BP: f, ff, fff, ffff

With all the discussions that come up about availability of ffff BP and what to use I wondered how high on the f scale we could actually go.

I know this always becomes an issue of reliable ignition, burn times, and deployment. I also find it difficult to locate ffff. I however am a rifle shooter and have plenty of ff on hand. I have done a bunch of ground testing with a 4” Madcow frenzy with ff and each time it has worked flawlessly.

Is there any reason not to use ff for ejection if it works 100% on the ground?

I’m open to whatever abuse the forum wishes to dish out but I have yet, out of dozens of ground tests to find a reason not to use it.

Out of respect for safety at this point I have always used ffff at launches but as my supply runs low......

Science and thoughtful reasoning wanted.

Brad

If the only size you can find in your area is too big of grain. I believe a mortar and pestle will become your friend.

Eric said:

If the only size you can find in your area is too big of grain. I believe a mortar and pestle will become your friend.

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Not sure I want to risk my hands. Besides, 100% on the ground out of several dozen tests???

GOEX (U.S.) Blasting Grade Black Powder

FA -3 mesh / +5 mesh
2FA -4 mesh / +12 mesh
3FA -10 mesh / +16 mesh
4FA -12 mesh / +20 mesh
5FA -20 mesh / +50 mesh
6FA -30 mesh / +50 mesh
7FA -40 mesh / +100 mesh
Meal D -40 mesh to dust
Meal F -100 mesh to dust
Meal XF -140 mesh to dust

The ‘-’ designation refers to the smallest size screen the powder will all pass though, and the ‘+’ designation is the largest size screen on which all the powder will be retained.

The “A” indicates it is a potassium nitrate based powder as opposed to the “B” blasting powders made with sodium nitrate

4FAg is a special version of 4FA that burns slightly faster than 4F due to a grain coating. 4FAg is the stuff to use if you have access to it. Most of the time you can use 3FA as a stand-in for 4FA but as you can see, 2FA is significantly larger than 4FA. If you're careful, use small amounts and don't confine it, hand grinding 2AF down into 4FA is very possible. 2FA can work for ejection charges if it is confined correctly. I make over 50 pounds of between 2FA and 4FA every year for personal fireworks. If you're the slight bit concerned with your ability or legality, don't hand grind it.

Eric said:

If the only size you can find in your area is too big of grain. I believe a mortar and pestle will become your friend.

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BrAdam said:

Not sure I want to risk my hands. Besides, 100% on the ground out of several dozen tests???

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Wear gloves and do small amounts, always wear safety glasses. If you get ignition, it will just be a poof and in small amounts, it'll be a small poof. I've used an old glass plate and a baby food jar to grind some down very fine to dip some starters in, not recommended but it worked.

If you have 100% success on the ground there is no reason it will not work in the air. You may have to use more than with 3f and especially 4f simply because you don't have as much surface and will be less energetic.

heada said:

GOEX (U.S.) Blasting Grade Black Powder

FA -3 mesh / +5 mesh
2FA -4 mesh / +12 mesh
3FA -10 mesh / +16 mesh
4FA -12 mesh / +20 mesh
5FA -20 mesh / +50 mesh
6FA -30 mesh / +50 mesh
7FA -40 mesh / +100 mesh
Meal D -40 mesh to dust
Meal F -100 mesh to dust
Meal XF -140 mesh to dust

The ‘-’ designation refers to the smallest size screen the powder will all pass though, and the ‘+’ designation is the largest size screen on which all the powder will be retained.

The “A” indicates it is a potassium nitrate based powder as opposed to the “B” blasting powders made with sodium nitrate

4FAg is a special version of 4FA that burns slightly faster than 4F due to a grain coating. 4FAg is the stuff to use if you have access to it. Most of the time you can use 3FA as a stand-in for 4FA but as you can see, 2FA is significantly larger than 4FA. If you're careful, use small amounts and don't confine it, hand grinding 2AF down into 4FA is very possible. 2FA can work for ejection charges if it is confined correctly. I make over 50 pounds of between 2FA and 4FA every year for personal fireworks. If you're the slight bit concerned with your ability or legality, don't hand grind it.

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Isn't it true that basically none of this applies to G series powders?

dhbarr said:

Isn't it true that basically none of this applies to G series powders?

