VansAirForceForums  
Home > VansAirForceForums

-POSTING RULES
-Advertise in here!
- Today's Posts | Insert Pics

Keep VAF Going
Donate methods

Point your
camera app here
to donate fast.






VAF on Twitter:
@VansAirForceNet

  #11  
Old 08-08-2022, 07:18 AM
DanH's Avatar
DanH DanH is offline
 
Join Date: Oct 2005
Location: 08A
Posts: 11,244
Default

Quote:
Originally Posted by wirejock View Post
Remove the cowl. Apply some flox or layers of fiberglass inside equal to the amount you need to remove on the outside. That way the finished thickness after sanding will be correct. Grind it down to the mark and move on.
The spinner-sized hoop at the front of the cowl is structure, and it's stressed more than most folks realize. Dynamic pressure inflates the cowl like a balloon, and total load (available dynamic pressure x Cp x area) can be hundreds of pounds. Take a look at the cracks near the inlets on some of the older polyester cowls.

So, don't fill from the inside and cut away the original layup. There's a good chance the result will not be as strong as the original.

Instead, continue trimming the rear edge of the cowls, shifting the entire cowl assembly rearward until the most narrow dimension in the spinner gap matches the desired gap. Finished fitting the cowl...all fasteners or hinges in place, all edges gapped for paint, completely done.



Now remove the cowl, set it upright on the floor with all the side and nose fasteners in place, and scuff sand the face of the flange with a coarse grit. Mix a batch of epoxy/flox and spoon on a generous quantify. Press it with a board or other flat surface which has been prepped for mold release...slick tape, wax, PVA, whatever works. Leave it in place until after cure, then pop it off, and sand the perimeter to a nice even radius, just like the original edge. If there are some voids in the surface, touch it up with dry micro. When if looks good, make two easy cuts across the flox with a hacksaw blade to separate the halves. Dress the cuts and you're done.

__________________
Dan Horton
RV-8 SS
Barrett IO-390

Last edited by DanH : 08-08-2022 at 07:22 AM.
Reply With Quote
  #12  
Old 08-08-2022, 08:27 AM
wirejock's Avatar
wirejock wirejock is offline
 
Join Date: Oct 2005
Location: Estes Park, CO
Posts: 5,888
Default Cowl fit

Thanks guys. Funny how the brain gets stuck.
Dan's method is the way to go.
The gap at the tip will increase, but that can be filled in as he recommends.
__________________
Larry Larson
Estes Park, CO
E-mail: wirejock at yahoo dot com
Builder Blog: http://wirejockrv7a.blogspot.com
Donated 12/2022, plus a little extra.
RV-7A #73391, N511RV reserved
Disclaimer
I cannot be, nor will I be, held responsible if you try to do the same things I do and it does not work and/or causes you loss, injury, or even death in the process.
Reply With Quote
  #13  
Old 08-08-2022, 08:39 AM
Stevea Stevea is offline
 
Join Date: Jun 2008
Location: San Jose, CA
Posts: 263
Default cowl nose ring buildup

Dan's method is perfectly acceptable for building up the cowl nose ring.

But, when I did mine, I wasn't that confident in my epoxy/flox buildup techniques, or my ability to get the shape to come out right. The nose ring on mine was out of parallel with the spinner from left to right, and the cowl halves were off top to bottom. The left side of the top cowl was recessed almost 1/4" aft from where it should have been, tapering to "almost right" on the right side. The bottom cowl was off in a similar way, but not as bad as the top. The net result was absolutely nothing on the nose ring was remotely parallel to the spinner back-plate, the gap varied in size all the way around the circle.

So, I ended up epoxying balsa wood to the front of the nose ring, then block sanding the parts back down so there was a constant gap between the spinner back-plate and the cowl. After that I put two layers of glass over the balsa, and sanded everything down to blend it in. The result came out great. (See....all that model airplane building as a kid did come in handy! )

Click image for larger version

Name:	build 2-282.jpg
Views:	70
Size:	524.4 KB
ID:	29185
Click image for larger version

Name:	build 2-284.jpg
Views:	69
Size:	511.5 KB
ID:	29186
Click image for larger version

Name:	build 2-290.jpg
Views:	65
Size:	538.4 KB
ID:	29187
Click image for larger version

Name:	build 2-294.jpg
Views:	83
Size:	547.3 KB
ID:	29188
__________________
Steve Allison
RV-6A - sloooowwww build
First flight - 3/8/14
Phase II - 5/19/14
Reply With Quote
  #14  
Old 08-08-2022, 08:53 AM
rockitdoc's Avatar
rockitdoc rockitdoc is offline
 
