"Endburn-Style" Closure with Core-burn Reload

My rocket has a 38 mm motor mount, and I built it to require a tapped forward closure for recovery rigging. Thus far, I've only flown it with an AeroTech RAS spacer and the tapped/vented closure. Now I want to fly a full-size reload, so I need a tapped/plugged forward closure.

I'd like to fly the AeroTech I59N reload, so I bought the "Endburn Style" forward closure. My question is, can I fly this "fully-plugged" closure with a regular core-burn reload, too?

It seems like the endburn closure just lacks a delay well, and has a little raised bump that should mate with the forward seal washer. So this seems like it ought to work, but I just can't find any confirmation one way or the other.

Casey

I don't see why not... You just won't get an ejection from the motor and need to use electronics to kick out the chute(s).

I have both the I49 and the I59 with the said closures.
I have yet to fly them...Maybe this year if all works out.


JD

Yes. I've flown the Endburn forward closure on regular 38 mm loads leaving out the delay grain components. You get no tracking smoke that way but otherwise there is no problem.

I've flown the I49N and I59WN and both are very cool.

Thanks for the responses, guys. I had thought about the lack of tracking smoke, but I can deal with that to save $50 on "yet another forward closure."

Casey

the reason you need a seal disk for the larger motors is because the intense heat and flame can damage the closures, and the seal disk only allows the delay grain to touch the flame.

it's not certified to fly that way, and it will damage the closure over time, i wouldn't do it.

edwinshap1 said:

the reason you need a seal disk for the larger motors is because the intense heat and flame can damage the closures, and the seal disk only allows the delay grain to touch the flame.

it's not certified to fly that way, and it will damage the closure over time, i wouldn't do it.

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Are you shure about that....

My logic -- not knowlege -- tells me the seal disk is to reduce the likelyness of 2 things.
1. the delay grain falling out and "clogging" the core causing a cato...
2. it possibly helps contain hot gasses that could cause blowby port ejection.(around the delay grain)
3. maybe to make a 1.00 off one more part to sell...(and replace when you loose it.)

seal disks, arent used in other motors but aerotech, I have LARGE motor's that dont use seal disks....
My 38mm that is an 800ns motor, has EYYODDS of flights, no seal disk.. and no damage...

Would it be possible to fly said motor with the delay grain in place?

This should provide you your tracking smoke and protect the closure at the same time. You could even grease the forward end of the delay grain for additional protection.

rdbones said:

Would it be possible to fly said motor with the delay grain in place?

This should provide you your tracking smoke and protect the closure at the same time. You could even grease the forward end of the delay grain for additional protection.

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What he is talking aobut is flying the "endburning" closure, not the plugged closure.
there is no well for the delaygrain. this is because on the endburning style, the system is made to not allow the top end of the grain to burn.

he is trying to save the cost of buying a plugged closure....

I think it would be fine....
If the 8second end burning Warp9 propellant doesnt melt the closure, a short 1second burning bates grain isnt going to hurt it either.

Short answers.

Will it work? Yes.
Is it certified that way? No

Depends if you're NAR/TRA or indy as to research "modifications" allowed.

-Ken

ClayD said:

Are you shure about that....

My logic -- not knowlege -- tells me the seal disk is to reduce the likelyness of 2 things.
1. the delay grain falling out and "clogging" the core causing a cato...
2. it possibly helps contain hot gasses that could cause blowby port ejection.(around the delay grain)
3. maybe to make a 1.00 off one more part to sell...(and replace when you loose it.)

seal disks, arent used in other motors but aerotech, I have LARGE motor's that dont use seal disks....
My 38mm that is an 800ns motor, has EYYODDS of flights, no seal disk.. and no damage...

Click to expand...

The longer cases (from RMS-38/480 and bigger) also come with a forward seal disk. This disk is inserted into the front end of the propellant liner and prevents the forward end of the case from discoloring and blistering from the intense heat of the bigger motors.

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yup since aerotech uses paper liners instead of phenolic, the paper can burn through really easily and the forward closure will be ruined after a while.

CTI doesn't need ti cuz the entire assembly is hosued in a 1 time use phenolic case, and the snap ring providers...idk :O

but yeah, no chance its safe to fly any reload besides an endburning reload in an endburning forward closure. if you need a threaded end so bad, there's always the tapped forward closure, it contains a delay well but no ejection well.

edwinshap1 said:

yup since aerotech uses paper liners instead of phenolic, the paper can burn through really easily and the forward closure will be ruined after a while.

CTI doesn't need ti cuz the entire assembly is hosued in a 1 time use phenolic case, and the snap ring providers...idk :O

but yeah, no chance its safe to fly any reload besides an endburning reload in an endburning forward closure. if you need a threaded end so bad, there's always the tapped forward closure, it contains a delay well but no ejection well.

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Aerotech's longer motors use phenolic liners - only the short ones use paper (and the CTI liners don't appear to be phenolic to me - they're some kind of plastic which can melt and become kind of soft and gooey after flight - phenolic doesn't do that).

As for whether the endburning closure is OK with a standard motor? Honestly, I think it would be fine, but it's true that it isn't certified that way.

cjl said:

Aerotech's longer motors use phenolic liners - only the short ones use paper (and the CTI liners don't appear to be phenolic to me - they're some kind of plastic which can melt and become kind of soft and gooey after flight - phenolic doesn't do that).

As for whether the endburning closure is OK with a standard motor? Honestly, I think it would be fine, but it's true that it isn't certified that way.

