VansAirForceForums  
Home > VansAirForceForums

- POSTING RULES
- Donate yearly (please).
- Advertise in here!

- Today's Posts | Insert Pics



Go Back   VAF Forums > Main > RV General Discussion/News
Register FAQ Members List Calendar Search Today's Posts Mark Forums Read

Reply
 
Thread Tools Search this Thread Display Modes
  #1  
Old 10-16-2008, 11:57 PM
Craig23's Avatar
Craig23 Craig23 is offline
 
Join Date: Jan 2005
Location: Santa Rosa, CA
Posts: 207
Default How should I repair this fiberglass crack?

Hi everyone,

I've been working on the canopy skirt for my RV-8. I glassed the two halves together at the back and got the surface prepped. I had a friend of mine with a body shop paint the inside so I could rivet it to the canopy and canopy frame. While clecoing the skirt to the frame tonight I saw a crack at the back where the two halves had been glassed together. The inside of the skirt is now painted, and I'm wondering what would be the best way to repair the crack. It is full thickness at the top. I imagine I should stop drill the crack, but what are your suggestions after that? Will I need to add layers of glass over the crack? I've included a picture of the crack below. Thanks for any advice.

[IMG]http://[/IMG]
__________________
Craig Schwartz
RV-8 (Flying!), IO-360B1PC2 (180 hp, 1 P-Mag, 1 Slick Mag), Whirlwind 200RV, AF-3500, G496, Digiflight II, Classic Aero Sportsman Ultraleather Seats
N868RV
Santa Rosa, CA
Reply With Quote
  #2  
Old 10-17-2008, 07:34 AM
pdecraene7a pdecraene7a is offline
 
Join Date: Jan 2005
Posts: 122
Default crack

Craig

I would not bother with stop drilling, I don't think it will matter in fiberglass. Just sand down the top surface into the glass and do a layup over the crack. I would do it while it is in place so that there is no stress on the parts after it cures. Just make sure you protect the canopy well.
__________________
Pete DeCraene
Joliet, IL
RV-7A CONVERTED TO RV-7 526PD
Reply With Quote
  #3  
Old 10-17-2008, 07:52 AM
Geico266's Avatar
Geico266 Geico266 is offline
 
Join Date: Feb 2005
Location: Huskerland, USA
Posts: 5,794
Default

Try to get as much of the stress out of the piece before you do the repair layup.
__________________
RV-8 : In the hangar
RV-10 : In the hangar
RV-12 : Sold
RV-15 : High Wing E-LSA On Order, w/ Removable Door Option.
Reply With Quote
  #4  
Old 10-17-2008, 09:26 AM
FredMagare FredMagare is offline
 
Join Date: Mar 2006
Location: Kyle, TX
Posts: 486
Default

I'd consider repairing it as one would repair a plaster wall. Open the crack line into a v-shape, fill with epoxy/flox, and lay-up with fiberglass.
__________________
Fred Magare
GySgt, USMC (Ret.)
magaref "at" hayscisd.net
RV-9A SB Fuselage
Reply With Quote
  #5  
Old 10-17-2008, 09:39 AM
DanH's Avatar
DanH DanH is offline
 
Join Date: Oct 2005
Location: 08A
Posts: 4,704
Default

Maybe this will help:



A one-sided scarf (not shown, but same principle) would work in the case of a fairing skirt joint. A two-sided scarf is far more durable in the case of a flexed part. Adding plies to the outside only is just a patch. It will work long-term only if the part never sees any stress.

Whatever you choose, take it back to bare glass before you add anything.

Addendum: relative strength by joint type, credit Niu:

__________________
Dan Horton
RV-8 SS
Barrett IO-390

Last edited by DanH : 10-17-2008 at 10:13 PM. Reason: Replaced illustration - better captions - added additional illustration
Reply With Quote
  #6  
Old 10-17-2008, 10:17 AM
Mike S's Avatar
Mike S Mike S is offline
Senior Curmudgeon
 
Join Date: Sep 2005
Location: Cameron Park Ca "o61"
Posts: 10,760
Default

Quote:
Originally Posted by DanH View Post
Maybe this will help:



A one-sided scarf (not shown, but same principle) would work in the case of a fairing skirt joint. A two-sided scarf is far more durable in the case of a flexed part. Adding plies to the outside only is just a patch. It will work long-term only if the part never sees any stress.

Whatever you choose, take it back to bare glass before you add anything.
Dan has it exactly correct. Dont try to save a bit of time by doing this quick and easy, you will only be re doing it later.
__________________
Mike Starkey
Rv-10, N210LM.
VAF 909
EAA 512


Flying as of 12/4/2010

Phase 1 done, 2/4/2011

"Flying the airplane is more important than radioing your plight to a person on the ground incapable of understanding or doing anything about it."
Reply With Quote
  #7  
Old 10-17-2008, 12:36 PM
N941WR's Avatar
N941WR N941WR is online now
 
Join Date: Jan 2005
Location: NC
Posts: 8,828
Default

Dan is the MAN! Good images too.

