Sanding Cured Fiberglass

[macleodm3]

I accidently left the peelply off of my right side fuselage layup, back where the landing gear bulkheads go. So, I've been experimenting with some different tools to see what sands the cured epoxy the best, especially getting down in the weave.

 

I'v been using the area that will get cut out for the main spar to do my different sanding tests.

 

I've tried

1.) 40 grit sandpaper

2.) 40 grit sandpaper on Fein

3.) "Fine" spinning wire brush on drill

4.) Stainless steel wire brush with handle

 

The hardest part for me, even as I approached sanding through both layers of UNI on purpose, is being able to tell if I'm messing up the top layer of UNI!!

 

Typically with the sandpaper, I can get the surface dull, but not in between the cured UNI ridges.

 

With the spinning wire brush and Fein with sandpaper, I can reach into the valleys, but can't tell how much I'm destroying the top layer of UNI (the ridges).

 

Sandblasting would fix it all, but my gosh the big compressors are expensive, and what a mess it would make at this point in the build.

 

Any advice or ideas on getting cured fiberglass sanded "enough" for a good additional layup?

 

I've searched the forums and archives of course.

[argoldman]

I accidently left the peelply off of my right side fuselage layup, back where the landing gear bulkheads go. So, I've been experimenting with some different tools to see what sands the cured epoxy the best, especially getting down in the weave.

 

I'v been using the area that will get cut out for the main spar to do my different sanding tests.

 

I've tried

1.) 40 grit sandpaper

2.) 40 grit sandpaper on Fein

3.) "Fine" spinning wire brush on drill

4.) Stainless steel wire brush with handle

 

The hardest part for me, even as I approached sanding through both layers of UNI on purpose, is being able to tell if I'm messing up the top layer of UNI!!

 

Typically with the sandpaper, I can get the surface dull, but not in between the cured UNI ridges.

 

With the spinning wire brush and Fein with sandpaper, I can reach into the valleys, but can't tell how much I'm destroying the top layer of UNI (the ridges).

 

Sandblasting would fix it all, but my gosh the big compressors are expensive, and what a mess it would make at this point in the build.

 

Any advice or ideas on getting cured fiberglass sanded "enough" for a good additional layup?

 

I've searched the forums and archives of course.

 

 

Andrew,

 

I hope you don't take this to be too abrasive!

 

There is a product, that I think you can get at Home depot, which is a abrasive impregnated plastic brush type affair. This is chucked in a hand drill.

 

It comes in three different grades of abrasive (I think orange, blue and gray) Get the heaviest abrasive , orange or gray. It comes in at least 2 shapes, conical and wheel shape. I think it is of French manufacture.

 

Use it somewhat slowly, don't build up heat and it should do your job.

 

 

Rich

[macleodm3]

Are you referring to any of these? (see picture)

[Jon Matcho]

Do you mean near the LWX/LWY build-up? Regardless, sanding with 40-grit sandpaper by hand should be well enough. You won't get all the crevices, but you'll be good enough IMO.

 

Trying those sanding discs might be good as well. As Rich said, go slow and light in different directions. Don't bother with perfect.

[TMann]

Sandblast it. Regular sanding only takes off the high spots. You can't affect the lower areas without damaging the fabric in the high spots.

You don't have to blow holes in it, just dust it.

A lttle messy but very effective.

[macleodm3]

Its unusual to get a consensus when I ask a question... this time is no exception:D

 

I will someday sandblast, now might be a good time to start.

[Jon Matcho]

I will someday sandblast, now might be a good time to start.

I'll respectfully disagree. Sure, a sandblaster would be a handy tool, but you just don't need it right now filling up space and complicating your build process. Grab some sand from a kid's sandbox and press it around and into the voids if you're that concerned about it.

 

Just my opinion. Don't buy tools you don't need.

[TMann]

I'll respectfully disagree. Sure, a sandblaster would be a handy tool, but you just don't need it right now filling up space and complicating your build process. Grab some sand from a kid's sandbox and press it around and into the voids if you're that concerned about it.

 

Just my opinion. Don't buy tools you don't need.

Rebutal:

This is a cheap tool to acquire ($25 at Home Depot) and is easy to set up.

Hook it up to an air source and stick the feed tube into a bucket of sand.

If you don't get the results you want, you're only out $25.

 

When I did my bulkheads, I floxed them and then taped only one side. When I flipped it over to do the other side, I sanded first then ran a bead of flox to fill any voids before I taped. The only way I could ensure a good bond to the irregular surfaces left by the original flox joint was to sandblast.

 

It's a worthwhile tool to have in your shop. I sweep up the used sand and put it in large zip lock bags and use it as shot bags to weigh down parts during hotwire cuts or while curing.

[Marc Zeitlin]

Sandblast it....