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ah, ive never handled phenolic so the one liner i did see in person sounded about right lol.

and if it was okay to mix and match forward closures i'd have gotten a delay kit, greased it, and used an end burning closure in that lol

Whoah, guys... Sorry for the confusion, but I never said anything about leaving out the seal disk. I fully intend to use the seal disk with the core-burn liner. My question was about using the end-burn closure instead of the plugged closure. And no, you can't put a delay grain in the end-burn closure because there's no void for it -- the closure is just solid metal.

The last photo on this page shows the back end of the closure:
https://www.australianrocketryclub.com.au/forum/index.php?topic=1213.0

My only real concern is that the little "nub" on the back of the closure might somehow interfere with the seal disk. It doesn't look like it would, but I didn't know for certain. From MarkH's response, I'm guessing it doesn't.

Now, if this is really an "uncertified" configuration, that's good to know. I might just buy the plugged closure to feel better about it. But it really seems to me that, as long as the nub doesn't interfere, the end-burn closure would be more reliable than other closures specifically because it lacks a delay void. Heck, as far as I'm concerned, no delay grain and no voids to fill with grease means one less thing to screw up at loading time.

Casey

I agree - I would think it would be more reliable, since there's no chance of a delay blowby or seal failure.

The nub just simulates the portion of the delay grain assembly that protrudes from a normal forward closure. I've only flown the EBFC a few of times on non-seal disk non-endburning W9 motors in a nearly minimum dia. rocket I designed to fly on the I 49. I didn't put any recovery mount in the rocket since I planned to use the tapped closure of the EBFC as the anchor point, so the EBFC was my only option if I planned to fly it on other motors. But I don't see a reason it wouldn't work on a seal disk motor.

caseybarker said:

My rocket has a 38 mm motor mount, and I built it to require a tapped forward closure for recovery rigging. Thus far, I've only flown it with an AeroTech RAS spacer and the tapped/vented closure. Now I want to fly a full-size reload, so I need a tapped/plugged forward closure.

I'd like to fly the AeroTech I59N reload, so I bought the "Endburn Style" forward closure. My question is, can I fly this "fully-plugged" closure with a regular core-burn reload, too?

It seems like the endburn closure just lacks a delay well, and has a little raised bump that should mate with the forward seal washer. So this seems like it ought to work, but I just can't find any confirmation one way or the other.

Casey

Click to expand...

To answer your question:
No.
It was only made to be used for the I49, I59 motors. It is not certified for use in any other way currently. You need to purchase the proper plugged/ tapped forward closure from AT or RT.

Ask Aerotech. If they say its ok to do it, then its a manufactures approved modification of the motor. Then ask the rso at your launch to see if hes fine with it. There have been many changes to the RMS system over the years, some which were never officially re-certified, and some where.

I have the amw 38 motors and I routinely fly them with their plugged (no delay well closures). The motors were certified with the delay elements but its recommended to fly them with plugged closures.

If the closures are properly anodize. they will take the beating of a core burner just fine.

Thanks for all the responses, folks. I'm convinced this configuration is safe and reliable, but probably also uncertified and unsupported.

Just to be certain, I forwarded my question to AeroTech. I'm told I should get a response next week, so I'll update this thread when I hear back.

Casey

I just got a response from Karl Baumann at AeroTech:

Yes, it works with all our 38mm loads where you need the Threaded boss and
do not need the smoke. It is a recommended use of this closure.

It is very safe and reliable, as you leave out all the delay components. It
is configured to use the standard Fiber / Metal seal Disc and forward O-ring

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Exactly what I thought. He doesn't mention certification, but this is clearly a manufacturer-approved configuration.

Unfortunately, about two hours before I got his response, I gave up waiting and ordered the plugged/tapped closure. Oh, well. I guess I can use it to fly tracking smoke.

So, to summarize for anyone who stumbles across this thread in the future: There's really no need to ever buy either of the 38mm "plugged" or "plugged/tapped" closures with the delay wells unless you really, really want tracking smoke. Otherwise, just buy the end-burn plugged closure. It's tapped for recovery mounting in case you need that, and you have manufacturer approval to use it for both end-burn and core-burn reloads.

Casey

huh? I must be either blind or daft. I just don't get it. Why not fly smoke. My old eyes can barely follow my rockets with smoke! Heck, if Gary came up with a "blind old fart 3 minute smoke forward closure" I'd buy a half dozen with a couple hundred smoke grains so I'll be able to see my rocket's flight until the time my old geezer bones won't carry me over to get the rocket......(hint, hint Gary).......probably never fly any other motor then!

rick

"but i'm not quite that old yet!"

I just don't get it. Why not fly smoke.

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Check the original post -- I already own the end-burn closure. So the point is, I could have saved $50+ because I don't care about smoke.

If nothing else, read this thread and you'll see just how much confusion and misinformation there is on this subject. (Some folks actually asserted that it was dangerous!) So the meta-point is to set the record straight: The 38mm end-burn closure is safe and AeroTech-approved for use with all 38mm reloads.

Casey

I use my seal disk to outline a disc to cut from automotive sheet gasket material to make closed seal discs when using cored reloads with my AT end burning forward closure. No issues. The closure is totally unharmed.

VONRANG said:

I use my seal disk to outline a disc to cut from automotive sheet gasket material to make closed seal discs when using cored reloads with my AT end burning forward closure. No issues. The closure is totally unharmed.

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well that's actually a really good idea lol, nice