Go Back  RCU Forums > RC Airplanes > Composites Fabrication And Repair
 PLEASE HELP! This is driving me BANANAS! >

PLEASE HELP! This is driving me BANANAS!

Notices
Composites Fabrication And Repair Carbon Fiber, Kevlar, Fiberglass and all the newest high tech composites

PLEASE HELP! This is driving me BANANAS!

Old 06-14-2007, 01:01 AM
  #1  
Senior Member
Thread Starter
 
Join Date: Jan 2006
Location: Melbourne, AUSTRALIA
Posts: 167
Likes: 0
Received 0 Likes on 0 Posts
Default PLEASE HELP! This is driving me BANANAS!

Hi All,

I know I have asked this question before - but I can't seem to get this right!

I have glassed my rudder. One coat of Z-Poxy. Scraped with a playing card so it was not white and not shiny, but matt. I think i did this part ok.

I have now started to spray "high build" primer from the local SuperCheap Auto. Photos of the products are below

I did 1 coat of beige, 1 coat of grey, 2nd coat of beige and 2nd coat of grey! 4 light coats in total! (I waited 5 mins between coats.)

There is STILL weave visible! What have i done wrong? (see 2nd pic below - zoom in to see what i mean).

Is there any point in trying to sand this, as I will clearly have hundreds of pin holes!

PLEASE HELP! At this stage i'm thinking i might try a flow coat of resin on the elevator to see if I get better results.
Attached Thumbnails Click image for larger version

Name:	Us53388.jpg
Views:	22
Size:	76.3 KB
ID:	703773   Click image for larger version

Name:	Je11048.jpg
Views:	22
Size:	44.7 KB
ID:	703774  
Old 06-14-2007, 03:53 AM
  #2  
Junior Member
 
Join Date: Dec 2004
Location: Bernie, AUSTRALIA
Posts: 13
Likes: 0
Received 0 Likes on 0 Posts
Default RE: PLEASE HELP! This is driving me BANANAS!

G'day, I'm a novice at this but, I have done a bit of research, and have recently completed my first attempts at F/Ging.
The rules that I have learnt, and have been sticking with, sofar, are:
1./ Give bare sheeting a once over with thinned (25% with acetone or alcohol) resin only,using a credit card or scraper to scrape off all excess.
(this first step is to fill the pores of the balsa, before applying the cloth. This will result in less resin being absorbed in subsequent coats . Another bonus is less weight)
2./ Mop up excess with paper towells.
3./ Allow to go off.
4./ Lay on cloth.
5./ Repeat steps 1, 2, 3.
By this time, I end up with a kind'a smooth, I suppose shiny surface. Do you think maybe, I am doing something wrong?
The learning curve is steeper than I thought.
I have read that some people fill the weave with filler, but it makes no sense to me why one would even apply cloth without filling the weave. This would defeat the purpose of the whole structure of the manufactured composite material.
Well, anyhow, thats what I think
Goodluck with your model. Glenn.
Old 06-14-2007, 04:25 AM
  #3  
Senior Member
Thread Starter
 
Join Date: Jan 2006
Location: Melbourne, AUSTRALIA
Posts: 167
Likes: 0
Received 0 Likes on 0 Posts
Default RE: PLEASE HELP! This is driving me BANANAS!

Thanks bigfella,

I'm not sure how to proceed now. I think I might try the thinned second coat as you describe on the next piece.

Thanks for the reply. Hopefully someone can give me a clue as to the primer path!

I was thinking that maybe the weave that shows in the photo might be a false impression - i.e the paint has formed evenly on the lows as well as the highs - maybe when i sand tomorrow it'll work out better. not sure. Will let you know.

Old 06-14-2007, 05:42 AM
  #4  
Junior Member
 
Join Date: Dec 2004
Location: Bernie, AUSTRALIA
Posts: 13
Likes: 0
Received 0 Likes on 0 Posts
Default RE: PLEASE HELP! This is driving me BANANAS!

