Fitting Johansen Tip Tanks

Gerry in Oz · #1 08-13-2015, 05:30 PM

Hi all,

I am in the 80% finished and 80% to go phase of my RV-8 build. I have been lucky enough to find a pair of Jon Johansen RV tip tanks which have never been fitted to an aircraft. They look like a very fine product and are in excellent condition. I guess about 12 years old. They hold about 12 U.S. gallons each. I understand that at one time Vans marketed these through their web site on Jon Johansen?s behalf. However, Van?s support no longer has any data.

As to be expected, the empty tanks are a little heavier than the wing tips that they replace at about 13 lbs each. Full of fuel we are looking at 85 lbs per side out there on the wing tips.

My feeling is that I should perhaps reinforce the mounting interface with respect to the taxi and take off ground run loads. (I would not envisage ever landing with fuel in the tip tanks. Emergency situations exempted naturally.)

So, has anybody had experience fitting and using these tanks? I would be very grateful for any advice or experiences with the fitting or operating of these tanks.

Many thanks,

Gerry in Oz

Far North Texan · #2 08-13-2015, 10:15 PM

I have a set of those tanks. Never installed them but I may have the instructions. I will go to the hanger tomorrow and check.

Gerry in Oz · #3 08-13-2015, 10:40 PM

Thank you very much for doing that for me. Very much appreciated.

If you have some luck and can find the installation instructions perhaps you can PM me and I can give you my email address?

BTW, these Johansen tanks have not been produced for some time and due to their scarcity, quality and large capacity, they are becoming quite sought after.

Gerry.

Far North Texan · #4 08-13-2015, 10:48 PM

They seem very high quality. I was just looking at mine the other day. I have seen very few planes with them installed for whatever reason. But no doubt there are builders on this forum that have installed them.
Anyway it's night in my time zone so it will be a few hours before I check.

Snowflake · #5 08-14-2015, 07:29 AM

I suspect many people bought/installed them thinking that more range was better, until they realized that the time limit on their bladder was shorter than what the stock tanks provided anyway.

rv7charlie · #6 08-14-2015, 07:33 AM

For me, it was never about bladder busting; it's always been about 'out and back'. (auto fuel at my hangar)

longranger · #7 08-14-2015, 08:06 AM

Quote:

Originally Posted by Snowflake

I suspect many people bought/installed them thinking that more range was better, until they realized that the time limit on their bladder was shorter than what the stock tanks provided anyway.

I continue to be unable to find an FAR that requires all available range to be used on a single leg....

jchang10 · #8 08-14-2015, 08:18 AM

Exactly. It's a time saver. It's extra safety margin. It's saving money. Last, it's about extending range or busting bladders.

The more i read about crashes after taking on bad fuel or other fuel issue, the better i feel as well.

If Vans designed a new wing with extra fuel, i would rebuild my wing in a heart beat.

jjconstant · #9 08-14-2015, 08:59 AM

I have installed a set of Johanssen tips on my 7a and have used them. When installing, I had to grind some of the fiberglass on the flanges to get the trailing edge to align with the aileron neutral trailing edge. I then added plies of bid fiberglass with structural epoxy on the inside of the flange to recover the lost strength.

Be sure to check for leaks. Mine didn't so much leak as POUR fuel from the tube that goes through the tank for the wiring to the nav/strobe lights. I wound up having to add plies of bid to the inside of the tube.

Verify that you have the correct check valves. There are some that seal completely and others that allow a slight bleed. Johanssen stipulates which you need. I believe it is the one that allows some bleed, but check to be sure.

Also check for fiberglass or epoxy fouling of the vent lines by the fuel filler hole. I had one vent that was blocked, but not completely, so it would not allow proper feedng of fuel. This was discovered during my Phase 1 testing of fuel feeding. You will need to verify that, in flght, the pressure on the main tank vents doesn't over power the vents from the tips, otherwise you won't have access to all the fuel in the tips until you slow down to the point that the head pressure of the remaining fuel can overcome the vent pressure.

Also, only put fuel in the tips right before takeoff or you will wind up pissing a lot of it out the main vents! Between the fuel expansion from the sun and the increased head pressure on the main tanks due to dihedral there's not a lot of room before it comes out the vent.

I have used the tips tanks on a number of occaisions and love having them for the flexibility they offer. With all the work lots of people do to get more speed, NOT having to make that one stop for gas when the destination is just out of prudent range is like adding over 100kts to your speed!

Gerry in Oz · #10 08-15-2015, 10:25 PM

Thank you for your exhaustive and detailed reply Jeremy.
I have done a test fit but not with ailerons attached and rigged. Thanks to you I?ll do that when I can and see where modification may be required.

A very kind gentleman (John) here in Australia has been able to forward me a copy of the original installation instructions so I am now at a much better starting point.. Also, your comment about leaks is consistent with other information folk have be giving me so thanks to all, I will be doing a leak test ASAP and well before installation.

Many thanks to all in particular, John, Jeremy, and Sherrie.

Blue skies and tailwinds,

Gerry in Oz.