95-10 aluminium wing

[skootaroo]

Thanks for the chat on saturday afternoon Arthur, I've got a few questions I guess only you can answer (relating to your aircraft) and a few that are more open to opinion and discussion.

 

What size angle did you use for your spar caps?

 

Which direction do they face?

 

Did you use a single size rivet/ spacing combination(fantasy I'm sure)?

 

We'll get to ribs and skins sometime, what thickness I guess is my most pressing question.

 

Of a more general nature:

 

I printed an appropriatly sized clark-y template and noticed that the original wing is +/-5mm at best! Do I copy the original profile or not?

 

As I'm ditching the wood rag and tube method (in favor of all aluminium) it seems reasonable to build everything behind the rear spar a control surface. Am I adding loads of work to include flaps, is it a waste of time, will I get the benefit?

 

I checked after I got home, the original main spar is timber with aluminium fittings which I think I'll reuse. The rear spar is a single tube glued, not glassed to the timber ribs.

 

I'm sure I've shortcut these questions somewhat, but I'm trying to get a basic drawing done before I lose the work I've already done.

 

Thanks

 

Carl

 

 

[pylon500]

Thanks for the chat on saturday afternoon

Wasn't it Sunday?

Anyway, here are some details to work with.....

 

Angle used on my wing is 0.5"x0.5"x0.050" 2024 extrusion, top and bottom of a 0.016" web at the back only, a similar 4' long extrusion is also fitted to the front above the strut attach point.

 

The web is 8' deep and has assorted 0.032" doublers at various hardpoints.

 

All rivets in the spar web are 'solid' variety.

 

The ribs are, as mentioned, moulded fibreglass.

 

Because of this, the front and rear ribs are attached to the web using AVDEL BULBEX rivets, if done again, I would form metal ribs and just use POP rivets.

 

When laying out the rivet pitch on the spars, I made sure that when I drilled the leading edge skin holes, they fell in between the spar cap rivets, no adjacent rivet holes.

 

From memory the rivet pitch was around 1 1/4" all over.

 

The leading edge skin is more 0.016", as is the rear spar, trailing edge ribs and the trailing edge itself.

 

Although my wing section is just a freehand curve, I was thinking more like a Clark 'YH' section which has a more shallow camber line (less pitching moment) and a raised leading edge profile (more docile stall).

 

Ask away.......

 

Arthur.

 

 

[skootaroo]

Oh, yea of course it was sunday but who can tell on a long weekend.

 

Thanks for the info, I've been beavering away with it.

 

I'm having trouble with finding 2024 angle in Aus, I can see it on aircraftspruce for $3/ft, does anyone know if they post 14ft pieces? or an alternate supplier in Aus.

 

The rear spar, is it a rear facing "c" section, with a verticle or sloping face?

 

I was trying to get out of using solid rivets until I noticed a common theme of solids used on spars, pops everywhere else. Is it just a given that I need to use solids?

 

Carl

 

 

[pylon500]

If you can't get 2024 angle, you could use 6061 (or even 7075 if you have lots of sharp drills).

 

Have a talk to the guys at Performance Metals out near Windsor.

 

My rear 'C' spar actually faces forward and is sloping to allow the original ailerons to move.

 

Is it just a given that I need to use solids?

A given?, yes, mandetory?, not really but when making the spar it is so easy to fit solids at that point that you may as well.

Solid rivets can be installed with a large hammer and punch, you just need a solid work bench and the right size rivet 'snap' (the bit that fits the rivet head)

 

Arthur.

 

 

[skootaroo]

The ribs are really under stressed, even at 0.016" but I don't have any info on making "D" cutouts in noseribs or circle cutouts, with or without flared edges. Are there standards for how close to the edge you take the cutouts and how much difference a flared edge makes.

 

I'm not sure if I've got the right plane but I thought the vampire mk3 had an AL rib with a "D" cutout and a plain edge.

 

Thanks for keeping me going.

 

Carl

 

 

[pylon500]

As for edge distance of a flared hole, I've never really thought about it. :;)4:

 

There may be something in AC:43-13, but it mainly deals with repair, not design.