G'day again, Sorry if i missed something, but, as a rule of thumb, always sand between coats. This allows the subsequent coats less area to do their work on, and this means more efficient use of the coating (less surface area for the coating to adhere to). This also adds up to less weight as well as a finer coating thickness. Hope this is some help.
Glenn.
P.S. what part of Sydney?
Old 06-14-2007, 07:07 AM
  #5  
Senior Member
 
Join Date: Dec 2001
Location: Brantford, ON, CANADA
Posts: 3,305
Likes: 0
Received 0 Likes on 0 Posts
Default RE: PLEASE HELP! This is driving me BANANAS!

You used Z-poxy but what weight cloth. If I counted correctly you have eight coats of spray can primer and no sanding between coats. It all went wrong.

First of all I never use z-poxy or any hobby store resin. I use a good quality epoxy resin, West Systems or MGS. I use a max weight of 3/4oz glass cloth. I NEVER seal the balsa surface first. I want the resin to soak into the wood and pull the cloth down with it. I use a stiffer squeegee than a playing card, 1/16 ply scraper or any of those plastic scrapers spold in paint stores. Never ever use spray can products for a good finish. I will not argue about this, I am not the one with the problems.

When sanding always us a sanding block. After the resin has cured using 320 grit wet sand the surface very lightly enough to remove any small pips but do not cut through the weave. Wipe down with a damp cloth let dry. Dust off with a tack cloth. Prime, use a quality high fill automotive primer with a proper spray gun. I use an HVLP gun. Wet sand again until the weave is just visible. Repeat the cleaning process. Prime again, this should be the last coat of primer.

If you do not sand between prime coats the surface will never get flat. Additional coats will just follow the previous lumps, bumps and valleys.

Ed S

Old 06-14-2007, 05:52 PM
  #6  
Senior Member
Thread Starter
 
Join Date: Jan 2006
Location: Melbourne, AUSTRALIA
Posts: 167
Likes: 0
Received 0 Likes on 0 Posts
Default RE: PLEASE HELP! This is driving me BANANAS!

I'm in Alexandria

Ed,

Thanks for your comments. Remember this is my first go. I used 3/4oz cloth.

There was 4 coats of primer. I did this based on the instructions on the can. It said "apply 3 light coats allowing 5 mins in between". I did a 4th coat so i ended up with grey at the end.

Unfortunately I am not in a position for a HVLP. I will apply my final coat at work with a gun, but I can't be carting all my bits to work in order to prime. I will do this with a spray pack in the house, and final coat at work with a gun. That is a long way off! though!

I will sand now - i figure that if it has followed all the lumps and bumps it should sand to a flat surface now?

For the next bit, I should apply one coat of primer then sand that off? Then another and sand that off?

I tried this process on a couple of test pieces in previous posts and it took 5 coats with sanding in between!

[link=http://www.rcuniverse.com/forum/m_5608164/anchors_5668821/mpage_1/key_/anchor/tm.htm#5668821]Here is the other post[/link]

That is why I am trying something different. I am at a loss as to what I am doing wrong because I follow everyones instructions about the glassing bit, but two coats of primer is just not enough! I think I might try a flow coat of resin on the next bit to compare if this is easier.
Old 06-14-2007, 06:09 PM
  #7  
 
saramos's Avatar
 
Join Date: Dec 2003
Location: Northridge, CA
Posts: 3,052
Received 2 Likes on 2 Posts
Default RE: PLEASE HELP! This is driving me BANANAS!

When you are sanding between coats, are you sanding all the primer off? You should only be sanding down to the top of the weave. This will leave primer in the low spots and in-between the weave. It's also possible that the primer you are using is not as high build as the products I've used. I noticed in your photo that neither product states as being specifically high build. These may end up needing more coats to fill the weave. It shouldn't add more to the weight as they are lighter coats and whether you use high build primer, primer filler, or sandable primer, in the end you will be sanding all but the low spots off. It'll just take more time to spray and sand and spray and sand and ...


