Thanks for the info Ezflap. Interesting about the progression of design, makes sense. I'm too busy to work on it at the moment but I'm going to tear into it later in the summer and I might have a couple of question for you if you don't mind? Mainly I'm thinking of fabricating the stiffners, angle section and re-reinforcements. They are pricey used and I would be using new gear boxes and what not so thinking it may be better to make these parts out of new materials but maybe that's a bit harder than I'm thinking as in the forward floor board you mentioned.

The Cessna landing gear system is a poster child example of how the same thing can be either really easy or damn near impossible depending on whether you are doing it before or after some other thing.

On the assembly line 60 years ago, the difference between building a Cessna 17x or 18x fuselage as a nosewheel or a tailwheel version was only a few minutes and a few dollars one way or another. I wouldn't be surprised of they built the 180 and 182 fuselages on the same jig, Tuesday was taildragger day and Wednesday was nosedragger day. (I have no idea if this was actually done or not). I believe that the 170 production was halted upon the release of the 172, so they never built 170's and 172's at the same time.

The only significant difference (in the main lower doorpost area) was whether they installed the steel bulkhead doubler at the bottom forward landing gear bulkhead (all of them had this same type of doubler at the rear bulkhead because it was the wing strut load path), and whether or not they installed the 70 degree angle at the top front bulkhead (all of them had the 90 degree angle on the rear bulkhead).

But these parts were (or were not) sandwiched in between other bulkhead, floorboard, longeron, stiffener, and outer skin parts as the airplane was built. Building a 170 versus a 172 was a very small difference as it was going together. But going back AFTER the rest of the parts were riveted together, and trying to simply put in the parts that were not installed at the factory? That's a HUGE difference, because you have to take a lot of it apart just to have room to put the (taildragger version) pieces into position.

More than you really wanted to know, ain't it

There are some people over here in NZ doing a similar project - experimental 172 fuselage with cub-style gear (scratch-built I guess).
I am not sure if the project is sitting on it's gear yet.
These guys are skilled engineers and experienced backcountry pilots, so if they think the idea has merit then there's something to it.

Great info again, thanks Ezflap, I'm pretty stubborn and not easily discouraged so the more info I can get the better! I'll make a decision once I can get a good look at it and go over all the pieces of the puzzle.

Hey Battson, that's encouraging, if you find any info on that project I'd sure be keen to know more.

Thanks to all for the suggestions and input on my project. Made the decisions on which way it will roll so just thought I'd shoot a quick update.

I mocked up the PA18 extended gear and it wasn't for me.

I was about to leave it in tricycle configuration mainly just because I set a budget for the project and the numbers weren't adding up. I got a call with an offer to buy a complete straight 180 fuselage that I couldn't pass up and worked well within my budget. The fuse has a float kit, folding rear seats, extended baggage, baggage door and other goodies that I planned on scrounging or building anyway so I'm very happy with the way it all fell into place and doesn't increase my build budget much at all just labor hours. So tail wheel conversion using the 180 parts it is.

Thanks again for the feedback and info, it was a great help.

Good to hear. Im sure youll be happy with it.

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Rogue wrote:Thanks to all for the suggestions and input on my project. Made the decisions on which way it will roll so just thought I'd shoot a quick update.

I mocked up the PA18 extended gear and it wasn't for me.

I was about to leave it in tricycle configuration mainly just because I set a budget for the project and the numbers weren't adding up. I got a call with an offer to buy a complete straight 180 fuselage that I couldn't pass up and worked well within my budget. The fuse has a float kit, folding rear seats, extended baggage, baggage door and other goodies that I planned on scrounging or building anyway so I'm very happy with the way it all fell into place and doesn't increase my build budget much at all just labor hours. So tail wheel conversion using the 180 parts it is.

Thanks again for the feedback and info, it was a great help.

There is a guy who posted his 172 taildragger project ideas over on the 172 club site awhile back and he is using the 180 "stinger" assembly back at the tailwheel. He says he has/is flying one already converted like that. I think it would be a lot better way to go that the leaf spring set up like the 170 uses and with your 180 fuselage it might be a good way for you to go. He is also from Canada btw. Here is a link to that discussion.

http://www.cessna172club.com/forum/ubbt ... Post324497


Look forward to seeing how your project goes.

If you have decided to proceed using 180 parts, the Fravel 172 tailwheel conversion "paperwork" STC is available through me if and when you are interested. This STC calls out the same main landing gear parts that are installed in your 180 fuselage. The use of the 180 stinger system (instead of the 170 leaf springs and "alligator" fitting) will require a separate approval as a deviation from the original STC. However I believe this deviation will be able to be approved with a modest effort. Feel free to contact me at victorbravo *$at{ sbcglobal#dot< net at your discretion.

Thanks guys!

