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Fit the Wings Now or Not

mfleming

Well Known Member
Patron
OK, Here it is September 2019 already :eek:

Back in June of 2018 I posted this thread about my center section being narrower than my wing spars.
Here are the numbers from my original post just for reference:

Left wing spar top - 1.4450"
Left Center Section top - 1.4080"
difference -.0370"

Left wing spar bottom - 1.4450"
Left Center Section bottom - 1.4270"
difference -.0270"



Right wing spar top - 1.4460"
Right Center Section top - 1.4315"
difference -.0145"

Right wing spar bottom - 1.4540"
Right Center Section bottom - 1.4365"
difference -.0175"


The how to's and what for's were figured out in that old thread. Now I'm at the point where the RV-7 Manual and common sense say's time to fit your wings.

I have a question about the wisdom of fitting the wings now.

Given all the discussion in the previous post about the tight clearances I will encounter, am I asking for trouble to fit the wings and then remove them for final install later?

One side of me says do it now and if I run into serious problems at least I'm early enough in the build process to make major corrections if needed.
On the other hand I'm thinking do the wing fit/install at final assembly and if the install is a bear at least its done and I won't have to remove them.

Looking for the collective wisdom of those that have gone down this road before.
 
I tried to finish as much of the panel wiring as I could before putting the wings on the last time. It is much easier to walk around and stand next to the forward part of the fuselage without the wings in the way.

Same argument for fitting the canopy. So, I guess it depends how much of that you have completed.
 
I fit mine to do control and fuel installation, then removed them. I want todo as much work as possible at home before going to the airport because the nearest realistic option is 45 minutes away.

All it takes to reinstall them now is a day of cleaning up the shop, plus some beers to bribe friends. I can do it again if needed.

Of you have the room, go ahead and do it. They can come back off.
 
Fit the wings

I fit mine to do control and fuel installation, then removed them. I want todo as much work as possible at home before going to the airport because the nearest realistic option is 45 minutes away.

All it takes to reinstall them now is a day of cleaning up the shop, plus some beers to bribe friends. I can do it again if needed.

Of you have the room, go ahead and do it. They can come back off.

I agree. Had mine on and off several times and made sure to complete all the little jobs.
Forward tank brackets
Fuel line connections
Vent line connections
Fuse/wing fairing
Plumbing connections
You would be suprised how long they take to get perfect.
 
I agree. Had mine on and off several times and made sure to complete all the little jobs.
Forward tank brackets
Fuel line connections
Vent line connections
Fuse/wing fairing
Plumbing connections
You would be suprised how long they take to get perfect.

Even with the prospect of a tight fit??
 
Even with the prospect of a tight fit??
I am not sure what "tight fit" means? Is that referring to the space you have or the wings are tight fit?
As others have mentioned, there is plenty of work to be done, once the wings are attached. You can use sacrificial (hardware store) bolts grinded a bit for an easier installation of the wings.
- The bottom skin overlap needs to be match drilled
- the rear spar can be match drilled
- All fuel line plumbing can be done and tested
- Aileron push/pull can be fitted
- All other task identified by others can be completed
 
I am not sure what "tight fit" means? Is that referring to the space you have or the wings are tight fit?
As others have mentioned, there is plenty of work to be done, once the wings are attached. You can use sacrificial (hardware store) bolts grinded a bit for an easier installation of the wings.
- The bottom skin overlap needs to be match drilled
- the rear spar can be match drilled
- All fuel line plumbing can be done and tested
- Aileron push/pull can be fitted
- All other task identified by others can be completed

By tight fit I mean that the center section is narrower than the spars and will require extra ordinary work to get the spars to slide into the center section.

Thats the numbers listed in the first post and, if interested, detailed in the link to an older post about the tight fit.

I realize that there is plenty to do by fitting the wings now. My concern is if I get the wings fitted and it's a huge struggle...I might be bummed to have to remove them as opposed to fitting them one time in the hangar during final assembly.

I am hoping someone who has had the same tight fit issues (Van's say's it's common) will jump in and say "no worries" OR "save the fitting till the end so you don't have to pull them again.
 
