Baffles vs nomex protektor +

[rsbhunter]

As title states, blanket vs baffles? Also, reinforcing the bt inside by motor retainer. Is JB weld best for Aerospace 29mm retainer. Are all the 1010 rail buttons equal, as far as lasting, etc.? Last one , for now....on plywood fins, should they get grain filler? Really want to make my DX3 2.6 nice, so any tips, suggestions are very welcome.?Thanks, rsbhunter

 

[mh9162013]

¿Por qué no los dos?

I use baffles and the parachute protector. The baffles make the parachute protector last longer. And the parachute protector keeps the laundry cleaner (and serves as a backup to protect the laundry).

 

[rsbhunter]

Thank you, I guess that would be the best of both worlds....rsbhunter

 

[cbrarick]

I'm baffled by people who use baffles. I'm more baffled by those that use both. Pick one or the other.

Seriously:
baffles reduce need for parachute protection
those that do not require any can clog up over time. Depending on how you make them it's a problem or a big problem
those that still require parachute protection are a waste of weight and add unnecessary complexity
Baffles also act to reduce pressure from the ejection charge...at least a little bit.
chute protectors are lighter weight (more performance from rocket)
chute protectors are easily used
chute protectors may become damaged over time, but are easy to replace
chute protectors are generally cheaper then baffles.
when you eventually decide to go bigger (and you will) baffles become increasingly difficult to upscale

However: It's your rocket, fly what you want. Neither will create a safety issue



JMHO

 

[Titan II]

Blanket only.

 

[cwbullet]

Blanket only.

My thoughts also. I suggest either or but not both.

 

[rsbhunter]

This site is a fantastic site...lots of good advice.

 

[Hobie1dog]

chute protectors for me

 

[Azamiryou]

I lean baffles because I lean low power. In a narrow tube, a chute protector requires extra care when packing to ensure a smooth deployment.

 

[Handeman]

I have a 2.2 PML Callisto I built in 2003. It has a piston. I have over 200 flights on it. The 1" nylon strap from the motor mount tube to the piston is still going strong. No baffle, no blanket. Just use 0.5g of powder in the motor ejection charge no matter what motor I use from F to H.

I know most use a baffle or blanket, but don't count out a piston. It doesn't have to be tight. I sanded the piston down to fit loosely on a cold January day and haven't had to adjust it in the last 15+ years. I clean out the BT about once a year, maybe every two years.

I'm still using the original parachute and it doesn't have a single powder burn in it.

Good Luck with your DX3

 

[teepot]

Blanket. I buy Nomex aramid cloth by the yard from Amazon and use it for blankets. It's cheap.

 

[cwbullet]

Blanket. I buy Nomex aramid cloth by the yard from Amazon and use it for blankets. It's cheap.

decent link to buy it: Fleabay Nomex

 

[4regt4]

I put baffles in almost everything. How effective they are depends on how they are designed. Some do little to stop laundry burning. But I use no other protection in most of my rockets (those with properly designed baffles), and don't notice any charred spots on my chutes.

The most effective ones force the ejection gasses to change direction, at least a little. The bad ones are those that have holes in the lower bulkhead near the center, and holes in the upper bulkhead near the edge. The ejection blast starts from the motor, sprays upward, goes through the holes in the lower bulkhead largely unimpeded, and then in a near direct line to the holes in the upper bulkhead. Bad design because the blast is mostly going in a straight cone shaped line. Reversing the position of the bulkheads is much better. Blast goes to the outer perimeter to go through the holes near the edge, then have to change direction to go through the holes near the center of the upper bulkhead. I have rockets with each design, and the difference in protection is huge.

Hans.

 

[Back_at_it]

For rockets under BT55 I typically only use wadding. BT55 up to about 3 inch I use baffles. Above 3 inch I prefer a blanket.

4 plate baffles completely eliminate the the need for wadding if built correctly.

 

[4regt4]

Another advantage of a baffle is that they serve as a laundry shelf. I mostly have tall-ish rockets, and need to keep everything from sliding all the way back to the motor.

Hans.

