My Removable BT-20 Baffle System

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Baffle 2.0

The next version of my removable baffle is complete. It weighs 6.0 grams with the stainless steel eyelet and the half-moon plates are made from card stock while the center support shaft is made from a wooden toothpick. All inner surfaces of Baffle 2.0 are coated with JB Weld. Here are a few pictures:

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I will do my initial tests in a modified Estes Alpha III. The The main body tube is from an A***ee Apprentice and the fin can and nose cones are from the Alpha III; more pics of the finished rocket later. The MMT is basically a stock MMT that's longer to accommodate the removable baffle. I also installed an Estes 18mm retainer ring on it. Here's how it looks on the Alpha III so far:

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I hope to do some testing tomorrow or this weekend. Will report back when I do.
That looks cool! What kind of longevity are you looking for?
 
That looks cool! What kind of longevity are you looking for?
Good question. I don't have enough C engines to do as many tests as I would like. So my goal is to do 8 C engine tests and after those tests, Baffle 2.0 is in well-used, but otherwise perfect condition. Then after that, I hope Baffle 2.0 lasts another 8-22 lanuches, depending on the engines used (A, B, C or a D composite).
 
Good question. I don't have enough C engines to do as many tests as I would like. So my goal is to do 8 C engine tests and after those tests, Baffle 2.0 is in well-used, but otherwise perfect condition. Then after that, I hope Baffle 2.0 to last another 8-22 lanuches, depending on the engine used (A, B, C or a D composite).
Well, between Estes and Quest Q-Jet you have 18 different motor options. Getting 2- and 3-packs of each works out to 44 tests.
 
Well, between Estes and Quest Q-Jet you have 18 different motor options. Getting 2- and 3-packs of each works out to 44 tests.
Oh, I don't need to test every engine. I just need to test the one with the more powerful ejection charges and ejection charges located as far up the engine casing as possible. But since I won't be doing all tests with a C or D engine, some of the tests (or launches) will naturally be done with an A or B engine.
 
Baffle 2.0 - Testing Results

Today I was able to run 8 tests with Baffle 2.0. These tests took place in 86 degree weather (F) with 51% relative humidity. The baffle was tested in the Apprentice + Alpha III hybrid rocket utilizing an extra long MMT as seen in the previous pics. I also tested my quasi-reusable denim wadding. Here are the test results:

Test 1: Used a C5-3 engine - perfect test

Test 2: Used a C5-3 engine - perfect test

Test 3: Used a C6-5 engine - perfect test

Test 4: Used a C6-7 engine - perfect test

Test 5: Used a C6-3 engine - perfect test

Test 6: Used a C6-3 engine - perfect test

Test 7: Used a C6-3 engine - Good test; nose cone ejected, but parachute didn't fully eject. The parachute was halfway sticking out the end of the main body tube. It got warm and had zero to very very slight charring. The parachute was not damaged in any way that would inhibit its ability to operate properly. The clay cap at the top of the engine was fully gone.

Test 8: Used a C5-3 engine - perfect test

Here are the pictures:

20220909_162232.jpg 20220909_162240.jpg

That is regular, untreated blue jeans denim in a 3" x 3" square. Up top/on the left is the inside of the wadding that touched the parachute and on the right is the part that was exposed to the exhaust gases coming from the baffle (in all 8 tests). I didn't do this test b/c I'm trying to save money on disposable wadding. Rather, I like the idea of nothing being ejected from my rocket during the ejection process.

Here's the top of the baffle, with the top picture showing Baffle 2.0 after the first launch, then the 4th launch, then the 8th launch (at the bottom):
Top GOOD.jpg

Here's the bottom of the baffle (that's closest to the ejection charge), with the top picture showing Baffle 2.0 after the first launch, then the 4th launch, then the 8th launch (at the bottom). That "blister" you see on the inside of the baffle? That's the JB Weld pulling away from the engine casing wall...interesting. I'm curious as to whether wood or white glue will avoid that problem. At the the very least, they're cheaper than JB Weld and dry much faster...
Bottom GOOD.jpg

And here's the outside othe baffle. A bit of charring on the outside edge closest to the bottom (that's closest to the ejection charge), but overall, looks good! Definitely no soft or weak spots as was the case with Baffle 1.0 after eight A8-3 tests.
L8 Outer Good.jpg

Discussion/Conclusion

Using the spent engine casing and JB Weld helped alot. Using a longer baffle helped, too. As expected, there aren't very many bright line conclusions to draw from these tests. Rather, any adjustments have resulted in a sliding scale of changes. For example, will Baffle 1.0 still work with C engines, despite being 17mm shorter and made from less robust materials? Sure, but it won't last as long as Baffle 2.0. But then again, it's a little bit lighter and easier to make. Pick your poison...

