Go Back  RCU Forums > RC Airplanes > Tips & Techniques
Reload this Page >

fiberglass covering question-blisters in sun

Notices
Tips & Techniques Want to share a tip or special technique you have either in the workshop or at the flying field or race track? Post it right here!

fiberglass covering question-blisters in sun

Old 10-16-2010, 01:31 PM
  #1  
frets24
Thread Starter
My Feedback: (15)
 
frets24's Avatar
 
Join Date: Dec 2007
Location: charlotte, NC
Posts: 1,243
Likes: 0
Received 0 Likes on 0 Posts
Default fiberglass covering question-blisters in sun

Hey guys,

I am working on my second scale plane and using the Tom Pierce method of applying the fiberglass cloth.

http://www.tompierce.net/190/html/paint/glassing.htm

My problem shows up after the glasscloth and all the poly has been applied, sanded, primed and finished sanded. I had a bit of puttying to do in order to blend in a fairing. I set the fuselage out in the sun to hasten the putty hardening. When I came back to it after 15-20 minutes the glass work had numerous blisters and bubbles where the sun had heated the light gray primer. At this time there were no blisters in places where the primer had been completely removed during the finish sanding. The blisters this time are only 1mm-3mm in size...so far.[]

I had this problem on my P51 build last year where the glass work delaminated in thumbnail sized blisters on the worst places. It happened mainly on the cowl where it was painted olive drab, I guess due to the darkness of the color/heat absorbtion. I cut most of them out and CA'd putty and filler in the spots and spot-paint repaired the areas satisfactorily, but it was a hassle. I have yet to leave the wing out in direct sun for any period of time. Haven't had it at the field yet for maiden, quite frankly I am a little worried to take it outdoors for any length of time in the sun.

This really sucks if it is inherent to the method, since these planes will be exposed to direct sunlight if you want to ever fly them. I am not interested in building them just to hang them on the ceiling.

Has anyone else experienced this? Has anyone got any ideas on rectifying the situation? Anyone know why it is happening?

If I can't figure this out I suppose I will have to just start using the epoxy method.

A few pics below. The P51 is a bit blurry, but you get the idea of where thespots had been(repaired now) The KI-61 fuse and some close ups...Kind of difficult to get the blisters to show up. most circles have 2-5 blisters in them.

Thanks.
Attached Thumbnails Click image for larger version

Name:	Bz79473.jpg
Views:	20
Size:	60.3 KB
ID:	1517702   Click image for larger version

Name:	So42569.jpg
Views:	22
Size:	72.0 KB
ID:	1517703   Click image for larger version

Name:	Bg93963.jpg
Views:	20
Size:	38.0 KB
ID:	1517704   Click image for larger version

Name:	Oi15252.jpg
Views:	19
Size:	44.1 KB
ID:	1517705  
Old 10-16-2010, 07:32 PM
  #2  
Jim_Purcha
My Feedback: (8)
 
Join Date: Sep 2003
Posts: 1,915
Likes: 0
Received 1 Like on 1 Post
Default RE: fiberglass covering question-blisters in sun

This was mentioned in the RC classic section under an Aurora build. The father of the builder had blisters appear on his wing in the hot sun. I believe it's because the polyacrylic is gassing off. I have a RCM F-18 pusher prop done in the polycylic method too. Not flown yet. I'm just waiting for this to happen. How hot is it out side? It fall temperatures in Manitoba today and only hitting the 50-60 degrees.

Jim
Old 10-17-2010, 06:32 AM
  #3  
gene6029
 
gene6029's Avatar
 
Join Date: Sep 2007
Location: wilson, NC
Posts: 1,219
Likes: 0
Received 11 Likes on 7 Posts
Default RE: fiberglass covering question-blisters in sun

Frets24, I just finished a Dynaflite Chipmunk done with the polycrilic method. I also have blisters forming only on the flat black areas of the nose portion of the model. If i remember correctly though, this was the only area i used the red auto putty to fill a seam. Im wondering if the poly, or the rattle can primer over the putty is whats causeing the blistering in the heat? My Chippy is painted in dark green camo, and there isnt another blister on the model anywhere. Im thinking there is something going on with the putty and something else in my case......[:@]Gene
Old 10-17-2010, 07:26 AM
  #4  
TomCrump
 
TomCrump's Avatar
 
Join Date: Apr 2003
Location: Traverse City, MI
Posts: 7,614
Likes: 0
Received 1 Like on 1 Post
Default RE: fiberglass covering question-blisters in sun

I have used the Poly C method for years, and haven't experienced this problem.

