Scratches on inside of skin

[Joe Parish]

I assembled the first side of my HS yesterday and match drilled it. When I took it apart this morning I noticed some scratches (pretty good ones?) I did the other half today, needless to say I did not hardley mark it at all(lesson learned). I will try to post a pic here I was wondering what to do? I assume I could just take 600 grit and sand them out but I am not sure? I had a good weekend in the shop except for that. I did have a countersink on the spar that was .007 too deep. Is there anything I can do with that or just move on?

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[cjensen]

Can't see the pics on my iPhone for some reason, but as far as the countersink...if you build to that tolerance for the whole build, you will have built the perfect airplane. Move on!

I did see the pics in the emailed post, so I have an idea of what the scratches look like. Sand it, prime it and move on...

[bullojm1]

Joe,

Those scratches are inevitable. What are your plans for priming? If you plan to prime the inside of the skins, you will have to rough up the alclad with a scotchbrite pad anyways. For deeper scratches, remove them with some 120 or 240 sandpaper/emory cloth, then scotchbrite, then prime. If you don't plan on priming, then do some "spot priming" on those spots after you use a scotchbrite pad on them.

As far as the countersink, definitely don't worry about being that little off. There are a number of countersinks on my plane that are too deep and it hasn't fallen out of the sky.....yet.

[cjensen]

On the computer now, and seeing the pics, Mike's advise is what I say too. These things happen my friend!

[Joe Parish]

Thanks guys, I was dissappointed when I noticed them and then did the other half of the HS and it came out with just a few little scratches from the nose ribs. I am going to prime the inside with what vans uses(sherwin williams) So I will sand them out before priming the inside.

Chad I think you may have misunderstood about the countersink? This is on the spar to accept the dimple from the skin so the rivet should sit .005 deeper than flush. That countersink was .012 deep with a rivet in the countersink. I could not think of a fix for it and really did not know if I needed to worry about it. Your post gave me the impression that you thought it was only .002 deeper than what it should be. I do not want a show plane just one that is airworthy!

[cjensen]

Nope, didn't misunderstand...I have no idea what the numbers should be to a thousandth of an inch. I did the first few to get the rivet to sit about right, and then did all the others, and never measured one after the fact. Most were just right, several were too deep. It won't matter.

You will build an airplane that is better than pretty much anything that a factory can turn out...trust me. You wouldn't believe some of the stuff we see at work on certified airplanes...

[Joe Parish]

Thanks Chad, that makes me feel good from a build stand point but not so much from a rental stand point. Motivation I guess to keep plugging away!

[BSwayze]

Joe,

If you don't have one already, get your local EAA chapter to set you up with a technical counselor. He will come to your shop, at no charge, and inspect your work and give you all kinds of valuable advice. Doing it early on will set you on a pathway to excellent workmanship and your confidence will soar. You'll also get a nice inspection slip to keep in your file. You never know how that may add to resale value someday down the road.

Keep up the good work!

[Joe Parish]

That is something I have been meaning to do. I have his name and number I just need to call him to set something up.

[cjensen]

Great advise! A good Tech Counselor is a fantastic card to have in your pocket!

[Spike]

Most will attest that by the time you get through the wings, you won't even bat an eye on these things. You are doing great, keep it up!

Spike

[Mike Balzer]

Joe,
do you have a micro-stop countersink? It allows you to do precise countersinking and make adjustments in .001 of an inch.

Always pre-test it in scrap and remember that you have to have a back up piece if your metal is to thin or you will get chatter

Always use micro-stop 2 times in each hole to clear from burs and chips and keep it consistant.

Happy Building,

Mike Balzer

[Joe Parish]

I was using a micro stop countersink. The one that was .012 deep with a rivet in it beleive it or not was the first one I did. I set the depth on a practice piece but what threw me off was the edge of the spar is at a slight angle and I was not perpindicular to it when I started and the bit seemed to grab and made it even worse. I believe that is what caused it. I backed the micro stop off and reset the depth on the next hole and it went pretty well. I set the depth originally one a thicker piece of angle but I can't believe the material thickness made and difference.