Ron's RV7 Factory: Extended Range Fuel Tanks HOBBS 335.0 hrs

Ron's RV7 Aircraft Factory

Welcome to my personal blog. This site was created as an informal description of my build progress in the construction of a Van's RV7 aircraft. A place where family/friends/builders/curiosity seekers can follow along. It is not intended to be a detailed description of every step in the building process as that would be much too time consuming. There are plenty of sites that do a great job in that arena, that is not my intention with this site. My intention is for this to be a philisophical/motivational/inspirational account of the emotional ups and downs of the life changing journey...and it will change your life. I hope this will give you an idea, through my eyes, of what its like to make this transformation. A note to other builders, I am not an expert so do not put your safety at risk by attempting anything you see on this site until you have done your own research, or send me an email so we can discuss it. Any deviations from the plans are not approved, nor endorsed by Van's Aircraft or myself. Thanks for visiting.

Wednesday, October 6, 2010

Extended Range Fuel Tanks HOBBS 335.0 hrs

The idea of adding range to my RV has been in the back of my mind since I decided to build one of these buggers. There are a few good after-market options out there, but they all have something I dont like about them. The Hotel Whiskey Tanks are a nice design and I have heard are well built, but they only give you 9 added gallons at a whopping cost of about $1700+...thats steep for something I wont use very often! Even with that being said, I almost went with this product. Some other ideas are Turtle Pac Bladders used by Bush pilots. What I dont like about these is, #1-the fuel is in the cockpit with me which doesnt give me a warm fuzzy feeling...#2-probably not a viable solution with a passenger aboard as putting the bladder in the baggage compartment would reduce or eliminate all baggage capacity because of weight and balance considerations.

So, the only other option is to build your own auxillary fuel tanks. I have heard of guys flying with leading edge tanks with success. I wasn't sure how difficult this might be but it definitely intrigued me. So, with the help of good ol' VAF I did a search and found a great write-up explaining how to do it. A gentleman by the name of Pat Tuckey came up with his version of extended range tanks. I have looked over his design for an agonizing week or more now and feel it is a good design. This is not something I have gone into lightly, nor should you. His calculations and assumptions seem in order and I now feel comfortable adding these to my plane. At least a hybrid version of the Tuckey tanks...I plan to call mine the 'Tuckey-Duren' tanks. There are many more details that went into this decision than I am going to write here, email me if you have questions about the details of my decision.

Pat built two 17 gallon tanks...I plan to go with smaller versions. My calculations are about 9.5 gallons a side. Although I dont see anything in Pat's 34 gallon design to cause me concern...I will just feel better limiting my tanks to a little less weight. I will still be able to cover some serious ground with an added 18+ gallons onboard.

I threw together a quick graphic (click to enlarge) to illustrate the point of what these tanks will do for me. With some nice round numbers of 175 kts cruising speed and 10 gph fuel burn I came up with the following range circles. These represent range (assume no winds) with 45 min reserve. I came up with approx. 600 nm for the standard tanks (42 gal) and 920 nm on the extended range (ER) (60 gal) tanks with that criteria. The circles arent exact, but close enough to illustrate the point. As you can see, with the ER tanks, I can cover almost the entire US from my home base in Denver without refueling, including Oshkosh and Los Angeles. Thats a nice option to have.