Join Date: May 2020
Location: Fort Collins, CO
Posts: 813
Default

Quote:
Originally Posted by DanH View Post
Instead, continue trimming the rear edge of the cowls, shifting the entire cowl assembly rearward until the most narrow dimension in the spinner gap matches the desired gap. Finished fitting the cowl...all fasteners or hinges in place, all edges gapped for paint, completely done.
As I indicated above, trimming the aft edge of the cowl on both sides at the bottom would allow for the top cowl to rotate counterclockwise looking at it from the port side, but the gap between the top front of the top cowl would not change unless the angle and washer/spacer installed are removed. By doing this, the front of the cowl at the top moves down in relation to the spinner mount. This would decrease the gap but change the elevation of the top of the cowl in front.

Of course this downward change in elevation could be adjusted with fiberglass/epoxy and flox bodywork. Is this what you had in mind? That would also add a bit of structure.
__________________
14A-EXP119 Thunderbolt
Begun 07-23-20
Emp Completed 11-12-20
Slo Fuse Completed 3-2-21
QB Wings 99% Complete 7-30-22
Wiring and Avionics 85%
Cowl Completed sans paint 10-30-22!
2023 Dues Paid
Reserved: N52XL
Reply With Quote
  #15  
Old 08-08-2022, 09:05 AM
wirejock's Avatar
wirejock wirejock is offline
 
Join Date: Oct 2005
Location: Estes Park, CO
Posts: 5,888
Default Cowl fit

Quote:
Originally Posted by rockitdoc View Post
As I indicated above, trimming the aft edge of the cowl on both sides at the bottom would allow for the top cowl to rotate counterclockwise looking at it from the port side, but the gap between the top front of the top cowl would not change unless the angle and washer/spacer installed are removed. By doing this, the front of the cowl at the top moves down in relation to the spinner mount. This would decrease the gap but change the elevation of the top of the cowl in front.

Of course this downward change in elevation could be adjusted with fiberglass/epoxy and flox bodywork. Is this what you had in mind? That would also add a bit of structure.
No. What Dan is suggesting is to sand the entire aft edge uniformly till the bottom edge of the nose bowl is the correct spacing. This retains the dimension with the washer at the top. When everything is done, the nose bowl to spinner gap will be the even wider at the top. That is repaired by adding material to the nosebowl instead of grinding off. It retains the structural integrity. I was wrong.
__________________
Larry Larson
Estes Park, CO
E-mail: wirejock at yahoo dot com
Builder Blog: http://wirejockrv7a.blogspot.com
Donated 12/2022, plus a little extra.
RV-7A #73391, N511RV reserved
Disclaimer
I cannot be, nor will I be, held responsible if you try to do the same things I do and it does not work and/or causes you loss, injury, or even death in the process.
Reply With Quote
  #16  
Old 08-08-2022, 09:19 AM
rockitdoc's Avatar
rockitdoc rockitdoc is offline
 
Join Date: May 2020
Location: Fort Collins, CO
Posts: 813
Default

Quote:
Originally Posted by wirejock View Post
No. What Dan is suggesting is to sand the entire aft edge uniformly till the bottom edge of the nose bowl is the correct spacing. This retains the dimension with the washer at the top. When everything is done, the nose bowl to spinner gap will be the even wider at the top. That is repaired by adding material to the nosebowl instead of grinding off. It retains the structural integrity. I was wrong.
Ahhha! Thanks Larry! That makes total sense. And, thanks Dan. Now I understand your second drawing.
__________________
14A-EXP119 Thunderbolt
Begun 07-23-20
Emp Completed 11-12-20
Slo Fuse Completed 3-2-21
QB Wings 99% Complete 7-30-22
Wiring and Avionics 85%
Cowl Completed sans paint 10-30-22!
2023 Dues Paid
Reserved: N52XL

Last edited by rockitdoc : 08-08-2022 at 09:21 AM.
Reply With Quote
  #17  
Old 08-08-2022, 09:21 AM
DanH's Avatar
DanH DanH is offline
 
Join Date: Oct 2005
Location: 08A
Posts: 11,244
Default

Quote:
Originally Posted by rockitdoc View Post
Is this what you had in mind?
No rotation. Just move it straight aft.

