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Stinson 108 wing tip fuel tanks

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Orange4sky

Active Member
Joined
Apr 14, 2020
Messages
33
Hi,

After a lot of deliberation I have decided on wing tip fuel tanks for my 108 experimental build. It only has about 38 gallons stock and I'm putting in an O-540 so it's going to need more fuel. I ike the idea of gravity feed to keep them simple and the fact that they will not alter the C of G. The wings are already extended and squared off for droop tips. I'm thinking of almost full chord, full profile design made of 5052 .050" welded with baffles that extend out from the tank and double as spar tie-ins. Tank construction will be like a stinson tank with bent flanges welded along the outside forming lips. The outermost side of the tank will have to be lap welded on the inside edge to allow for a drillable flange where the tips are screwed on. They will be bolted to the existing spar extensions to allow for both strong attachment and removal. They will hold about 10 gallons each, have cap vents and be gravity feed. I calculated that each linear inch of chord equals about one gallon so they will add about ten inches of length and 4 sq feet of wing area as well.

My questions are mainly structural. Do you think a through spar design like this would be strong enough? I was thinking about screwing them on like a fibreglass tip but was concerned that would not be strong enough. Does anyone have any suggestions or any issues that you can see with this design?

CamScanner 11-26-2020 12.52_1.jpg
 

akwrencher

Well-Known Member
HBA Supporter
Joined
Oct 16, 2012
Messages
1,312
Location
Gustavus, AK
Sorry, no structural Info for you. I am Interested however in your experimental 108. If you are so inclined to start a thread about it, that would be cool. I'm sure I'm not the only one interested. Would love to know if/where you found plans, etc.
 

narfi

Well-Known Member
Log Member
Joined
Feb 23, 2016
Messages
981
Location
Alaska
The interior volume of a well modified 108 is insane. With bushwheels, a few moved tubes, a few extra doors and a bit more power it makes a great bushplane.
 

Orange4sky

Active Member
Joined
Apr 14, 2020
Messages
33
I'll think about it. I already have a thread on back country pilot but I think there are more homebuilders and experts here. It's not from scratch. It's in the Canadian amateur build category but I'm modifying it quite a bit.

I'd like to move some tubes and open up the rear like those tricked out Alaskan Stinsons but the previous owner put in a nice cargo area already and I'd hate to tear that all out. I will probably make a cargo tube for long stuff though. As for a cargo door, for the passenger area, that I might do as it's tight to get things in the back and that's one of the few big practical issues that keeps the Stinson from being a really great bush plane.
 

Orange4sky

Active Member
Joined
Apr 14, 2020
Messages
33
That's what I'm talking about. I would love to see how they compensated for the cut tubes. And how they moved the control cables. Huge job, but darn, that's a cavern back there. I am also going to have to incorporate float fittings.
 

Mcmark

Well-Known Member
Joined
Sep 24, 2013
Messages
428
Location
Owings, MD
I’m very partial to the 108. Got most of my training and took the exam in ours. My Dad has it tucked away in a container, and will get to it someday... something about the most toys! I'll get it eventually.
At least give us the link to the other site. I want to follow along.
 
Last edited:

Orange4sky

Active Member
Joined
Apr 14, 2020
Messages
33

Orange4sky

Active Member
Joined
Apr 14, 2020
Messages
33
Wing tip fuel tanks, for instance. Technically, it's in the amateur built category in Canada but stateside, it's called experimental. I'm making some modifications to the original design.
 
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