-3 fuel tanks in a straight, 108. Exploring the possibility

I know this is a common desire for us non -3 people and I have a partial answer from what I have researched and that is: Maybe. It’s possible, but it’s not easy. There is at least one rib in the way and there needs to be some reinforcements installed that the 3 wing has from the factory. I need some more info before I can determine if and how.
Here is my ask: Could someone please, with an -3 wing take some pictures and take some measurements of the reinforcing in and around the outer end of the tanks. I have seen a few pics of a -3 wing online but they are too low res and obviously don’t have measurements. Perhaps if you post the pics and then I can compare mine to see what I need measured. That would be awesome.
I’m going to need extra fuel for my O-540 and I think -3 tanks is the simplest add on. The area above the baggage on my plane is already taken.
Before you get concerned, my Stinson is in the experimental category. I’m going to make sure my installation is at least as strong as a -3.
Cheers.



@stinsono The way the description reads it sounds like someone installed the tanks in the past and then asked for forgiveness by finding someone to approve a 337.

I still need someone to take some pictures of a stripped -3 wing around the outboard end of the removed tank showing ribs, drag wires and reinforcing structures. I need enough detail so I can duplicate what the factory did. Measurements would be helpful too.
I’m not on Facebook. Could someone please broadcast this request on Facebook?

I have seen a 108-1 with Dash Three tanks in it here in NH. I was told that it was done by grafting in Dash Three parts but do not know what was involved to actually do the work. That plane was a ramp queen down in southern NH (maybe at Keene airport?) that had not flown in a long time. It may still be there, dunno. The plane was owned by a deceased person whose son was keeping the plane and planned to fix it up someday. I am not sure if the son is a flyer or not.
Another option would be get a pair of Dash Three wings and install them on your plane. They bolt right on, I am told, and all the controls and such connect right up just fine. You would not be able to increase your gross weight by using the Dash Three wings since the higher gross of the Dash Three is not only due to wing improvements but also due to some heavier tubes in the fuselage structure and stronger main wheel axles. However, the Dash Three wing (with the bigger tanks) could be bolted right onto your plane. Since you are registered experimental you could do this easily.
If you shop for Dash Three wings, be sure to check out the main spars carefully. They use a stronger but more corossion prone alloy than the earlier versions of the wings did. That stronger alloy is part of the way they were able to bump up the gross weight limit but also makes the main spar a bit more vulnerable part in the later model wing than in the earlier ones. It's not a huge deal but it's worth checking the spars out carefully, just in case.
I have a friend here in NH who is restoring a Dash One and his wings are pretty grim. He is considering buying a pair rather than trying to save the ones he has. If you replaced your wings with Dash Three wings he might be interested in your current wings if they are sound. That would help pay for your buying the Dash Three wings, at least a bit.
Bob and Pat and the two Stinsons

Thanks, Bob. If I had known before I started my wing extensions this might have been a possibility. I think it may be easier or only a little more work to add another tank outboard. There is another experimental Stinson near me that I just discovered owned by an airframe AME and he’s adding tanks outboard. The bonus to that is I could probably easily add another 15-20 gallons. I have not had the chance to talk to him yet but it should be interesting.


Posted by: @dcn6102m@rjpustellgmail-com Hi Bob. Are you still holding on to Miss Rose? Did you get Blue Belle fixed the way you want it?
Dennis Crenshaw
Hi, Dennis. I have been working on Blue Belle and am soooooo close to flying her again. Threre were a ton of little things I wanted to get done on her so I just parked her and set to it. That started last Fall and of course has taken a lot longer than I would like but I am almost there. Hopefully she will fly within a week or two, she needs a bunch of paperwork and 337's signed off and sign off the Annual Inspection that has happened along with all the work, plus just a little bit of final assembly work.
Rose is still with me and currently out of Annual since I have been focusing on Belle. Rose should be back in annual and up for sale sometime soon. I am thinking within a month or so but most likely this project will take longer than thought also. They usually do.
I guess I will post updates on both planes as they get back onto flight status. Thanks fore thinking of me.
Stay safe, everyone.
Bob and Pat and the two Stinsons

@rjpustellgmail-com I'll be interested in seeing pictures of Blue Belle when you get her back together. I remember when that airplane showed up on Barnstormers...looked like a real nice one for a very good price. I've been out of the saddle for a while,too. Lots of personal stuff in my life to occupy my time. AirWorx is overhauling my engine now. Plus I've had some airframe issues. I had a stringer underneath the baggage compartment break. Its one of those at the aft end of the cabin which is held clear of the steel tube framework with a standoff. The cotter pin which goes through the stringer and the standoff holding the stringer in position broke. The standoff then proceeded to break the stringer (from vibration) and poke through the fabric on the bottom of the fuselage. So I've had to splice the stringer and now do some fabric work on the bottom for that area and a couple of other little places. Since I had to remove the baggage compartment and the whole interior of the airplane (argh!) I'm going to install a new 406 elt behind the baggage area where the old 121.5 unit was located. Now is the time since I can string the wire underneath the floorboards up the right side to mount the remote switch, which my old unit didn't have.

