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

[overklock]

In pretty much all of my rockets 29mm and below, I've always used standard 15 minute epoxy for internal fillets and fin mounting, and then rocketpoxy for external fillets.

After reading a few threads here, I've realized it's generally a better idea to use a high temp epoxy to connect the fins to the MM/internal fillets.

Unfortunately, the fins and internal fillets are connected to the MM using standard epoxy. External fillets have been created using rocketpoxy, and JB weld has been used on the motor retainer.

Question: Keeping in mind that the Zephyr is a paper rocket, how likely is it that my Zephyr is going to crash and burn due to internal fillets melting? Total burn time being roughly 3 seconds before engine burnout.

 

[dhbarr]

You're fine.

 

[Hobie1dog]

zero chance, or almost zero.

 

[overklock]

You're fine.

zero chance, or almost zero.

Cheers!

 

[Hobie1dog]

losing your rocket is usually the worst thing that can happen.

 

[overklock]

losing your rocket is usually the worst thing that can happen.

Main concern here is that I'm going for my level 1. I've got two rockets. Both of them built using the same method with the 15 minute epoxy being the primary weak point. Hoping that the external fillets keep everything bonded enough for a solid landing.

 

[MClark]

I use Home Depot 5 minute for everything

 

[overklock]

I use Home Depot 5 minute for everything

Considering that's where I got mine, that's great news!

 

[Hobie1dog]

Main concern here is that I'm going for my level 1. I've got two rockets. Both of them built using the same method with the 15 minute epoxy being the primary weak point. Hoping that the external fillets keep everything bonded enough for a solid landing.

take both Rockets with you to the launch

 

[Steve Shannon]

As everyone else has responded, you'll be just fine. I use Bob Smith 5 minute epoxy to tack fins down and then 15 or 30 minute epoxy to do fillets on cardboard rockets.
You will never destroy epoxy with heat in a through the wall design; not nearly enough heat is transferred unless the motor has some kind of failure. Also, epoxy is a thermosetting resin. It doesn't melt. If you heat it to the point where it softens, you have destroyed it. The outside of metal motor cases just doesn't reach that temperature.

 

[overklock]

As everyone else has responded, you'll be just fine. I use Bob Smith 5 minute epoxy to tack fins down and then 15 or 30 minute epoxy to do fillets on cardboard rockets.
You will never destroy epoxy with heat in a through the wall design; not nearly enough heat is transferred unless the motor has some kind of failure. Also, epoxy is a thermosetting resin. It doesn't melt. If you heat it to the point where it softens, you have destroyed it. The outside of metal motor cases just doesn't reach that temperature.

Thank you, your posts are always helpful.

Looks like the epoxy i'm using is rated at 180F. You'd say it doesn't get that hot?

 

[Sandy H.]

When I BAR'd (early 2000's) there were a lot of people talking online (here and RP) about whether they should use 4oz or 6oz to do tip to tip fiberglass for their level 1 rockets. Most of the old guard were saying "WHY ARE YOU DOING FIBERGLASS FOR AN L1!!!" or similar. I followed both paths - way overkill on fiber-glassing cardboard tubes for mild motors and wood glue and cardboard for bigger motors. It has been a learning experience for me for sure.

I can say for fact that a LOC Lil 'Diter kit built with 5 minute epoxy, no big fillets and no paint can fly on an I-435 multiple times without failure. Cardboard, plywood, right at mach. Most of the damage the rocket had was on landing, not flight, but for fact a fin or two delaminated during flight right at mach transition after a few landings. A fin never turned loose due to the 5 minute epoxy.

I've never built an Apogee Zephyer, but if it is cardboard and plywood, I bet it will be fine, just like everyone with more experience than me said above.

The biggest challenge you'll have on a rocket when you are moving from MPR to HPR is reliable ejection (motor based - make sure you build it right) and parachute inflation (i.e. get the ejection timing right and also make sure things are packed properly). Both of those challenges can be greatly helped by asking a club member who is a consistent flier for advice. If they consistently auger one in the ground, ask someone else, but if they consistently fly well and recover well, ask for them to coach you and/or look over your shoulder during your first prep or two. All, IMO, of course.

Sandy.

 

[Steve Shannon]

Thank you, your posts are always helpful.

Looks like the epoxy i'm using is rated at 180F. You'd say it doesn't get that hot?

It doesn’t get that hot. Not enough heat transfers into the epoxy to cause an issue.

 

[overklock]

When I BAR'd (early 2000's) there were a lot of people talking online (here and RP) about whether they should use 4oz or 6oz to do tip to tip fiberglass for their level 1 rockets. Most of the old guard were saying "WHY ARE YOU DOING FIBERGLASS FOR AN L1!!!" or similar. I followed both paths - way overkill on fiber-glassing cardboard tubes for mild motors and wood glue and cardboard for bigger motors. It has been a learning experience for me for sure.