Also, I think using wood or white glue on the inside might be a better option than JB Weld. As long as it perform 90% as well as JB Weld, it's a worthy substitute as they dry much faster, are easier to work with and are less expensive.

I think Baffle 2.0 in an extended MMT (a la stuffer tube) and retainer ring is a great set up. It's clean, neat, more consistent and lasts longer. But it's heavier and requires a BT-50 or larger rocket. Based on how Baffle 2.0 looked after the 8th test, I wouldn't be surprised if it could easily last 20 launches, even when using C engines.

Addendum: I think my next removable baffle built will have some sort of "lip" at the bottom thrust ring to "mate" with the top of the engine. I'll see if this can reduce the charring on the bottom of the baffle (and the small amount of black/soot build-up on the inside of the MMT. I'm thinking this lip will be small...maybe 2-3 mm? Can't be too long to interfere with the clay cap of engines with bigger delays, like the C6-5 and C6-7. This lip can help deal with variations in model rocket engine length. Check out this picture as a demonstration:
20220909_201646.jpg
That's about 1mm or so of play where the baffle and rocket engine and slide forward and backward within the MMT (I added those red marks to make it easier to see). I'm guessing a combination of me not fully screwing on the retainer and some play between the engine casings caused the "ejection bleed through" between the baffle and engine which the lip should help deal with. I could also add some spacer to the inside of the retainer ring, too...
 
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Well I think you’ve perfected this system.

I’ve got a Hi-Flier that I’m going to be building as a second stage pretty soon, that will be set up for a removable baffle. I’m convinced.
Not quite perfect, but getting there. I thought of another modification to try for my next baffle build (see the addendum in my above post).
 
I finally had a chance to launch my Hi Flier with the removeable baffle. Launched once at the club launch last weekend and another flight at a local park yesterday. First flight was an A8-3 and the second flight was A8-5. Looking at the baffle I see some minor debris on the inside of the baffle but nothing that would hinder the performance. Good news is that I don't see any signs of degradation of the baffle for the ejection. Granted I'm only two flights in.

Here are some pics. Looking forward to additional flights.

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Any thoughts on using a boric acid solution to fireproof your baffle? I believe this is what Estes uses to fireproof their wadding. https://www.instructables.com/Homemade-Flame-retardant/
Using boric acid might work, but probably unecessary, at least given my objectives.

First, it requires me to buy additional materials/supplies. One of the benefits of this baffle system is that you don't need to use any materials that you don't already have.

Second, using white glue, wood glue or epoxy (or JB Weld) should sufficiently protect the baffle from burning. The biggest issue is the buildup of ash/char or w/e that "gunk" is that coats the inside of the baffle.

Third, remember, these baffles are designed to be removable. So there's this "balance" between time, effort and money spent on the baffle and the idea that it's supposed to be disposable (or rebuildable).
 
That would probably work however I’m wondering if it would cause the cardboard to swell in any way shape or form.

I have eight flights on this rocket now and the baffle does not show any signs of deterioration from the ejection. There is a small amount of buildup on the very first two plates of the baffle but nothing that is causing issue with its function. In all honesty, I could probably get in there with a small brush and remove it but I want to see how far this baffle will go without any maintenance.

The nice thing about this is that I was able to do it with materials that I had in the shop
 
I 3D printed some baffles from ABS plastic (BT-20, BT-50, BT-55, BT-60). If someone would be willing to test them (and pay for shipping) I can send a couple to you...

I originally planned for a Kevlar line to go though the hole in them. However, maybe it makes more sense to look at the hole as a pre-drilled screw hole for a couple of small anchors.

1672253571167.jpeg
 
I 3D printed some baffles from ABS plastic (BT-20, BT-50, BT-55, BT-60). If someone would be willing to test them (and pay for shipping) I can send a couple to you...

I'll be testing a few of those as soon as they arrive and the burn ban gets lifted. Not a lot of BT-20 baffles around tp compare them to.
 
Baffle 2.0 - Testing Results

Today I was able to run 8 tests with Baffle 2.0. These tests took place in 86 degree weather (F) with 51% relative humidity. The baffle was tested in the Apprentice + Alpha III hybrid rocket utilizing an extra long MMT as seen in the previous pics. I also tested my quasi-reusable denim wadding. Here are the test results:

Test 1: Used a C5-3 engine - perfect test

Test 2: Used a C5-3 engine - perfect test

Test 3: Used a C6-5 engine - perfect test

Test 4: Used a C6-7 engine - perfect test

Test 5: Used a C6-3 engine - perfect test

Test 6: Used a C6-3 engine - perfect test

Test 7: Used a C6-3 engine - Good test; nose cone ejected, but parachute didn't fully eject. The parachute was halfway sticking out the end of the main body tube. It got warm and had zero to very very slight charring. The parachute was not damaged in any way that would inhibit its ability to operate properly. The clay cap at the top of the engine was fully gone.