For folks thinking of sandblasting, you may want to take a look at the "Composite Bonding Forum" presentation from 2005 at:

 

http://www.cozybuilders.org/Oshkosh_Presentations/index.htm

 

Abaris claims that this is a "high risk method" of increasing the surface energy of the substrate, and dependent on operator skill. (Page 23 of 51).

 

Scaled never sandblasts composite surfaces to be bonded (or finished in any way) - we alway peelply/sand.

 

Personally, spraying dirt at high pressure at my layups is not something I'm interested in doing. Aluminum, steel, other metals, sparkplugs - sure. Not composites - at least not for me.

[TMann]

Personally, spraying dirt at high pressure at my layups is not something I'm interested in doing. Aluminum, steel, other metals, sparkplugs - sure. Not composites - at least not for me.

<sigh> This has been covered in this forum before in previous threads.

Wayne Hicks (a reliable source I would say) seemed to think highly of the technique ...... enough to state he had become a convert (Post is here.)

</sigh>

Of course I could search around the internet and find some oppositional positions ........but I trust Wayne's opinion/research. He speaks from a position of experience.

[Wayne Hicks]

I'll contact the author, but I'm fairly certain that what he meant by "High risk method - somewhat operator dependent", was the risk of damaging the fiberglass if the operator got careless or didn't know what he/she was doing. I'm fairly certain the author didn't mean that you can't get acceptable surface prep and adhesion by sand blasting.

[Jason Heath]

<sigh> This has been covered in this forum before in previous threads.

Wayne Hicks (a reliable source I would say) seemed to think highly of the technique ...... enough to state he had become a convert (Post is here.)

</sigh>

Of course I could search around the internet and find some oppositional positions ........but I trust Wayne's opinion/research. He speaks from a position of experience.

<sigh> what's with all the <sigh>ing anyways? With all due respect for Wayne and I would personaly trust his opinion/research more than others (no offense anybody) "SANDBLASTING" is a far to generic term for what he has done and he makes reference to the media he used and what to watch for, but to tell Andrew to go out and buy the cheap Campbell Hausfeld suction gun and stick it in a bucket o' sand and blast away could create a very bad day for him. Oh I forgot to add, In my opinion.

[macleodm3]

Yeah we don't want to get any of us kids hurt now...

Wayne basically used a very inexpensive gun. Nothing fancy.

It must be more gentle than me with my 120V corded drill and spinning stainless steel wire brush attachment. Oh the sweet smeel of smoking Epoxy

 

What I'm still looking for is a reasonable power tool attachment for sanding in the Grooves. The "Composite Bonding Forum" recommends scotch-brite. I'll try that nest.

 

So, whats the consensus.... worry or don't worry about the unsanded valleys?

 

<sigh> what's with all the <sigh>ing anyways?

You just HAD to Ask.... thats the sound of friction.

[TMann]

<sigh> what's with all the <sigh>ing anyways? With all due respect for Wayne and I would personaly trust his opinion/research more than others (no offense anybody) "SANDBLASTING" is a far to generic term for what he has done and he makes reference to the media he used and what to watch for, but to tell Andrew to go out and buy the cheap Campbell Hausfeld suction gun and stick it in a bucket o' sand and blast away could create a very bad day for him. Oh I forgot to add, In my opinion.

Have you tried it?

You would have to lock in the nozzle to one area and let it run for some time to do any damage. You are more likely to do more damage and achieve poorer results with 40 grit.

 

When I was working my way through college, I worked on a crew sandblasting bridges with big deisel compressors and the like. This is what people visualize when the topic of sandblasting comes up. Big difference between that and the tool mentioned here.

 

I've tried it both ways and believe that it has merit.

That was based on the thread quoted.

 

You should try it. Experience may mold your 'opinion' as well.

 

And as a footnote: You buy the 'sandblasting' sand for this. It is already cleaned and is of a sharper edge than 'play sand' or sand you would use for mixing concrete.

[Marc Zeitlin]

I'll contact the author, but I'm fairly certain that what he meant by "High risk method - somewhat operator dependent", was the risk of damaging the fiberglass if the operator got careless or didn't know what he/she was doing. I'm fairly certain the author didn't mean that you can't get acceptable surface prep and adhesion by sand blasting.

That was my interpretation as well. You, obviously, have more than enough experience to know what you're looking at/for during surface prep.

 

For Jason, Mr. Mann continually sighs either because there's a lack of O2 in his location, or else because he's subtly expressing his displeasure with my know-it-all attitude, albeit an attitude that he shares. See:

 

http://www.answers.com/topic/sighing?cat=health

[TMann]

For Jason, Mr. Mann continually sighs either because there's a lack of O2 in his location, or else because he's subtly expressing his displeasure with my know-it-all attitude, albeit an attitude that he shares.

