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Z-bracket height (again) - Help!

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matronics(at)cencula.com
Guest

Posted: Sat Mar 17, 2007 3:10 pm Post subject: Z-bracket height (again) - Help!

Guys, I'm stumped!



My when I set my leading edges on the spar, the leading edge skin butts right 

up to the main wing skins (both top and bottom) perfectly.  With the tanks, 

it's a different story.  I've been trying to figure out what's causing the 

gap and the only thing I can come up with is that the Z-brackets are a little 

too high.



If y'all have a couple minutes and would be willing to look at what I've 

tried, I'd sure appreciate any feedback how to fix it.  At this time, the 

only solution I can think of is to put a joggle in the web of the Z-brackets 

which will effectively shorten them by  .040 inch.  That seems like it'll be 

pretty difficult, though so I'm really hoping for a better solution.



Here's some pics that document the problem:



http://www.our7a.com/20070315.html

http://www.our7a.com/20070317.html



Thanks,



Mike Cencula

ceengland(at)bellsouth.ne
Guest

Posted: Sat Mar 17, 2007 5:06 pm Post subject: Z-bracket height (again) - Help!

Michael D. Cencula wrote:

 	  Quote: 	
		   

 

 Guys, I'm stumped!

 

 My when I set my leading edges on the spar, the leading edge skin butts right 

 up to the main wing skins (both top and bottom) perfectly.  With the tanks, 

 it's a different story.  I've been trying to figure out what's causing the 

 gap and the only thing I can come up with is that the Z-brackets are a little 

 too high.

 

 If y'all have a couple minutes and would be willing to look at what I've 

 tried, I'd sure appreciate any feedback how to fix it.  At this time, the 

 only solution I can think of is to put a joggle in the web of the Z-brackets 

 which will effectively shorten them by  .040 inch.  That seems like it'll be 

 pretty difficult, though so I'm really hoping for a better solution.

 

 Here's some pics that document the problem:

 

 http://www.our7a.com/20070315.html

 http://www.our7a.com/20070317.html

 

 Thanks,

 

 Mike Cencula

Have you tried pulling the tank down (back) on the spar with ratcheting 
	


strap clamps? (You'll need a spacer at the rear spar to keep from 

bending the trailing edge skin.) Run the straps directly over ribs; I 

think I put them one bay in from each end of the tank.



With the ribs, it's easy for slight flange irregularities to add up & 

push the back baffle back.



Have you checked to see if the back baffle is totally flat (not bowed to 

the rear) when it's assembled to the ribs & skin? If it's not, that 

would be another indicator that the flanges are pushing the baffle back.



Charlie

matronics(at)cencula.com
Guest

Posted: Sat Mar 17, 2007 7:05 pm Post subject: Z-bracket height (again) - Help!

<snip>

 	  Quote: 	
		   Have you tried pulling the tank down (back) on the spar with ratcheting

 strap clamps? (You'll need a spacer at the rear spar to keep from

 bending the trailing edge skin.) Run the straps directly over ribs; I

 think I put them one bay in from each end of the tank.



 With the ribs, it's easy for slight flange irregularities to add up &

 push the back baffle back.



 Have you checked to see if the back baffle is totally flat (not bowed to

 the rear) when it's assembled to the ribs & skin? If it's not, that

 would be another indicator that the flanges are pushing the baffle back.



 Charlie


	


Charlie,

Thanks for the response.  Indeed I have tried pulling it down with ratcheting 

strap clamps.  I can close the gap up by doing that, but doing so flexes the 

baffle.  Is it normal to need to pull the tank towards the spar before 

driving the screws into the platenuts?



With no clamps on, the baffle is mostly straight, but the center is bowed *up* 

a little.  I believe that bowing is because the weight of the tank is resting 

on the Z bracket.



Mike

ceengland(at)bellsouth.ne
Guest

Posted: Sat Mar 17, 2007 8:51 pm Post subject: Z-bracket height (again) - Help!

