VansAirForceForums  
Home > VansAirForceForums

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

- Today's Posts | Insert Pics

  #1  
Old 02-17-2020, 06:24 AM
cduster cduster is offline
 
Join Date: Aug 2019
Location: Hertford, NC
Posts: 45
Default Making small fit adjustment: Cowling

Rookie fiberglass question here...In an attempt to help combat higher than desired CHTs on my rocket, we faired in the lip on the upper cowling to try and make a smooth transition and eliminate the possible eddy current caused by the abruptly concave lip. We used three layers of cloth with West epoxy that spans a gap from the trailing edge of the upper lip back to the interior of the upper cowling covering a distance of about 8-10". Well, I'm sure you have already guessed that this greatly strengthened the upper cowling, and it is more difficult than it should be to insert the piano hinge wires since the cowl previously compressed just a bit when the wires were inserted.

My question is, for a minor adjustment like this (probably need to compress the width of the upper cowling by about 1/4" to make things fit well), would heat and a little persuasive pressure have any possible positive effect? I was thinking an insulating blanket and heat lamps for the better part of a day with the pins inserted and maybe even a rigged up clamp of some sort.

If that is a useless method, whats next, cutting lengthwise slits in the new glass and then fixing those slits with the cowling either installed or compressed to proper dimensions?
Reply With Quote
  #2  
Old 02-17-2020, 07:11 AM
SPark SPark is offline
 
Join Date: Sep 2018
Location: Sydney Australia
Posts: 6
Default

I have had great success adjusting fibreglass using a heat gun and clamping the part. I’ve straightened leg fairings, adjusted intersection fairings and other non structural parts. I don’t know if it would create any strength issues in parts though.
Reply With Quote
  #3  
Old 02-21-2020, 06:03 AM
DanH's Avatar
DanH DanH is offline
 
Join Date: Oct 2005
Location: 08A
Posts: 9,197
Default

Quote:
Originally Posted by cduster View Post
My question is, for a minor adjustment like this (probably need to compress the width of the upper cowling by about 1/4" to make things fit well), would heat and a little persuasive pressure have any possible positive effect?
I wouldn't fool around with a heat gun. The upper cowl is going to reach around 200F every time you shut down after a summertime flight.
__________________
Dan Horton
RV-8 SS
Barrett IO-390
Reply With Quote
  #4  
Old 02-21-2020, 03:22 PM
Kyle Boatright Kyle Boatright is offline
 
Join Date: Aug 2005
Location: Atlanta, GA
Posts: 4,094
Default

Quote:
Originally Posted by DanH View Post
I wouldn't fool around with a heat gun. The upper cowl is going to reach around 200F every time you shut down after a summertime flight.
Reading into this... Are you saying that once the cowl goes through a few heat cycles it'll "give" enough to fit a little better, or are you just saying that a heat gun won't work well in this application?

My personal experience was that the cowl fit well once installed, but fit even better after a few heat cycles.
__________________
Kyle Boatright
Marietta, GA
2001 RV-6 N46KB
2019(?) RV-10
Reply With Quote
  #5  
Old 02-21-2020, 04:24 PM
DanH's Avatar
DanH DanH is offline
 
Join Date: Oct 2005
Location: 08A
Posts: 9,197
Default

Quote:
Originally Posted by Kyle Boatright View Post
Reading into this... Are you saying that once the cowl goes through a few heat cycles it'll "give" enough to fit a little better, or are you just saying that a heat gun won't work well in this application?
High probability of both. Likely one heat cycle. I doubt the cowl itself will budge, but the added troublesome patch, being low Tg West 501, may reshape, in particular if not well cured (like slow hardener and low temperature to date).
__________________
Dan Horton
RV-8 SS
Barrett IO-390
Reply With Quote
  #6  
Old 02-21-2020, 04:58 PM
cduster cduster is offline
 
Join Date: Aug 2019
Location: Hertford, NC
Posts: 45
Default

Well, a couple of heat lamps, a blanket over the top of the cowl and a little 110v ceramic heater shooting up through the cowl exit heated up the top cowl enough to get the pins in without any undue force. After a couple of test flights, I think things are going to relax enough that cutting relief slots won't be necessary. If I had it to do over again, I'd probably try and put the cowls together as soon as the resin wasn't sticky anymore. Thanks guys.
Reply With Quote
  #7  
Old 02-21-2020, 05:51 PM
BillL BillL is offline
 
Join Date: Sep 2007
Location: Central IL
Posts: 5,334
Default

Quote:
Originally Posted by cduster View Post
If I had it to do over again, I'd probably try and put the cowls together as soon as the resin wasn't sticky anymore. Thanks guys.
This is the best practice, as indicated my my bad experiences.
__________________
Bill

RV-7
At Paint Shop
No Photo? => PM me.
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 03:08 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.