f22 instrument panel bulkhead question

[Ratdog]

Someone cut out the center section of the F22 bulkhead in my Lone Eze project.  Below are some photos . My question is about if the center section of this bulkhead is structural or just a place to mount radios etc.  How should I go about fixing this?  I can easily attach a new center section as per the plans but if its structural it will have to be done so the load transfers properly not just glue in. 

Edited September 23, 2023 by Ratdog

[Kent Ashton]

It looks like you started to cut out the instrument panel with the round instrument holes.  I would rebuild that IP to the size shown in the plans, but trimming it so as to attach it to the leftover flanges on the sides with several (4?) layers of BID on each side of the flanges.  I would extend it down to the stub center behind the wheel well and reattach it there with BID overlapping onto the stub.  Fill the wheel-viewing hole for now and recut it later.  You might get away without the center section but why?  It all adds strength and rigidity to the fuselage.  Remember that a 200 # pilot at 4.4G is loading that centersection with part of 880 pounds.

This would be a good time to cut off the top of the fuselage off of the longerons and make a removable cover over the instruments.  It is not hard to do with some hinge hardware on cover and the longerons to make it removable.  You will thank me when  you start wiring the airplane and working on instruments.  The Cozy plans show how to do it.

However what bothers me is the structure and UNI layups shown on p. 4-2 of the plans (pic) which have been cut away or left off the sides of F-22.   They were likely designed there to transfer the canard load to the fuselage.  At the very least, I think I would replace the missing F-22 pieces there,  replace the 9 UNI layups on each side of F-22 and replace the BID attaching F-22 to the fuselage.  You could overlay the existing layups with new all over the F-22.  It would make the F-22 a bit thicker but it won't matter.  OTOH, you could sand away most of the existing layups with a die-grinder and abrasive disc, attach new foam at the sides, and rebuild according to plans.  It sounds like a mess but it goes pretty fast.

[Ratdog]

Basically the best course of action is to  cut whole bulkhead out and grind down flush with the fuselage sides .  Then build a new bulkhead according to plans fit grind it down on the sides until it fits then glass it all in ?  sounds like that would be easier than trying to piece it back together.  so im not sure what you mean by " attach new foam? at the sides.  So basically grinding it all down flush with the sides and the top being careful not to dig into the fuselage side fibers obviously.  I suppose for a lot of it I could take a ocillating tool with a flat blade and cut it flush with the fusulage sides rather than a grinder that might eat into the fuselage fibers.  i also wonder if I could just leave it all there and make a new bulkhead that just glues to the back of the old one . Not sure if that creates clearance problems.

Edited September 23, 2023 by Ratdog

[Kent Ashton]

4 minutes ago, Ratdog said:

Basically the best course of action is to  cut whole bulkhead out and grind down flush with the fuselage sides . Then build a new bulkhead according to plans fit grind it down on the sides until it fits then glass it all in ?  sounds like that would be easier than trying to piece it back together.  so im not sure what you mean by " attach new foam? at the sides.  So basically grinding it all down flush with the sides and the top being careful not to dig into the fuselage side fibers obviously.  I suppose for a lot of it I could take a ocillating tool with a flat blade and cut it flush with the fusulage sides rather than a grinder that might eat into the fuselage fibers.  i also wonder if I could just leave it all there and make a new bulkhead that just glues to the back of the old one . Not sure if that creates clearance problems.

Yes, you could remove both F-22 and IP if you want to and it would probably be best.  I was just trying to give you alternatives.  Cut them close to the fuselage with your oscillating tool or Sawzall and grind off the leftover flanges and overlaps to the fuselage with an abrasive disk and a shop vac.    I removed and replaced a winglet once--that had 13 or so layups.  It is pretty easy to tell where the fuselage sides are if your go gradually.  If you remove a bit of the fuselage sides or less, it won't hurt.  I wouldn't try glue a new bulkhead on top of an existing bulkhead.

Most everything on these airplane can be fixed.  Just remove bad structure back to good structure and rebuild.

[Ratdog]

ok thanks that sounds like the best plan just rebuild it according to plans.  

[Marc Zeitlin]

7 hours ago, Ratdog said:

Someone cut out the center section of the F22 bulkhead in my Lone Eze project... My question is about if the center section of this bulkhead is structural or just a place to mount radios etc.  How should I go about fixing this?

So first of all, you show a picture of the Instrument Panel center section being missing, not the F-22 bulkhead. As much as can be seen in the pictures of the F-22 (which is almost nothing) it looks as though you have a Wright Nose Gear System, which extends aft of F-22 through a hole in the center section. But that's unclear without an actual picture of F-22, not the IP.

Both center sections are structural, although there have not been any failures of F-22's that can be attributed to the hole created for the Wright Nose Gear System "WNGS".

What DOES seem to be missing from the F-22 is the vertical portion of it that extends from the floor to the cross-piece. That is structural as well, as it stiffens the fuselage sides. Given that modification, I'd be examining the whole plane with a fine tooth comb to try to determine just what else the builder did differently from what the plans call for.

Either repair the IP and F-22 as described by Kent (or by total replacement) and _IF_ the center of F-22 has been removed, replace as much as you can while avoiding the WNGS.

Read through the plans a few times so that you can refer to the airplane parts correctly.

[Ratdog]

Sorry i was confused about the bulkhead number on the plans .  The bulkhead in question is the instrument bulkhead.  I think f22 is ok .  now i will have to look more closely at the actual f22 bulkhead as well. 

Edited September 24, 2023 by Ratdog

[Ratdog]

"What DOES seem to be missing from the F-22 is the vertical portion of it that extends from the floor to the cross-piece. That is structural as well, as it stiffens the fuselage sides."

Yup .  I wont have a chance to look until tomorrow but you are right from the photos the f22 bulkhead is missing sides .  Glad I didnt overpay for this project looks like I have a lot of work ahead.  Will get more photos soon .  thanks Marc

[Patrick]

Hi there Ratdog,

I hate to see people struggling to rescue projects that are almost certainly perfectly OK. I am just in the process of finishing my second Long Ez, so please let me help here.

The F22 bulkhead is the structure upon which the canard is mounted. The instrument panel is 18.5 inches further aft, at fuselage station 40.5 (depending on which side of the bulkhead you measure it). The parts of the F22 bulkhead which react the vertical loads of the canard are buried inside the fuselage walls. The vertical piece in the middle of  the F22 is needed to stiffen the whole area, and from what I can see in your photos is still intact. 

It looks as though someone has cut out the the middle of the instrument panel. This bulkhead needs to be intact to stiffen the box structure of the fuselage in that area, but it is not as critical as the F22. I don't think you have a huge problem. You could do one of 2 things.

1. The easy solution. Make a complete new instrument panel from 1/4 in aircraft quality plywood and bolt it to the remaining flange that is still there. This needs a bolt every 4 inches or so, to ensure it is properly secured. You would also need to insert some plywood hard points at the bolt points to prevent the foam from crushing.

2. The more elegant solution. Remove the bits of the old panel and glass in a completely new instrument panel in exactly the same place, using the correct number of glass plies. One of the very early Canard Pushers suggests that plywood is OK for the instrument panel and a few other components, with a slight weight penalty. 

I hope this is of some help, please let me know how it goes.

Cheers, Patrick.