@dcn6102m That was one of the many things Belle got. a new 406 ELT, behind the cargo compt, mounted on the fuselage tubes. It was a real project to run the wire forward but I was also running several other wires fore and aft at the same time for other upgrades so at least the misery accomplished three purposes for one project worth of work. This is Belle's new ACK ELT.

@rjpustellgmail-com Bob, that's exactly where mine's going, too. That's where the old Pointer 3000 was located. I'm getting the same ACK unit, also. So, did you run the wires up the right side under the rear floor and then tuck it behind the upholstery under the bottom of the door jam, and then up the right forward sidewall upholstery? That's what I'm thinking, anyway. Remote switch will be on the extreme right side of the panel, somewhere.

There was an old Ameri-King ELT in that location. It uses a four conductor wire to a panel mounted control and I was able to use the wire already in place for the Ameri-King. ACK actually sells an adapter to make the Ameri-King cable work with their ELT and panel mount control box. That cable was run when the plane was being reassembled, I suspect. It goes up from the ELT and then forward in the ceiling above the baggage compartment and passenger compartment, then down the door pillar ahead of the front door on the passenger side. I would not want to attempt that routing in an assembled airplane but it works well.
For the wires I added i used the route you describe. Tedious work but it ends up as a good installation.
To mount the ACK ELT I was able to use the Ameri-King mount that was already installed in the plane. Since a good mouning system had already been worked out I took advantage of it. I was able to bend down a couple of end tabs on the Ameri-King mount and it became a flat surface to mount the ACK bracket onto. Since the ACK is not as wide as the Ameri-King I left the side tabs standing up on that mount and theyprovided convenient mounting points for the cable adapter mentioned earlier on the bottom side of the ELT and an Adel Clamp on the top to hold the connector for the GPS signal cable. I elected not to provide a GPS signal to the new ELT (it is optional, not required) but one still has to secure the six inch stub of connetcor cable that would be hooked to a GPS signal. ACK provides a plug body to connect your GPS and power wires with so I clamped that empty connector above the ELT and plugged that loose stub of wire into it. Poof! That wire is no longer loose and flopping around dangling off the ELT.

@rjpustellgmail-com Thanks for the info, Bob. I should be getting my unit shortly from Chief. I won't be hooking up a gps cable either. I do carry an Artex PLB with me when I fly. Apologies to all for hijacking this thread on fuel tank installation and taking the discussion in a different direction.

@dcn6102m One quick reply and I will stop contributing to a hijacked discussion. When installing the panel mounted control unit it is a very frustrating job to get the four little tiny number four machine screws to engage with little tiny number four nuts behind the panel. They are very easy to drop and very easy to not find once dropped, especially when working upsidedown under an instrument panel. The chap who restored Blue Belle came up with a nice idea that I have shamelessly copied. I had to make a new plate up for the ACK control head because it used slightly different screw spacings than the old Ameri-King control head but it was worth the effort.
Take a hunk of fairly thick aluminum sheet, somewhere between about 1/16 to 1/8 inch thick, whatever you have handy. It just has to be thick enough to hold screws in threaded holes in the metal - if it's too thin the screws will strip the threads in the holes. Cut out a rectangular piece a bit larger than the size of the instrument panel cutout needed to mount your control head. Be sure it is cut large enough to include the area where the mounting screws go. Cut a rectangular cutout into the plate that is the same dimensions as the mounting cutout for the little control panel. Then drill and tap number four threaded holes in line with the mounting screw holes on the control panel flange. Now you put your threaded plate on the inside face of your instrument panel cutout for the new control panel. When you insert the control panel into the mounting cutout hole from the pilot side of the panel it will also go through the threaded plate you have on the other side of the panel. Now all you need to do, from the pilot side of the panel and while not upsidedown, is insert your little number four machine screws into the threaded holes of your plate that's behind the panel and snug them up, no laboring (and swearing) on the back side trying to get those tiny little nuts started.
I should also mention that the reason I went with the ACK ELT is the recommedation of an aquaintance who runs an ELT repair station in CT. He tells me the ACK is a nice design but most importantly he tells me that he hardly ever sees an ACK ELT in for repairs at his shop. He sees plenty of the other brands but hardly ever an ACK. That is not a scientific survey but it's good enough for me so I bought the ACK. Several years ago I put one of them into the Cessna 175 I am partners in and it has worked flawlessly so far. Disclosure - I have no financial or personal interest in either my friend's ELT shop or the ACK company, I just like them both.
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