 

Truth is, it's pretty much an 'art' thing, what looks good will do.

 

The photo shows a vampire rib, 0.016" T3, cold pressed with a machined aluminium die on a rubber press, note the 'bead' as well as the shaped cutout.

 

For low production numbers you could beat these on a wooden block, after you cut out that awkward shape, or you could just fly-cut round holes and flange them.

 

To make quick hole flanges of various sizes (even shaped ones if you want..), find some hard medium, perspex is good, and cut two matching shapes, inside and outside with a minimal clearance, then bevel the inner piece at 45°.

 

A properly shapened fly cutter will do this automatically.

 

Then cut the hole in the rib to match the inside dimension of this bevel profile.

 

I usually tape the two patterns either side of the hole (bevel facing in) and press the lot between two large/strong flat plates.

 

Trying to make stiffening beads is harder and usually requires a 'Jenny'.

 

Hopefully a vampire will be at The Oaks tomorrow (14Apr07)

 

Arthur.

 

 

 

[Guest Teenie2]

Make sure that it is worth the while spending the time cutting the holes if it is only for weight saving.My Teenie has no lightening holes fitted at all. A few people have gone to the effort and cut the holes then weighed the removed material and found out it saved them a staggering 250 grams .If you need a flanging tool they are avail on the sonex web site cheap.

 

 

[Ultralights]

I have access to a nice puch made for making lightning holes, just drill a 1/4 hole in the rib where you want the hole, place the punch dies over through the 1/4 hold, stick the whole lot in a press, then BANG! remove dies, and you have a perfect round and formed flanged lightning hole...

 

i will ask next week where they can be sourced, but i know we have the technology to make the dies in house..

 

I think the purpose of the flanged lightning holes is not so much weight saving, but the stiffening properties of the round flared edge of the hole.

 

 

[Guest micgrace]

Hi

 

I always thought flanged lightening holes were for exactly that. The flange being used to prevent crack propagation from the edge of the hole.

 

Anyway, glad you have use of some flange punches, beats use of a flycutter for sure.

 

Micgace

 

 

[skootaroo]

Thanks for the input guys.

 

I'm looking at the cutouts from the point of doing the job right, as I understand it a rib with cutout and flange is stronger and stiffer than a straight panel. I'm not entirely convinced they're necesary in this application I still feel compelled to find a compatable way to do it.

 

Ultralights, these one hit, cut and flange dies, are they rubber mounted, I can't really picture how they're doig both ops in one hit.

 

I have a little fly press at home here, I can turn some dies up to press the flanges, I guess I really need to see what fits and see how close to the edge is still OK.

 

Anyway still drawing.

 

Carl

 

 

[Ultralights]

when i go back to work i will snap some pics for you. the dies can be made easily by most good toolmakers, the dies we use are made here to our specifications as required and are solid steel.

 

the Dies we have in stock for the F18 Hornet are no good for Hawk aircraft, as the edge of the hole, and the flange has to end at 90 deg to the flat and be a constant radius to the flat part of the rib, (like the side profile of a skateboard ramp) whereas the ribs on the hornet only require a 45 deg bend in the flanged section

 

 

[skootaroo]

I'm looking at the idea of ripping my sparcaps from a larger section of aluminium angle. Can the bulge of a solid rivet expand over some of the filet radius in the angle?

 

 

[Ultralights]

As mentioned earlier by me, here are the pics of the tooling we had made to make lightning holes, and flange the edges at the same time

 

 

this is the 3 pieces together, cut a centre hole in the material the same diam as the central spigot, the black steel inner piece cuts the hole and the outer ring forms the flange..

 

 

The outer ring and flange forming section.

 

 

the small black centre piece has the cutting edge

 

place the job over the spigot, place the cutting piece over the spigot and metal, then place the outer ring over the whole lot, stick it in a press, then BANG! centre is cut out and the flange forms all in 1 hit..... this tool will produce a 45 deg flange.

