What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

Torpedo style tip tanks

Webb

Well Known Member
Sponsor
One of the guys at my airport is restoring an older plane (non RV). He didn’t want to have the fuel tank in the fuselage.

So he made torpedo style tip tanks by using RV wheel fairings for the front and rear and fabricated a tube in between.

It makes me wonder why somebody hasn’t done this on an RV……or have they?
 
Tip Tanks....

One of the guys at my airport is restoring an older plane (non RV). He didn’t want to have the fuel tank in the fuselage. So he made torpedo style tip tanks by using RV wheel fairings for the front and rear and fabricated a tube in between. It makes me wonder why somebody hasn’t done this on an RV……or have they?

Hmmmm....Interesting. So they are fiberglass? Or are the wheel fairings just for aerodynamics? Is this a tail-dragger? In an incident involving tail-draggers (say, for instance, a ground loop or near ground loop or other minor incident) the wing TIPS are what takes a lot of the damage. Having fuel spreading around from a ruptured tip tank doesn't sound like something I'd want happening.....IMHO...:eek:
 
Without proper analysis, tip tanks can cause unwanted structural, stability, and control issues…

True but there are a lot of planes out there with them. One of my favorites is the Marchetti 260 in the James Bond flick.

According to D’Shannon Aviation, they can also increase the useful load which I assume is from added lift. Also, improved stability and control.

We’ve seen an entire leading edge tank, extra leading edge tank, wing tip turned into a tank, and a tank that is partially in the wing tip and a tube that is in the lightening holes. None of which can claim all the benefits of an external tank.

With the potential benefits, I am curious as to why the RV experimental world hasn’t done it.

Perhaps it’s looks.
 

Attachments

  • IMG_0892.jpg
    IMG_0892.jpg
    256.8 KB · Views: 59
  • IMG_0894.jpg
    IMG_0894.jpg
    105.1 KB · Views: 82
Last edited:
Hmmmm....Interesting. So they are fiberglass? Or are the wheel fairings just for aerodynamics? Is this a tail-dragger? In an incident involving tail-draggers (say, for instance, a ground loop or near ground loop or other minor incident) the wing TIPS are what takes a lot of the damage. Having fuel spreading around from a ruptured tip tank doesn't sound like something I'd want happening.....IMHO...:eek:

They are fiberglass and on a taildragger. The wheel fairings provided the airfoil as a start for him which I thought was creative.

For risk reduction, I would think tanks are usually empty except when traveling. Burn fuel off the mains and pump tips into mains so when you land, tips are empty.
 
True but there are a lot of planes out there with them. world hasn’t done it.....

Engineering was done specific to those applications most certainly.

The RV spar extensions I've seen (which is limited) are 032 with integral rolled caps. Adding tip tanks is not a "make it fit" type endeavor.
 
I have the Joh Johansen (sp?) tip tanks on my RV7A. Additional 12.5 gallons each side. He is in Australia and designed them to their certification standards with Van checking the design and giving his blessing. He originally designed them for his RV4 and has been around the world both ways. They are exactly the same shape as the batwing tips but heavily reinforced with many layers of fiberglass and some carbon fiber (I believe for both stiffness and conductivity of static). They screw into the same holes as the regular tips and are completely gravity fed, with checkvalves to prevent sling fuel from the mains into the tips.

They have been very useful for long trips. I don’t believe he makes them anymore, but the ideas and executions are out there.
 
True but there are a lot of planes out there with them. One of my favorites is the Marchetti 260 in the James Bond flick.

According to D’Shannon Aviation, they can also increase the useful load which I assume is from added lift. Also, improved stability and control.

We’ve seen an entire leading edge tank, extra leading edge tank, wing tip turned into a tank, and a tank that is partially in the wing tip and a tube that is in the lightening holes. None of which can claim all the benefits of an external tank.

With the potential benefits, I am curious as to why the RV experimental world hasn’t done it.

Perhaps it’s looks.

Webb- Airplanes with tip tanks typically have them designed in from the start and the wing shape & structure designed to accommodate.

In the cases where they increase the gross weight it's typically because they are actually transferring some of the dead weight outboard in flight so that the weight the wing has to support is more evenly distributed along its span.

On something like an RV where the spars scale down to a much thinner profile the further outboard you go, I would want to see a lot of data supporting why you don't need to beef up spars that weren't originally designed to support extra lbs out on the skinny end before I was okay with that.

It obviously works to some degree because planes with hotel whiskey tip tanks don't seem to have any problems, but unless somebody has done the engineering you really don't know how much margin you have.

Also it will undoubtedly change the roll and spin characteristics in potentially unexpected ways, so you've become a test pilot in the truest sense if you start doing stuff like that.

Interesting side bar- On the Cessna 340, those 50 gallon tip tanks are actually the mains. The ones in the wings are the auxes. That airplane was designed with that intent and it works great.
 
I’m just surprised that nobody as far as I’m aware hasn’t made a test set yet and checked out the empty flight characteristics.
 
I’m just surprised that nobody as far as I’m aware hasn’t made a test set yet and checked out the empty flight characteristics.

I would think a big concern is the full-fuel characteristics. This would change the rotational moment of inertia, and possibly effect spin recovery.
 
Without a doubt!

Yes, putting that weight at the tips WILL change the moment of inertia...to what extent? That is what a proper analysis will tell you. You certainly don't want to find out that a spin is unrecoverable the hard way.

Also, as previously posted, the approved gross weight increase was mainly due to the reduced bending moments on the wing while fuel is in the tip tanks. Again, a proper analysis will tell you.
 
Tip tanks on a tail dragger....

True but there are a lot of planes out there with them. One of my favorites is the Marchetti 260 in the James Bond flick.

Tricycle gear.........

According to D’Shannon Aviation, they can also increase the useful load which I assume is from added lift. Also, improved stability and control.

For a Bonanza: tricycle gear.....



With the potential benefits, I am curious as to why the RV experimental world hasn’t done it.

I think if it was such a good idea, a lot of people would have done it. Or there would be some enterprising group that would be selling them "after market". Must be a good reason not many have been done.
 
My 8 I’m building is not a likely candidate but a RV-10 seems like a likely candidate. Tricycle and a thirsty engine.

Just a guess as to why is cost, effort, and uncharted territory.

A funny side note - a good friend of mine with a Bo w/ tip tanks and I flew for the $100 hamburger. He told the line boy to top the tanks. The line boy did….all 4 tanks. It was the first time I’ve ever seen Tom speechless when he got the bill for 90 gallons.
 
Back
Top