It may have to do with the method of application. If Poly C is applied heavily, it takes much longer to "cure" than if applied in light coats. I usually wait at least a week after application, before I sand and prime. This allows plenty of time for the water to evaporate.

I usually apply 2-3 light coats of Poly C. The weave is then filled, (after 1 week) with high build automotive primer.

I feel that patience is the key. The poly C method is easier than using epoxy, but not necessarily faster.
Old 10-17-2010, 08:28 AM
  #5  
Avaiojet
 
Join Date: Sep 2002
Location: Jupiter , FL
Posts: 3,153
Likes: 0
Received 0 Likes on 0 Posts
Default RE: fiberglass covering question-blisters in sun

My opinion only,

I've had great success with using Polyester resins and never had any lifting, or bubbles.

The list is endless why guys don't use Polyester resin, but it's what I've gotten used to and what works well for me. There many others that use it also. I'm not alone. Well, almost. [sm=bananahead.gif]

Try Polyester resin. Has to be someone in your Club using it?
Old 10-20-2010, 01:11 AM
  #6  
John Sohm
My Feedback: (9)
 
Join Date: Jul 2002
Location: Stone Ridge, NY
Posts: 366
Likes: 0
Received 0 Likes on 0 Posts
Default RE: fiberglass covering question-blisters in sun

Surprisingly, there are precious few who still glass models in our club and our membership is top heavy with senior citizens. It seems everyone was seduced by the simplicity of plastic iron-ons. As a matter of fact, I'm going to do a demo at our next meeting just to show some of the guys that never glassed before that it isn't all that intimidating to do. Don't get me wrong, a lot still apply glass tape for reinforcing the wing joints but thats about it.

I've tried all three methods and to be honest, I find the polyester resin to be the hardest, toughest finish of all. Second is epoxy and if you just want a soft yet relatively durable surface, then use the polycrylic method.

I need to remind you that with the last method, you're bonding the glass with a clear paint and not a true resin. I've mentioned in posts in the past that I had my reservations regarding this method since there is no true chemical bonding as in the epoxy and polyester methods. You see the fiberglass manufacturers coat the glass cloth with one of several types of finishes that form a chemical bond between the glass fibers and the resin. So the resin sticks not only to the balsa wood but also to the glass so you get a coating that is bonded to the wood and not just lightly stuck to it. You definitely need to allow the polycrylic to dry completely. It too will be fairly tough. I suspect that moisture was the culprit for the bubbling too.

Don't get me wrong, you can mess up applying with epoxy too. Such as thinking you can thin it enough with denatured alcohol or acetone and not affect the bonding qualities. You should use a finishing resin.

And as for polyester resin, I stay away from the stuff you find at auto stores even though I'm sure many people use it and are happy with it. I tend to find it a bit too thick to flow out and many times, it remains a bit too tacky since it is in reality a laminating resin meant to apply several layers of glass cloth and you want the tackiness when applying the next coat. The type I use is a thin resin with wax added to facilitate sanding when done. If you need to thin polyester, you would add styrene monomer to the mix. There is a wealth of knowledge that can be gathered if you select the right websites.

The info on the glass cloth I got from Thayercraft ... http://www.thayercraft.com
The info on polyester and for supplies I go to U.S. Composites ... http://www.uscomposites.com and also AeroMarine Products at ... http://www.jgreer.com

Hope this helps.
Old 10-20-2010, 06:43 AM
  #7  
R8893
My Feedback: (20)
 
Join Date: Oct 2002
Location: Cincinnati, OH,
Posts: 947
Likes: 0
Received 4 Likes on 3 Posts
Default RE: fiberglass covering question-blisters in sun

I did one model with the polycryllic method, got bubbles, went back to Z-poxy finishing resin and lived happily ever after.
Chuck
Old 10-20-2010, 10:48 AM
  #8  
Charlie P.
 