Scott
Old 06-14-2007, 06:38 PM
  #8  
DHG
Senior Member
My Feedback: (7)
 
Join Date: Apr 2002
Location: Arvada, CO
Posts: 928
Likes: 0
Received 1 Like on 1 Post
Default RE: PLEASE HELP! This is driving me BANANAS!

Ed,

But if you sand off the Pips, that will leave Gladys Knight standing there all by herself!

Tasesq,

Ed's right; spray-can primers aren't great, but I understand why you may need to use them. They're definitely not all created equal. Generally, the less you spend, the less they will fill the weave. Cheap spray-can primers can easily take 5 or more coats to fill 3/4 oz. cloth, so from that standpoint you don't really have a disaster, just a source of frustration.

At this point I'd recommend shopping around for a "Filler and Primer", not a "Primer and Filler." Sand lightly between coats, as suggested, and fill any dents or stubborn pinholes with either Bondo Glazing & Spot Putty (stinky stuff, in a tube ... knead the tube to remix it because the solvent can separate from the putty) or vinyl spackling paste from the paint department of a hardware store. These both need to dry overnight, but they both will sand very nicely with 100-grit drywall screen (also from the hardware store). When the finish looks smooth, shoot 1 more light coat of primer and then start with the color.

Painting airplanes is like washing dishes: The more of them you do, the better and faster you get.

Duane Gall
RCPRO
Old 06-14-2007, 10:46 PM
  #9  
Senior Member
Thread Starter
 
Join Date: Jan 2006
Location: Melbourne, AUSTRALIA
Posts: 167
Likes: 0
Received 0 Likes on 0 Posts
Default RE: PLEASE HELP! This is driving me BANANAS!

Hi guys,

thanks very much. I sanded off most of the 4 coats of primer today with 360 grit, and it left a mostly shiny smooth surface. I used two sheets of paper for this little rudder as it clogged quickly. I sanded dry as I do not have a water atomiser in the house - hoping to get one this arvo.

There were a few low spots left over (areas where the primer would not sand off with a block). I sprayed another 3 coats of primer again, and you could see some pinholes after the paint dried. I filled these with a two part product called "kahfil". It was an oily brown filler with a red hardner i mixed 1/50 by weight. I spread it on lightly over the areas i could see had pinholes, or weave patterns (the low spots).

It's dring now - i'll sand it all off tomorrow morning and see what the result is.

Can anyone from Australia recommend a spray pack filler / primer brand they have had good results with?

The speco product (VHT) was from Repco, and the Septone product was from SuperCheap Auto. The Septone product actually says "high build" on it, but it only came in beige - so not much good for priming balsa/glass! Although it seemed to work ok with a coat of grey then a coat of beige etc.

Thankyou everyone for all your help so far.

Here is a photo of the rudder drying - and a photo of my homemade "spray booth" - I'm sure my landlord would love this sight! all i need is a little fan to blow the smell out the window while i am spraying and I am set!
Attached Thumbnails Click image for larger version

Name:	Bz78932.jpg
Views:	17
Size:	62.7 KB
ID:	704292   Click image for larger version

Name:	Ql34538.jpg
Views:	18
Size:	31.0 KB
ID:	704293  
Old 06-15-2007, 03:32 AM
  #10  
Junior Member
 
Join Date: Dec 2004
Location: Bernie, AUSTRALIA
Posts: 13
Likes: 0
Received 0 Likes on 0 Posts
Default RE: PLEASE HELP! This is driving me BANANAS!

