Maxi Alpha III Ejection Baffle

After doing some research and deciding it was worth a shot, I picked up a Maxi Alpha III for my son, who has been bugging me for one for quite some time.

I have been wanting to try out ejection baffles for a while, and just happen to have a couple on hand for BT-80 tubes, so I thought I would give it a shot with the MAIII.

I spent a good amount of time last night mocking up the MAIII and figuring out how I might incorporate the ejection baffle. I came up with a plan, but I wanted to see if I could get the opinions of those more experienced than I am on whether or not my plan will work.

My plan:

Use the ejection baffle in place of the short tube coupler in between the two longer BT sections, inserting the ejection baffle about one inch into the lower tube.

Given the rule I have read of having at least one tube diameter's length between the motor mount and the ejection baffle, I figured I would need to cut off about 3.75" of the motor mount.

I still plan on using the card stock bulkhead, just moving it down the tube to the shortened motor mount. I figured this was included in the design to reduce the amount of space in the tube needing to be pressurized during ejection, so I thought I should still use it to reduce the amount of space in the tube as much as possible.

I will move the shock cord from the card stock bulkhead to the screw eye on the ejection baffle, maybe adding a short length of Kevlar cord before the shock cord.

The rest of the MAIII I will build stock, except maybe using controlled amounts of epoxy on the fin can and fins.

Of course, I will check the CG after adding this extra weight and adjust as necessary.

Besides getting opinions on my plan, a question I have is will the ejection baffle and extra space in the tube created by cutting the motor mount cause ejection issues with the 24mm BP motors or Aerotech reloads I am planning on using at times?

Thanks for any and all help and opinions, and I can post pictures once I get the build going, if anyone is interested.

Steve

You could go zipperless design.You only need the top 6" of the tube to store your chute.Make sure your nosecone is attached to the tube with screws.The higher the coupler is the better your CG will be.If using half moon discs,coat the motor side with epoxy.The bottom half of the coupler is glued to the lower bodytube.The rockets seperates at the coupler/ baffle.Hope this helps.

Thanks for the idea cjp. I had not thought about making the rocket separate at the coupler location.

Two more questions, then, if I may.

My baffle is from Apogee and has the holes in the motor side plywood disc. If I go your way, should I still coat the motor site with epoxy?

Would the shock cord still get attached to the nosecone, which is semi-permanently attached to the upper body tube (the other end attached to the screw eye in the baffle, of course)?

I will still need to cut the motor tube, and even a little more with this idea, as the baffle would be an extra inch inside the lower body tube, compared to my initial idea.

I will definitely think about this way.

Steve

smoon said:

Thanks for the idea cjp. I had not thought about making the rocket separate at the coupler location.

Two more questions, then, if I may.

My baffle is from Apogee and has the holes in the motor side plywood disc. If I go your way, should I still coat the motor site with epoxy?

Would the shock cord still get attached to the nosecone, which is semi-permanently attached to the upper body tube (the other end attached to the screw eye in the baffle, of course)?

I will still need to cut the motor tube, and even a little more with this idea, as the baffle would be an extra inch inside the lower body tube, compared to my initial idea.

I will definitely think about this way.

Steve

Click to expand...

I always coat the engine side to protect the baffle.Yes you still attach the shockcord to the nosecone.I drill two holes in the bottom of the nosecone and loop it threw.I don't use the tab on the nosecone as they can break.I make my own baffles with 3 half moon discs and top disc I put a eyehook and holes around the outer edges.

This is how I set up this rocket.Works out great.All my baffles are made the same way.I have a clean chute with no holes.You just put the half moon discs in about half inch apart with the slots opposite of each other that way the gasses have to snake thru the baffle trapping the hot partials.Hope this helps.

Thanks for the clarification and pictures cjp. I went ahead and laid a layer of epoxy on the aft end of my ejection baffle, as I was sure it was a good idea. The ejection baffle I got from Apogee has a solid aft disc with a series of holes drilled near the center of the disc, with the forward disk having larger holes drilled at, and past the edge of the disc. The ejection gasses have a straighter shot than with the half moon design, but I am guessing that they get interrupted enough to not cause an issue. I have pictures that I will post over the weekend. I do plan on using a sheet or two of wadding over the end of the baffle on the first flight, just to make sure.