Michael D. Cencula wrote:

 	  Quote: 	

 <snip>

> Have you tried pulling the tank down (back) on the spar with ratcheting

> strap clamps? (You'll need a spacer at the rear spar to keep from

> bending the trailing edge skin.) Run the straps directly over ribs; I

> think I put them one bay in from each end of the tank.

>

> With the ribs, it's easy for slight flange irregularities to add up &

> push the back baffle back.

>

> Have you checked to see if the back baffle is totally flat (not bowed to

> the rear) when it's assembled to the ribs & skin? If it's not, that

> would be another indicator that the flanges are pushing the baffle back.

>

> Charlie

 Charlie,

 Thanks for the response.  Indeed I have tried pulling it down with ratcheting 

 strap clamps.  I can close the gap up by doing that, but doing so flexes the 

 baffle.  Is it normal to need to pull the tank towards the spar before 

 driving the screws into the platenuts?

 With no clamps on, the baffle is mostly straight, but the center is bowed *up* 

 a little.  I believe that bowing is because the weight of the tank is resting 

 on the Z bracket.

 Mike

Are the tank holes/spar holes offset by the same amount as the skin gap? 

(I've 'over-prepped' an edge or two & that could leave a gap at the 

point in question.)

Is the gap between the tank skin & wing skin perfectly consistent along 

the entire length & on both top & bottom of the wing? If not:

Is the spar perfectly straight? (Jack under middle of trailing edge spar 

& tweak it up/down to see if the tank will fall into place with a little 

help from the straps.)

Is there any twist in the spar?

If you haven't riveted on the outboard leading edge, have you tried the 

tank without the outboard leading edge in place?

dhall(at)donka.net
Guest

Posted: Sun Mar 18, 2007 8:04 am Post subject: Z-bracket height (again) - Help!

Modifying the zbracket is crazy talk.    Van's isn't perfect, but  

they get it right more than we do.



IMO, you should not be concerned about that small of a gap just yet.   

The tank skin is extremely stiff, and by the time you rivet the  

structure together, it should tighten up enough to close that gap.



Even so, I offer the following suggestions for you at these stage.

- cleco every hole.

- maybe drill out the screw holes and try putting in screws.





On Mar 18, 2007, at 1:50 AM, Charlie England wrote:



 	  Quote: 	
		   

 <ceengland(at)bellsouth.net>



 Michael D. Cencula wrote:

> 

> <matronics(at)cencula.com>

> <snip>

>> Have you tried pulling the tank down (back) on the spar with  

>> ratcheting

>> strap clamps? (You'll need a spacer at the rear spar to keep from

>> bending the trailing edge skin.) Run the straps directly over  

>> ribs; I

>> think I put them one bay in from each end of the tank.

>>

>> With the ribs, it's easy for slight flange irregularities to add  

>> up &

>> push the back baffle back.

>>

>> Have you checked to see if the back baffle is totally flat (not  

>> bowed to

>> the rear) when it's assembled to the ribs & skin? If it's not, that

>> would be another indicator that the flanges are pushing the  

>> baffle back.

>>

>> Charlie

> Charlie,

> Thanks for the response.  Indeed I have tried pulling it down with  

> ratcheting strap clamps.  I can close the gap up by doing that,  

> but doing so flexes the baffle.  Is it normal to need to pull the  

> tank towards the spar before driving the screws into the platenuts?

> With no clamps on, the baffle is mostly straight, but the center  

> is bowed *up* a little.  I believe that bowing is because the  

> weight of the tank is resting on the Z bracket.

> Mike



 Are the tank holes/spar holes offset by the same amount as the skin  

 gap? (I've 'over-prepped' an edge or two & that could leave a gap  

 at the point in question.)



 Is the gap between the tank skin & wing skin perfectly consistent  

 along the entire length & on both top & bottom of the wing? If not:



 Is the spar perfectly straight? (Jack under middle of trailing edge  

 spar & tweak it up/down to see if the tank will fall into place  

 with a little help from the straps.)



 Is there any twist in the spar?



