was aware it helped keep a more stable descent, but not aware that it would increase the drag coefficient.

Oof, that price for the fruity chutes though. More than the cost of my rocket for a 36'

Where do you usually put your nomex blanket?

 

[overklock]

Where do you usually put your nomex blanket?

Near the mouth of the rocket. See my pics here: https://www.rocketryforum.com/threa...ny-issue-with-this-setup.176311/#post-2354935

 

[bobbyg23]

Here is how I do my chutes and nomex. 100% success rate.

 

[overklock]

Here is how I do my chutes and nomex. 100% success rate.

Looks really clean. I guess my concern with this setup is that I’m purely nylon. No Kevlar. How would nylon hold up to the ejection charge when not being protected by the nomex?

I unfortunately cannot add a shock cord protector at this point as the cord is securely knotted at the end of the tube

 

[bobbyg23]

Looks really clean. I guess my concern with this setup is that I’m purely nylon. No Kevlar. How would nylon hold up to the ejection charge when not being protected by the nomex?

I unfortunately cannot add a shock cord protector at this point as the cord is securely knotted at the end of the tube

Super easy to add one anytime. Loop in the shock cord then a quick link to hold everything.

 

[NateB]

Five lb minimum eh? Definitely going to wind up on a list lol. Maybe I should get my level 1 first before ordering.

Lists aren't so bad. I got a Christmas card from the ATF one year.

 

[mtnmanak]

Five lb minimum eh? Definitely going to wind up on a list lol. Maybe I should get my level 1 first before ordering.

Ahh, yes, sorry, last time I put in an order, I bought 10 pounds. I didn't even realize there was a 5 pound minimum.

The kit referenced above is good - Buyrocketmotors has them a little cheaper: https://www.buyrocketmotors.com/ejection-charge-kit-12-pack/

Have to agree with the sentiment of asking around locally. I always keep the charges that come with the Aerotech motors and give them away at launches to folks that need them - you should be able to find someone that will part with a gram of FFFFg, no problem.

How would nylon hold up to the ejection charge when not being protected by the nomex?

I unfortunately cannot add a shock cord protector at this point as the cord is securely knotted at the end of the tube

Nylon will hold up fine for a number of launches (it will eventually degrade after exposure to the black powder, but it will take a bit). Easy solution if it is already fixed in place is to just wrap it in tape all the way up from the bottom. Lots of people use duct tape, but I find that gets kind of melty/sticky. The green "frog" painters tape works great and is easy to remove/replace.

 

[waltr]

There are lots of ways that do work.

I've been putting the Nomex just below the Chute attachment and chute has never failed to deploy.
Having the Nomex lower also works fine with added benefit of giving some protective to the shock cord.
Braiding the cord as in the linked thread is also a Very Good idea since it absorbs some of the energy of the nose blowing off and reduces 'shock' loading of the cord and attachment points.

 

[bchaltraw]

Here is a Zephyr with an I235DM single deployment I used for my L1. Now stretching it adding in dual deployment as a test bed. As I read in this thread the landings are what beat them up. I’m in Arizona so hard desert ground is a fact of life. Now I do one wrap of 4oz fiberglass to help with bumps.

 

[msjohnso]

You're fine.

Agreed. There's so much overkill in the strength of even cheap, quick setting epoxies (mixed properly, of course) that the paper and wood will fail long before the epoxy joint gives way.

 

[beeblebrox]

To add to the epoxy temperature thread... This blurb is from NFPA-1125 Manufacture of Model and High Power Rocket motors. Certification requirements.

This is the maximum for the regulation, it does not mean that motors will necessarily get that hot. Generally they do not. Shorter burn time motors don't get as hot as long burn ones also...simple physics of heat transfer.

 

[Zeus-cat]

To comment on the original post; I have built five high power rockets and seen many more being built at my club's weekly meetings. I can't recall anyone ever using a high temp epoxy for attaching fins or centering rings. People only use high temp epoxies for motor retainers.