Canard Community Forum  

Go Back   Canard Community Forum > Firewall Backward and Forward
FAQ Members List Calendar Search Today's Posts Mark Forums Read

Reply
 
Thread Tools Display Modes
  #1  
Old 12-29-2006, 08:06 PM
tnt's Avatar
tnt tnt is offline
Member
 
Join Date: Apr 2004
Location: Denver Colorado
Posts: 1,202
Default Foam Surface Irregularities & Finishing

Guys & Gals,

I've seen it mentioned getting a more perfect foam surface on the wings, winglet, & canard before glassing can result in fewer imperfections that need to be filled and reduces the effort to finish them. But when I look at pics of fuselages being finished, it seems that the exterior foam commonly had rather large imperfections that simply gets filled with micro after glassing. Has anyone made an attempt to lightly sand the fuselage exterior to remove surface deviations so they wouldn't need to glob in micro after the layups?
__________________
http://ttcse.com/cozylinks
Reply With Quote
  #2  
Old 12-29-2006, 10:28 PM
Steve parkins's Avatar
Steve parkins Steve parkins is offline
Member
 
Join Date: Apr 2004
Location: wa state
Posts: 2,163
Default

Quote:
Originally Posted by tnt View Post
Guys & Gals,

I've seen it mentioned getting a more perfect foam surface on the wings, winglet, & canard before glassing can result in fewer imperfections that need to be filled and reduces the effort to finish them. But when I look at pics of fuselages being finished, it seems that the exterior foam commonly had rather large imperfections that simply gets filled with micro after glassing. Has anyone made an attempt to lightly sand the fuselage exterior to remove surface deviations so they wouldn't need to glob in micro after the layups?
i sanded my tanks before i glassed them, and if the foam was good to start with then the sanding was good but if the foam is bad then sanding won't help much. you should not sand the foam thin. unless you have a engineer to say "thin is OK"
__________________
edited by steve for a good reason
Reply With Quote
  #3  
Old 12-30-2006, 12:16 AM
tnt's Avatar
tnt tnt is offline
Member
 
Join Date: Apr 2004
Location: Denver Colorado
Posts: 1,202
Default

Thanks Steve. I don't know why I put this under Firewall Back & Fore. I better not get retracts. No, I wouldn't want to sand elevated areas to the point where it gets thin, but maybe just a little. And there must be a way to deal with depressions by pressing them out from the inside or filling with a thin layer of similar foam (rather than the soft pour foam) in a way that you could sand it level. It just seems like it's common to not do anything about depressions until after glassing then you glob in micro. Easier to sand foam than micro, so I hear.
__________________
http://ttcse.com/cozylinks
Reply With Quote
  #4  
Old 12-30-2006, 12:39 AM
Steve parkins's Avatar
Steve parkins Steve parkins is offline
Member
 
Join Date: Apr 2004
Location: wa state
Posts: 2,163
Default

the plans are good, if you made the wing flat and glassed it and spots turned up too high, then what do you do? i think just a good job following the plans and all is good
on my #2 strake it was so flat that it would of ta kin primer to fill
i think the wings could be the same
besides, 1/6 or 1/4, its a small part of the big picture
get a straw, blade and dream.......
__________________
edited by steve for a good reason
Reply With Quote
  #5  
Old 12-30-2006, 07:45 AM
Wayne Hicks Wayne Hicks is offline
Member
 
Join Date: May 2004
Location: Carrollton, VA
Posts: 1,376
Default

Sigh....

No matter how perfect your surfaces turn out to be, it still requires the same amount of work to mix the micro, spread it, and contour it. If you follow the Big Fill directive, you'll only fill once and sand once. That's the key.

My advice is:

(1) yes, strive for well-cut cores. But there's no need to overdo it. Whatever work you do to overcut the cores, then sand to exact contour might make you feel good and elevate your stature as one who cares about workmanship. But, it's going to get lost in the work it will take to hide the staggered plies at the wingtips and the strengthening plies around the bolt holes.

(2) Strive for adjoining surfaces that mate well together. Fixing mismatches -- like between the wings and the center spar -- does take extra work.