 

for forming a larger radius flanged to 90 deg, we have had this punch tool made up

 

 

cut a hole in the job to sit over the lip on top of the radiusd part on the part on the left.

 

line up the 2 parts with the central spigot and put in a press.

 

 

or for larger diams we have had this one made.

 

 

though this entire tool is about 6 inches tall and about 5 inch wide and bloody heavy.

 

all these were made in house by our toolmakers using a lathe. im sure a skilled toolmaker could easily make your own set to suit whatever diam and flange shape required.

 

 

[hiperlight]

Back in the days when the world was flat, beautiful women had child-bearing hips and radios had valves, we had a similar tool for cutting holes in steel chassis to mount valve sockets. The tool had a bolt with a nut through the centre which eliminated the need for a press. All that was needed was a hole drilled in the chassis to take the bolt.

 

It would be relatively easy to turn a similar tool (with a flange) for use on aircraft.

 

Bruce

 

 

[pylon500]

Hey, them's some fancy hole flangers you got there!

 

Possibly a little overkill for a one-off project, especially if you want a variety of sizes, but can't knock the offer.

 

When rivetting to exrtrusion or folded angle, the aim is to not have any part of the rivet in the radius, do you really need to come this close?

 

Give me some dimensions..

 

The bolt driven hole punch (known as a chassis punch) tends to leave a slightly ragged edge to holes which can then crack during the flanging process.

 

Arthur

 

 

[skootaroo]

The angle is 38.1x38.1 x 4.75 with a 5.33 fillet radius.

 

On the (shear)web flange I can mill that down to 3/4" or even 5/8" if I can fit rivets in there.

 

I have now read that I need to keep an 1/8" rivet 1/4" from the edge. This makes 5/8" interfere and 3/4" miss the radius by 1/16.

 

If I could just thread the holes and put a row of capscrews in!!!!!

 

"pop" rivets in the skin wont be a problem they have a smaller shop head and keeps away from the rad, it's just these solids!

 

Where do I get them from anyway?

 

An "AN470AD4-6" is a few thou short of the "material thickness+1.5D" is it still within range? (3/16" + 0.016")

 

AN470AD4-7 doesn't seem to be common or am I just not looking in the right places?

 

 

[pylon500]

WOW, that's some beefy spar caps!, are you going cantilever?

 

OK, bit of a close call but if you are going to use 1/8th rivets, and you cut the cap to 5/8ths, ten you have a 1/4 (2/8ths) either side of a 1/8th rivet!

 

Having said that, given the choice of where to locate a rivet, it's probably better to maintain the clearance distance from an actual edge than from a fold or fillet.

 

Don't even think about trying to screw together a structure like a spar!

 

Apart from the fact that a couple of hundred capscrews will add a couple of pounds to your spar, unless they are locked somehow, the normal vibration of flying will start to undo some of them!

 

Rivets;

 

Understanding the numbering system helps, AN470AD4-6 breaks down to, AN470 means a solid dome head rivet, AD implies a rivet composed of 2117 aluminium alloy (structural),the '4' means a 4/32nd inch diameter (1/8th) and the last digit '6' means 6/16ths in overall length from under the head.

 

When calculating the length of rivet required for a job, when placed in the hole you should have 1 and a 1/2 times the diameter of the rivet protruding.

 

You can then generally have about a quarter of a diameter of leeway in each direction, BUT, having the 'tail' too long and you run the risk of the rivet bending instead of flattening when you drive it.

 

Another number sequnce for the same size rivets is; MS 20470 AD 4-6, you can get these rivets from most suppliers at Bankstown.

 

Rivet sizes from 4-2 up to 4-8 are pretty common, after that they may jump lengths.

 

A point to remember, when buying POP rivets, they are measured by their diameter the same, but their length only measures the thickness of the material they are to join;ie[/i] joining 0.063" to 0.063" (1/16th + 1/16th) would require a -2 POP, but a -5 solid rivet!

 

Most 'BLIND' rivets, POPS, CHERRIES, AVDELS etc measure this GRIP length as opposed to the rivets length.