Actually, it is just a communication technique that I picked up from a super-intellectual type. I assumed it was an acceptable form of communication.

 

I do apologize if my choice of role model was a poor one.

I hope that message is appreciated by all.

 

Sigh. Since neither of these things is an issue in building a structurally sound aircraft per plans, I'm truly at a loss in trying to ........

[Jason Heath]

Have you tried it?..

I've gone through more than 15 tons of various blasting media this year that we use for different stages of our manufacturing process, all of which I have to qualify for the specific task (as well as the safe handling, storage and disposal of each) so I have a vague clue as to its many uses, so the answer would be, Yes.

 

 

When I was working my way through college, I worked on a crew sandblasting bridges with big deisel compressors and the like. This is what people visualize when the topic of sandblasting comes up. Big difference between that and the tool mentioned here..

Which was the only reason for my original post, which has brought out more information from others as well as you.

 

I've tried it both ways and believe that it has merit.

That was based on the thread quoted..

I agree, if done properly with the right equipments and experience.

 

You should try it. Experience may mold your 'opinion' as well. .

I have and wouldn't have any problems with or doing what Wayne has done, on the same areas that he has done. Blasting flox joints that I didnt clean up before they dried isn't one of them. Not that it didn't work for you, but that's an awfully messy way to deal with them, Experience in laying glass and prepping such areas would serve a greater purpose.

 

And as a footnote: You buy the 'sandblasting' sand for this. It is already cleaned and is of a sharper edge than 'play sand' or sand you would use for mixing concrete.

You might!

 

<sigh> Has my communication technic resembled that of your poor role model or should I hit him up for some pointers? maybe theres an outline I could follow. <sigh>

[TMann]

Blasting flox joints that I didnt clean up before they dried isn't one of them.

That's no way to build, Jason.

You should always tool and peel ply everything you can.

After I pull my peel ply, I sand where I can but I always give extra attention to the flox joints to be sure.

When you get to some of the areas like where the back of the pilots seat meets the floor, it's an area that is tough to prep (to my standards.)

 

It is best to save areas like this for a time when you have the time to do it right.

 

(uh, don't do the sigh thing. I think it is pissing off my mentor.)

 

So... what chapter are you up to?

[argoldman]

Are you referring to any of these? (see picture)

No, those are the 3-m deals. The ones to which I refer look like wire brushes but instead of wire they are nylon with impregnated abrasive. They are one piece.

[Jason Heath]

That's no way to build, Jason.

your tellin' me...see below

The only way I could ensure a good bond to the irregular surfaces left by the original flox joint was to sandblast.

That was your quote brutha', not mine

:You should always tool and peel ply everything you can.

Really!

:After I pull my peel ply, I sand where I can but I always give extra attention to the flox joints to be sure.

When you get to some of the areas like where the back of the pilots seat meets the floor, it's an area that is tough to prep (to my standards).

Probably to everyones standards, unless Gumby's building one of these.

 

:It is best to save areas like this for a time when you have the time to do it right..

I believe this is the attitude Marc was refering to.

 

So... what chapter are you up to?

Stuck in chapter 10, no time to build right now

 

Sorry for jackin your thread Andrew

[TMann]

Yeah, well anyway, back to the question at hand:

 

So, I've been experimenting with some different tools to see what sands the cured epoxy the best, especially getting down in the weave.

I think Wayne's way should work for you.

It would be interesting to do a test piece, sandblast one half and sand the other, magnify the area and compare thread/fiber damage.

[Big Steve]

Why dont you try to do it the way Burt said to. Get some 36 grit sandpaper and work off some of that dinner. I know I sure need to get my plane to loose 20 lbs maybe a little more sanding will help.

[Edge 513]

Big Steve,

You make too much sense. Thats been working for me too. Big thumbs up for techniques for us overweight builders.

If you don't need to lose ten pounds then you can try some super whiz-bang method.

A couple thousand Rutan birds been flying for years using the old 36 grit elbow effort up there.

[macleodm3]

Why dont you try to do it the way Burt said to.

If I had DONE it the way Nat said to do it, it would have been Peel-plied.

 

I've got the sandpaper, now I'm just trying to figure out how to get the gloss out of the valleys.... which sandpaper does just fine if you sand away the ridges and the corresponding glass fibers.

 

My goal is to prep an area without messing up the top layer. But really, I'm with you on this one BIG Steve.... I believe that with a good sanding, the bond will be fine. And the weight (builder weight) will be less.

 

I also know that if I sandblasted the bond areas, the result would an area prepared better than if sanded, with less damage to the glass fibers. I would expect a stronger bond.

 

Either way will give good results

[macleodm3]

You make too much sense. Thats been working for me too.

Have you been building?

 

The ones to which I refer look like wire brushes but instead of wire they are nylon with impregnated abrasive

How about this one?