Black Hawk Stunt Rocket Fuel Tank HELP!!

[brian thomas bennett]

Hi Guys, I am building the blackhawk stunt rocket, I have built the wing and fixed the keel and fuse formers on. I opted for the side mounted engine setup which now has me scratching head as to how the hell I will get a 3oz tank in the space available. This has now stopped the build as I cannot plank the fuse until I have the tank sorted.  Need advice on the tank setup from someone who has built one please.  

Regards Brian UK.

[Alan Hahn]

I am not sure if it will help, but you should probably move this post to the OT section. Maybe some guys there will have a suggestion (although I am guessing they would have seen your request here in General Section.

[Robert Zambelli]

Hi, Brian. Here's how I did mine. I cut a hole in the front firewall flush with the mounts (yop and bottom) and around 2 1/2 inches wide. Then, I carved a balsa "plug" that would just fit inside, going all the way back. I rounded both sides so that it gave maximum volume.
I sanded around 1/32 off all sides to allow for material thickness.
Using it as a form, I formed brass sheet around it.  When it was the proper shape, I made end caps - front & rear.
After removing the form, I installed the tubing (no uniflow) and it worked perfectly. It's wedged in place and before installing it, I wrap a loop of dental floss around it, in case I have to pull it out. It has worked flawlessly for many hundred flights.

Bob Z.

[gwassenaar]

Robert, allow me to emulate your method? The nose of the fuse is circularly conical. So the maximum space between the engine mount carrying formers and the insides of the engine mounts is conical too. The front side being smaller than the rear side.
Now, when you make your balsa plug by inserting the plug sideways between the mounts and formers, you can put more volume into it than when you insert from the front. Then you make your tank, it can be uniflow, and only then you start planking. I went over the top once by making a glass/epoxy tank in this way. Alas the epoxy was not up to the job and the end wall came off. But in brass or tin plate it would work miracles. But the crux of the matter remains: how big can the final tank be? For an OS46LA I would think you want at least 4 ozs?

[Robert Zambelli]

Gents - may I present the Stunt Rocket tank plug as described?

This works perfectly. The volume is approximately 9.36 in^2 = 5.2 ounces (feel free to check my math)

Mine is vented over and under. I fill it from the lower vent and then cap it off. The vent tube goes directly into the airstream.

This tank feeds the Atwood Triumph .49 and is more than adequate - yes, I have had overruns.

If anyone needs to borrow it, just contact me and you can use it - just pay shipping.

Also, I have a fuselage plug that I used to mold a fiberglass fuselage for the Stunt Rocket - anyone interested in seeing it?

Bob Z.

[brian thomas bennett]

Thanks robert, I have had a few idea's myself but as yours is tested over many flights i think i will use a similar method. I already have the brass shim available in the workshop and will get straight down to building one as soon as i have finished my banshee.

[Larry Renger]

How about a floppy balloon tank inside a balsa box?  Easy, no possibility of fuel foaming,  the tank can be installed and removed through a 1/2" hole as needed for replacement.

I have a gazillion flights on this system in several aircraft, including a Saito 30 powered Flite Streak.  Do a search on Balloon tanks, and you will be rewarded with photo instructions.