 

Enough for now,

 

Arthur.

 

 

[skootaroo]

So I've started spending money, I'll cut metal in a week or so. I'm still having trouble with an470ad 4-7 rivets (I think I need 100 ok x3 for practice and square the result to counter optimism =900) I haven't found rivetsrus in bankstown in the yellowpages and I'm finding it dificult to tell the difference between one type of aviation business and another.

 

On to pop rivets, even among the good brands it seems dificult to tell the difference between their bunnings grade product and the good stuff, unless they have a fancy add on like a sealed base or a ring to capture the stem (as shown on auf.asn.au) is any advel or cherry product the real deal or do they try to compete with china too?

 

I guess there's some product sensitive questions here phmmm.

 

Carl

 

 

[Ultralights]

i think the genuine Cherrymax rivet is made by Textron.

 

 

[skootaroo]

They just seem to have multiple product lines, down to what looks no different to hardware store rivets. Maybe you really can't tell the diference until you pull a few, I don't know.

 

 

[pylon500]

Rivet, rivet, ribett!

 

Rivets are easily found at Bankstown, as you come down the main drag (from Marion St.), on your right you have a choice of Hawker Pacific followed by Aviall and finally Paul McGuire, who has a shop called A.P.E., but he doesn't have a website, just a plug by some-one else.

 

Solid rivet are available from all these outlets, although A.P.E. tends to have random openning times?

 

Alloy 'Pop' rivets are OK in most low loaded areas like holding skins to ribs, but maybe not skins to spars, here you may want to use steel or monel 'Pops'.

 

Spar caps can be rivetted to spar webs with Pops, but it's not the done thing, solids are best here, same as places like strut attach and wing pickups.

 

These can also be done with bolts.

 

You need to go to bigger places to get bulk Pop rivets, like Blackwoods, Cedray, Textron; try the yellow pages.

 

In most places you want alloy Pop rivets, and could use alloy stems.

 

These are commonly part numbered 73(dome head, {72 for flush}) AA(alloy rivet and alloy stem, {AS for alloy rivet, steel stem}, and then the usual numbers for diameter and length.

 

Yes, you can get 3/32"Ø alloy Pops!

 

If you want a slightly better quality of Pop rivet, you need to chase up an 'AVEX' rivet, very popular with the Zenith builders.

 

These were an Avdel product, but avdel has been bought out by Cherry Textron.

 

As for CherryMaxâ„¢ rivets, these are recognised as equivalent to structural solids, but are frightfully expensive, I'm talking around $2.oo~3.oo each!

 

Ballpark, solid rivets cost about $30.oo for a pound bag, there would be about 2000 in a pound bag of MS20470AD 4-6.

 

Pops would cost around $50.oo for a bag of 1000 of 73AS 4-4.

 

Avdels would cost about twice as much? (there's a bit of guessing going on here!)

 

Arthur

 

 

[skootaroo]

Not ribetting yet, still a tadpole.

 

I was cutting a sheet of 0.016" last night and on the middle of a long run I closed the snips too far. I've got a 1mm nick in my job, it is well outside the row of rivets. It's a small nick do I ignore it? File it out and leave a bow in my job? Get a new sheet and start again?

 

Carl

 

 

[pylon500]

Depends on exactly where the snip is....?

 

Not many places would be highly stressed, and made of 0.016", as such you can most likely 'blend' the nick into the local area.

 

Just where is it?

 

Arthur.

 

 

[skootaroo]

It is on the main spar shear web!

 

If I file the edge there will be a dip in my straight cut, but there's 12mm of material to the row of rivets, so blending it in won't go near them.

 

Even in 0.016" there's only 5000psi @ 6g's when 6061 can go to 25000psi shear.

 

I think I can place it under a doubler as well, or is it better to have it out in the open?

 

Carl

 

 

[pylon500]

With those sort of strengths and edge distances, you could have the nick anywhere.

 

Just blend with about a one in eight gradient and polish a bit to avoid any stress raising.

 

Did you ever find those rivets?

 

Arthur.