Charlie P.'s Avatar
 
Join Date: Feb 2003
Location: Port Crane, NY
Posts: 5,088
Likes: 0
Received 2 Likes on 2 Posts
Default RE: fiberglass covering question-blisters in sun

I've built two small sailboats and reglassed many hull repair sections.  Blistering is caused by one of two things: improperly mixed/cured resin and moisture intrusion.  The latter takes years to appear, so I am guessing the former.  Be sure when you mix either epoxy or polyester resins to mix very well and then allow them to sit and link before applying them.  How long depends on the cure rate of the hardener you are using.  If you mix fast and apply immediately you can get places in the suspension where the hardner is thin or absent.  These take days, weeks or years to harden. 

Sunlight warms the uncured resins unevenly, the darker areas increased the temperature difference.  As a rule of thumb you should not work in direct sun with paint, glues, waxes, dyes, stains or epoxies where it can be avoided.  It's just one more thing you can't control.

When you step aboard a new boat and get that "new bost smell" . . . that's uncured resins.  It can take months to fully set.
Old 10-20-2010, 11:17 AM
  #9  
frets24
Thread Starter
My Feedback: (15)
 
frets24's Avatar
 
Join Date: Dec 2007
Location: charlotte, NC
Posts: 1,243
Likes: 0
Received 0 Likes on 0 Posts
Default RE: fiberglass covering question-blisters in sun

ORIGINAL: John Sohm

Surprisingly, there are precious few who still glass models in our club and our membership is top heavy with senior citizens. It seems everyone was seduced by the simplicity of plastic iron-ons. As a matter of fact, I'm going to do a demo at our next meeting just to show some of the guys that never glassed before that it isn't all that intimidating to do. Don't get me wrong, a lot still apply glass tape for reinforcing the wing joints but thats about it.
Thanks for the links, I was actually pleasantly surprised at the affordability of the polyesther resin and catalys combos and the glass cloth prices will keep me from ever buying a baggie at a time from the local supplier!! (Your links also are going to save me a heap of cash in my winter project of re-flooring my '88 Bayliner ski boat. YEA!!!!)

I think that most of the "true builders" have become a very small minority in the hobby since the appearance of ARFs. So, it doesn't surprise me that a lot of guys are timid about glassing and painting. For me there just is no better way to get a nice fuse or wing surface that takes and holds a decent paint job than glassing. Iron on covering is great for a lot of planes but, its really hard to get feathered lines between colors with it!

I haven't tried polyesther resin yet, although I have done a few planes with epoxy glassing using the West Systems 105/206 combo and it was not a bad experience, just a bit time consuming in the clean up and sanding. I was trying the Polycrylic method because it sands alot easier and clean-up is ridiculously quick and easy

Old 10-21-2010, 04:00 PM
  #10  
91zulu
My Feedback: (2)
 
Join Date: Feb 2002
Location: Orange, NJ
Posts: 1,319
Likes: 0
Received 0 Likes on 0 Posts
Default RE: fiberglass covering question-blisters in sun

The initial sealing of the wood with sealer is critical. If there is a spot that was not properly sealed then when the glass is laid with the Poly c it will soak into the not properly treated area leaving a dry spot that will show up later as a bubble. The key is to make sure you check over your sealing and the first two coats used to lay the glass down. It can be hard to see dry spots in bad lighting so be sure to have good lighting when doing this. Also making the coats too light is also no good. Remember there will be hardly anything left when the water is gone.
Old 10-21-2010, 09:57 PM
  #11  
frets24
Thread Starter
My Feedback: (15)
 
frets24's Avatar
 
Join Date: Dec 2007
Location: charlotte, NC
Posts: 1,243
Likes: 0
Received 0 Likes on 0 Posts
Default RE: fiberglass covering question-blisters in sun

Good point Zulu. That is something I'll check more closely when I do the wings. I usually apply about 3 coats of the Deft and then sand lightly, but there could still be spots where the wood just really drinks it in. I think though, that my problem is likely not enough time betwween coats. On a warm afternoon I'll get in 3-4 coats of the Poly-C in a 5-6 hour time. It always seems to be dry....new plan will be 48 hours on the Deft, 10-12 hours between Poly coats. We'll see......
Old 10-21-2010, 11:39 PM
  #12  
91zulu
My Feedback: (2)
 