 If you haven't riveted on the outboard leading edge, have you tried  

 the tank without the outboard leading edge in place?

fvalarm(at)rapidnet.net
Guest

Posted: Sun Mar 18, 2007 12:03 pm Post subject: Z-bracket height (again) - Help!

If the concern is "overlap" this is not a problem. Wait until all is

riveted.  I had some overlap until the center of the wing was raised to

straighten the small amount of sag. The skins were still a little close for

my liking so I used a small body file to trim a hair off. No big deal here.



Bevan

RV7A finishing kit

 



--

dan(at)rvproject.com
Guest

Posted: Sun Mar 18, 2007 4:51 pm Post subject: Z-bracket height (again) - Help!

Check the aft flange bend angle on the fuel tank ribs.  If it's not 90 

degrees, then it pushes the baffle "aft" and causes the problem you're 

seeing.



Also make sure the fuel tank ribs are well seated inside the tank skin. 

That means all flanges on all tank ribs are square, and the "flats" around 

the nose aren't causing "high spots" that prevent the nose of the rib from 

seating all the way fwd.



)_( Dan

RV-7 N714D (1230 hours)

www.rvproject.com / www.weathermeister.com / www.weighmyplane.com



---

matronics(at)cencula.com
Guest

Posted: Tue Mar 20, 2007 7:19 pm Post subject: Z-bracket height (again) - Help!

Charlie, you rock!



I dunno what the heck happened, but my wing jig was completely out of kilter.  

The wing wasn't level and it wasn't straight either.  I had a post under the 

center of the rear spar to support it, but that wasn't enough to support it 

evenly.  Instead of one long U shaped bow, I had two smaller ones.  I ended 

up putting three supports under the rear spar at 25%, 50%, and 75% of the 

length.  I also redid all the mounting points and re-leveled everything up.



The only thing I can guess is that either the 4x4s I made my jig out of warped 

or twisted, or maybe my basement floor shifted some since I put the jig up 

last fall.  I also discovered that the bubble in my carpenter's level shifts 

probably a full 1/32 inch just by flipping it around.  Arghhh!



Anyway, spending a couple evenings with a borrowed precision machinist's level 

(I'm tempted to throw out that carpenter's level I originally used) got 

everything straight, level, plumb again.   And now, the skins fit together 

PERFECTLY!!!!  I'm soooo happy!  



Thanks, Charlie, and thanks everyone else who took time from their day to look 

at the problem and respond.



Best regards,



Mike



On Sunday March 18 2007 01:50 am, Charlie England wrote:

 	  Quote: 	
		   > Mike



 Are the tank holes/spar holes offset by the same amount as the skin gap?

 (I've 'over-prepped' an edge or two & that could leave a gap at the

 point in question.)



 Is the gap between the tank skin & wing skin perfectly consistent along

 the entire length & on both top & bottom of the wing? If not:



 Is the spar perfectly straight? (Jack under middle of trailing edge spar

 & tweak it up/down to see if the tank will fall into place with a little

 help from the straps.)



 Is there any twist in the spar?



 If you haven't riveted on the outboard leading edge, have you tried the

 tank without the outboard leading edge in place?

fstringham

Joined: 10 Jan 2006
Posts: 87

Posted: Tue Mar 20, 2007 7:54 pm Post subject: Z-bracket height (again) - Help!

Mike

Relief I am sure. During my build I have always found that, "if it doesn't 

fit you must ........ I have done something wrong. The problem was usually 

simple/something that was right in front of me/and usually someone else 

(Charlie/Dan/Walter/ lectric Bob/Don my very own A&P build partner/Vans help 

desk /and many many others helped me see the light. For me, I now, in the 

face of a problem step back,access the problem,review the many great web 

sights (can you say Dan), and never force the issue or forge a head thinking 

that the problem will somehow magically fix itself later in the build 

process.

Mike, I have really enjoyed following your thread on the tank fit. It 

brought back memories I would like to forget, memories of things learned, 

and the enjoyment of seeing another problem solved by our great RV family.

