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help with putty - 1/23/2008 8:24:04 PM   
rxAxilleas


 

Posts: 231
Joined: 11/2/2006
From: katerinipieria, GREECE
Status: offline 		hi all.
i need a putty to aply over 3/4 oz cloth to make the surface smooth prior priming.
i found that there are many products with varius names : spot putty, red glazing blue green....
please help.i do not understand what the diferences are.
the collor mean something?
all are acryl?
all are sandable?
can i use one from an automotive store or they are diferent, heavier for our task in aiplanes?
many thanks

i am thinking to use of 3m red putty. is it ok?
achilles
       Post #: 1

RE: help with putty - 1/23/2008 9:06:55 PM   
Campy



Posts: 3396
Joined: 1/2/2002
From: Baltic, CT, USA
Status: offline 		f you are referring to 3/4oz fiberglass cloth, and need to fill the weave, the lightest option would be waterbase polyurethane and microballons in a 1 to 4 or 1 to 5 ratio. I usually use a 1 to 5 ration for filling the weave on my builds. Dries fairly quick and is easy to sand.

Another option would be a resin and microballoon mix. Noticeably harder surface, but noticeably harder to sand also

(in reply to rxAxilleas)
       Post #: 2

RE: help with putty - 1/23/2008 9:39:24 PM   
Ed Smith


 

Posts: 2834
Joined: 12/29/2001
From: Brantford, ON, CANADA
Status: offline 		I would not recommend spreading putty over the whole airplane. Any putty is for filling dents and imperfections. I always use a "High Fill" primer. Available from automotive stores it is sprayed on fairly heavily and sands off easily. Sand it down until the weave of the cloth is just visible.

Campy suggests water based polyurethane with a filler. Maybe I did something wrong but I have tried water based polyurethane and each time the water caused the balsa to warp.

Ed S

(in reply to rxAxilleas)
       Post #: 3

RE: help with putty - 1/24/2008 12:27:27 AM   
JKEpps



Posts: 605
Joined: 12/10/2004
From: Greenbelt, MD, USA
Status: offline 		I want to second the recommendation of not using automotive putty, including glazing putty. I know some folks have had success with them, but from my experinces, the successes are short lived. Most autobody fillers/putties are polyester based. They typically shrink over time. I have been a victim of this numerous times. I refuse to use the stuff on any surface or detail application. It'll look good initially, but will eventually drive you crazy chasing low spots and cracks that weren't there before.

I use the "Flow Coat" method mentioned above by Campy. Resin to fill the weave, mix in phenolic (the Red ones, not the white powdery ones) microballoons where needed to fill divits or gouges. Sand down, starting with 80 grit paper, but not aggressively, or you'll burn right through the resin and the weave. If you do, then fill any gouge crated, and go over the area again with epoxy resin. No need to use glass cloth again. Prime with a "filling primer to get those stubborn areas that still show weave. Sand the primer down to a nice smooth finish.

I have used Z-Poxy Epoxy resin with success, but I have recently converted to West Systems Epoxy resin.

Hope that helps.

-Jorden

(in reply to Ed Smith)
       Post #: 4

RE: help with putty - 1/24/2008 5:25:54 PM   
Campy



Posts: 3396
Joined: 1/2/2002
From: Baltic, CT, USA
Status: offline
quote:

ORIGINAL: Ed Smith

I would not recommend spreading putty over the whole airplane. Any putty is for filling dents and imperfections. I always use a "High Fill" primer. Available from automotive stores it is sprayed on fairly heavily and sands off easily. Sand it down until the weave of the cloth is just visible.

Campy suggests water based polyurethane with a filler. Maybe I did something wrong but I have tried water based polyurethane and each time the water caused the balsa to warp.

Ed S


Ed, if you are going to glass using waterbase poly, you need to seal the balsa 1st.. I use 1 medium coat of the commercial type sanding sealer. When dry, I sand off the fuzzies and proceed to glass.

I have not had any problems glassing 1/16" balsa.

If you are interested, I have written a basic "How To" on glassing with waterbase polyurethane .

FWIW - I use MinWax Polycrylic for my glassing and have had very good results with it. I see no reason that other brands of waterbase poly would not achieve similar results.

(in reply to Ed Smith)
       Post #: 5

RE: help with putty - 1/24/2008 6:07:58 PM   
Ed Smith


 

Posts: 2834
Joined: 12/29/2001
From: Brantford, ON, CANADA
Status: offline
quote:

Ed, if you are going to glass using waterbase poly, you need to seal the balsa 1st.. I use 1 medium coat of the commercial type sanding sealer. When dry, I sand off the fuzzies and proceed to glass.



