VansAirForceForums  
Home > VansAirForceForums

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

- Today's Posts | Insert Pics

  #11  
Old 12-19-2019, 12:50 PM
TASEsq TASEsq is offline
 
Join Date: Aug 2017
Location: Melbourne, Australia
Posts: 246
Default

Hi all,

Thank you for all the replies! I’m a little overwhelmed and confused but let’s see if I understand this correctly!

@danh - firstly thanks for your reply and all the great info you have on this topic scattered through the site. I’ve searched and read most all of it I reckon! Second, these are gel coated (grey) vans elevator tips. The finish was really good. I’ve just fitted them and contour sanded them. I.e, where they were thicker than the aluminium they were abutting they got sanded down, or the mould lines sanded off etc). This has left some exposed glass and left them deliberately lower than the aluminium edge as per section 5.

My goal is to simply fill the gap against the aluminium edge, and fill the areas where I’ve sanded through the gel coat and into the glass.

I used the word “Pinholes” wrongly I think.

So, from everyone’s replies and the great cozy website link (thank you!) here is my proposed process. Please correct my misunderstandings if you have the time!:

- use a “dry coat” of micro to fill the edge against the aluminium and over any bits where the glass is exposed or where there are any large holes or scratches. (Or do I do it over the whole part??) The consistency is so that it does not run on its own and does not drip off the stick. Squeegee it on quite thick (thicker than the high spots).

-sand this back off to make the edge I want and get the contour I want using a flat sanding board and maybe 80 grit? (Or go finer for micro?)

-once sanded apply a skim coat of raw mixed epoxy, let it go tacky, then another coat.. I will use danh’s method of rolling it on with a foam roller to get the ridges to help in sanding it back off later and not going back down into the micro it glass etc.

-wet sand this with say 180 or 240 on a block?

Have I got an acceptable process do you think?

The only question I don’t get is whether flox would be better to fill the edge against the aluminium skin and also the 1/8” thick section at the front of the counterbalance arms where the skin is curved but the fg part is flat. Can I use flox to fill these edges, sand it back once cured, then micro over the rest of the part as above? Or do the different hardnesses cause issues?

And should I remove the electrical tape and add a few thicknesses of packing tape instead? I really don’t want it to stick and I haven’t tested to see if epoxy sticks to electrical tape.

Thanks for everyone’s time. Apologies if the initial question was confusing or used the wrong terminology. (Apple’s autocorrect changes “pinholes” to “pringles” - a topic I do have ample experience with &#129315
__________________
___________
Trent Stewart
Melbourne, Australia
http://www.tasrv14.blogspot.com.au/
May 2020
Reply With Quote
  #12  
Old 12-19-2019, 02:12 PM
Carl Froehlich's Avatar
Carl Froehlich Carl Froehlich is offline
 
Join Date: Dec 2007
Location: Dogwood Airpark (VA42)
Posts: 2,410
Default

On your specific question on filing in the gap between the fiberglass tips and the aluminum skin, this is what I do:
- Fill in the gap with micro
- Sand the micro flush
- Apply a single bid of medium glass over the gap
- Skim coat of micro over the glass after it sets
- Prep for paint

Do not fill up a gap with just mico or flox and expect the paint not to crack - it will. This is why the glass is needed.

Do not glass over a gap, fill it with micro and sand flush first. If you glass over a gap then you just need to fill it with micro later after it sags into the gap - and now you recreate the paint cracking issue.

Note - same process for finishing windows on the RV-10.

Carl
Reply With Quote
  #13  
Old 12-19-2019, 02:53 PM
TASEsq TASEsq is offline
 
Join Date: Aug 2017
Location: Melbourne, Australia
Posts: 246
Default

Quote:
Originally Posted by Carl Froehlich View Post
On your specific question on filing in the gap between the fiberglass tips and the aluminum skin, this is what I do:
- Fill in the gap with micro
- Sand the micro flush
- Apply a single bid of medium glass over the gap
Hi Carl,

Thank you. Won’t this however make the fairing sit above the aluminium? And when you try and sand it flush you will just sand back into the glass? Keep in mind I am not glassing the tip onto the elevator - I just want a nice clean even gap. I.e. I’m not putting micro across the gap between the tip and the elevator to make the seam disappear. I could imagine if you did this it would certainly crack without glass support.
__________________
___________
Trent Stewart
Melbourne, Australia
http://www.tasrv14.blogspot.com.au/
May 2020
Reply With Quote
  #14  
Old 12-19-2019, 04:06 PM
DanH's Avatar
DanH DanH is offline
 
Join Date: Oct 2005
Location: 08A
Posts: 9,207
Default

Quote:
Originally Posted by Carl Froehlich View Post
Do not fill up a gap with just mico or flox and expect the paint not to crack - it will. This is why the glass is needed.
Probably true if the tip is simply riveted into place per plans.