Frank (at) SGU  RV7A   "NDY"

 	  Quote: 	
		  From: "Michael D. Cencula" <matronics(at)cencula.com>

Reply-To: rv7-list(at)matronics.com

To: rv7-list(at)matronics.com

Subject: Re: Z-bracket height (again) - Help!

Date: Tue, 20 Mar 2007 23:18:14 -0400

<matronics(at)cencula.com>

Charlie, you rock!

I dunno what the heck happened, but my wing jig was completely out of 

kilter.

The wing wasn't level and it wasn't straight either.  I had a post under 

the

center of the rear spar to support it, but that wasn't enough to support it

evenly.  Instead of one long U shaped bow, I had two smaller ones.  I ended

up putting three supports under the rear spar at 25%, 50%, and 75% of the

length.  I also redid all the mounting points and re-leveled everything up.

The only thing I can guess is that either the 4x4s I made my jig out of 

warped

or twisted, or maybe my basement floor shifted some since I put the jig up

last fall.  I also discovered that the bubble in my carpenter's level 

shifts

probably a full 1/32 inch just by flipping it around.  Arghhh!

Anyway, spending a couple evenings with a borrowed precision machinist's 

level

(I'm tempted to throw out that carpenter's level I originally used) got

everything straight, level, plumb again.   And now, the skins fit together

PERFECTLY!!!!  I'm soooo happy!  

Thanks, Charlie, and thanks everyone else who took time from their day to 

look

at the problem and respond.

Best regards,

Mike

On Sunday March 18 2007 01:50 am, Charlie England wrote:

 > > Mike

 >

 > Are the tank holes/spar holes offset by the same amount as the skin gap?

 > (I've 'over-prepped' an edge or two & that could leave a gap at the

 > point in question.)

 >

 > Is the gap between the tank skin & wing skin perfectly consistent along

 > the entire length & on both top & bottom of the wing? If not:

 >

 > Is the spar perfectly straight? (Jack under middle of trailing edge spar

 > & tweak it up/down to see if the tank will fall into place with a little

 > help from the straps.)

 >

 > Is there any twist in the spar?

 >

 > If you haven't riveted on the outboard leading edge, have you tried the

 > tank without the outboard leading edge in place?

_________________________________________________________________

Exercise your brain! Try Flexicon. 

http://games.msn.com/en/flexicon/default.htm?icid=flexicon_hmemailtaglinemarch07

matronics(at)cencula.com
Guest

Posted: Tue Mar 20, 2007 9:15 pm Post subject: Z-bracket height (again) - Help!

Thanks for the nice comments, Frank.  That really makes me feel like part of 

the family.  Hopefully I'll one day get to fly out and meet you guys.  



Do not archive.



On Tuesday March 20 2007 11:53 pm, Frank Stringham wrote:

 	  Quote: 	
		   



 Mike



 Relief I am sure. During my build I have always found that, "if it doesn't

 fit you must ........ I have done something wrong. The problem was usually

 simple/something that was right in front of me/and usually someone else

 (Charlie/Dan/Walter/ lectric Bob/Don my very own A&P build partner/Vans

 help desk /and many many others helped me see the light. For me, I now, in

 the face of a problem step back,access the problem,review the many great

 web sights (can you say Dan), and never force the issue or forge a head

 thinking that the problem will somehow magically fix itself later in the

 build process.



 Mike, I have really enjoyed following your thread on the tank fit. It

 brought back memories I would like to forget, memories of things learned,

 and the enjoyment of seeing another problem solved by our great RV family.



 Frank (at) SGU  RV7A   "NDY"



 >From: "Michael D. Cencula" <matronics(at)cencula.com>

 >Reply-To: rv7-list(at)matronics.com

 >To: rv7-list(at)matronics.com

 >Subject: Re: Z-bracket height (again) - Help!

 >Date: Tue, 20 Mar 2007 23:18:14 -0400

 >

 >

 ><matronics(at)cencula.com>

 >

 >Charlie, you rock!