Test 8: Used a C5-3 engine - perfect test

Here are the pictures:

View attachment 536932 View attachment 536933

That is regular, untreated blue jeans denim in a 3" x 3" square. Up top/on the left is the inside of the wadding that touched the parachute and on the right is the part that was exposed to the exhaust gases coming from the baffle (in all 8 tests). I didn't do this test b/c I'm trying to save money on disposable wadding. Rather, I like the idea of nothing being ejected from my rocket during the ejection process.

Here's the top of the baffle, with the top picture showing Baffle 2.0 after the first launch, then the 4th launch, then the 8th launch (at the bottom):
View attachment 536935

Here's the bottom of the baffle (that's closest to the ejection charge), with the top picture showing Baffle 2.0 after the first launch, then the 4th launch, then the 8th launch (at the bottom). That "blister" you see on the inside of the baffle? That's the JB Weld pulling away from the engine casing wall...interesting. I'm curious as to whether wood or white glue will avoid that problem. At the the very least, they're cheaper than JB Weld and dry much faster...
View attachment 536936

And here's the outside othe baffle. A bit of charring on the outside edge closest to the bottom (that's closest to the ejection charge), but overall, looks good! Definitely no soft or weak spots as was the case with Baffle 1.0 after eight A8-3 tests.
View attachment 536938

Discussion/Conclusion

Using the spent engine casing and JB Weld helped alot. Using a longer baffle helped, too. As expected, there aren't very many bright line conclusions to draw from these tests. Rather, any adjustments have resulted in a sliding scale of changes. For example, will Baffle 1.0 still work with C engines, despite being 17mm shorter and made from less robust materials? Sure, but it won't last as long as Baffle 2.0. But then again, it's a little bit lighter and easier to make. Pick your poison...

Also, I think using wood or white glue on the inside might be a better option than JB Weld. As long as it perform 90% as well as JB Weld, it's a worthy substitute as they dry much faster, are easier to work with and are less expensive.

I think Baffle 2.0 in an extended MMT (a la stuffer tube) and retainer ring is a great set up. It's clean, neat, more consistent and lasts longer. But it's heavier and requires a BT-50 or larger rocket. Based on how Baffle 2.0 looked after the 8th test, I wouldn't be surprised if it could easily last 20 launches, even when using C engines.

Addendum: I think my next removable baffle built will have some sort of "lip" at the bottom thrust ring to "mate" with the top of the engine. I'll see if this can reduce the charring on the bottom of the baffle (and the small amount of black/soot build-up on the inside of the MMT. I'm thinking this lip will be small...maybe 2-3 mm? Can't be too long to interfere with the clay cap of engines with bigger delays, like the C6-5 and C6-7. This lip can help deal with variations in model rocket engine length. Check out this picture as a demonstration:
View attachment 536962
That's about 1mm or so of play where the baffle and rocket engine and slide forward and backward within the MMT (I added those red marks to make it easier to see). I'm guessing a combination of me not fully screwing on the retainer and some play between the engine casings caused the "ejection bleed through" between the baffle and engine which the lip should help deal with. I could also add some spacer to the inside of the retainer ring, too...

Sorry, I'm not following with how the baffle is secured and still removable. I guess if the Kevlar passes through the baffle, it will still do it's job even if it does eject with the chute.

I did have one of my Qualman baffles almost pop out. I ended up removing the baffle and securing the Kevlar to the retainer because I didn't think it would be easy to fit the baffle back in. With the spent motor case, it would be a simple matter of removing some of the outer layer until it can slide in again.

I've found that if there isn't enough gap between the MM and baffle, then the cardboard heats up and causes bubbles in the paint so the positioning of the baffle is important. This is less of an issue if the baffle acts as a piston to push the laundry out.
 
Sorry, I'm not following with how the baffle is secured and still removable.
Maybe these pictures will help?

20221123_104822.jpg20221123_105040.jpg
20221219_173852.jpg
The top picture shows the entire MMT that holds both the removable baffle and engine. In this case, it's going to be a 24mm removable baffle plus a 24mm engine (or an 18mm engine with an adapter).

The middle picture shows the top of the MMT. You can see the motor thrust ring that keeps everything from sliding forward (or towards the top of the rocket). Then at the back of the rocket (towards the bottom), you have the 24mm screw-on retainer ring to keep everything in place during ejection.

The bottom picture shows the shock cord and removable baffle. The shock cord and stainless steel eyelet both poke out the top of the MMT you see in the first picture. I'll add a fourth picture that maybe shows this better:

20221229_082305.jpg
 

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