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The difference for g series is the added coating to ease pouring and reduce clumping and an off-set in mesh size. The ratios between sizes are the same, g series is a smaller mesh.
2FA is -4/+13 mesh and 2FAg is -14/+24
4FA is -12/+20 mesh and 4FAg is -40/+60. I had my blasting grade handy so that's what I gave as an example.

The relative difference from 2F to 4F is the key, not the corning process. I'd assume anyone that wants to make their own, either from chems or grinding, would do their own research. No different than making your own APCP.

Appreciate the informative posts, I rarely encounter blasting grades.

I’ve never seen an A grade powder. I use Goex FFg in the rifle and in all the ground testing.

Would altitude affect ability of FF to generate enough pressure???

You have a better than average understanding of powders, due to your re-loading skills.
You will be fine using the FF.

The issue of using BP at higher altitudes [depending on your ground level altitude, I'm only 230ft at our site] can begin around 20,000 ft.
If you fly at 4,000ft above sea level, then issues can arise around 16,000 ft.
You need better containment above this. It is more about temperature than actual pressure.
You are firing at temps 50-100 below O The heat transfer between the grains becomes very difficult.
If you have ever attempted to light a normal match when it's snowing out or below 30. You can watch how slowly the head burns.

In an ejection charge at altitude the grains transfer heat so much slower, due to cold, this will happen:

You start with 1 gr. BP....enough powder burns to pressurize the charge where it ruptures the container, but not enough to completely burn all the BP, it falls unburned.
You end up with only .2 amount burned..... [.8] unburned and not enough pressure to separate parts.
This has been verified with vacuum chambers that catch unburned charge that falls to bottom. Jim Jarvis has PDF somewhere outlines all this.

The solution is contain charge in plastic tubing , [aquarium clear is one type] OR use long skinny charge holders or "gun barrel" containment, I call it. The powder goes in first, with e-match on top. When match fires, the BP must go past the burning match to exit, ensuring complete combustion & full pressure.
Just as in gun barrels the smokeless powder is contained long enough to fully combust.

Not typical short fat holders, but skinny long ones like these:

Powder first
then match on top
some wadding [dog barf etc] to hold in place.
Wrap opening with some tape to seal .

PS. it will be more difficult at altitude when using the 2F due to grains being larger & more space between them for heat transfer. Definite quality containment needed to ensure pressure build up.

This slow mo video show how when placing match under BP effects it vs placing op top.....MUCH MUCH better...even at ground level extremely obvious.

https://www.rocketryforum.com/threa...e-nike-smoke-success-flew-today.144294/page-3

blackjack2564 said:

PS. it will be more difficult at altitude when using the 2F due to grains being larger & more space between them for heat transfer. Definite quality containment needed to ensure pressure build up.

This slow mo video show how when placing match under BP effects it vs placing op top.....MUCH MUCH better...even at ground level extremely obvious.

https://www.rocketryforum.com/threa...e-nike-smoke-success-flew-today.144294/page-3

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Thanks Jim.

I fly at Bong so not an altitude problem for me. Also I use long charge holders. BP on bottom, lighter sits on top of it, then dog barf then taped to hold. In the larger rocket it’s about 3” of “barrel”.

I’ll use what I got when I need it then do some shopping around.

Jim: great stuff.

Success on the ground should translate to success in the air as long as your loading and igniting methods are consistent (wherein lies the problem for many). You get a lot more leeway in technique with FFFFg than with other powders. But if you are consistent (where is the match head, how many matches, how tightly packed, etc.), then there is nothing about the air that should alter anything, unless you are going trans-sonic or to extreme altitude.

One disadvantage to using black powder other then FFFF , is that the larger particles burn longer and are more likely to damage the nylon chute during the ejection process.

terryg said:

One disadvantage to using black powder other then FFFF , is that the larger particles burn longer and are more likely to damage the nylon chute during the ejection process.

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I haven’t noticed it in the ground tests yet. The only thing I protect my nylon harness with is blue painters tape (for the part within the tube not covered by nomex blanket) and aside from residue on it there is no sign of melting, heat damage or burning. I think based on comments above I will give it a go when the ffff runs out and if I don’t find a local source for more.

I know the tape thin is unconventional but it works. Pull a piece the length you want and fold it over the harness. Dirt cheap and replaceable.

Brad

BrAdam said:

I know the tape thin is unconventional but it works. Pull a piece the length you want and fold it over the harness. Dirt cheap and replaceable.