 >

 >I dunno what the heck happened, but my wing jig was completely out of

 >kilter.

 >The wing wasn't level and it wasn't straight either.  I had a post under

 >the

 >center of the rear spar to support it, but that wasn't enough to support

 > it evenly.  Instead of one long U shaped bow, I had two smaller ones.  I

 > ended up putting three supports under the rear spar at 25%, 50%, and 75%

 > of the length.  I also redid all the mounting points and re-leveled

 > everything up.

 >

 >The only thing I can guess is that either the 4x4s I made my jig out of

 >warped

 >or twisted, or maybe my basement floor shifted some since I put the jig up

 >last fall.  I also discovered that the bubble in my carpenter's level

 >shifts

 >probably a full 1/32 inch just by flipping it around.  Arghhh!

 >

 >Anyway, spending a couple evenings with a borrowed precision machinist's

 >level

 >(I'm tempted to throw out that carpenter's level I originally used) got

 >everything straight, level, plumb again.   And now, the skins fit together

 >PERFECTLY!!!!  I'm soooo happy!  

 >

 >Thanks, Charlie, and thanks everyone else who took time from their day to

 >look

 >at the problem and respond.

 >

 >Best regards,

 >

 >Mike

 >

 >On Sunday March 18 2007 01:50 am, Charlie England wrote:

 > > > Mike

 > >

 > > Are the tank holes/spar holes offset by the same amount as the skin

 > > gap? (I've 'over-prepped' an edge or two & that could leave a gap at

 > > the point in question.)

 > >

 > > Is the gap between the tank skin & wing skin perfectly consistent along

 > > the entire length & on both top & bottom of the wing? If not:

 > >

 > > Is the spar perfectly straight? (Jack under middle of trailing edge

 > > spar & tweak it up/down to see if the tank will fall into place with a

 > > little help from the straps.)

 > >

 > > Is there any twist in the spar?

 > >

 > > If you haven't riveted on the outboard leading edge, have you tried the

 > > tank without the outboard leading edge in place?



 _________________________________________________________________

 Exercise your brain! Try Flexicon.

 http://games.msn.com/en/flexicon/default.htm?icid=flexicon_hmemailtaglinema

rch07

Bob Collins

Joined: 11 Mar 2006
Posts: 470
Location: St. Paul, Minnesota

Posted: Wed Mar 21, 2007 5:24 am Post subject: Z-bracket height (again) - Help!

Boy, I'm kicking myself. Everytime I see one of these (tank gap) things I

post that the problem is the rear spar has sagged. This time I didn't,

figuring this was already a well known fix, but I guess it's not.. It turns

out when it happened to me, Van's had never heard of the fix before but it's

so easy. But, boy, I can sure rememember when it made me CRAZY for a few

hours before I gave the floor jack one and half pumps and "pop" everything

went back into place. 



I read on the RV List once where someone filed down their Z brackets to get

it to fix. Too bad. That likely wasn't the problem and I'm unsure of

changing the Z brackets becoming a safety issue.



Pass it on.



Do Not archive

_________________
Bob Collins
St. Paul, Minn.
Letters from Flyover Country
http://rvnewsletter.blogspot.com/

dan(at)rvproject.com
Guest

Posted: Wed Mar 21, 2007 6:04 am Post subject: Z-bracket height (again) - Help!

The old DWG 12A shows a "jack" supporting the center of the rear spar as the 

wing hangs on the stand.  It says "REMOVE SAG FROM WING WITH A JACK OR 

EQUIVALENT SUPPORT."  Lame!



I really wish Van's didn't even show or mention a JACK on the drawing.  To 

state the obvious at this point, jacks might leak down and retract over 

time, and there goes your perfect alignment.  Given how long it takes some 

builders to build their wings, you really gotta consider something much more 

"fixed" in nature that won't vary over a period of time.



Here's what I did instead:

http://rvimg.com/images/2002/20020715_skeleton_on_jig.jpg



It's a piece of threaded rod with a deep hole drilled into a 4x4 base block. 