I can say for fact that a LOC Lil 'Diter kit built with 5 minute epoxy, no big fillets and no paint can fly on an I-435 multiple times without failure. Cardboard, plywood, right at mach. Most of the damage the rocket had was on landing, not flight, but for fact a fin or two delaminated during flight right at mach transition after a few landings. A fin never turned loose due to the 5 minute epoxy.

I've never built an Apogee Zephyer, but if it is cardboard and plywood, I bet it will be fine, just like everyone with more experience than me said above.

The biggest challenge you'll have on a rocket when you are moving from MPR to HPR is reliable ejection (motor based - make sure you build it right) and parachute inflation (i.e. get the ejection timing right and also make sure things are packed properly). Both of those challenges can be greatly helped by asking a club member who is a consistent flier for advice. If they consistently auger one in the ground, ask someone else, but if they consistently fly well and recover well, ask for them to coach you and/or look over your shoulder during your first prep or two. All, IMO, of course.

Sandy.

Thank you for the in depth reply! After quite a bit of searching, I've found that glues are quite the debated topic on this forum. Hearing that you flew on an I with 5 minute epoxy on the fin can puts my mind at ease.

It doesn’t get that hot. Not enough heat transfers into the epoxy to cause an issue.

Good to know. Wasn't too sure, those motor casings always feel quite warm after a flight!

 

[thzero]

As everyone else has responded, you'll be just fine. I use Bob Smith 5 minute epoxy to tack fins down and then 15 or 30 minute epoxy to do fillets on cardboard rockets.
You will never destroy epoxy with heat in a through the wall design; not nearly enough heat is transferred unless the motor has some kind of failure. Also, epoxy is a thermosetting resin. It doesn't melt. If you heat it to the point where it softens, you have destroyed it. The outside of metal motor cases just doesn't reach that temperature.

And if the motor has some kind of failure... its going to probably burn through, but even then outside of the burn through area, it'll still hold together.

 

[thzero]

The biggest challenge you'll have on a rocket when you are moving from MPR to HPR is reliable ejection (motor based - make sure you build it right) and parachute inflation (i.e. get the ejection timing right and also make sure things are packed properly).

Its exactly the same as mid-power. There is no magic here going from a G to a H. As long as you follow the same techniques that successfully eject an F or G you should have no issues with a H powered.

 

[bobbyg23]

This is not an issue at all. I build a lot of cardboard rockets with 15 minute epoxy. I fly 54mm k motors on them. Zero issue with the epoxy. You are good to go.

 

[Sandy H.]

Its exactly the same as mid-power. There is no magic here going from a G to a H. As long as you follow the same techniques that successfully eject an F or G you should have no issues with a H

Fair enough and I agree. I think often people fly smaller motors to lower altitudes on lighter rockets with LPR/MPR, but when going to HPR the weight often builds more than it needs to and the failure modes may be the same but the impact of those failures tend to get bigger.

I agree 100% that good practices at the MPR level translate very well to L1/L2 HPR, but that's the limit of what I can comment on as I have not attempted L3.

Nonetheless, I think our friend overklock is in good shape for the L1 attempt!

Sandy.

 

[overklock]

And if the motor has some kind of failure... its going to probably burn through, but even then outside of the burn through area, it'll still hold together.

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!

This is not an issue at all. I build a lot of cardboard rockets with 15 minute epoxy. I fly 54mm k motors on them. Zero issue with the epoxy. You are good to go.

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!

 

[overklock]

Fair enough and I agree. I think often people fly smaller motors to lower altitudes on lighter rockets with LPR/MPR, but when going to HPR the weight often builds more than it needs to and the failure modes may be the same but the impact of those failures tend to get bigger.

I agree 100% that good practices at the MPR level translate very well to L1/L2 HPR, but that's the limit of what I can comment on as I have not attempted L3.

Nonetheless, I think our friend overklock is in good shape for the L1 attempt!

Sandy.

Cheers! Wish me luck!

 

[Steve Shannon]

Cheers! Wish me luck!

Good luck!

If you ever want to set your mind at ease, put a gob of epoxy on a piece of cardboard. Let it set for 24 hours. Now, heat the other side of the cardboard until the epoxy softens. You’ll have proven to yourself how difficult it is to damage epoxy. It takes a lot of heat and it doesn’t happen instantly. And that’s just for the first layer. In a through the wall fin setup, if you have good internal and external fillets on the body tube, you could never deliver enough heat inside the motor mount tube to soften the body tube fillets unless you’re burning out the motor mount.