I was just wondering on the tail, I saw that thread as well. I've never had much experience with anything but a leaf tail, is there any benefits in handling with a stinger vs leaf spring? I already have the 170 tail bracket which would be easier to install than the stinger but can go either way. I put an ABW spring on the Scout, it's great on and off pavement, couldn't imagine ever busting it, I was thinking of using a similar spring. Thoughts?

Thanks for the offer EzFlap but its not a certified build so no need for the STC, I've just been using the 180 drawings for reference. What are your thoughts on the stinger vs leaf tail?

Rogue wrote:Thanks guys!

I was just wondering on the tail, I saw that thread as well. I've never had much experience with anything but a leaf tail, is there any benefits in handling with a stinger vs leaf spring? I already have the 170 tail bracket which would be easier to install than the stinger but can go either way. I put an ABW spring on the Scout, it's great on and off pavement, couldn't imagine ever busting it, I was thinking of using a similar spring. Thoughts?

Thanks for the offer EzFlap but its not a certified build so no need for the STC, I've just been using the 180 drawings for reference. What are your thoughts on the stinger vs leaf tail?

I would leave the 170 setup for the tail and put a T3 tailwheel suspension on it. They were working on getting them setup for the C170 and bird dogs.


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I can't say from any personal experience but the guys at the 170 asociation site recommend replacing the main spring about every 500 hrs as I remember, just so a broken spring is not encountered. If it does break it wrecks havoc on the rudder. The Bird Dog main spring is thicker so a lot of guys go that route. I have heard of the 180 stinger breaking but it is pretty rare and I think they hold up to a side load a little better but I'm just guessing. Probably six of one or half a dozen of another.

I have the Stoots tail wheel conversion kit and there is a reinforcement bracket that is installed in the tail cone and then a 170 bracket and tail spring are used. I guess whatever the 170 uses back it the tail cone is what you should probably replicate?

I have mixed feelings about the 170 system, the 180 system, and a brand new system. I've looked at all of them, and we designed a new system halfway between the two for my Fravel upgrade.

FWIW, as far as the leaf spring itself I would look into the composite leaf springs if I had an experimental 170.

But the bracket causes as much problem, and engineering gymnastics to fix it, as the spring does. The big problem for the engineer is that you really really don't want that brittle cast aluminum rear fuselage bulkhead to bend, twist, or flex.

Let me put it this way. After a LOT of time spent with a very very very highly educated and experienced aero-structures engineer, when I am finally able to continue my tailwheel STC upgrade program, my tailwheel spring will be a square or round rod similar to the 180 system, but mounted on the 172 airframe differently. Installing and certifying new structural fuselage bulkheads is not necessary for this mission. My last version of the tail spring ass'y used the existing bulkheads, and we found that the load paths were good that way. We just were trying too hard to make it look like a baby 180 because I personally thought that it would be more easily accepted by the market.

Long story short, the 170/L-19 "alligator bracket" is not a perfect fit on the 172.... the rear fuselages are slightly different. But if you are willing to fit it to the rear fuselage,and you are very good about careful and "clean" removal of the rivets at the rear cast aluminum bulkhead, then the Alligator fitting and associated small brackets and blocks from the 170/L-19 are the fastest and easiest way to go. If you do that, look into a custom carbon fiber tailwheel leaf spring. The composite springs are lighter and softer on the structure. I would strongly recommend the larger ABW size tires because you can get more shock absorption and put less "shock loads" or "spike load" on the rear fuselage structure.

I flew a 170 for 1700 hours, never swapped out the main tailspring and never broke it either.
Periodic replacement or an L19 spring should be the solution for any worries re it holding up

Before you decide on a stinger, go price them and all the associated parts.
Also realize that the 3400 series tailwheel assembly is an interference fit on the stinger, usually installed by heating one and cooling the other.
IMHO tailwheel maintenance is much easier to do with the t/w assembly up on the workbench,
but (also IMHO) that interference fit makes the 3400 series pretty much impossible to easily remove from the stinger.

.

Great points all around, I definitely want to be able to remove the tail wheel relatively easily for servicing, I think for me that's the point that wins out. I agree as well it would be more for looks than practical using the stinger to make it look like a baby 180 anyway. I prefer the leaf in any case and I really like that T3 suspension adaption, looks sweet, more than what I would need but I bet it there's lots of absorption for hits there. I'll beef up the the tail cone and between the bulk heads anyway and it'll have a bush wheel on it to soak things up. At least with the 170 fish mouth I can keep an eye on it for any stress or cracks as well.

I designed mine to use 2 main leafs so you have a chance to find one broken during pre flight, I haven't broke one on this plane but have on my Cub, found it before the other broke.

That makes a lot of sense. Is it stiff with two main leafs or do you use one a bit softer?

All of the leafs are 1/4 X 1 3/4 re arched car springs, one of the main leafs has a slot milled where it attaches to the tail wheel. Many of the pipers use this method and probably others. Most of my flying is on rough fields and I wouldn't change anything.