The rod can slide in and out of the hole in the 4x4.  With a nut & washer on 

each end of the threaded rod, I could fine tune the support height/pressure. 

Once it was "locked in," it wasn't going anywhere.



I definitely recommend doing something like that instead of using a jack.



)_( Dan

RV-7 N714D (1230 hours)

www.rvproject.com / www.weathermeister.com / www.weighmyplane.com



---

20020715_skeleton_on_jig[1].jpg

Description:

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625 Time(s)

matronics(at)cencula.com
Guest

Posted: Wed Mar 21, 2007 7:44 pm Post subject: Z-bracket height (again) - Help!

Dan,



That's almost exactly what I did, except I added two more of them at the 25% 

and 75% spots.  My blocks are 2x2 and have 2" long hex bolts threaded into a 

tee nut in the bottom end:



http://www.our7a.com/20070320.html



Mike



On Wednesday March 21 2007 10:03 am, Dan Checkoway wrote:

[quote] The old DWG 12A shows a "jack" supporting the center of the rear spar as

 the wing hangs on the stand.  It says "REMOVE SAG FROM WING WITH A JACK OR

 EQUIVALENT SUPPORT."  Lame!



 I really wish Van's didn't even show or mention a JACK on the drawing.  To

 state the obvious at this point, jacks might leak down and retract over

 time, and there goes your perfect alignment.  Given how long it takes some

 builders to build their wings, you really gotta consider something much

 more "fixed" in nature that won't vary over a period of time.



 Here's what I did instead:

 http://rvimg.com/images/2002/20020715_skeleton_on_jig.jpg



 It's a piece of threaded rod with a deep hole drilled into a 4x4 base

 block. The rod can slide in and out of the hole in the 4x4.  With a nut &

 washer on each end of the threaded rod, I could fine tune the support

 height/pressure. Once it was "locked in," it wasn't going anywhere.



 I definitely recommend doing something like that instead of using a jack.



 )_( Dan

 RV-7 N714D (1230 hours)

 www.rvproject.com / www.weathermeister.com / www.weighmyplane.com



 ---

dan(at)rvproject.com
Guest

Posted: Wed Mar 21, 2007 8:25 pm Post subject: Z-bracket height (again) - Help!

Way to go Mike.  You'll have a nice straight wing, that's for sure. 

Straight = Fast 



I want to share a story that's kinda relevant...



Two hangar doors down there's a guy with the fastest "stock" RV-4 I know of. 

His hangarmate also started building an RV-4 around the same time he did, 

but the hangarmate is still "building" -- although he hasn't touched it for 

several years.  His wings are still sitting there still unfinished.  He says 

he managed to inadvertently build a fair amount of twist into one wing, and 

I think that's what caused him to take a break.



All that is ho-hum, but he tells an interesting story about how he built 

major twist into that wing...



According to his story, he jigged the wing up dead nuts on, perfect.  He 

dropped plumb bobs from the corners to confirm everything was square, but he 

didn't clamp it down right away.  Apparently when he finally came back to 

clamp it, he found the wing skeleton was out of alignment.  So he squared it 

up with the plumb bobs and clamped it to the jig.  He drilled the skins to 

the skeleton.



Later on, he (apparently) ended up discovering that a SPIDER had built a WEB 

between the plumb bob and the wing, pulling the string over to the wing and 

throwing everything off!



Dunno if I buy it, but I always thought it was an interesting story. 



do not archive

)_( Dan



---

fstringham

Joined: 10 Jan 2006
Posts: 87

Posted: Thu Mar 22, 2007 5:52 am Post subject: Z-bracket height (again) - Help!