By tight fit I mean that the center section is narrower than the spars and will require extra ordinary work to get the spars to slide into the center section.

Thats the numbers listed in the first post and, if interested, detailed in the link to an older post about the tight fit.

I realize that there is plenty to do by fitting the wings now. My concern is if I get the wings fitted and it's a huge struggle...I might be bummed to have to remove them as opposed to fitting them one time in the hangar during final assembly.

I am hoping someone who has had the same tight fit issues (Van's say's it's common) will jump in and say "no worries" OR "save the fitting till the end so you don't have to pull them again.
Fitting the wings into place was not much of a struggle for me at all, took very little time with a help of friend. The real struggle is to put the close tolerance bolts in, specially in a 7A with the gear tower. Another struggle in a 7A is to build the gear leg fairing but you won't have to do that and I believe now days one can just buy those instead of building them.
When times come for the close tolerance bolts, try freezing them or better yet put them in dry ice and 90% alcohol to contract them slightly.

With best wishes, you are getting close and it is exciting times.
 
building in a hangar?

Did Van's say that removing the wings if there is a "tight fit" will be hard? Mine was a "normal" fit, so it was easy to get the wings off. Final assembly in the hangar was just a few hours work.

How comfortable is your hangar? There are several days of work after the wings are fit for the first time, and several steps are really important to get right, like setting the wing incidence. I'd suggest doing this in a comfortable place so you are not tempted to rush. I'd guess after the initial tight fit, subsequent installations will be easier.
 
I personally don't really see the point in fitting the wings and then just taking them off. Seems like a bit of wasted time. I just plan on doing the fitting towards the end of the build and call it good. Many a builders have followed this plan as well.
 
They have to come off at least once anyway

The wings need to be fit and the rear spar aligned and drilled. Then the bottom flange of fusealage marked and drilled. Then they have to come back off to install nutplates @ the bottom inboard part of the wing and counter sink(dimple) the flange on the fusealage. If you remember everything the first time you can get by with only removing them once. I only did the rear spar hole the first time so I had to refit them to mark and drill the fusealage flange holes. I would also do the front tank to fusealage bracket as well.
 
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Getting Ready to Fit The Wings

I decided to go ahead and fit the wings now and deal with the center section width issues sooner rather than later.

So I'm doing all the jobs needed to get ready for a wing fit. One of the jobs was to make some drift pins out of hardware store bolts.

Well I tried to test fit a pin just to see how the holes line up and I ran into this.

pin.jpg


The pin doesn't seem to be even close to lining up on the aft side. All the holes are some variation of this. It's as if the center section is out of register.

Granted the drift pins are not greased yet but :eek:

Am I being to anal and just need to get a big hammer or do I have a problem :confused:
 
Center section

Is this a QB? If so, I think a call to Vans is in order. Not sure what they would suggest but there are too many QC issues.
Ideally, the two Center Sections are bolted together with a set of spacers matched to the wing spar dimension plus about .005". The spacers hold alignment both in width and hole alignment. They stay there till the center section is completely riveted. If it's an "A" model, you also have two gear towers that may not bolt into place.
 
Is this a QB? If so, I think a call to Vans is in order. Not sure what they would suggest but there are too many QC issues.
Ideally, the two Center Sections are bolted together with a set of spacers matched to the wing spar dimension plus about .005". The spacers hold alignment both in width and hole alignment. They stay there till the center section is completely riveted. If it's an "A" model, you also have two gear towers that may not bolt into place.

Yes, this is a QB tail dragger fuselage.

If I had to do it over again, I WOULD NOT buy a QB.
I could easily go on a rant about all the problems I've had with QBs but I'll leave that for later :D
 
That is going to be hard to fix! Even with a new counter section, the rivet holes are not going to line up with the fuselage bottom skins. There will probably be other problems too. It will be interesting to hear what Vans has to say.
 
Have you tried to put the wings in and try it? I suspect this is what VANS may want to see.
For my RV7A, there was no rivet holes at the bottom skin to line up, those were match drilled manually by drawing lines on thru the wings rivet holes and then extended to the bottom skin to match drill. So no mismatch will be there if it is still the same process.
 