Try bonding the glass flange into the aluminum with Hysol 9430 or similar, riveting while wet, prior to fill.

900 hours and counting, just micro, no cracks.
__________________
Dan Horton
RV-8 SS
Barrett IO-390
Reply With Quote
  #15  
Old 12-20-2019, 06:17 AM
snopercod's Avatar
snopercod snopercod is offline
 
Join Date: Aug 2016
Location: Asheville, NC
Posts: 2,033
Default

Quote:
Originally Posted by krwalsh View Post
...follow the Cory Bird Method...Wayne Hicks...Sam Hoskins...
There is a lot of good information in those links.
__________________
(2020 dues paid)
Reply With Quote
  #16  
Old 12-20-2019, 11:19 AM
RV10Pilot RV10Pilot is offline
 
Join Date: Jan 2005
Location: Medford, NJ USA
Posts: 259
Default

Quote:
Originally Posted by DanH View Post
Try bonding the glass flange into the aluminum with Hysol 9430 or similar, riveting while wet, prior to fill.
Would West System G-Flex qualify as "similar"?
Reply With Quote
  #17  
Old 12-20-2019, 12:00 PM
DanH's Avatar
DanH DanH is offline
 
Join Date: Oct 2005
Location: 08A
Posts: 9,207
Default

Quote:
Originally Posted by RV10Pilot View Post
Would West System G-Flex qualify as "similar"?
Not really. The addition of G-flex would be better than rivets alone. However, the goal is to minimize relative movement between the aluminum and the glass tip. The specification of interest is tensile modulus, in effect a measure of how much a material will stretch under load. Tensile modulus for G-Flex is given as 1.44E+05 psi (144,000), vs 380,000 psi for the 9430, so the Hysol product is more than twice as stiff.
__________________
Dan Horton
RV-8 SS
Barrett IO-390
Reply With Quote
  #18  
Old 12-20-2019, 03:07 PM
dmn056 dmn056 is offline
 
Join Date: Aug 2014
Location: Sydney, Australia
Posts: 21
Default

Also, for the newer tips with gray gelcoat, it would be a good idea to remove the gelcoat from the mating flange surfaces before bonding. Otherwise, you're transferring loads through resin which is much less stiff than the glass.

I cut mine back using 240 grit on a long sanding block, cleaned up the fiddly bits with a dremel, then bonded the mating surfaces with 3M EC-2216 while installing the rivets.
__________________
Dan Newman
RV-8 empennage complete
wings in progress
Reply With Quote
  #19  
Old 12-20-2019, 03:16 PM
TASEsq TASEsq is offline
 
Join Date: Aug 2017
Location: Melbourne, Australia
Posts: 246
Default

Quote:
Originally Posted by dmn056 View Post
bonded the mating surfaces with 3M EC-2216 while installing the rivets.
Interesting. I hadn’t thought of bonding the part in addition to riveting it. Just curious as to what the advantage of this is if you are not glassing over the seam?

Also the 2216 seems like just an epoxy - why not just used west systems and some flox to thicken it up a bit? (That’s now I bonded on my metal strips for the rivers to bear against).
__________________
___________
Trent Stewart
Melbourne, Australia
http://www.tasrv14.blogspot.com.au/
May 2020
Reply With Quote
  #20  
Old 12-20-2019, 03:36 PM
snopercod's Avatar
snopercod snopercod is offline
 
Join Date: Aug 2016
Location: Asheville, NC
Posts: 2,033
Default

Quote:
Originally Posted by TASEsq View Post
what the advantage of this is if you are not glassing over the seam?
It's been my experience that epoxy makes a terrible bond to aluminum - even if you prep the aluminum properly by sanding and etching. The Hysol or 2216 makes a much better bond but I wouldn't trust those either without riveting or some kind of mechanical attachment.
__________________
(2020 dues paid)
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 11:06 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.