Help with cracking fish shells.

[Raceman17]

Hello everyone. This is my first post. I've been reading a ton of posts for about 3 weeks now and have got myself on pretty deep with this "hobby"

 

So I have made good black powder that can launch a baseball to a flight time of 10 seconds. According to skylighter this is a good mix. I think I have got a good system down that works for making consist black powder. I'm launching all my shells with a -20 mesh black powder. It seems to be working great on a 3" shell that is filled with stars. My shells are weighing around 120-140 grams. I'm using the 10% lift suggestion and that seems to work for the heavy shells. So here's my problem.

 

If I go and make a cracking fish or falling leaf shell they only weight 75-80 grams. If I use the 10% suggestion for lift this just doesn't lift the shell over 100 feet.

 

So my question. Should I add something in the Shell (dog food or rice or something with some weight) to give it more Weight therefore making the 10% suggestion of adding more bp or just add more BP to the lift and keep a light shell?

 

Thanks for the great site. There seems to be a lot of good people on the forum.

 

Thanks

[Zmuro]

If your 3" shell weigh just 80g instead of 140g just use 14g of lift for smaller shell and it will go high enough. There is no need for additional weigh.

[ExplosiveCoek]

I second what Zmuro says. Most of the time it is better to have standard lift per x '' shell, than let the lift amount be determined by weight. Just use what works.

[Mumbles]

I agree with the previous two posters as well. If you want to be certain, you can always make a dummy shell of the appropriate mass and fire it. Lighter shells tend to need proportionally more mass. It's more important to get it lifted safely than to stick to some arbitrary rule of thumb.

[Raceman17]

Thanks everyone for the suggestions. I will try to see if I can get a standard lift for x type of shells and see how that works.

[MadMat]

Yeah, I don't want to beat a dead horse, but that 10% is just a starting point and adjustments are sometimes necessary.

[schroedinger]

The 10% rules has a real drawback, it can only be applied for shells up to 3" (and light 4") which are normal shells. Not extra heavy or very light. But it gives a starting poitn for these using 4FA.

Up to 3" you are best of just using a fixed ammount of lift, that you know works for the size. Over that use the ounce per pound rule.

[Raceman17]

I shot off a few shells yesterday evening. Kinda a success but really not. The flying fish fuse did great. I got the height I was looking for. The other two shells ended up flowerpoting. I have narrower it down to either the way I'm gluing the fuses in or the shell fitting to tight in the mortar. On the fuse I was taking two pieces of visco Cannon fuse and taping the delay of 3 seconds. I usually hot glue on both inside and out and I wanted to see if I could get away with just glueing the outside. So it may have been a combination of the tight shell and the two fuses not secured in the Shell. I Laffer I shot those off in went back and made new shells that were glued on both sides and had about an 1/8" clearance all the way around the mortar. I shot that one off tonight and it went great. I felt could have went alittle higher because some of my rolled stars hit the ground still lit. It had about 13 grams of lift in it. I stars were the aluminum firefly formula. I broke the shell with BP coated rice hulls and whistle mix. Edited July 30, 2016 by Raceman17