Trimming stifferners for elevator

[Flyin4Fun]

I am just starting to build the elevators on my -7. DWG 5 has a note to trim 3 of the stiffeners shorter for the left elevator. The same note says to match drill the aft hole using the skin as a guide.

The problem: If i trim the stiffeners as noted, they do not even reach the last hole on the skin.

Looking at the drawings for both elevators, the stiffners in question look the same. Same length, same number of holes.

Any ideas??

 

[blueflyer]

When I cut my stiffeners, I did not pay close enough attention to the plans. I cut the stiffeners incorrectly and had to order replacements.

The last hole on some of the stiffeners need to be match drilled once they are clecoed in place (using the skin as a drill guide).

Keep reviewing the plans. I believe the plans are accurate here.

 

[Stalldog]

I just finished my stiffeners. Follow the plans, piece mark the stiffeners as you lay them out, counting how many of each you require. I followed the notches provided by Van's and everything worked out perfectly. You also have one separate piece that 5 "H's" are prepared from, so be sure you have that.

If you have a stiffener that does not reach the last hole, you've got the wrong stiffener in the wrong place.

 

[Flyin4Fun]

Jim,

Did you shorten 2 of the D,E and F stiffneres to make the J, K and L stiffeners per note 1?

Jerry

 

[Stalldog]

Yes, sir, sure did. Then cleco'd and match drilled everything, including the holes in the rear of the stiffeners. Everything worked out fine. Have you already trimmed all of your stiffeners and piece marked them? If so, be sure you have the correct stiffener in the correct location. I can't imagine what else would be causing you a problem.

 

[N355DW]

Jim,

Did you shorten 2 of the D,E and F stiffneres to make the J, K and L stiffeners per note 1?

Jerry

I think the plans can be a little confusing here. I vaguely remember looking at the plans and wondering which hole to measure from per the notes - and thinking to myself "that won't work - the stiffeners will be too short". I remember measuring the spots for the stiffeners to see how much I really needed to trim, and having an "ah ha" moment as to how the note should be read, but for the life of me I can't remember the specifics of this.

Basically they need to be long enough to give you the edge distance on the last hole.

 

[Flyin4Fun]

I have all of the stiffeners trimmed from the bar stock and I have marked A thur H. I have not made the trim per note 1. But I have clecoed the D, E and F to the correct (I think) locations and they fit without trimming.

Looking at the drawings for both elevators, the stiffeners in those locations appear to have the same number of holes. If I trim them this will not be the case.

Jim,

If your skins are still open, could you take a couple of pictures and e-mail them to me, please?

Thanks,

Jerry

 

[Stalldog]

Sure, Jerry, be glad to. I'm at work right now so it will be this evening before I can take some photo's. I've just finished dimpling the skins and stiffeners and ready to prime, so they are not yet riveted in place. It's like N355DW said, it was confusing at first regarding measuring the length of the ones to be trimmed, but I think I did it right -- it all seems to fit anyway and the holes in the end seemed to end up in the right place when drilled. Going from memory, none of them had to be trimmed very much, so maybe that's what you're seeing when you cleco them in place and ask why you need to do it. One thing I think I've picked up on is that you don't want them too long, or else when you bend the trailing edge the vertical portion of the stiffener will hit the opposing skin and imprint, creating a stress problem I suppose. I'll take some pics and send to you tonight.

 

[N355DW]

Going from memory, none of them had to be trimmed very much

Yes, I remember that part!

I just finished riveting mine together, and unfortunately did not take pictures before riveting, sorry!

Just looked at the plans again, and noticed that the 1 is hard to notice on the note for the 702 J & K, so are you you using 1 & 7/8", and 1 & 27/32" for your distances? I'm thinking that is what confused me, just a thought, anyway.

 

[Flyin'Bryan]

Feel (Felt) your pain

So I managed to dig up my experience with this same problem. Click on the link and read my entire post to get the answer you seek. I believe the "light bulb on" moments are down toward the end where I explain what "X" on the plans is equal to. I think the RV-7 and the RV-8 plans are the same here, but keep any potential differences in mind as you read through it.

Hope this helps.

http://bryansrv8project.blogspot.com/2011/11/372-hours-on-hobbs-trimming-stiffeners.html

 

[Flyin4Fun]

A slap the forehead moment

Thanks everyone for your help. I just got home from work and made one more scan of the drawings and saw what Bryan was talking about the value of X. I had seen that on the drawings when I was first cutting the stiffeners but completely spaced it out when I got ready to make the last cuts.

So "Ah ha" (thank you Damon) the "light bulb came on" (thank you Bryan).

Jim, I will no longer need to see your pictures but I will still be happy to look at what you have done if you want to send them. Thank you for your help.

I can move forward now.

Jerry

 

[Stalldog]

Jerry, I read your post that said you probably don't need these, but thought I'd go ahead and send them to you just so you can double check ME! There is a very slight difference between the stiffeners, but as you've learned the distance is measured from the second to last hole, so only minor adjustments are made. Let me know if you've found anything different, as I'm getting ready to rivet my stiffeners to the skins.

Jim

PS: I always have trouble posting pictures, so here goes.

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[Flyin4Fun]

Looks good

Hi Jim,

Thanks for the pictures. The stiffeners appear to be trimmed the same as mine do after I got through my senior moment (only took about 24 hours).

I really appreciate all of the replies.

It sounds like we are both at about the same place in the build. That might be a big plus in the future.

I guess it is time to "build on"

 

[Stalldog]

Good to hear, Jerry. Also, you'd better slow down if you want to keep up with me!

Went flying today -- had a RV-7 land in front of me as I was awaiting clearance to t/o. I had not seen it before at my airport, but it must be someone hangared there as he was a full stop. Hadn't been painted yet, so I'm guessing he's in his testing phase. Sure was a good motivator for me!

 

[bill v]

last two rivets by trailing edag

nobody posts that they had trouble pushing the top skin out of the way to back rivet these two rivets. i think my skin might have been over bent as i had a terrible time here if you have trouble pm me. the jest of it is to clamp the bottom skin to the steel plate so that it cannot rise as you push the top skin out of the way.

 

[Stalldog]

I know they call out backriveting, but for the last two rivets I don't see any reason why we can't just drive the rivets normally from the front and put the bucking bar on the stiffener side of the rivet, right? Shouldn't be any different than riveting the skin to a rib unless I'm missing something here.

 

[longranger]

I know they call out backriveting, but for the last two rivets I don't see any reason why we can't just drive the rivets normally from the front and put the bucking bar on the stiffener side of the rivet, right? Shouldn't be any different than riveting the skin to a rib unless I'm missing something here.

I was able to bend the other side out of the way to reach the trailing couple of rivets. It looked a bit extreme while doing it, but there was no distortion. Here's an edge-on view of mine after riveting the stiffeners and just before doing the final bend.

 

[Stalldog]

Probably a better way than "freehand." Thanks for posting the pic. Guess the only other logical way to do it would be with a piece of flatstock steel with a rivet gun/flat set to offset drive the rivet. Sort of like driving a rivet at the narrow end of a rib.

 

[bill v]

yes thanks for the picture

now i know my skin was over bent

 

[carrollcw]

I screw up the "value of X" too. Had to buy a few more stiffeners as well. I wish they made this step a little more clear. Luckily it was a cheap fix, and I just moved on to another part while waiting for delivery.