Have you tried to put the wings in and try it? I suspect this is what VANS may want to see.
......<snip>.

I talked to Gus at Van's this afternoon. He said it was not uncommon for the drift pins to be slightly out of alignment without the wing spars to help line things up. LPF-3 and some tapping with a hammer after the wing spars are inserted was his advice.

I also talked to him about the main topic of this thread, i.e. the center section is narrower than the spars.
A previous Van's support tech said use an axe handle to pry apart the center section while inserting the wing spars :eek:
Gus confirmed this advice was valid. BUT when I told him I planned on using some ⅜" all thread with nuts and wide area washers to go in the 7/16" holes in-between the center section to spread the sections apart, he thought that was a really good idea.

I'll post some photos when I get that made up.
 
I talked to Gus at Van's this afternoon. He said it was not uncommon for the drift pins to be slightly out of alignment without the wing spars to help line things up. LPF-3 and some tapping with a hammer after the wing spars are inserted was his advice.

I also talked to him about the main topic of this thread, i.e. the center section is narrower than the spars.
A previous Van's support tech said use an axe handle to pry apart the center section while inserting the wing spars :eek:
Gus confirmed this advice was valid. BUT when I told him I planned on using some ⅜" all thread with nuts and wide area washers to go in the 7/16" holes in-between the center section to spread the sections apart, he thought that was a really good idea.

I'll post some photos when I get that made up.
I have had the best and soundest advise from Gus, his words carry a lot of logic and weight with me.
Best of luck, this is exciting times.
 
Final Assembly

Because it?s been suggested that your Nas bolts be frozen , I had a buddy make me up a brass driver to put in my three X rivet gun , take your prelubed bolts and drive them home while they are still frozen, a few thousandths of an inch shrink makes a big difference in this scenario ,
Good luck jacking your center section apart !!
 
Glad you got a fix. That 3/8" All Thread is bloody brilliant.
Keep us posted.

So here's my attempt at a center section spreader.

I tried ⅜" all thread but felt like I couldn't protect the burnished holes as well as I liked. Any plastic tubing I put on the threads was to large for the 7/16" holes and putting tape on the threads was a pain.

So I'm using ?" all thread. this allows me to have plastic tubing on the threads and as I snug up the nuts, the nuts push the tubing deaper in the hole...protecting the hole at all times.

I'm hoping this will be more controlled than an axe handle :rolleyes:

Click refresh if all the images don't load...

spreader1.jpg


spreader2.jpg
 
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So here's my attempt at a center section spreader.

I tried ⅜" all thread but felt like I couldn't protect the burnished holes as well as I liked. Any plastic tubing I put on the threads was to large for the 7/16" holes and putting tape on the threads was a pain.

So I'm using ?" all thread. this allows me to have plastic tubing on the threads and as I snug up the nuts, the nuts push the tubing deaper in the hole...protecting the hole at all times.

I'm hoping this will be more controlled than an axe handle :rolleyes:

Click refresh if all the images don't load...

spreader1.jpg


spreader2.jpg

Well I did a test to see if this affair would help with the narrow center section problem and it was a success.

I took a series of measurements with an inside gauge before and after putting some pressure on the center section and I easily gained .050". This was at the top of the center section and will give me the clearance needed to fit the wing spar.

I have not attempted to put pressure on the lower center section and will only do so if this method does not work.
 
spreader idea

As wirejock said, brilliant idea. Hope it works, these are scary times I'm sure, but hang in there.

Modern_Problems_Require_Modern_Solutions.jpg
 
Looking good!!

That looks good Michael - making measurements indicates you are being careful. My bolts were a bit different in size but this will do the job, and you can remove them when the wing spar is partially inserted.

I sized my holes, measured them and selected the NAS bolts for specific bores based on the sizes. A large table of measurements extremes. I numbered all the bolts on the heads for the selected locations Right/L, Upper/L, Inner/O

My plans did not show it, but due to available threads, all the large bolts need washers under the heads, unless there is an .063 metal bracket there. This is important. You will need this information for the fitting if you use the NAS bolts.
 