Brad

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Been doing the same tape thing for years...it just plain works.

blackjack2564 said:

Been doing the same tape thing for years...it just plain works.

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Always nice when something is confirmed by CJ. Thanks again for all the advice and info you provide to us.

Brad

Bat-mite said:

then there is nothing about the air that should alter anything, unless you are going trans-sonic or to extreme altitude.

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Why is trans-sonic important? Ejection charges are only fired at low speeds.

terryg said:

One disadvantage to using black powder other then FFFF , is that the larger particles burn longer and are more likely to damage the nylon chute during the ejection process.

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+++ On this. I started out using FFFg before moving to FFFFg. Even with that small difference I noticed more small burn holes in the chute protectors.

What I wasn't doing then was containing the powder. I was using a piece of duct tape and layed the match into it and poured the powder over it and folded over the tape. Putting it in a container and packing with dog barf and taping over my allow all the FFg to burn without the slow burning particles burning holes in your protectors and chutes.

Buckeye said:

Why is trans-sonic important? Ejection charges are only fired at low speeds.

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Good point. Wasn't thinking clearly.

terryg said:

One disadvantage to using black powder other then FFFF , is that the larger particles burn longer and are more likely to damage the nylon chute during the ejection process.

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Handeman said:

+++ On this. I started out using FFFg before moving to FFFFg. Even with that small difference I noticed more small burn holes in the chute protectors.

What I wasn't doing then was containing the powder. I was using a piece of duct tape and layed the match into it and poured the powder over it and folded over the tape. Putting it in a container and packing with dog barf and taping over my allow all the FFg to burn without the slow burning particles burning holes in your protectors and chutes.

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Just gonna chime in on this, too. I was originally given a year's supply of 3F by a generous rocketeer, but I didn't know what I didn't know at the time. Pin holes in parachutes, nomex blow through, and dog barf choking. Then I learned to contain my charges in centerfuge vials, and things got better, but still not on the GOOD scale.

Then one day a veteran flyer, noticing my post flight blues on having schorched another chute loaned me a charge of 4F for my next flight. PROBLEM SOLVED. Smaller grains = faster burn = less problems.

I use ffffg for the flash pan of flintlocks, with ffg propellant for rifles and fffg for pistols.

For practical purposes I have seen no difference in ffffg and fffg for ejection charges. Visually there is not much difference between the two. I have never tried ffg, but sincerely doubt there would be much practical difference in burn rate.

I do use centrifuge vials, and good Nomex covering for recovery stuff.

Centrifuge vials work great. I throw away the caps in my cardboard rockets because I had on the damage the tubing. I stopped using the caps with cardboard and never had the problem again.

I use 4f in these. The top ones I used for a while. Now I don't even drill them but insert the starter in the top.
I use wads of dog barf until it's full. Elec tape cross cross over the top, then around the top.
Both use the cardboard tubes from the coat hangers from the dry cleaners. I plug the bottom with a small piece of dowel. Now I don'thave to drill them.

Interesting. I have never seen someone use Molex connectors for their ejection charges.

cwbullet said:

Interesting. I have never seen someone use Molex connectors for their ejection charges.

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Effective, but introduces another connection point of possible failure. Still, probably reliable enough. I'm actually of the school of thought that we over complicate our av bays.

Banzai88 said:

Effective, but introduces another connection point of possible failure. Still, probably reliable enough. I'm actually of the school of thought that we over complicate our av bays.

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That is probably true.

Banzai88 said:

Effective, but introduces another connection point of possible failure. Still, probably reliable enough. I'm actually of the school of thought that we over complicate our av bays.

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I have an aluminum av bay that doesn't need opening an entire weekend. I tried screw terminal strips and they corroded constantly where 1 igniter wouldn't show continuity. The female plug is turned away from the cup, they're a snug connection, wrap a little tape around it. I can turn them around in minutes, that's the reason.
I find ways to minimize build-time.

Dave A said:

I have an aluminum av bay that doesn't need opening an entire weekend. I tried screw terminal strips and they corroded constantly where 1 igniter wouldn't show continuity. The female plug is turned away from the cup, they're a snug connection, wrap a little tape around it. I can turn them around in minutes, that's the reason.
I find ways to minimize build-time.

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That's something that I can identify with! I like the idea, and using the red connectors it's probably more 'sealed' than about anything else out there for a quick fit type application.