Go to a hobby shop (Hobby Town is our local chain) and buy some of their lightweight BID FG cloth and use that. This stuff is thin and will let you get a couple of layers on there. Lay them 45 degrees to each other to take up any stress you might encounter.
__________________
Bill R.
Astronaut Candidate Trainee Assistant Third Class
RV-9 (Yes, it's a dragon tail)
Putting the "mental" in "Experimental"
O-360 w/ dual P-mags. I don't need no stink'n JATO bottles.
Build the plane you want, not the plane others want you to build!
SC86 - Easley, SC
www.repucci.com/bill/baf.html
Reply With Quote
  #8  
Old 10-17-2008, 12:44 PM
az_gila's Avatar
az_gila az_gila is online now
 
Join Date: Jan 2005
Location: 57AZ - NW Tucson area
Posts: 6,724
Post A lttle confusing....

Quote:
Originally Posted by DanH View Post
Maybe this will help:

<pic snipped>

A one-sided scarf (not shown, but same principle) would work in the case of a fairing skirt joint. A two-sided scarf is far more durable in the case of a flexed part. Adding plies to the outside only is just a patch. It will work long-term only if the part never sees any stress.

Whatever you choose, take it back to bare glass before you add anything.
...on the pictures.

Dan's pictures show repair techniques for a fibreglass composite structure with an internal core. Techniques are quite different, and the lower picture probably woud not be a factory approved repair on a German sailplane.

However a scarf joint is definitely the correct technique here.

My certified sailplane repair manual in front of me uses 30:1 as a correct scarf angle when a single layer of glass is involved - as is the case here.

This is probably just over an inch of scarf on each side of the crack and should be easy to do. Lay up the same number of layers as the original work, and add an extra layer. Make the first layer the size of the repair area after scarfing, and every subsequent layer a little smaller. This will aid the final sanding and finishing. Use Saran wrap or a peel ply so excess resin can be squegeed out.

This repair would classify as the same strength as the original on a certified plane, and the glider guys may be better at this since they have been selling (and repairing) composite planes since the mid-60's....

I can scan some pictures from the manual if you want, but have lost my web space in my switch to DSL...
__________________
Gil Alexander
EAA Technical Counselor, Airframe Mechanic
RV-6A VSB (Very Slow Build)
Grumman Tiger N12GA - flying
La Cholla Airpark (57AZ) Tucson AZ

Last edited by az_gila : 10-17-2008 at 12:48 PM. Reason: added saran wrap bit
Reply With Quote
  #9  
Old 10-17-2008, 01:13 PM
DanH's Avatar
DanH DanH is offline
 
Join Date: Oct 2005
Location: 08A
Posts: 4,704
Default

<<Dan's pictures show repair techniques for a fibreglass composite structure with an internal core. >>

Whoops, not what I intended. I'm sorry Gil, my fault, poor captions. Shouldn't have used the word "core". I'll repost an improved version this evening when I get back to the home computer. For now, please substitute "original laminate" for "core" <g>

You're entirely right about cored structure...pot in new core, scarf the skins.

<< My certified sailplane repair manual in front of me uses 30:1 as a correct scarf angle when a single layer of glass is involved - as is the case here.>>

Works for me.

<<Make the first layer the size of the repair area after scarfing, and every subsequent layer a little smaller. >>

I'd reverse the order; small first, largest last, not that it matters in a non-structural fairing. My reasoning is best illustrated with a picture, again later. However, I'll bet you have a reason too. How about it?
__________________
Dan Horton
RV-8 SS
Barrett IO-390
Reply With Quote
  #10  
Old 10-17-2008, 01:17 PM
Mike S's Avatar
Mike S Mike S is offline
Senior Curmudgeon
 
Join Date: Sep 2005
Location: Cameron Park Ca "o61"
Posts: 10,760
Default

Quote:
Originally Posted by DanH View Post

<<Make the first layer the size of the repair area after scarfing, and every subsequent layer a little smaller. >>

I'd reverse the order; small first, largest last, not that it matters in a non-structural fairing. My reasoning is best illustrated with a picture, again later. However, I'll bet you have a reason too. How about it?
Contact area of single layer, versus contact with many edges of layers. The first large piece ties all the sub layers together at the exposed ends of the scarf joint.
__________________
Mike Starkey
Rv-10, N210LM.
VAF 909
EAA 512


Flying as of 12/4/2010

Phase 1 done, 2/4/2011

"Flying the airplane is more important than radioing your plight to a person on the ground incapable of understanding or doing anything about it."
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 03:35 AM.


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.