I am also in the middle of building a QCC Explorer right now and had purchased a baffle for it, but in my haste to build, completely forgot it was in my supplies box. The point where the tubes join sure would have been a great place for the baffle. DOH! on me. Oh well, now I have one for the next build of this size.

One last question (or two), if I may. Where is the best place to attach the parachute when the rocket is set up to separate in the middle? Should I attach it part way down the shock cord, like on my larger mid power rockets?

Thanks again,

Steve

I don't know if you have a drill press but if you do,you could make your own discs with a circle wheel cutter.You could also use saw hole cutter and any coupler that comes with a kit could be made into a baffle.Do a search on how and where to attach your parachute and folding the shockcord using zipperless design.Thats what I did,found some helpfull information.Hope I can help you if you have any more questions.

I found the site,Info Central,at Rocketry on line.They have a great picture on zipperless design.I found what I needed there.Hope this helps,let me know,I'll try to help you if I can.

cjp said:

View attachment 256009This is how I set up this rocket.Works out great.All my baffles are made the same way.I have a clean chute with no holes.You just put the half moon discs in about half inch apart with the slots opposite of each other that way the gasses have to snake thru the baffle trapping the hot partials.Hope this helps.

Click to expand...

The three discs in the picture under the top tube I cut into half moons.the baffle is the coupler from the kit and I used paracord for my shockcord.When you cut the discs,cut them in half 3/4 of the way across and fill in the hole in the center with epoxy.The top disc I used my drill press to drill holes around the outer edge.Hope this make sense.

When your on Rocketry on line,go to Info Central,on the top left side go to design then airframe and then anti-zipper design.

Thanks again cjp. I already found it and read through the article. I really like the design and issues is prevents. Looks like the Maxi Alpha III is going to go ziperless. :blush:

I had not heard about using paracord for shock cords before, so I looked it up, and it sounds like it may be worth a try. Can you give me your reasoning for using it over Kevlar or tubular nylon (maybe too big for smaller rockets)?

Does the ejection baffle prevent any issues with the nylon paracord?

Alas, I do not have a drill press at the moment. I have been longing for one, but space in my garage is at a premium until I can talk myself into unloading some of the excess other hobby items (RC everything, trains, Legos,...). Having one would certainly make many things in my hobbies easier, so I am sure I will get one eventually. Making my own baffles sounds like something that is right up my alley, so maybe this will get me to get off my butt and start selling off excess items.

Steve

smoon said:

Thanks again cjp. I already found it and read through the article. I really like the design and issues is prevents. Looks like the Maxi Alpha III is going to go ziperless. :blush:

I had not heard about using paracord for shock cords before, so I looked it up, and it sounds like it may be worth a try. Can you give me your reasoning for using it over Kevlar or tubular nylon (maybe too big for smaller rockets)?

Does the ejection baffle prevent any issues with the nylon paracord?

Alas, I do not have a drill press at the moment. I have been longing for one, but space in my garage is at a premium until I can talk myself into unloading some of the excess other hobby items (RC everything, trains, Legos,...). Having one would certainly make many things in my hobbies easier, so I am sure I will get one eventually. Making my own baffles sounds like something that is right up my alley, so maybe this will get me to get off my butt and start selling off excess items.

Steve

Click to expand...

I use both,bought it at a outdoor camping store here for around .15ct a foot.You want the 550lb. paracord.I have 250# kevlar that works as well with this design and is better with heat.It is much easier to fold as paracord is thicker.Also I go at least 3 time the length of the rocket.The trick I found is to make sure the parachute and shockcord are side by side in the tube.That's way you want a short tube to pack it in as the chute could be pushup into the tube and become tangled.Hope this all has helped you.I been doing this to all my larger rockets and it has worked out very weel for me.