Size (swage) the holes an the NAS require much less pounding.

Because it’s been suggested that your Nas bolts be frozen , I had a buddy make me up a brass driver to put in my three X rivet gun , take your prelubed bolts and drive them home while they are still frozen, a few thousandths of an inch shrink makes a big difference in this scenario ,
Good luck jacking your center section apart !!

I measured all the holes and confirmed the fit was caused by minute misalignment of the various layers of the thinner webs. So - rather than accept a onetime installation of the NAS, or reaming (eek) swaging was selected. I made some tapered steel plugs and measured specifically for each bore, then pushed ( drove) them through. The taper was about .0003 per inch. Some holes required progressive sizes , but with matching of the measured NAS bolts, they all fit snugly, never larger than the heavy web diameter, and were removable. Generous lubrication always. The same pins were used to get perfect alignment on assembly. Pushed through with the NAS bolts. Rounded on the ends to prevent expansion damage or thread damage. They were shorter than the wingspan thickness so they could be removed after each hole.

Measure of success: I had to remove 4 NAS bolts to install washers, and although snug, a small hammer and force was able to remove and reinstall the bolts. No IPA/dry ice slurry bath, although I did have some on hand.
 
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I personally don't really see the point in fitting the wings and then just taking them off. Seems like a bit of wasted time. I just plan on doing the fitting towards the end of the build and call it good. Many a builders have followed this plan as well.

Normally I would agree with you. For my build, I plan on painting before final assembly. I'm hoping to have all the fit and finish work completed before paint.
 
Normally I would agree with you. For my build, I plan on painting before final assembly. I'm hoping to have all the fit and finish work completed before paint.

Well in that case I agree with you that fitting the wings now is of great benefit. Glad to see you gained the space you needed!
 
Wing Fitting Success

The wings are hung and the rear spars drilled.

My little spreader device worked like a champ. the main wing spars slid in with no trouble. the spreader was removed after the main spar was inserted into the center section and the spar was slid in the rest of the way.

The sweep and incidence were set but I could not get better than a ?" forward sweep. The left rear spar was hitting a fuselage rivet, stopping the wing from coming further back. I slid the wing out of the center section enough to relive the rear spar were it was hitting the rivet. This brought the forward sweep to 3/16" and allowed for a more generous edge distance. Although the right wing had only a 3/32" margin for edge distance....kinda scary.

If the photos don't show, just do a refresh until they show up.

Here's the left main spar just after removing the spreader.
spar1.jpg


Here's all four drift pins inserted into the left main center section.
pins1.jpg


Checking the plumb bobs.
bob.jpg


Here's the left rear spar with the section relieved due to the rivet.
spar.jpg


Checking wing incidence angle.
level.jpg


The rear spar drilled and the bolt installed :D
bolt.jpg
 
Congrats!

Congrats Mike! Glad it worked out ok. Don't forget the tank bracket. Now's the right time for that if you have not already done it.
 
Thanks for the pic

I am following Bruce Hill’s blog and replaced that rivet with a flush one during the fuse build. At the time, I had no idea why this was needed, but now I know. Thanks for the pict and thank you Bruce for the heads up.
 
Mike - Fantastic - thanks for sharing your results and pics. I'm building some temporary supports for my wings this weekend, then going recruiting for some help with the installation. Fingers crossed.
 
Congratulations. Also the wing root fairings.

OK, I think all the jobs I can do are done while the wings are on. Here's what was completed:

? Fuel tank bracket (where does one safety to?)
? Main fuel line attached
? Fuel vent line fabricated
? Wing root fairings (Thanks Larry)
? Flaps fitted
? Ailerons rigged

I think that's it. Holler if there something I'm missing.
 
If ailerons and flaps are rigged, install the wing tips.

Interesting...I was going to wait on the wingtips until I get geared up for fiberglass.

Did your wingtips have to be modified to fit the wing? I assumed they would but getting them fitted now is tempting :)
 
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