Fuel Tanks and Propellers

[BES]

About to start the from-scratch rebuild of my PA-12 wings, I need to decide which fuel tanks to use. I have a set of serviceable 18 gallon PA-18 tanks at hand. They probably could be used (the plane will be experimental), but I would like to know some facts about possible alternatives. I have looked at Atlee Dodge's 31.5 gallon tanks and like idea of the possible range they provide. However, I seem to remember from previous posts on this site that the installation may be troublesome and that they are prone to leak. A set is approx. $2,500. I have looked at the DakotaCub 2 gallon tanks and think they are nice. They are quite expensive though, at approx. $3,500 for a set.

Regarding propellers, I am told that - since I will be using the Kenmore STC to install an O-320 - I need to install a Sensenich 74DM6-0-54. Please could I have some comments as to how this prop will perform in a PA-12 with flaps and vortex gens.?

Thanks for your input.

Bent

 

[cubunltd]

I have installed lots of Atlee Dodge Tanks and not had a problem with any of them. If installed properly,They won't crack. The first PA18 I installed them in is still around my area and never leaked. They are 10 years old. And by the way they are on a float plane. I just installed a set in a 180 hp PA12 that I built and am installing another set in a 12 now.
Three years ago I installed an 0-320 in a stock 12 with an 82-44 Borer prop and it performs quite well. Good takeoff performance and cruise around 110 mph. The owner loves it.
cubsunlimited@verizon.net

 

[StewartB]

If your plane is experimental, why would you use the Kenmore engine STC, and why the limitation of the prop choices?
SB

 

[BES]

In this country, you need engineering paperwork to do the engine change. Therefore, it was either paying $100 for the STC or $100 an hour for an engineer from the Danish 'FAA' to do the stress analysis, weight and balance calculations, etc. Kenmore won..!

The prop limitations are due to noise considerations. To operate an airplane in Europe, you need a noise emission certificate. If you are flying a combination (airframe-engine-prop) already measured, it means paying $300 for the certificate and that's that. If you want a previously unmeasured combination, you pay for having the noise emission measured and the paperwork issued. It is financially impractical for the purpose of one single, privately owned aircraft. As an example of how much the actual measurement may cost, I can tell you that, when we needed to renew the environmental permit for skydiving on the airfield where I am based, the noise emission measurements cost approx. $10,000 to have. I'd rather use a prop which has been previously certified..

Bent

 

[diggler]

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[BES]

Thank you very much for your input Gentlemen.

Diggler, please pardon if this is a dumb question, but - assuming I was offered a used prop - what would I need to look for to form an opinion on value? Can I find the measurements the chord is supposed to be, somewhere?

Bent

 

[klm_ak]

Bent,
Just a quick question, are you sure it is a 54 pitch for the Kenmore STC? I don't have the original paperwork in hand, but I have written down that it's a 52 pitch.
KL

 

[BES]

You know what - you're right! In the drawing from Kenmore it says that the M74DM52 or the IAI70GM7450 may be used.
I got the info on the 56 prop from the old German paperwork that came with the project. Also, the LBA (the German FAA) states in the "Noise-List" for this airplane that it used to have a 54 prop.
This needs to be looked into. Thanks very much for drawing my attention to it.

Bent

 

[Sam Beckett]

Fuel Tanks vs Bladder....

I carry 36 Gallons just like most other SC's and my bladder, back and legs are good for about 3 hours. After that, I am ready to stretch the legs, drain the bladder and move around a bit.
I would save my money and install something that you will get more use of rather than a bloated look.
Just another 2cents.
Sam

 

[klm_ak]

Bent,
Most of the folks I have known with Atlee's tanks have had no problems, but all of them received strong instructions from him on doing the fit up after the wing is washed out correctly.

I'm with Sam on the tanks though, if I only flew 300 or fewer miles between fuel stops I would stick with the original tanks. Here in Alaska, the larger tanks are very useful.

If I were building an experimental and thought extra fuel might be useful, I'd probably consider a 4 tank system so the mains could be topped off each time I planned to fly, and the auxilliaries left empty unless I planned on a long trip. A belly tank might be just as nice and the weight would be removeable.
KLM

 

[rsmarch]

Bent,

I am a beginner doing a 12 rebuild and just about finished with installing my first Dodge tank. If you follow the STC, plan to spend about an additional $1000 in parts in addition to the cost of the tanks from Atlee. The STC requires a "hard" full wrap leading edge which 12s don't originally have. I got mine from Atlee for about $450 (6 pieces at $75 each) without shipping. Then there are a couple hundred $ in commonly available parts that are not include with Atlee's kit, and then it requires a larger gascolator which Atlee recommended getting from: http://www.stevesaircraft.com/gascolator.htm for about $200.

I also looked at the Dakota tanks which had just been approved last winter when I made my tanki decision and though they seem more expensive, their kit is more complete. I think the only thing you have to buy not in their kit is the glass sight gages (maybe on the order of $300 for a pair).

As a beginner rebuilder, I have had a few minor problems with the installation of the tanks and leading edge and found it to be very time consuming. Nevertheless, I think I'll be happy with them when done. The Dodge tanks have some good and bad design features. People seem to love them or hate them. There are lots of comments here in other posts. One selling point for me is that they seem to be the most weight efficient way to add fuel capacity to cub. Every time I see cub with a belly tank, I think they are probably carrying about an extra 20 lbs of weight to get about the same fuel capacity as the Dodge set up.

Rod

 

[diggler]

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