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IBob

Savannah S Build Notes - Some Tools

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I am preferring not to speak of grommets right now: I bought, online, a box labelled 'Wildcat Rubber Grommet Assortment'.It appears to contain a rubber grommet assortment.

 

What it actually contains is an assortment of black plastic objects shaped just like grommets.......

So what is wrong with them?

 

Are they not rubber or are they not Wildcat?

 

 

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So what is wrong with them?

Are they not rubber or are they not Wildcat?

They are of such a hard material, I doubt they could be inserted (though I know where i'd like to try inserting them).

 

And as a final, if minor touch, the edge to the hole could almost be described as sharp...

 

 

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I use the ones with the hex drive and quick change chuck. If you are doing grommets put a black permanent pen line around the step above the one you want to drill to so you don't get carried away.

I stretch an 'o' ring over the one above; easier to notice.

 

 

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You and I must be the only two silly enough to debur all the lightening holes. For myself it was a therapeutic procrastination to extend the preparation before I had to get organised enough to actually build something.

Am I understanding correctly that no-one (or very few) de-burr and polish all the edges when building these things?

 

 

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Am I understanding correctly that no-one (or very few) de-burr and polish all the edges when building these things?

The factory certainly don't. Many people homebuilding dress up the edges of the sheets to get a much better finish. Many of the lightening holes get buried in the structure so most wouldn't bother. Many of the frame parts can use a bit of a dress up to more evenly support the sheeting.

 

In a full time six week build that I was involved in, there is still time for deburring, I have no idea how long a factory build actually takes, perhaps 4 - 5 weeks.

 

 

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And to clarify (nobody said I was quick!) your last sentence: so, you are removing the bulk of the burrs with a file. Then you are sanding where you have filed? Presumably with some sort of coarse emery paper? The then a final polish with the wheel?

Use a file on straight edges and a de-burring tool on holes to remove the burrs, followed by a Scotchbrite pad (the maroon colour) to smooth the edges. Or use a Scotchbrite deburring wheel to do both jobs - depends on the size and shape of the part. You should be able to get Scotchbrite pads from a decent paint shop. Burrs act as local stress raisers and can initiate fatigue cracking, so deburring rough edges in aluminium components is important.

 

rgmwa

 

 

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Absolutely....deburring is not about looking nice (it does though) it's about removing stress raisers. The scotchbrite conditioning discs do wonders, also abrasive flapper wheels do edges and inside lightening holes beautifully. Care should be taken deburring drilled holes so that they don end up knife edged on thin sheet, a square edge on rivet holes is fine.

 

 

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Thanks for the various input on deburring.

 

I understand that the principal reason is to remove those rough places where cracks or faults may start. In a similar way, a crack may be arrested in lexan (and many other materials) by drilling a small hole at the end of the crack. Without that, the end of the crack is an ongoing weak point, where forces are concentrated. If a hole is drilled, those same forces are no longer concentrated at one point, but spread around the wall of the hole. So the force at any one point is much smaller.

 

A secondary point would be that paint tends to thin at sharp edges and points.

 

And then, yes, there's looking nice.

 

What I am doing at present is removing the manufacturing tags with a file worked square along the edge (not across) but keeping this to a minimum, as often the rest of the edge is usually pretty good. The last very light swipes with the file then remove the side burrs that has raised. With the edge now free of lumps and bumps, I put the piece at the lip of my worktable for support, and go along it at an angle with the deburring cutter (the red thing above), in one swipe if I can.

 

I find I'm getting much better at working this tool with practice, and usually it gives a really good clean edge. When I get it wrong, which is less often, it judders and makes corrugations, which is just what you don't want. I am finding it very quick and effective in the lightening holes.

 

Corners I have been dressing with a file, running it round the corner not across it, then last very light touches to take of the burrs that raises. It has taken some practise, it is very easy to make a sharp corner by beveling the edge too much.

 

I have learnt to stay right away from inside corners with anything but the round needle file. It is very easy to accidentally run a flat file in there and nick the curve in the corner: a near perfect failure point! And I tend to use the needle files for the difficult little bits: they are quite fine and can be used quickly without the risk of making large marks or removing much material.