Dan and Mike



Very Interesting........................I must confess that I spent way to 

much time on alignment/cutting/contemplating/rereading the plans/checking 

out Web sites/realigning/drilling/riviting parts together/realigning/double 

checking/had the frame dead nuts on/drilling plexie to the frame/screwed 

canopy to the tip up frame/Fiberglassed the canopy to the 

frame.............................WHAT>>>>>even after all that work and 

aligning double checking .....left side frame of canopy is even with the 

longeron............right side is another story......about mid span forward 

from the roll bar it has a gradual outboard of the longeron miss alignment 

of about 1/8 inch at its extreme. So even after all the WORK of aligning, 

tons of duct tape it still isn't show quality. Really dums me out, but, I 

know it is only a slight blemish. Look on the bright side that slight miss 

alignment here on the right side will make up for what I will probably have 

as a heavy left wing. So the plane will fly true, straight and level, hands 

off............at least that is my story and I am sticking with it.



Mike build on and know new surprises and learning experiences a wait you but 

NEVER GIVE UP!!!!!!!!!!!!!



Frank (at) SGU  RV7A  "NDY"

"Dan Checkoway" <dan(at)rvproject.com>

[quote]Reply-To: rv7-list(at)matronics.com

To: <rv7-list(at)matronics.com>

Subject: Re: Z-bracket height (again) - Help!

Date: Wed, 21 Mar 2007 21:24:30 -0700






Way to go Mike.  You'll have a nice straight wing, that's for sure. 

Straight = Fast 



I want to share a story that's kinda relevant...



Two hangar doors down there's a guy with the fastest "stock" RV-4 I know 

of. His hangarmate also started building an RV-4 around the same time he 

did, but the hangarmate is still "building" -- although he hasn't touched 

it for several years.  His wings are still sitting there still unfinished.  

He says he managed to inadvertently build a fair amount of twist into one 

wing, and I think that's what caused him to take a break.



All that is ho-hum, but he tells an interesting story about how he built 

major twist into that wing...



According to his story, he jigged the wing up dead nuts on, perfect.  He 

dropped plumb bobs from the corners to confirm everything was square, but 

he didn't clamp it down right away.  Apparently when he finally came back 

to clamp it, he found the wing skeleton was out of alignment.  So he 

squared it up with the plumb bobs and clamped it to the jig.  He drilled 

the skins to the skeleton.



Later on, he (apparently) ended up discovering that a SPIDER had built a 

WEB between the plumb bob and the wing, pulling the string over to the wing 

and throwing everything off!



Dunno if I buy it, but I always thought it was an interesting story. 



do not archive

)_( Dan



---

ceengland(at)bellsouth.ne
Guest

Posted: Thu Mar 22, 2007 5:44 pm Post subject: Z-bracket height (again) - Help!

Glad it worked for you. I've worked around wood long enough to know that 

it's almost never in the same place from one day to the next. I left the 

alignment string stretched on my spar even after riveting started. I was 

so paranoid I rechecked the level across the spar every time I started a 

riveting session on the wing.



BTW, the cheap scissor jacks the come with some foreign cars work great 

& are easy to adjust without tools.



Charlie



Michael D. Cencula wrote:

 	  Quote: 	
		   

 

 Charlie, you rock!

 

 I dunno what the heck happened, but my wing jig was completely out of kilter.  

 The wing wasn't level and it wasn't straight either.  I had a post under the 

 center of the rear spar to support it, but that wasn't enough to support it 

 evenly.  Instead of one long U shaped bow, I had two smaller ones.  I ended 

 up putting three supports under the rear spar at 25%, 50%, and 75% of the 

 length.  I also redid all the mounting points and re-leveled everything up.

 

 The only thing I can guess is that either the 4x4s I made my jig out of warped 

 or twisted, or maybe my basement floor shifted some since I put the jig up 

 last fall.  I also discovered that the bubble in my carpenter's level shifts 

 probably a full 1/32 inch just by flipping it around.  Arghhh!

 

 Anyway, spending a couple evenings with a borrowed precision machinist's level 

 (I'm tempted to throw out that carpenter's level I originally used) got 

 everything straight, level, plumb again.   And now, the skins fit together 

 PERFECTLY!!!!  I'm soooo happy!  

 

 Thanks, Charlie, and thanks everyone else who took time from their day to look 

 at the problem and respond.

 

 Best regards,

 

 Mike

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