 

[mtnmanak]

I have built a number of Zephyrs - first with 5 min epoxy, now I just use wood glue when I build them. The ones with epoxy are no longer in service (crashes due to recovery failures, not build issues). Most of the ones with wood glue are going strong.

I like to use Zephyrs and LOC IV's as test beds for things like new electronics, configurations, deployment mechanisms, etc (hence the recovery failures). When testing out something new, I would rather lose a Zephyr or LOC IV than a large FG rocket. Point is, I am now building my Zephyrs and LOC IVs with wood glue, so 15 min epoxy will be more than good enough.

Good luck on your Level 1!

 

[mtnmanak]

I should have added in my post above (and have noted in other Zephyr threads) - your best bet for protecting your Zephyr is to replace the stock parachute that comes with the kit. It is adequate, but not great. I don't blame Apogee - they have built a great kit and the build materials are excellent, but they needed to keep some things lower in cost so they could keep the price of the kit down and, in my opinion, the parachute is one of the things that got short shrift. If you bump the chute up a bit, you can count on that Zephyr surviving almost anything. The 36" size is fine, but something a little more beefy with a higher drag coefficient (maybe a LOC nylon chute or a Fruity Chute) would be better. I have launched and watched a whole ton of Zephyrs and can't recall a single time the fins came off or the rocket shredded due to construction issues, but I have seen a whole bunch of recovery failures.

The TL;DR is - you will be fine on the up part of the flight, spend a lot of time making sure your down part is good.

 

[jmasterj]

The only point of epoxy on cardboard rockets it to work faster and avoid waiting for wood glue to dry. You're definitely overthinking things: the epoxy won't be the source of any joint problems you may have. Surface prep is much more important.

 

[overklock]

Good luck!

If you ever want to set your mind at ease, put a gob of epoxy on a piece of cardboard. Let it set for 24 hours. Now, heat the other side of the cardboard until the epoxy softens. You’ll have proven to yourself how difficult it is to damage epoxy. It takes a lot of heat and it doesn’t happen instantly. And that’s just for the first layer. In a through the wall fin setup, if you have good internal and external fillets on the body tube, you could never deliver enough heat inside the motor mount tube to soften the body tube fillets unless you’re burning out the motor mount.

That's a great visual proof of concept. I went ahead and actually tried putting an open blowtorch flame to some epoxy this morning, being sure to give it 2-3 inches of space so it wouldn't immediately start of fire. Even without cardboard between the two, it took quite a bit of heat!

I have built a number of Zephyrs - first with 5 min epoxy, now I just use wood glue when I build them. The ones with epoxy are no longer in service (crashes due to recovery failures, not build issues). Most of the ones with wood glue are going strong.

I like to use Zephyrs and LOC IV's as test beds for things like new electronics, configurations, deployment mechanisms, etc (hence the recovery failures). When testing out something new, I would rather lose a Zephyr or LOC IV than a large FG rocket. Point is, I am now building my Zephyrs and LOC IVs with wood glue, so 15 min epoxy will be more than good enough.

Good luck on your Level 1!

Thanks you! Regarding the parachute, what exactly tends to fail on it? Is it just too thin and gets burned out? Looks like many of the Fruity Chutes have a centered hole, this would lower the drag coefficient, no?

 

[waltr]

The only thing I have seen on the Zephyr I don't like is the way Tim says to setup the chute and recovery in his video.

The stock chute does work if properly setup and packed.
1- Do not attach chute to nose cone loop. Instead put a loop on the cord a foot or two down from the cone and attach chute to the loop. This way the weight of the rocket is directly from cord to chute instead of reling on the nose cone loop, have seen these break and the nose floats away while the rocket takes a core sample (an L1 cert failure).
2- Put the Nomex blanket on the cord below the loop.
3- The way the chute is folded, shroud lines laid inside the Nomex as it is folded over the chute. This keeps the shroud lines from tangling and deploys the lines before the chute.

 

[cls]

ke many of the Fruity Chutes have a centered hole, this would lower the drag coefficient, no?

No, counterintuitively, the spill hole increases circulation of air over the top of the cute, which increases Cd.

Can't beat the Fruity Chutes toroidial design. But I think it's overkill for a Zephyr.

PML used to offer 8 gore chutes with spill hole, those worked great. I might still have 1 or 2 but I'm certain they are singed and holey, after 20 years of hard service...

 

[mtnmanak]

Thanks you! Regarding the parachute, what exactly tends to fail on it? Is it just too thin and gets burned out? Looks like many of the Fruity Chutes have a centered hole, this would lower the drag coefficient, no?