Hey Tasesq, sorry to maybe give you a bum steer, but that was a method used by someone on another sight, and I assumed that he knew what he was talking about. I suppose in the end, it is what works best for you. I am reentering this hobby after around 30 years. Ask me anything about tissue and dope!
Ed's method and reasoning seems pretty good to me, I just can't see why we don't just cover our models with cotton or an open weave cloth, if we don't fill the weave with the resin to produce the chosen F/G's structural properties.
I am in an area that makes me rely on the advice of people who have been in the game awhile. I would like to know why we fiberglass at all. I know that it seems to be the most popular method, but what about, for example covering an airframe in resin soaked brown paper panels cut to scale and applied from the rear of the airframe to the front, just like the real thing?
The one thing that I noticed, was that on the coating on the Hstab. seems overly brittle. I have already cracked it by handeling. I used the method above...
I hope more Ideas come to your posting, I will be watching intently. Glenn.
Old 06-15-2007, 05:42 PM
  #11  
Senior Member
Thread Starter
 
Join Date: Jan 2006
Location: Melbourne, AUSTRALIA
Posts: 167
Likes: 0
Received 0 Likes on 0 Posts
Default RE: PLEASE HELP! This is driving me BANANAS!

Hi Gents,

Well this morning I sanded the rudder back - with mixed results. (360 grit)

As you can see from the attached photos, in my attempt to wet sand most of the primer and red filler off, and in an attempt to sand out the low spots, I have inadertently sanded through the cloth in a couple of places!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! [:@]

Is is a complete disaster? Or can i just brush on some finshing resin to seal, then sand again?

I was not able to remove all the low spots as you can see in the photo - so will need another coat of primer anyway. However, I assume that primer direct on the balsa is a no go.

I don't think i will wet sand next time. It is just way to hard to tell if you are getting too close to the weave. I even cheated, by sacrificing a complete flat surface by trying to sand the low spots with my fingers rather than a block, but still went through the cloth!

The first sand back of the primer was done dry - i had to wear a mask, is made a mess, and clogged the paper quickly resulting in a lot of paper use, but I think i would perfer this!

Thanks for everyone's help.
Attached Thumbnails Click image for larger version

Name:	Qo40921.jpg
Views:	18
Size:	24.3 KB
ID:	704662   Click image for larger version

Name:	Ok28825.jpg
Views:	19
Size:	30.1 KB
ID:	704663  
Old 06-15-2007, 05:47 PM
  #12  
Senior Member
Thread Starter
 
Join Date: Jan 2006
Location: Melbourne, AUSTRALIA
Posts: 167
Likes: 0
Received 0 Likes on 0 Posts
Default RE: PLEASE HELP! This is driving me BANANAS!

ORIGINAL: saramos

When you are sanding between coats, are you sanding all the primer off? You should only be sanding down to the top of the weave. This will leave primer in the low spots and in-between the weave.
Hi Saramos,

How do I know when i am at the top of the weave? Is it simply when there is no more primer left and I am back to clear cloth/resin?

When I wet sanded just now, i had areas where there was no primer but i kept on going to try and get the low spots out. I guess I should have stopped, accepted the low spots and gone on to spray another few coats of primer.

Oh well - hopefully someone can help me save my rudder so I don't have to build again!
Old 06-16-2007, 03:43 PM
  #13  
My Feedback: (85)
 
Join Date: Dec 2001
Location: CygnetTasmania, AUSTRALIA
Posts: 274
Likes: 0
Received 0 Likes on 0 Posts
Default RE: PLEASE HELP! This is driving me BANANAS!

If you go to one of the Auto Cheap stores they have a big mob of primer fillers and you have access to a gun your problems are half over. If you follow what Ed said in his post you will solve the other half.

Regards.

Bill.
Old 06-16-2007, 06:09 PM
  #14  
Member
 
Join Date: Apr 2007
Location: ChristchurchCanterbury, NEW ZEALAND
Posts: 61
Likes: 0
Received 0 Likes on 0 Posts
Default RE: PLEASE HELP! This is driving me BANANAS!

Man you guys do things the hard way. Use a good resin, Not "Hobby resin". Use it at full strength NOT THINNED and don't squeegee it all off. You can easily sand excess off but it's much harder to put more resin on the thin spots and get good adhesion. I've never had to fill weave doing it this way and my surfaces are almost ready for paint with a light sand to give the paint something to bite.
Old 06-16-2007, 10:48 PM
  #15  
My Feedback: (8)
 
Deadstik's Avatar
 
Join Date: Mar 2002
Location: Rougemont, NC
Posts: 1,301
Likes: 0
Received 1 Like on 1 Post
Default RE: PLEASE HELP! This is driving me BANANAS!

