Most effective baffle design?

[Cape Byron]

Just out of curiosity, how many baffle users put in a sheet or two of wadding as “insurance”?

I try to use baffles in all my kit designs for a number of reasons:

Ejected wadding may be biodegradable, but it still sits around for a while. Small mammals and birds may try to eat it, and this results in bowel obstruction. Even on the small 'B-Test' area next to the house on the farm we have three endangered mammals and a similar number of birds.

Lots of fliers here in Oz use small farm holdings for launches. They tend to have a strict 'No rubbish' rule that means you pick up every igniter, plug, wadding sheet, lawn dart part before you leave or risk losing the flying area.

Personally, I just prefer baffles. I use the Qualman ones and have never had to use wadding in those rockets.

If the rocket is 13mm md I'll use a tethered plug. On super stubby Gooney type birds I'll use a Nomex sheet.

 

[lakeroadster]

Personally, I just prefer baffles. I use the Qualman ones and have never had to use wadding in those rockets.

Wow.. their prices look great too! Qualman BT-sized Plywood Baffles

Thanks for the tip!

 

[Ronz Rocketz]

I’ve been making my own baffles for the past several months. I have bought premade baffles from erockets but only BT-60. What’s worked is two half moon, offset cuts in balsa with epoxy on top. I don’t get any burnt chutes.

There’s two components to the ejection blast, pressure gas and hot particles. The trick is to get a vortex going in the baffle that traps the hot solids but not block the pressure gas. When the NC pops, most of the solids are sucked out along with the chute. Anyone know of a slomo of the baffle in action?

 

[Cape Byron]

Wow.. there prices look great too! Qualman BT-sized Plywood Baffles

View attachment 438237

Yep. David Qualman's products are outstanding value for money.

 

[Joshua Smith]

Yep. David Qualman's products are outstanding value for money.

I have to agree and he's very quick to ship and honestly he's put up with a lot of questions from me Dave even made me a size of lite-ply centering rings that weren't on his website. Big fan

 

[Joshua Smith]

I’ve been making my own baffles for the past several months. I have bought premade baffles from erockets but only BT-60. What’s worked is two half moon, offset cuts in balsa with epoxy on top. I don’t get any burnt chutes.

There’s two components to the ejection blast, pressure gas and hot particles. The trick is to get a vortex going in the baffle that traps the hot solids but not block the pressure gas. When the NC pops, most of the solids are sucked out along with the chute. Anyone know of a slomo of the baffle in action?

We need to get the Slow Mo guys from YouTube on it I live in the same city as Gav from that show (not sure this helps anything, but hey)

 

[Joshua Smith]

I try to use baffles in all my kit designs for a number of reasons:

Ejected wadding may be biodegradable, but it still sits around for a while. Small mammals and birds may try to eat it, and this results in bowel obstruction. Even on the small 'B-Test' area next to the house on the farm we have three endangered mammals and a similar number of birds.

Lots of fliers here in Oz use small farm holdings for launches. They tend to have a strict 'No rubbish' rule that means you pick up every igniter, plug, wadding sheet, lawn dart part before you leave or risk losing the flying area.

Personally, I just prefer baffles. I use the Qualman ones and have never had to use wadding in those rockets.

If the rocket is 13mm md I'll use a tethered plug. On super stubby Gooney type birds I'll use a Nomex sheet.

Cape Byron,
How much space, minimum, do you feel you need between the ejection charge and the start of the baffle? I only recently started using them and I have an Estes Bullpup that I've modded to take 24mm full length and there isn't a whole lot of body tube remaining. Dave suggested 3" typically. I could fit it in, but I would have to origami a parachute to get it to fit in what remains. Come to think of it, a custom baffle might be better due to the 1g ejection charge of an E. Might need extra air flow so I don't turn it into a real missile

Josh
P.S. I think I'm going to name my next custom build "Chunder from Down Under" LOL. If I can fit that many letters on it

 

[Ronz Rocketz]

We need to get the Slow Mo guys from YouTube on it I live in the same city as Have from that show (not sure this helps anything, but hey)

This is close but the flash suppressor is meant to trap the gases along with the particles as the bullet leaves the barrel. In a way, the baffle acts as a catalytic converter in that it traps the unburnt solids (fuel) before reaching the chute. Someday, someone will create a better plug that doesn't throw hot clay down the tube and can eliminate the unburnt powder before reaching the chute, someday.

 

[Cape Byron]

Cape Byron,
How much space, minimum, do you feel you need between the ejection charge and the start of the baffle? I only recently started using them and I have an Estes Bullpup that I've modded to take 24mm full length and there isn't a whole lot of body tube remaining. Dave suggested 3" typically.

Yep, as far forward as you can leaving room for the laundry is a good rule of thumb. I've gone as close at 1" (2.5cm) from the top of the motor mount if you protect the baffle. I've had good results with using epoxy to protect the ply baffle structure using these instructions (PDFs attached, read both).

Remember to shake out all the ejection crud after each flight.

Good luck!

 

[cbwho]

I think a 4 moon shape in a coupler is probably best but I lack a spare coupler. I tried to glue in the disks individually but that is too clumsy.

Using the no straight line rule, I ended up making a lipped 2 baffle design. It's actually my 4 baffles glued in a zig zag manner supported by toothpicks. This I can slide in and glue. I believe it will work despite it's lack of elegance?

 

[shockie]

Yep, as far forward as you can leaving room for the laundry is a good rule of thumb. I've gone as close at 1" (2.5cm) from the top of the motor mount if you protect the baffle. I've had good results with using epoxy to protect the ply baffle structure using these instructions (PDFs attached, read both).

Remember to shake out all the ejection crud after each flight.

Good luck!

to prevent ejection crud from getting into the baffle.......cut out a piece of fine screen and place it on the bottom of the baffle.....that will accumulate the crud, or at least most of it , while allowing the gases to pass thru unobstructed.... I once saw a baffle that had these screens on both top and bottom and it was said they also acted as sort of a heat sink to absorb some of the ejection charge hot gas heat and moderate it some....don't know if that was true or not

 

[Ronz Rocketz]

I once saw a baffle that had these screens on both top and bottom and it was said they also acted as sort of a heat sink to absorb some of the ejection charge hot gas heat and moderate it some....don't know if that was true or not

Sounds like sorcery to me...

 

[Bill S]

Wow. Lots of interesting stuff here. As I probably should have guessed, there doesn't seem to be a clear cut answer. Consensus seems to be 3 half moons are fairly reliable for small tubes, so that might be what I go with. I wonder if anyone has conducted any study on the various baffle types. Nothing in the NAR R&D database, so maybe a good topic for a future project. Thanks for your help.

That sounds like the basis for a good Apogee newsletter article.

 

[cbrarick]

https://wildmanrocketry.com/collections/nomex/products/fcp6x6
simpler, dependable and easier to use.