Trap Doors

[SeanB]

I'm considering installing trap doors in both my tanks, and don't plan to use flop tubes. Will have floats as well.

Anyone have any thoughts/input on this idea? Am I wasting my time with this idea for a little extra fuel in positive G maneuvers?

Thanks,

[Kyle Boatright]

In positive G maneuvers, you don't need the trap doors. The fuel will already be where you want it - at the pickups...

[Bevan]

I put them in, cause I wanted to have max fuel in the inner bay during low fuel scenarios (and it was very easy to do during assembly). Not flying yet.

Bevan
RV7A wiring

[TomVal]

Originally Posted by SeanB

I'm considering installing trap doors in both my tanks, and don't plan to use flop tubes. Will have floats as well.

Anyone have any thoughts/input on this idea? Am I wasting my time with this idea for a little extra fuel in positive G maneuvers?

Thanks,

Yikes! How long and hard of a "g" pull are you planning to execute?

[SeanB]

Thanks for the responses. Bevan...did you also cover the other large hole in the center of the same rib?

[SeanB]

Tom,

I'm just planning way ahead, and don't have aerobatics training/knowledge...yet.

What happens if: I do a sustained sharp turn to the left and the fuel selector is on the left tank with say,less than half a tank? It will be a positive G manuever, but the fuel will go outboard. Wouldn't the trap door help?

I guess without experience, I don't know what is expected in this situation and would like to build in some extra capability.

Am I way off base?

Thanks again!

[ao.frog]

Hi.

As long as you're flying coordinated turns, the fuel won't go anywhere.

BUT... when landing in X-wind, you will always want to fly the last portion of final and touchdown with a low wing. In those cirumstances you want as much fuel as possible in the inboard chamber and trapdoors will help you there.

Also, when sideslipping to loose energy, (on final for example) the trapdoors will prevent fuel from flowing towards the lowest side of the tank.

Of course you can always select the high wing (the wing which will be downwind) during landing.

But I say to install them during construction.

[SeanB]

Alf,

I hadn't considered some of your points regarding slips and and crosswind situations for these trap doors. That alone has convinced me to install them in both tanks.

Thanks so much for the great advice.

Best regards,

[Ironflight]

Originally Posted by SeanB

Alf,

I hadn't considered some of your points regarding slips and and crosswind situations for these trap doors. That alone has convinced me to install them in both tanks.

Thanks so much for the great advice.

Best regards,

I have a lot of respect for Alf, please don't forget that...but with more than 1200 hours on my -8, much of it Acro, lots of it with slips and skids for crosswinds, I have never had an issue with fuel feed. No trap doors. Never even considered them along the way. Not sure how many others have them or not (without flop tubes), but I have not heard of this concern before. it would be interesting to hear from anyone who has experienced a fuel feed problem under these conditions with standard tanks.

It's good to consider all the possible pitfalls of the stock design, but then again, it's nice to not have to build something that you don't need.

Paul

[Greg Arehart]

Well, not exactly the same thing, but I once did some photo shoots out of my old C172 and wanted to fly straight while tipping the airplane for the shoot so ended up uncoordinated. Wasn't particularly thinking about the tanks at the time, but after about 5 minutes of flying this way my engine quit because I was selected for the low wing at the time. I don't know if a trap door arrangement would have made a lot of difference (I had half-full tanks at the time).

My two cents of experience. I don't fly any acro.

greg