 

[cbrarick]

oh, yea one more huge problem with baffles in md and high power- you can't put a motor in that would normally extend beyond where the baffle is. this isn't a problem for estes rockets because all the motors are the same length. You shouldn't build rockets in a manner where you limit your options - because you might want to do tomorrow what you don't want to do today.

 

[4regt4]

oh, yea one more huge problem with baffles in md and high power- you can't put a motor in that would normally extend beyond where the baffle is. this isn't a problem for estes rockets because all the motors are the same length. You shouldn't build rockets in a manner where you limit your options - because you might want to do tomorrow what you don't want to do today.

Err.... Plan ahead when designing and building the rocket and baffle?

Hans.

 

[SolarYellow]

Yeah. If you're building a standard design that has plenty of space so you could package the longest possible motor and all your recovery, plan ahead and do that. If you're building your own design or modifying another, making a rocket longer than needed to accommodate a longer motor you will never use will sacrifice performance with the motors you do use. Plus, what rocketeer really has a problem with building another lower airframe or whole rocket, even?

 

[4regt4]

Yeah. If you're building a standard design that has plenty of space so you could package the longest possible motor and all your recovery, plan ahead and do that. If you're building your own design or modifying another, making a rocket longer than needed to accommodate a longer motor you will never use will sacrifice performance with the motors you do use. Plus, what rocketeer really has a problem with building another lower airframe or whole rocket, even?

I have a few rockets with limited "head room" because of a baffle. But it was by design. For example, in one I can only fit a max of the 29/240. Am I missing out because the 29/360 won't fit? No, as it is doubtful if this rocket would handle the I200 motor. It's pretty much maxed out with an H180.

Hans.

 

[cbrarick]

best plan = don't use a baffle, then you don't have to worry about it!
just say'in

 

[mh9162013]

best plan = don't use a baffle, then you don't have to worry about it!
just say'in

Instead of worrying about a baffle, you can worry about other things. Pick your poison.

 

[4regt4]

best plan = don't use a baffle, then you don't have to worry about it!
just say'in

I don't worry about it because I plan ahead!

Hans.

 

[4regt4]

I sim dozens of motors for a prospective rocket before ever opening the glue bottle. The rocket in my avatar showed the possibility of fin flutter - based on 3 different sim programs - above 900fps. It simmed to that on a couple of 29/240 motors. So why build it to accept something larger? And it did hit 920fps (carrying 2 different altimeters) on an H180W. Baffle was placed to accept the largest prudent motor.

Hans.

 

[cbrarick]

fin flutter at 545 mph / mach 0.72? The rocket in your avatar? What are the fins made of, balsa? Otherwise I'd say your calculations are way, way off. I've taken plywood fins like that to over mach 1.7 without problems, similar fiberglass fins to mach 3.4. Plus I never tip to tip. Not even on my BALLS project, which will be well above mach 4

I'd look at the formula you're using and see if it's correct, and appropriate for the rocket you've calculated it for. then I'd look at the material properties you entered. Something isn't right.........

 

[4regt4]

Aero finsim and the recent newsletters from Apogee Components. And another that escapes me.... They pretty much agreed. Seems the issue is the exaggerated sweep back from the aft end. Biggest issue is the variations in the listed figures for the strength of the plywood.

Hans.

 

[4regt4]

I'll just add that if I trim a couple inches off the bottom (swept back) portion of the fins, the calculations improve dramatically. But I like those fins, and I'm not in this to win contests.

Hans.

 

[Back_at_it]

Instead of worrying about a baffle, you can worry about other things. Pick your poison.

Why “worry” about anything. A little preplanning will go a long way.

 

[mh9162013]

Why “worry” about anything. A little preplanning will go a long way.

Designing and building a rocket (and most engineering in general) almost always involves trade offs, no matter how much preplanning you do.

 

[MidOH]

Baffles in my BT80 rockets serve as a laundry shelf, coupler to stiffen the tube, good spot to epoxy shock cord, or stronger placement of the forward rail button (if applicable).

Chute protection is the least of it's uses. Mine are two or three simple 2/3 moons. Still use a cheap scap of something for chute protection. Doesn't have to be expensive Nomex.