BTW, When using flox or micro, don't miss the opportunity to rough off excess material when the epoxy cures to the cheese stage...still soft, but no longer sticky. It can be sliced with a knife, or grated away with a Sureform, or shaved with a vixen file.

Quote:
Originally Posted by Stevea View Post
So, I ended up epoxying balsa wood to the front of the nose ring, then block sanding the parts back down so there was a constant gap between the spinner back-plate and the cowl. After that I put two layers of glass over the balsa, and sanded everything down to blend it in.
Nicely done. More than one way to skin a cat!
__________________
Dan Horton
RV-8 SS
Barrett IO-390

Last edited by DanH : 08-08-2022 at 09:35 AM.
Reply With Quote
  #18  
Old 08-08-2022, 09:28 AM
Bavafa Bavafa is offline
 
Join Date: Oct 2007
Location: Sacramento, CA
Posts: 4,194
Default

Quote:
Originally Posted by rockitdoc View Post
As I indicated above, trimming the aft edge of the cowl on both sides at the bottom would allow for the top cowl to rotate counterclockwise looking at it from the port side, but the gap between the top front of the top cowl would not change unless the angle and washer/spacer installed are removed. By doing this, the front of the cowl at the top moves down in relation to the spinner mount. This would decrease the gap but change the elevation of the top of the cowl in front.

Of course this downward change in elevation could be adjusted with fiberglass/epoxy and flox bodywork. Is this what you had in mind? That would also add a bit of structure.
As Larry also has mentioned, you will need to readjust the lower cowl to get the proper alignment to the spinner. Then setup the top cowl with the correct alignment with the spinner and then the alignment between the top and bottom cowl.
If you have not cut the sides to a perfect fit yet, the only area that you might need to redo between the top and bottom is the screw holes on the inward part of the inlets which is easy to do.
__________________
Mehrdad
N825SM RV7A - IO360M1B - SOLD
N825MS RV14A - IO390 - SOLD
N258SM RV14A - IO390EXP119 - Out of Paint shop & flying
Dues paid
Reply With Quote
  #19  
Old 08-08-2022, 10:10 AM
mfleming's Avatar
mfleming mfleming is offline
 
Join Date: Sep 2016
Location: Joseph, Oregon
Posts: 1,019
Default

Not to argue with anyone on repair techniques for the cowling nose but I just got off the phone with Vans tech support.

My cowling is already fitted and needs the gap widened between the spinner backing plate and cowl nose. I had planned to add fiberglass/flox to the back side of the nose and remove material from the front side as Larry suggested.

Vans agreed this was a good approach as long as I added the same or more to the back side.
__________________
Michael Fleming
Joseph, OR
sagriver at icloud dot com

RV-7 Slider #74572
Started 11/2016
Empennage completed 11/2016
Ailerons and flaps completed 3/2017.
Wings completed 12/2017
Started on QB fuselage 01/2018
Sliding canopy mostly completed 10/2020
Wiring and Avionics harness completed 9/2/2021
FWF Completed 11/1/2022
Final assembly Started 11/10/2022
Wings on 11/12/2022

N526RM

Donated for 2022 and so should you
Reply With Quote
  #20  
Old 08-08-2022, 11:30 AM
rockitdoc's Avatar
rockitdoc rockitdoc is offline
 
Join Date: May 2020
Location: Fort Collins, CO
Posts: 813
Default

Quote:
Originally Posted by DanH View Post
No rotation. Just move it straight aft.
Yes. That makes perfect sense, and what I will do.

Quote:
Originally Posted by DanH View Post
BTW, When using flox or micro, don't miss the opportunity to rough off excess material when the epoxy cures to the cheese stage...still soft, but no longer sticky. It can be sliced with a knife, or grated away with a Sureform, or shaved with a vixen file.
Thanks for that. I found out this the hard way once by epoxying/floxing in the wrong place, then removed it fairly easily using the procedure you describe.
__________________
14A-EXP119 Thunderbolt
Begun 07-23-20
Emp Completed 11-12-20
Slo Fuse Completed 3-2-21
QB Wings 99% Complete 7-30-22
Wiring and Avionics 85%
Cowl Completed sans paint 10-30-22!
2023 Dues Paid
Reserved: N52XL
Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump


All times are GMT -6. The time now is 12:17 PM.


The VAFForums come to you courtesy Delta Romeo, LLC. By viewing and participating in them you agree to build your plane using standardized methods and practices and to fly it safely and in accordance with the laws governing the country you are located in.