Hmmm...baffle holes not large enough

[NewEntity1]

I made a ...rather unique... baffling system for my Executioner.

However, when I talked to the guy at Hobby Town today about my system, he thought that the holes in the sides of the motor mount tube might not be a good idea. He said directing the ejection gases sideways like that would probably lead to it just blowing the sides out of the body tube, rather than pushing the nosecode out of the top of the rocket.

He also thought the 3/8" holes I put in the top plywood centering ring I added would not be large enough to let the ejection gases through quickly...resulting in the rocket either spitting the motor out the back at ejection or, again, just blowing the sides out of the body tube. Unfortunately, with the rocket fully built now, I have no way to get at the top centering ring to make the holes larger, or to remove the "cap" I put on the top of the mount tube.

What do folks on this forum think? I'm going to attach a picture I took of the top baffling before the rocket was finished. These holes look awwwwfully small...will the ejection gases go through these fast enough to kick the nose cone off?

 

[Ryan S.]

you could probably get a long enough drill bit to open those holes but I doubt they will be too small. In some rockets (smaller with 18mm engines) all that is used is a 1/4" hole to vent the gasses, I think this will probably be plenty, but you can always widen the holes because they arent that deep

 

[astronboy]

What engine(s) are you using? The E-9?

Holes in the sides of a BT were succesfully used by the ESTES bandit in the 1970's. Here is a link to the plans on Jim Z'z site.

https://www.dars.org/jimz/k-48.htm

The basic rule of thumb I have always heard is that your holes should be the at least the same area as the end of the motor.

 

[Maelstrom]

Go to EMRR and read reviews for the Gemini DC. Side porting of the exhaust gases could lead to BT failure over time.

 

[NewEntity1]

Thanks for the replies, folks!

Ryan...the picture above shows the rocket as it was before the body tubes were glued together. I'm including a new image that shows how deep I would have to go now, without cutting the body upper body tube open. I would need a drill bit nearly 24" long . I thank ya for your imput though, Ryan...if you think the holes will be large enough, then maybe I'll just leave 'em be for maybe two flights and see how it does.

After that, I'll cut open the upper body tube (assuming I still have a rocket after two flights ), and drill a hole right smack in motor mount cap , and attach a new upper tube. I would have to go back to using wadding, of course.

edit: Buggers! I forgot to attach the new image!

 

[NewEntity1]

Ok, here is the new pic, showing the way down to the motor mount, with flashlight in hand

 

[doxiedog315]

My Bet is, it will work just fine.

 

[wwattles]

You could always just take a dowel or metal pipe, attach a large nail to it (very securely, of course), and pound it through to make some more holes. They won't be pretty, but who's looking inside your rocket for prettiness anyway?

WW

 

[rbeckey]

If I am not mistaken, Bob Kaplow published plans for a baffle like yours long ago. It has worked fine in many high power designs. Add up the total of the area of the holes in the tube and compare to the area of the end of the motor mount. If they are similar, you should be fine.

 

[DavRedf]

You could always have a word with your local friendly electrician, the usually have long series drills.
I got one 1/4" X 36".

David

 

[shockwaveriderz]

you might want to try some of that foil lined bt50 body tube (T50mf) that Jim Fackert at Totally Tubular has...thats what I am going to use for both my engine spacer/baffle combos in my Executioner.... you could also get some nomex paper there too.....or kapton plastic....both are high temp resistant materials....

https://www.wooshrocketry.org/misc/TT-6-2-03.htm

 

[loopy]

I wouldn't worry about it - looks fine to me. I did kinda the same thing with my Big Daddy, and never had a problem. Eventually, it did lawn dart on a D12-5, but it was the time when D12-5s were experiencing weak ejection charges all over the place. Put it this way - nose didn't come off +sides didn't split + the motor didn't kick = really weak ejection charge. Your baffle looks fine. Of course, only one way to know for sure!!!

Loopy

 

[Adam Selene]

I think it will probably work just fine. My Gemini DC has flown lots of times and shows no sign of body tube damage. lot's of carbon build up but no damage. great rocket btw, always flies nice.

if you're really worried you can get long drill bits just about anywhere that sells drill bits.

 

[wolf06]

The baffle in my Binder Thug has series of 3/8" holes and works great! (29mm motor tube)

 

[NewEntity1]

The baffle in my Binder Thug has series of 3/8" holes and works great! (29mm motor tube)

Wow! Then I truly shouldn't have any problems...mines only a long 24mm