 

Rivet holes typically are good on one side and raised a bit on the other. Usually ICP have the good side to the skin, which is nice. I debur the raised sides if I can get to them.

 

I use my sense of touch almost more than my eyes for all this, and when I think a piece is done, I run my fingers all round it before putting it in the done pile.

 

I have Scotchbrite for prepping the skins, but didn't know about the wheels. At this point I'm verrrrry interested in anything that makes life easier...I shall be getting some.

 

 

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I should add that if I sound like I know what I'm doing...I don't.

 

The above is just what I arrived at so far, and if there are better ways....like the Scotchbrite disks....and if some of what I'm doing is less than good, please do let me know.

 

Bob

 

 

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I'm sure I've posted this link somewhere before, but download Section 05 (scroll down, third item. It may take a few minutes to download). It has a lot of good information on proper construction techniques and other useful data that should come in handy. Van's Aircraft - Total Performance RV Kit Planes

 

rgmwa

 

 

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I'm sure I've posted this link somewhere before, but download Section 05 (scroll down, third item. It may take a few minutes to download). It has a lot of good information on proper construction techniques and other useful data that should come in handy. Van's Aircraft - Total Performance RV Kit Planes rgmwa

Thanks for that. I hadn't seen it before. If this site has one fault, it's that there is so much good info I miss bits!

 

 

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Thanks for that. I hadn't seen it before. If this site has one fault, it's that there is so much good info I miss bits!

Okay, while it says there are 10 pages at the link, when I download it I get only the first page...hm

 

 

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I should add that if I sound like I know what I'm doing...I don't.The above is just what I arrived at so far, and if there are better ways....like the Scotchbrite disks....and if some of what I'm doing is less than good, please do let me know.

 

Bob

There have been lots of goodies invented over the years. When I was introduced to aircraft sheetmetal work, the standard practice was draw filing the edges, cleaning them up with aluminium oxide, then polishing them with brasso by rubbing the along the edge on top a of a canvas covered bench (which was your normal sheety bench to reduce sheet damage).

 

Now we just use the aluminium oxide belt on a linisher, running it along the edge, the move to a different linisher fitted with a scotchbrite belt (green/blue), and it polishes the edges beautifully. Large sheets still require a lot of hand work though. Flapper wheel in a die grinder can reduce the time taken.

 

The Boeing manufacturing specs provide very good data about deburring, not sure if they are available online (proprietary information)

 

 

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Rivet holes typically are good on one side and raised a bit on the other. Usually ICP have the good side to the skin, which is nice. I debur the raised sides if I can get to them.

Don't get too excited about ICP getting the good side out, when you get to the other side wing skin for instance you will find that they have got it exactly wrong in a lot of cases, just as bent and folded parts will be right on one side and wrong on the other.

 

 

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Back to the tools: $15 adjustable square (and the one it replaced). Great tool for marking out fuel tanks...DSCF0604.JPG.b3da41ca9d5afa2817ea776f966d96b2.JPG

 

 

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And a bit of learning for me on the Rivnuts:

 

First I bought a cheap rivnut tool shaped like a hand riveter, but found I had almost no 'feel' with the thing at all.

 

When I decided to (also) Rivnut the tank covers, I then bought the proper tool. Or thought I did. This one is like tongs (or bolt cutters) in shape, and allows much better 'feel' and control.

 

But it put in the countersunk Rivnuts with a pronounced raised lip. As per the first pic. At first, I thought I was pulling the Rivnuts too hard, so backed the tool off, but same result.

 

I then discovered that the manufacturer had cut a countersink into the head of the die, and the Rivnut was pulling up into this.

 

Fortunately, there was enough meat for me to file the head down and get rid of the countersink. The result is not flat, but slightly domed, and very nice to use that way. I polished it up with fine emery. It's the shinier one on the right.DSCF0606.JPG.831e1d41dd8825de5703af0f453638c5.JPG

 

DSCF0597.JPG.1a838de398e82f40f229ea5be1ad6079.JPG

 

 

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Sorry my fault. Full version here, 10th item down at the bottom of the page. Van's Aircraft - Service Information and Revisions RV-12rgmwa

Is this the correct document? http://vansaircraft.com/pdf/revisions/RV-ALL_05.pdf

 

 

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If you start your build at the Fin, as I did, the very first thing you will need are A3 countersink rivets. And chances are you will then spend the next several hours trying to find them, since most kits don't seem to contain them. You will next discover that you cannot buy them, either locally or nationally.