Tas,

After reading over your posts, and the issues you have had, it seems your problems may have been caused by two factors. The first was possibly the type of resin. If you don't use a good quality resin, you aren't going to get good results. Not meant as a plug, but I use Zap products finishing resin... works great in applying the glass to the wood. I believe the biggest part of your problem is the quality of your primer. I use PPG DP 401 epoxy white auto body primer not only to prime my kit fuselages in the mold but also on the wings/stabs of my planes. I would check with your local body shops and ask them what EPOXY primers that they use. As with most craftsmen, they will be happy to tell you what they use and where to get it. This is a VERY high fill primer and usually only takes 2 coats w/sanding and I'm ready to shoot color. Good luck with your project, and if you are really worried about messing up an ongoing project, first try it on a piece of scrap.... that way you can be positive of your results without a risk to your real project. Good luck,

Dan
Carolina Custom Aircraft
Old 06-16-2007, 11:34 PM
  #16  
 
iron eagel's Avatar
 
Join Date: Jul 2004
Location: Middleboro, MA
Posts: 3,275
Likes: 0
Received 0 Likes on 0 Posts
Default RE: PLEASE HELP! This is driving me BANANAS!

The first step to do this properly you must put on a thin as you can (a small area at a time) coat of fast drying epoxy 5 min thinned by 50 % acetone. You want it to stick to and seal the balsa without soaking in to much, in order to keep the weight down. After it has dried sand it down with 300 grit sandpaper so it is smooth to the touch but still has the hard surface. This will prevent the epoxy from sinking into the wood when you apply the glass. What happened to you is you used a slow drying epoxy without the wood sealed and lots of your resin soaked into the wood. While the glass was wetted properly when you applied it a lot of it was wicked into the balsa creating the voids you are now trying to fill with paint and filler. You omitted this step, used something like a finishing resin which soaked in.
I agree with the other in the quality of materials, what you use and how you use it is important.

I have found that the quick seal method on the balsa helps a great deal, enough of it soaks in and when it has hardened you can and sanded you can apply your glass with a lot less epoxy and get a good surface to sand so you have a nice finish with one or two coats of primer and a coat or two of paint depending on color.
As far as your current project you can just paint it and sand it best you can and write it off as a lesson learned, unless this is a fine scale piece you are working on.

Old 06-17-2007, 01:04 AM
  #17  
Senior Member
Thread Starter
 
Join Date: Jan 2006
Location: Melbourne, AUSTRALIA
Posts: 167
Likes: 0
Received 0 Likes on 0 Posts
Default RE: PLEASE HELP! This is driving me BANANAS!

Thanks everyone for all your help.

I will take all into advice - it seems there are many ways to skin a cat!

I'll post some photos of the finished product. Cheers.
Old 06-17-2007, 09:23 AM
  #18  
My Feedback: (1)
 
Join Date: Dec 2001
Location: Waseca, MN
Posts: 8,456
Likes: 0
Received 0 Likes on 0 Posts
Default RE: PLEASE HELP! This is driving me BANANAS!

There are definately better finishing resins out there, but Zpoxy is perfectly fine for getting a good surface. I've used it quite a bit, and it works fine, although it sets a little quicker than I would like. Learning to fiberglass, prime, and paint, takes a little practice, but the results are worth it.
Old 06-17-2007, 11:21 AM
  #19  
My Feedback: (1)
 
Join Date: Mar 2003
Location: Over da rainbow, KS
Posts: 5,087
Received 5 Likes on 5 Posts
Default RE: PLEASE HELP! This is driving me BANANAS!

There may be "many ways to skin a cat", but if you do as some advise on this thread it would have to be changed to "many weighs to skin a cat".

