Avid MKIV stringer

[larrym 1]

Sorry, I don't have a picture, or airframe right now to look at....

There is a steel tube stringer that runs at the lowest part of the fuselage all the way to the tail. It is the lowest stringer. I would like to cut about 18" out of it in the "handles" area at the tail, in order to put in an access pannel. Anyone see any concern with it possibly adding to the strength of the backend or is it only for looks?

I won't have a chance to look at it for myself for a couple weeks, but am thinking in advance....

Thanks,

larry

Edited 26 Dec 2012 by larrym

[dholly 718]

If it is the lower most side longeron it is structural. If it is the belly center stringer you ask a good question..IIRC my Avid Mk-4 had a steel belly stringer but my KF3 was wood, which leads me to think that you might be ok taking out a piece of a metal belly stringer provided that the rest of the tail structure, longerons etc. on your Avid were similar to the KF3. Never heard of a KF tail folding up.

Note: just speculating here, not an engineer!

[birddog486 21]

How about making an access in the side like this.

[EDMO 1078]

If it is the lower most side longeron it is structural. If it is the belly center stringer you ask a good question..IIRC my Avid Mk-4 had a steel belly stringer but my KF3 was wood, which leads me to think that you might be ok taking out a piece of a metal belly stringer provided that the rest of the tail structure, longerons etc. on your Avid were similar to the KF3. Never heard of a KF tail folding up.

Note: just speculating here, not an engineer!

I am with Doug on this - and not an engineer either - the wood Kitfox stringer is there only to keep the fabric off of the bottom crosstubes - am sure the Kitfox could be flown without it, but makes things flow better.

If you are determined to put a bottom access instead of the side access Birddog showed, then could you add the center profile to your access door, just to flow the lines better? Probably makes little difference how you do it, IMO.

ED in MO

[larrym 1]

How about making an access in the side like this.

Thanks, I used to have one on the side, but this time I put a larger one on the bottom, in prart to use it as accsess to the front as well as a larger opening. Only problem, I can't get my head in it to have the access that I thought because of the stringer. With that removed, it should be good. I'll have to wait until next week to see.

[ChrisBolkan 130]

I think the lowest piece of tubing helps strengthen the tail cone assembly in TD configuration. Tail wheel loading will put it into tension where it will help strengthen the entire structure. I wouldn't mess with it if it were me, but I'm not a mechanical engineer either...

Chris

[1avidflyer 1983]

I did a bit of digging through some of my pics and also went out and took a few pics of a C model and my MK IV fusaloge that I just took the covering off of. The MK IV has the metal stringer as was mentioned. The C model does not have it. Then I found a pic I had of my B model that shows down inside the fusaloge and it has a wooden stringer. I'll post the pics of all three. No doubt the stringer on the MK IV adds some strength. Question is: do you need it? As the models advanced, of course they got heavier so perhaps that is why the steel stringer was added to the MK IV. I don't know that answer myself. Would be nice if Steve Winder was on this site and could answer that question. He was around the factory then and would know. We can all do as we like, but if I feel the need to put a door in the back, it would be on the side. If you are mounting a battery there, I would think it would be a lot harder to install if you did it from the bottom. Anyway, here are the pics, hope they are of some help. The C model fusaloge is the brown one, the MK IV is black with some green on the bottom tubes. I'm going to sandblast it clean after I get the tubes repaired. In the pic of the Yellow B, you can see the bottom of the plane under the handle is flat. I think the C would have been the same way with a wood stringer. Neither is like the MK IV at that point. Take care, Jim Chuk

I think the lowest piece of tubing helps strengthen the tail cone assembly in TD configuration. Tail wheel loading will put it into tension where it will help strengthen the entire structure. I wouldn't mess with it if it were me, but I'm not a mechanical engineer either...

Chris

[SuberAvid 617]

Don't think the bottom longeron provides any real structural support to the tail but if yours is a TD and you use it off airport you might want to reinforce the tailspring area while you are welding in there.