Join Date: Feb 2002
Location: Orange, NJ
Posts: 1,319
Likes: 0
Received 0 Likes on 0 Posts
Default RE: fiberglass covering question-blisters in sun

For me I don`t worry about adding weight too much during the glassing and painting in a giant size plane. An extra 16 or 20 oz is not going to hurt. I fly Meister size warbirds and trust me these planes need the weight because they fly like crap if they are too light. I should be able to fly my planes in 25- 30 mile winds and it stays where I put it. Guys worry too much about weight in big planes with all the power thats in these things. G62, Brison 4.2 , 5.8s. An extra pound and a half will not make much difference. Even in 3D planes. They already have most times 1:1 and more thrust ratio.
Old 10-22-2010, 01:53 AM
  #13  
frets24
Thread Starter
My Feedback: (15)
 
frets24's Avatar
 
Join Date: Dec 2007
Location: charlotte, NC
Posts: 1,243
Likes: 0
Received 0 Likes on 0 Posts
Default RE: fiberglass covering question-blisters in sun

I don't worry wieght too much either. So, I'm right there with you on that count.

I hung a 2lb chunk of lead on the CG in my GreatPlanes 40 size cub to get it to handle ethe way I wanted it to. With a 76'' WS and almost 10'' chord it could still probably use another lb...or a clipped wing. Both of my Kyosho warbird nARFs came in at about 165% of the higher weight advertised once the cutting, adding on to, modifying, and detailing/painting was done. (Nothing like it was when it came out of the box; hence, nARF...noddanARF) They both fly like they're on rails. Just have to be diligent about keeping them moving on approach and landing.

This current nARF is a KI-61 "Tony" and has a 68'' WS and the airframe/box contents weighed all of 5lbs 6oz. Having seen a few vids of it fly as it was intended to be assembled I think it would also be a prime candidate for a big honkin' chunk-o-lead on the CG as well. It'll have a Saito 90 up front so 10-12lbs should be fine and that gives me alot to play with.

So far the fuse started off at 2lbs 9oz and with slabbing out and carving/sanding the sides for some shape along with glassing and begining to detail I'm at 2lbs 14oz and only have my finish colors and clearcoat to go...glass and primer are light...the balsa was 4.5 oz before shaping(forgot to weigh after carving/sanding)
Attached Thumbnails Click image for larger version

Name:	Tr50565.jpg
Views:	21
Size:	59.9 KB
ID:	1520895   Click image for larger version

Name:	Je10012.jpg
Views:	17
Size:	60.3 KB
ID:	1520896   Click image for larger version

Name:	Ty66223.jpg
Views:	14
Size:	59.5 KB
ID:	1520897   Click image for larger version

Name:	Pj19319.jpg
Views:	14
Size:	61.0 KB
ID:	1520898   Click image for larger version

Name:	Kv15362.jpg
Views:	21
Size:	60.9 KB
ID:	1520899   Click image for larger version

Name:	Qg63800.jpg
Views:	19
Size:	59.1 KB
ID:	1520900   Click image for larger version

Name:	Km99097.jpg
Views:	18
Size:	59.3 KB
ID:	1520901   Click image for larger version

Name:	Ut66955.jpg
Views:	17
Size:	56.2 KB
ID:	1520902  

Old 10-22-2010, 02:55 AM
  #14  
91zulu
My Feedback: (2)
 
Join Date: Feb 2002
Location: Orange, NJ
Posts: 1,319
Likes: 0
Received 0 Likes on 0 Posts
Default RE: fiberglass covering question-blisters in sun

O yeah adding weight to these things we do all the time. We had 2 Meister Me 109s. One was repainted and was about 33lbs. The other nice at 26lbs, both using G62s. The one that is 33lbs flies a hell of a lot better than the 26lbs. Flies like its on rails the other bounces all over the place especially on a hot day.
Right now I`m building another 109 and I`m shooting for 30lbs. Power is a Sachs 50.
Old 11-13-2010, 12:05 PM
  #15  
Ron101
My Feedback: (22)
 