Campy,

Thanks for the explanation. That is the first time I have heard that.

Ed S

(in reply to Campy)
       Post #: 6

RE: help with putty - 1/25/2008 8:03:11 AM   
rxAxilleas


 

Posts: 231
Joined: 11/2/2006
From: katerinipieria, GREECE
Status: offline 		HI Guys ,
thanks for the help!!
i am planing to use the putty only after glasing to fix the imperfections. not to spread all over the wing. probably there will be some low spots, that i want to repair.
i found a product from 3m called acryl-green spot putty. can i use this and aviod cracks? or it is the same product as the polyester based ?
the idea of waterbased poly is better but i can not find similiar products here in Greece.
also in some spots and sadle fillets i used automotive putty with good results directly on the wood . have you tried this? is it pposible to crack or just to fall of? i dont know how good in time is the bondage to the wood.

many thanks again
achilles

(in reply to Ed Smith)
       Post #: 7

RE: help with putty - 1/25/2008 3:14:56 PM   
Campy



Posts: 3396
Joined: 1/2/2002
From: Baltic, CT, USA
Status: offline
quote:

ORIGINAL: Ed Smith

quote:

Ed, if you are going to glass using waterbase poly, you need to seal the balsa 1st.. I use 1 medium coat of the commercial type sanding sealer. When dry, I sand off the fuzzies and proceed to glass.



Campy,

Thanks for the explanation. That is the first time I have heard that.

Ed S


Ed, here is the basic "How To".

Glassing with Water Base Polyurethane


1. Sand the model with 220 grit and remove any highs/lows you may find.
Fill as needed with lightweight filler and sand.

2. Give the wood 1 thin - medium coat of wood sealer. I use the
commercial stuff. What this does is twofold - it stops the balsa
from soaking up too much of the poly and at the same time protects
the balsa from the water in the polyurethane.

3. When dry, sand lightly with 220 to remove the "fuzzies".

4. Some people say to apply a light coat of 3M #77 adhesive to the
wood at this point. I have found that this is more trouble than it
is worth since if you have a wrinkle, the complete piece of fiberglass
has to be removed to straighten it out.

I prefer to lay the fiberglass cloth on the part/area to be covered and
smooth it out using a SOFT brush. Brush FROM THE CENTER TOWARDS THE
EDGES. The static electricity usually holds it in place. I normally
use 1/2 oz (.5 oz) or 3/4 oz (.75 oz) fiberglass cloth.

5. Using WATER BASE polyurethane and a FOAM brush, start at the center
and brush towards the edges of the fiberglass. All you want to do is
stick the fiberglass to the balsa, so excessive amounts are not needed.
Any additional pieces of fiberglass should overlap each other about
1/2 - 3/4 inches.

Let this dry. DO NOT SAND !!

Brush on another coat of polyurethane. This coat can be a little heavier.

Let this coat dry. DO NOT SAND !!


6. Mix up some polyurethane and microballoons. I use 1 part
microballoons to about 5 parts polyurethane. This will be on the thick
side.

Brush on a medium coat of this mixture and let dry.

7. Wet sand this with 220 or 320 grit paper. BE CAREFUL, AS YOU CAN
VERY EASILY SAND RIGHT THROUGH THE FIBERGLASS.

8. Check the fiberglass carefully to insure the weave is filled. If
the weave is not completely filled, repeat step 6 and 7.

9. SPRAY a coat of water base polyurethane on the plane and let dry.
DO NOT SAND !!

10. Spray a THIN coat of primer on the plane. When this is COMPLETELY
dry, block wet sand with 220 or 320 grit as much of the plane as
possible to highlight any highs/lows you may have missed during your
sanding/prep. The areas that can not be block sanded, CAREFULLY sand
by hand. (TIP: CA some of the wife's/girlfriends fingernail file boards
together. Wrap the sandpaper around them so you can block sand in tight
areas. The CA helps prevent the boards from disintergrating in the water)
Fill any low areas with a lightweight filler and sand when dry.

Apply a THIN coat of polyurethane to these areas.

When the poly is dry, repeat this step until you are satisfied that all
the highs/lows are removed.

11. SPRAY a thin coat of polyurethane on the plane. When dry, spray
the primer.

12. When the primer is dry, you can apply your rivets, panel lines and
other detailing desired.

13. Now you can spray your paint.



Campy

(in reply to Ed Smith)
       Post #: 8

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