Smoke Tank & Fuel System

4/9/2010

Smoke

I decided on fitting a smoke tank for grins. Yeah I know....weight - and this isn't no airshow circuit plane. But I figured weight isn't an issue, since it wouldn't often have oil in it, and when using it I wouldn't have a PAX on board. During the build, I have noticed over time I tend to make purchase decisions that are not consistent... i.e. I spent lots of time and energy researching boost fuel pumps [automotive v airplane], a ready to go solution from Vans Aircraft for $450, or buy and self design for $230... I went for the lower option and possibly the extra work that goes with it. This time, instead of researching heavily into homemade smoke systems, I decided to bite the bullet and go for a ready made kit from smokingairplanes.com. You pay more, but everything is there in the box down to safety wire and clear instructions all tried and tested [very nice and comprehensive kit BTW]. So, I just did the opposite of the fuel pump saga? I have come to the conclusion that my inconsistent purchasing methodology is down to how I feel at a certain stage of the build...sometimes I feel burn-out coming on, and I think those are the times when I am thinking 'oh man, just pay the extra $$$ for the easy route", another time, I may be on a high, so I have the motivation to 'tinker' a little, that's when I end up playing with fuel pumps instead of buying a done deal. I don't know if all that crap made sense, but it does to me :0)

A few weeks back I had prepared the fuselage to house a smoke tank by welding a cradle deal in front of the PAX stick. I was relieved to see that when dry fitting the tank, I had gotten everything right and the tank fits nicely with no clashes anywhere. This tank also has an external fill kit, very convenient. I created this link here for a fellow builder who was hoping to retro-fit the kit to a flying Skybolt: http://www.biplaneforum.com/smoke.html

Fuel System

I fitted a fuel valve extension to the Allen valve. I used 4130 .375 x .035 tubing [ I did try aluminum as the tube extension, but decided the wall wasn't thick enough by the time I had reamed up for it to fit the spigot at the allen valve.]. I added a supporting tube/sleeve in the middle of the run approx 1.5 inch in length. This supporting tube was reamed up to .385 so as to allow for paint thickness, later. The tricky part was welding the sleeve to the fuselage while keeping everything aligned for the extension tube so it will end up rotating nicely...aligning everything cold would no longer be straight after welding, so I made sure the extension tube and sleeve were ever so slightly bowing out from the fuselage when cold...once welded, the sleeve weld joint shrunk as planned, and everything was dead straight post-weld - the extension tube rotates lovely. The lever and part of a brass spigot were cut off an old brass isolation valve and adapted for use on the cockpit end using rivets. I will be powder coating the lever red.

After much deliberation, I decided to go with an automotive inline high pressure Waldro pump and separate regulator. I also decided to add a gascolator and inline filter. The sequence will be: flop tube -> cut off valve -> gascolator -> pump with bypass and check valve -> regulator -> inline filter -> firewall. The wing tank fuel system is totally separate, and will be a simple drain into the main tank with a cut off valve near the rear cockpit. I plan on fitting a one piece stainless steel teflon coated braided line from the wing tank directly to the rear cut-off valve, this line fits inside the removable cabane strut, so will be completely hidden when the banana fairing is fitted. Even though it's teflon coated, I will still be adding rubber grommets to the entry and exit holes in the cabane strut.

The gascolator bracket has been welded in place. The material I used was rather too robust, so I added a bunch of lightening holes to it.

Someone on the forum mentioned if the flop tube was fitted at the rear of the tank [like mine], during vertical flight, the thing would be sucking air, additionally, if low on fuel, the flop tube pick-up may end up sucking air as the plane is stalling on landing.. not a good time for that to happen. So, my purdy painted tank is now at an aluminum TIG buddy's shop having paint removed from the front end and a flange welded in. I feel much better...