New Tanks On Flying Airplane

Toobuilder · #1 07-25-2016, 06:58 AM

There are two fuel tanks commonly used on the Rocket: the standard 21 per side and the one rib bay longer 29's. Mine was built with the standard tanks and I'm wanting for longer legs.

I'm considering building the bigger tanks and modifying the airplane to accept them, but would like to hear from anybody who's been down the path before. I have reasonable sheet metal skills and the job seems straightforward, but I'd like to know if there are any "**** on earth" aspects of the job before I start cutting up a perfectly good airplane.

F1Boss · #2 07-25-2016, 08:23 AM

Grab a new set of wings & build 'em with the larger tanks. No aircraft downtime with this plan.

You can build in some of the F1 mods if you'd like - the production line thinking makes a few things easier.

Sell your small tank versions to an F4 builder (4 cyl engine). Talk to Vince about this part of the plan.

Problem solved!

Carry on!
Mark

Toobuilder · #3 07-25-2016, 09:09 AM

That is a possibility that I had not considered Mark, thanks for that. I will add that to the options rattling around in my head.

However, I'd also like to get smarter on the retrofit of bigger tanks to my existing wings.

RV Jerry · #4 07-25-2016, 09:44 AM

The problem with building new wings is that the spars are match drilled to the carry thru. Bulkhead. Although new spars can be matched you would have to buy spars undrilled and then match to your existing bulkhead, a major pain unless you have some sophisticated eguipment.l have converted serval rv-4s to larger fuel tanks and built ten Rockets with large tanks , not rocket science , just work

RV Jerry · #5 07-25-2016, 10:06 AM

To answer you question as to what is involved, wings need to be removed bottom wing skins removed existing leading edge and fuel tank removed install additional flange on spar for fuel tank to screw to ,build new tank as per plans ,either build new L.E. Section or modify the one you have . The only thing you will have to do in addition to plans is matching exsisting mounting holes to new tanks everything else as per plans.
Jerry

Toobuilder · #6 07-25-2016, 01:21 PM

Thanks Jerry. Match drilling the center section was the first red flag that came up in my mind concerning the new wings, though a new set of wings does have a certain appeal.

Will likely be in contact with you to discuss the tank retrofit. Adam and I have both been talking about this for our airplanes.

Fred.Stucklen · #7 07-25-2016, 04:29 PM

Why not just make your existing wing tips into tip tanks? That's what I did on my RV-7A. The plane now can carry 60 gals of fuel instead of the original 42 gal's. Just order a new set of wing tips that you can modify while you're still flying.... And it's best to have them custom made using epoxy resin....

Quote:

Originally Posted by Toobuilder

There are two fuel tanks commonly used on the Rocket: the standard 21 per side and the one rib bay longer 29's. Mine was built with the standard tanks and I'm wanting for longer legs.

I'm considering building the bigger tanks and modifying the airplane to accept them, but would like to hear from anybody who's been down the path before. I have reasonable sheet metal skills and the job seems straightforward, but I'd like to know if there are any "**** on earth" aspects of the job before I start cutting up a perfectly good airplane.

Toobuilder · #8 07-25-2016, 05:14 PM

Tip tanks have been considered, but I'm not a fan of what that will do to the polar moment. Not that I'm planning on competing in the Red Bull Air Races with full fuel, but that much gas so far out is cause for concern for my flying mission.

Also, there is a certain simple elegance with a single, large tank vs. the multiple smaller tanks and the plumbing that goes with them.

hohocc · #9 07-25-2016, 07:48 PM

So by installing the larger tanks, you are increasing the length of the tank, and decreasing the length of the outboard leading edge D box.
Is there any info on how this affects the wing in an engineering/strength sense?
Don't get me wrong, I prefer the idea of 2 larger tanks to 2 standard tanks plus 2 other (tip) tanks, and lots of 4s have 6 tanks, HRs have several tank capacities etc, but I wonder if anybody has done any numbers on this or is it proven to work by being experimental?
The spar bars in the 6 spar have the third longest bar running to the end of the standard tank, all on the aft side of the spar, with the longer 2 (of which the longest is half the thickness) being on the forward side. Are these lengths normally unchanged with longer tanks?
Not trying to put the principle down, just trying to understand what effects it has!
Thanks.

Toobuilder · #10 07-25-2016, 08:13 PM

I dont know what analysis has been done, but since Harmon offers the 58 gallon tanks as an option and a bunch are so equipped, I think its ok.

I believe John's only objection to the big tanks is that it reduces the roll rate and takes away from the minimalist, hot rod feel he was trying to achieve when he created the airplane.