(3) And think about this. UNI fibers on wings are supposed to be straight to within 1/16th of an inch. If your cores are wavy due to wire lag, then you should fix the cores or sand to make them more true to meet the fiber inspection criteria, not to improve the chances of doing less work in the finishing process. If your surfaces are within this sixteenth inch structural criteria, you're already a leg up on the finishing process!

(4) Understand the finishing process now. You can hide a myriad of sins with micro. I spent many an extra hour trying to fix or perfect the fiberglass layups -- not to improve structural quality, but to improve chances of doing less finishing work. That was a hopeless effort and an eventual waste of time. I spent extra hours with no retrieved benefit. (See note #1.) You only gain this knowledge by discovering this yourself or by listening to others.
__________________
=============
Wayne Hicks, Cozy Plans #678
http://www.maddyhome.com/canardpages...cks/index.html
Reply With Quote
  #6  
Old 12-30-2006, 10:22 AM
tnt's Avatar
tnt tnt is offline
Member
 
Join Date: Apr 2004
Location: Denver Colorado
Posts: 1,202
Default

Quote:
Originally Posted by Steve parkins View Post
the plans are good, if you made the wing flat and glassed it and spots turned up too high, then what do you do? i think just a good job following the plans and all is good


Quote:
Originally Posted by Wayne Hicks View Post
Sigh....

No matter how perfect your surfaces turn out to be, it still requires the same amount of work to mix the micro, spread it, and contour it. If you follow the Big Fill directive, you'll only fill once and sand once. That's the key.

My advice is:

(1) yes, strive for well-cut cores. But there's no need to overdo it. .............. That was a hopeless effort and an eventual waste of time. I spent extra hours with no retrieved benefit. (See note #1.) You only gain this knowledge by discovering this yourself or by listening to others.
My question boiled down to: is it worth the effort to smooth foam depressions & elevations of the >>fuselage exterior<< before glassing. Sounds like you guys saying "not really".

I should've explained that I've seen some fairly sizeable depressions on a fuselage exterior, about 1/4inch, getting filled with micro after the layups cured. I guess there must be a limit to the size of these foam surface imperfections, a case-by-case judgement call is needed.
__________________
http://ttcse.com/cozylinks
Reply With Quote
  #7  
Old 12-30-2006, 10:27 AM
John Slade's Avatar
John Slade John Slade is offline
Flying TurboRotaryCozyIV
 
Join Date: Apr 2004
Location: KWST
Posts: 3,836
Default

If you're talking about dings and gouges in the foam, sure. Cut out a small block of foam around the ding, 5 minute or micro a new piece in (keeping the glue away from the edges) and sand smooth. No one will ever know.

It depends on the size of the ding. The micro prep before glassing will fill the small stuff.
Reply With Quote
  #8  
Old 12-30-2006, 10:33 AM
tnt's Avatar
tnt tnt is offline
Member
 
Join Date: Apr 2004
Location: Denver Colorado
Posts: 1,202
Default

OK, thanks Steve, Wayne, John.
__________________
http://ttcse.com/cozylinks
Reply With Quote
  #9  
Old 01-02-2007, 11:23 PM
Dust's Avatar
Dust Dust is offline
Super Moderator
 
Join Date: Apr 2004
Location: Troy, Michigan
Posts: 7,963
Default

Well - i believe most of us are as careful as possible in surface creation and prep, BUT, #$%^ happens. Also, when inserting things into the foam i always try to have the area either slightly depressed or flush, problem with micro is - it shrinks when cured so when you fill a blem with micro - it ends up being a depression

problem i have had when filling with foam blocks - tend to end up proud

in the end - easier to fill a small depression than to bring the surrounding area up to a slight bump, ask me how i know
__________________
Enjoy the build,njut av byggandet, godere il costruire, nyd bygningen, geniesse den Bau, apolafse tin kataskevi, disfrute la construcción, curta a construção, Pidä hauskaa rakentamisen parissa, bouw lekker,uživaj grade?inaslajdaites postroikoi, geniet die bou
dust

maker of wood, fiberglass, foam dust, metal bits and one day a Cozy will pop out and swiftly whisk me from meeting old friends and family to adventures throughout the world
Reply With Quote
  #10  
Old 01-03-2007, 02:54 AM
Ron Springer Ron Springer is offline
Member
 
