Help with F-721B Aft Canopy Deck

[macrafic]

I realized, when I tried to fit the F-721B aft canopy deck to the longeron that I had not cut enough off. Now, I've lost my reference for the measurements (the measurements on the plans all stem from the aft end of the canopy deck, which I long ago cut). Could I get some measurements/verification from you guys?

For those of you who have NOT yet cut the canopy decks, what is your measurement from front to aft on the inside flange (includiing the tab at the front)?

For those of you who HAVE cut, how much slot do you have remaining (remember, this is a tip-up, which is different from the slider)?

Also, for those of you who HAVE cut, can you verify where my understanding has gone awry (tip-up)?
- It looks like the aft 1 15/16" is cut completely off (after match drilling the longerons)
- For the tip-up, it looks like another 13/16" is cut off of the rear, but only on the inside flange, from the "slot" downward
- This leaves a slot of length x"

After all the building I've done, I have no idea why this is giving me so much trouble. I would appreciate your help!

 

[Brantel]

I am sure someone will chime in but if no one has before this evening when I get home, I will measure mine up for you.

Here is what it is suppose to look like....

 

[roee]

Reference measurement

Rich,

Study Brian's photo to get the picture, and here are the measurements: The distance between the top aft cut and the center of the aft-most rivet in the F-721B is 5/16". That gives you a reference, and you can derive the measurements for the other cuts from that using the plans.

And to sanity-check your measurements, keep the following in mind. The top aft cut should just clear the F-631C cabin frame (a.k.a. roll bar) mounting angles. The other cuts are meant to clear the holes in the F-757 gussets for the canopy latch lugs.

-Roee

 

[macrafic]

Still need additional info?

I do appreciate your help guys. Brian, your picture is just like the plans and helps verify the general shape of things.

Roee, I'm having trouble using the rivet as a point of reference. I went home last night and none of the current measurements in the plans originate from the rivet, so I'm still in the dark about measurements.

If I could get 3 measurements from a cut deck, I should be on my way:
- measurement from front of the slot to aft of the inside flange
- measurement from the front of the slot to the aft of the canopy deck
- length of the slot

Thanks, guys.

 

[roee]

Let's try again

Roee, I'm having trouble using the rivet as a point of reference. I went home last night and none of the current measurements in the plans originate from the rivet, so I'm still in the dark about measurements.

Rich,

I gave you a measurement relative to that rivet because the rivet hole was accurately pre-punched in F-721B, and is therefore a reliable reference point. From there I gave you a measurement to the cut of the top flange. That cut is referenced on the plans relative to the original aft end (DWG 18 Detail E), and from there all other measurements can be derived. Let me walk you through it:

1. Identify the rivet hole that I'm talking about on your part. This was the 3rd aft-most rivet hole in the F-721B before you did any cutting, and should be the first aft-most rivet hole remaining in the F-721B after correct cutting. It is also the 30th rivet hole in that row if you count from the front. Make sure you have identified the correct rivet before proceeding!

2. Locate the aft cut of the top flange. The aft cut of the top flange should be located 5/16" aft of the center of that rivet. Mark it on your part.

3. Locate the aft cut of the vertical web and bottom flange. Looking at DWG 18 Detail E, you can see that the aft cut of the top flange should be 1 15/16" fwd of the original aft end, and the aft cut of the vertical web and bottom flange should be 3" fwd of the original aft end. Therefore, the aft cut of the vertical web and bottom flange should be 1 1/16" fwd of the aft cut of the top flange. Mark it on your part.

4. Sanity check against the fwd end of the slot (which was also originally a pre-punched hole, but may have been elongated in fitting the slot, and is therefore not such a great reference). There should be *approximately* 2 9/16" from the aft cut of the top flange to the fwd end of the slot. There should be *approximately* 1 1/2" from the aft cut of the vertical web to the fwd end of the slot. These are *not* exact dimensions, just rough measurements that I took on my fuselage. If you ended up with something quite close to this, then all is good to proceed. If you ended up with something significantly different, STOP and let's figure it out.

5. Cut!

Let me know if this clears it up.

 

[macrafic]

Rich,
1. Identify the rivet hole that I'm talking about on your part. This was the 3rd aft-most rivet hole in the F-721B before you did any cutting, and should be the first aft-most rivet hole remaining in the F-721B after correct cutting. It is also the 30th rivet hole in that row if you count from the front. Make sure you have identified the correct rivet before proceeding!

Roee, therin lies the problem. I have already cut off part of the deck. On the plans, there are two references, one for the tip-up only and the other for both. I did not recognize the one for both, so have only done the one. That leaves me with a deck from which I can not identify the rivet you are talking about.

Sorry for the confusion. I guess I didn't explain my problem quite enough. Hopefully you understand my situation now and can help me from another direction. The only reference point I have left is the front of the slot, which was already pre-drilled when I got the deck from Van's. If you could provide measurements from there, we are in business.

Thanks for your patience!

 

[roee]

Rich,

You can still identify that rivet by counting to 30 rivets from the forward end. But I won't press the issue if you really don't want to do it that way.

If you really really prefer to use the slot as the reference, then you can use the measurements that I gave you in my previous post that I first suggested to use only as a sanity check. Those were measurements of the cuts relative to the slot:

There should be *approximately* 2 9/16" from the aft cut of the top flange to the fwd end of the slot. There should be *approximately* 1 1/2" from the aft cut of the vertical web to the fwd end of the slot.

They're not going to be as accurate as the other method, but I think those are the measurements you've been asking for. Let me know if I misunderstood.

We will figure this out

-Roee

 

[macrafic]

Success!!!!

Thanks, Roee!!!!! The 30-rivet count puts me back in the game!

Appreciate your patience!