As others have noted, the included parachute will work fine, if setup properly (wholeheartedly agree with the recommendation above not to attach it to the nosecone loop).

My issues with it are that it is lightweight and the shroud lines are less robust than other, higher quality chutes. I do not like the Estes style shroud line loops. They work, but, for HPR, I much prefer a chute design that has individual shroud lines professionally attached to a properly sized swivel. The Estes style loops require you to tie a knot that shortens the overall length of the shroud lines, which, I believe, decreases the ability of the parachute to open fully and achieve it's max lift capability. If the lines then twist at all, you lose lift almost linearly to the amount of twists (no math to back this up - just empirical observation of thousands of flights).

The Apogee 36" printed chutes has a Cd of 0.75. The 36" Fruity Chute Classic Elliptical has a Cd of 1.5. And the 36" Fruity Chute Iris Ultra Compact has a Cd of 2.2. The same size Iris will bring your rocket down almost 3 times slower in theory. In practice, it may actually perform better than 3x due to a better design, longer shroud lines and a built in swivel that reduces shroud line twists.

I know a lot of people have opinions about things like "best" parachute - and they are all correct! I think one universal truth, though, would be that investing in better parachutes is never wasted money. You will want to build up a good portfolio of chutes as you progress in your HPR journey.

I have been doing this for the better part of 50 years now and I have never heard anyone at a launch say "Man, I wish I had worse parachutes!"

Long ago, I invested in a full line of Fruity Chutes and use them in all my rockets under about 80 pounds (I use a two different manufacturers for rockets larger than that). I use a Fruity Chute Iris Ultra Compact 30" chute in my single deploy Zephyrs and a 36" Iris Ultra Compact as the main in my dual deploy Zephyrs. Are they overkill? Definitely. But, I have them, so I use them. Another nice thing about having them is that they work great as drogues in larger rockets.

 

[overklock]

The only thing I have seen on the Zephyr I don't like is the way Tim says to setup the chute and recovery in his video.

The stock chute does work if properly setup and packed.
1- Do not attach chute to nose cone loop. Instead put a loop on the cord a foot or two down from the cone and attach chute to the loop. This way the weight of the rocket is directly from cord to chute instead of reling on the nose cone loop, have seen these break and the nose floats away while the rocket takes a core sample (an L1 cert failure).
2- Put the Nomex blanket on the cord below the loop.
3- The way the chute is folded, shroud lines laid inside the Nomex as it is folded over the chute. This keeps the shroud lines from tangling and deploys the lines before the chute.

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.

No, counterintuitively, the spill hole increases circulation of air over the top of the cute, which increases Cd.

Can't beat the Fruity Chutes toroidial design. But I think it's overkill for a Zephyr.

PML used to offer 8 gore chutes with spill hole, those worked great. I might still have 1 or 2 but I'm certain they are singed and holey, after 20 years of hard service...

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'

 

[overklock]

As others have noted, the included parachute will work fine, if setup properly (wholeheartedly agree with the recommendation above not to attach it to the nosecone loop).

My issues with it are that it is lightweight and the shroud lines are less robust than other, higher quality chutes. I do not like the Estes style shroud line loops. They work, but, for HPR, I much prefer a chute design that has individual shroud lines professionally attached to a properly sized swivel. The Estes style loops require you to tie a knot that shortens the overall length of the shroud lines, which, I believe, decreases the ability of the parachute to open fully and achieve it's max lift capability. If the lines then twist at all, you lose lift almost linearly to the amount of twists (no math to back this up - just empirical observation of thousands of flights).

The Apogee 36" printed chutes has a Cd of 0.75. The 36" Fruity Chute Classic Elliptical has a Cd of 1.5. And the 36" Fruity Chute Iris Ultra Compact has a Cd of 2.2. The same size Iris will bring your rocket down almost 3 times slower in theory. In practice, it may actually perform better than 3x due to a better design, longer shroud lines and a built in swivel that reduces shroud line twists.

I know a lot of people have opinions about things like "best" parachute - and they are all correct! I think one universal truth, though, would be that investing in better parachutes is never wasted money. You will want to build up a good portfolio of chutes as you progress in your HPR journey.

I have been doing this for the better part of 50 years now and I have never heard anyone at a launch say "Man, I wish I had worse parachutes!"

Long ago, I invested in a full line of Fruity Chutes and use them in all my rockets under about 80 pounds (I use a two different manufacturers for rockets larger than that). I use a Fruity Chute Iris Ultra Compact 30" chute in my single deploy Zephyrs and a 36" Iris Ultra Compact as the main in my dual deploy Zephyrs. Are they overkill? Definitely. But, I have them, so I use them. Another nice thing about having them is that they work great as drogues in larger rockets.

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.