Join Date: May 2005
Location: Folsom, CA
Posts: 77
Default

Quote:
Originally Posted by Wayne Hicks View Post
(3) And think about this. UNI fibers on wings are supposed to be straight to within 1/16th of an inch. If your cores are wavy due to wire lag, then you should fix the cores or sand to make them more true to meet the fiber inspection criteria, not to improve the chances of doing less work in the finishing process. If your surfaces are within this sixteenth inch structural criteria, you're already a leg up on the finishing process!
This requirement always bugs me because I think it is unobtainable. I know from experience now that I can have something twelve feet long that is not straight to within 1/16" and it can look good to the eye. It can also look good with a 4 foot straight edge. But, when I use a laser or taught fishing line (if Wayne is the king of drywall screws, then I am the king of fishing line), then I can tell it is not perfectly straight. Now, how are you going to do this when laying up the canard or wing on a fiber by fiber basis?

I think this is more like a goal to motivate you to do your best. Kind of like the places in the plans that ask you to cut particle board to an accuracy of 0.01" with a power saw! I am guessing that is why you said "supposed to" above.
__________________
Ron Springer
Folsom, CA
Cozy Mk IV #1334
Reply With Quote
  #11  
Old 01-03-2007, 08:28 AM
Wayne Hicks Wayne Hicks is offline
Member
 
Join Date: May 2004
Location: Carrollton, VA
Posts: 1,376
Default

I agree that 1/16th inch is a very tight tolerance. Seems out of whack given that tolerances are a bit lax on other areas in the plans. But it can be met by pulling each individual uni fiber from both ends. (Takes two people to do that.) I did it on my canard and main wings. Pulled every single fiber and got them all straight. And yes, I did spot check alot of them with a long straight edge. Took some time, but I bet I got very close to that tolerance.

I highly suspect that the 1/16th inch tolerance is a carryover from the VariEze plans. The tolerance would be more obtainable on VariEze wings since they are not as long as Long-EZ or Cozy wings. The tolerance may be more important on the Vari wing since the most of the wing doesn't have a spar. IIRC, the Vari wing spar is about 2 feet long, starting at the wing attachments. After that, the wing relies on the UNI fibers to carry to bending loads.

I'll go back and study the inspection criteria. Could I have read it wrong?
__________________
=============
Wayne Hicks, Cozy Plans #678
http://www.maddyhome.com/canardpages...cks/index.html
Reply With Quote
  #12  
Old 01-03-2007, 10:09 AM
Glos Glos is offline
Member
 
Join Date: Mar 2005
Location: Roselle, IL
Posts: 252
Default

I seem to recall a picture in the canard publisher where the builder glassed a canard chordwise instead of spanwise.

This canard was loaded up to something lke 8+ G's before it broke.

In any case keep the fibers as straight as possible. I pulled like Wayne did but not each and every fiber.
Reply With Quote
  #13  
Old 01-03-2007, 10:25 AM
Dust's Avatar
Dust Dust is offline
Super Moderator
 
Join Date: Apr 2004
Location: Troy, Michigan
Posts: 7,963
Default

One of the great things about these planes is the long history and the many built by many people.

I am quite sure the quality varies greatly, each persons good enough will vary.

Consider this and consider the number of structural failures - near or at zero
__________________
Enjoy the build,njut av byggandet, godere il costruire, nyd bygningen, geniesse den Bau, apolafse tin kataskevi, disfrute la construcción, curta a construção, Pidä hauskaa rakentamisen parissa, bouw lekker,uživaj grade?inaslajdaites postroikoi, geniet die bou
dust

maker of wood, fiberglass, foam dust, metal bits and one day a Cozy will pop out and swiftly whisk me from meeting old friends and family to adventures throughout the world
Reply With Quote
Reply


Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools
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 -4. The time now is 01:53 PM.


Powered by vBulletin® Version 3.6.7
Copyright ©2000 - 2018, Jelsoft Enterprises Ltd.