Ron101's Avatar
 
Join Date: Aug 2004
Location: Brentwood, CA
Posts: 1,833
Likes: 0
Received 1 Like on 1 Post
Default RE: fiberglass covering question-blisters in sun

Zula good tips,
The funny thing is I've heard the exact opposite, that sealing the balsa is the problem. Guys were complaining in the warbird forums that they to were getting blisters... one member said that he used to get blister then discovered it was the gassing of the lacquer based sealer being trapped under the ploy c....

it then went to apply light coats of poly c straight to the model... he said that he got no warpping and no bubbles

To me what he said really made sence, having that lacquer under the poly c sounds like a bad idea.. I also don't like mixing products.... mean if your going water based go all water based

I'm going to try an experiment that I have wanted to try for some time on an old wing... stick with one product for the whole finish... meaning all water based

I had the idea of sealing the wood with water based sanding sealer, but put it in my spray gun and build it up in three very light coats to not warp the wood. Then glass as normal with poly c.
If any filler is need I wood use hobby grade epoxy and micro ballons.. not harsh automotive filler used for metal cars. Then for primer use water based laytex... I have found that kiltz primer when sprayed on and thinned with washer fuild sands pretty well... then paint with water based paint.

This way we don't mix products and have a reaction... I'm going to give it a try soon. I know one member is also just putting on silkspan with poly c straight without sealer and having no problem with warping... you will get bad warping if there is no structure under the sheeting, but I think with a few light coats first you will be fine....

I'll let you guys know how the experiment goes
Old 11-13-2010, 07:55 PM
  #16  
91zulu
My Feedback: (2)
 
Join Date: Feb 2002
Location: Orange, NJ
Posts: 1,319
Likes: 0
Received 0 Likes on 0 Posts
Default RE: fiberglass covering question-blisters in sun

Ok , but they might be a new process in town. Check out this thread...


http://www.rcuniverse.com/forum/m_10...m.htm#10133543
Old 11-15-2010, 07:55 AM
  #17  
Oosiksmith
My Feedback: (1)
 
Join Date: Sep 2002
Location: Charlottesville, VA
Posts: 618
Likes: 0
Received 0 Likes on 0 Posts
Default RE: fiberglass covering question-blisters in sun

I had the same problem. I think it boiled down to I needed to allow a lot more time for the outgassing to occur:

http://www.rcuniverse.com/forum/m_79...tm.htm#7964284
Old 11-15-2010, 09:28 AM
  #18  
spasmatic
My Feedback: (4)
 
Join Date: May 2002
Location: knoxville, TN
Posts: 79
Likes: 0
Received 0 Likes on 0 Posts
Default RE: fiberglass covering question-blisters in sun

I had a few blisters/bubbles when covering with poly c and polyester dress lining. A hot sealing iron applied to them eliminate the spots.
Old 11-15-2010, 11:42 AM
  #19  
tfarmer96
 
tfarmer96's Avatar
 
Join Date: Nov 2005
Location: Wylie, TX
Posts: 1,969
Likes: 0
Received 0 Likes on 0 Posts
Default RE: fiberglass covering question-blisters in sun

I had this happen on my first topflite spitfire. I glassed it in the early spring with deft brushing lacquer. Painted over it with rattle can paint. When i took it out to fly and set it in the sun it got blisters on it. The weather was in the mid-50s to low 60s as the day went on. All i could figure out was the deft had not cured completely and it was a result of off gassing.

I now use water based water based polycrylic. Use the same procedure. See link below:

http://www.wyliewarbirds.com/howto/howto.htm
Old 11-15-2010, 06:11 PM
  #20  
Avaiojet
 
Join Date: Sep 2002
Location: Jupiter , FL
Posts: 3,153
Likes: 0
Received 0 Likes on 0 Posts
Default RE: fiberglass covering question-blisters in sun

If I had blistering, I believe I would cut the blister open and peel the glass back until I knew I would damage the wood. If it's not sticking, it's not sticking.

I'd cut away all the remainder of lifted glass and for those areas, I would start the process over.

I'm never concerned about weight. Never!

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

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off


Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service - Do Not Sell My Personal Information -

Copyright 2021 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.