Follow Ed's advice if you are using epoxy. He has done this more times than he would want to admit, and mostly on airplanes where finished weight matters.
Old 06-18-2007, 03:06 AM
  #20  
My Feedback: (2)
 
j.duncker's Avatar
 
Join Date: Jun 2004
Location: Sailing in the Eastern Caribbean
Posts: 4,045
Likes: 0
Received 1 Like on 1 Post
Default RE: PLEASE HELP! This is driving me BANANAS!

NEVER EVER DRY SAND EPOXY

Unless you have a full body suit, positive facial ventilation and some serious dust extraction. Epoxy dust in your lungs is not good news. It is also a cumulative irritant leading to severe allergic reactions. I know.

Now re your pinhole problem. ! have found I always need two coats and still get a few pinholes. First coat laminating resin, very light wet sand, wipe over with acetone then a second coat of finishing resin. Wet sand again checking with a strong oblique light to see if I am going too far.
Old 06-18-2007, 05:41 PM
  #21  
Senior Member
Thread Starter
 
Join Date: Jan 2006
Location: Melbourne, AUSTRALIA
Posts: 167
Likes: 0
Received 0 Likes on 0 Posts
Default RE: PLEASE HELP! This is driving me BANANAS!

Hi Gents,

Thanks everyone for their help.

I didn't know that about exoxy sanding! Thanks!

ED:
When you say:

ORIGINAL: Ed Smith
Wet sand again until the weave is just visible. Repeat the cleaning process. Prime again, this should be the last coat of primer.
I have been sanding back the primer so most of the grey is gone - so there is just grey left in some spots. This is how I sanded into the balsa by accident - was trying to level a low spot and went through the cloth on the high spot next to it!

Should I just sand back until some grey is gone (not all) and some clear is showing? Then prime again to keep on fillin the low spots and repeat? Is that how you do it?

I was under the impression you should sand as much grey off as humanly possible - but maybe i went to far.
Old 06-18-2007, 05:43 PM
  #22  
Senior Member
Thread Starter
 
Join Date: Jan 2006
Location: Melbourne, AUSTRALIA
Posts: 167
Likes: 0
Received 0 Likes on 0 Posts
Default RE: PLEASE HELP! This is driving me BANANAS!

Hi Daven,

Is it possible to get some Klass Kote here is Australia?

Do you have a distributor yet?

Last time I enquired the ORM freight to Sydney was enormous!

Thanks!
Old 06-19-2007, 06:05 AM
  #23  
Senior Member
 
TeamSeacats's Avatar
 
Join Date: Mar 2007
Location: Greenville, SC
Posts: 174
Likes: 0
Received 0 Likes on 0 Posts
Default RE: PLEASE HELP! This is driving me BANANAS!

When you see ANY clear, you should stop sanding and begin working on the next coat of primer. When you first see the glass at the peaks of the glass strands, you are already cutting into the fiberglass. You should be attempting to fill the small voids with the primer - not sanding away the fiberglass.

It may also help you if you do the fairing of the low spots before you start to fiberglass. Use a lightweight filler. Bondo makes a blue lightweight polyester resin based filler or you can make your own using Epoxy (if you are going to use epoxy resin for the fiberglass later) mixing it with microballoons until it has a peanut butter consistency. The microballoons will thicken the epoxy and make it much easier to sand.
Old 06-19-2007, 06:42 AM
  #24  
My Feedback: (1)
 
Join Date: Dec 2001
Location: Waseca, MN
Posts: 8,456
Likes: 0
Received 0 Likes on 0 Posts
Default RE: PLEASE HELP! This is driving me BANANAS!

I have no idea if Nate has a distributor of KlassKote in Australia.

I would send him an email and check. I lived about 25 miles from his shop, so shipping was about a gallon of gas

[email protected]

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
Trackbacks are Off
Pingbacks are Off
Refbacks are On


Thread Tools
Search this Thread

Contact Us - Manage Preferences Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service

Copyright © 2024 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.