 

Later, you come to know that none of this is a big deal, but as an optimistic newbie, standing next to your big box of bits, it definitely casts a shadow across your first day....

 

I chose to drill out the fittings to A4 and use the A4 countersink rivets that were in the kit.

 

Since then, I have again wanted A3 countersink rivets (at the fittings for the mixer inspection hatch). This time I made my own, and if there should be a next time, I would also use them at the Fin.

 

I would not do this for 'structural' rivets: in each case, these rivets are holding anchor nuts or the like from rotating. Once those nuts or fittings are done up, the rivets are not under load.

 

The Pics show:

 

1. Steel block drilled and countersunk to take (domed) A3 rivet. (Depth of countersink is trial and error, two holes there are too deep.)

 

2. Second piece of steel drilled to fit over rivet mandrel.

 

3. Socket or some such placed over mandrel and hit with hammer.

 

4. Countersink A3 rivet.

 

DSCF0893.JPG.8310334723672b746b02d2cd12cc7d85.JPG

 

DSCF0894.JPG.89ca673cd6faa4e02725268c4af34772.JPG

 

DSCF0895.JPG.5dbf4e57865b403c9854ff936b69858d.JPG

 

DSCF0896.JPG.edacec6cdcbdae4421d49ece08cdac29.JPG

 

 

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For the solid riveting at the trailing edge of the flying surfaces, I borrowed a rivet squeeze, and bought the correct die (snap). I also bought 1/4lb of the specified rivets, as the soft rivets supplied have a different shaped head and can be difficult to work with.

 

Because I am not particularly good at holding tools straight, and because the squeeze should be held the same for every rivet, I used the edge of the bench to align the squeeze. For the flaperons, I made simple wooden supports, screwed to the bench, which are shown here. I also found them useful when fitting the plastic tips.

 

I posted this elsewhere, but I guess it's a tool too.

 

DSCF0780.JPG.add760d12b3ee2583764fa26baf9619b.JPG

 

DSCF0777.JPG.e801b7bc024323a758512a3487f6a095.JPG

 

 

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If you start your build at the Fin, as I did, the very first thing you will need are A3 countersink rivets. And chances are you will then spend the next several hours trying to find them, since most kits don't seem to contain them. You will next discover that you cannot buy them, either locally or nationally.

Later, you come to know that none of this is a big deal, but as an optimistic newbie, standing next to your big box of bits, it definitely casts a shadow across your first day....

 

I chose to drill out the fittings to A4 and use the A4 countersink rivets that were in the kit.

 

Since then, I have again wanted A3 countersink rivets (at the fittings for the mixer inspection hatch). This time I made my own, and if there should be a next time, I would also use them at the Fin.

 

I would not do this for 'structural' rivets: in each case, these rivets are holding anchor nuts or the like from rotating. Once those nuts or fittings are done up, the rivets are not under load.

 

The Pics show:

 

1. Steel block drilled and countersunk to take (domed) A3 rivet. (Depth of countersink is trial and error, two holes there are too deep.)

 

2. Second piece of steel drilled to fit over rivet mandrel.

 

3. Socket or some such placed over mandrel and hit with hammer.

 

4. Countersink A3 rivet.

Try visiting your local GA workshop. Tell them you are after 3/32 blind countersunk pull through rivets for anchor nuts. I use them frequently for attaching anchor nuts, but I cant remember what the part number is. The good thing with them is that they aren't grip length sensitive as long as they are longer than they need to be.

 

 

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Sometimes the simplest things turn out to be very useful:

 

The wings include simple L section skin stiffening strips, of a very light gauge, flexible and fiddly to debur.

 

I screwed a strip of ply to the benchtop to hold these strips while I worked on them, and it worked so well I used it on all similar parts.DSCF0574.JPG.a1fce7a827120c73c384a1e719d9a68b.JPG

 

 

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