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Dec 01, 2019, 09:53 PM
I fly, therefore, I crash!!!
SteveT.'s Avatar
Thread OP

Drill rod for wing rods?

Question for for guys. I have local access to .218" drill rod to be used as a wing rod for an Oly II I am building from my own laser cut kit. Would this be ok? Unfortunately, there are no hobby shops in the area that carry K&S music wire any more, so, that's out, and to order it online, the only place I found was Brodak, and I have to order three pieces, so, $24.95 including shipping.

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Dec 01, 2019, 10:35 PM
Registered User
A lot of people like to ejector pins. Do you have any of those locally?

Is this drill rod tempered? I've seen some drill bits that fail in a brittle manner. The old K&S wire failed gracefully, i.e. it would bend a long way before it broke. My favorite Oly II bent three or four .219 (i.e. 7/32) rods without any damage to the rest of the model. If I was building one, I think I'd want 1/4 inch music wire with a bit more attention paid to the spar construction. I think Skybench went even larger, but I think that's overkill unless the structure was revised. It's best if the wing rod bends before the wing breaks.

If you test the drill rod and it bends before breaking, then it's probably ok to use. You might want to find out just how strong it is, though. Music wire of that size is supposed to be somewhere above 200,000 psi yield strength. A piece of 7/32" music wire might support 18 or 20 lbs cantilevered out a foot from a fixed support before it deforms permanently. If you're going to winch the model, I'd consider that a minimum.

Maybe you have long hardened bolts locally too. Those might be worth considering. Just lop off the inconvenient parts with a Dremel abrasive cutting wheel or similar.

BTW, should you choose to sell them, I imagine a lot of people would be interested in your Oly II kits, at least until Skybench makes them available again.
Dec 01, 2019, 10:49 PM
B for Bruce
BMatthews's Avatar
Drill rod is sold annealed and soft. As such it bends easily without the springiness we need. Not until you harden and temper it can you use it for wing rods. So look for some other solution.

These days I would go for 1/4 or 5/16 carbon rod.
Last edited by BMatthews; Dec 01, 2019 at 10:54 PM.
Dec 01, 2019, 11:07 PM
Registered User
P.S. Grainger lists K&S music wire. Do you have a Grainger near you?

It will only save you a couple of bucks, though, because you have to buy 3 or 4.

McMaster-Carr used to sell 1/4 inch music wire, but I don't see it on the site at the moment.

If you have hardened 7075 aluminum rod available, a piece of 3/8" should be almost as strong as 1/4 inch music wire. As I recall, the spar caps on the Oly II are 3/8" wide, aren't they? I guess you'd need to relieve the plywood about 1/64 inch if you put it in a brass tube, though. A 9mm rod wouldn't require that. Anything less than hardened 7075 wouldn't be enough, IMHO. Maybe the brass tube wouldn't be necessary? You could wax the rod REALLY WELL.
Dec 01, 2019, 11:13 PM
Registered User
If you're going to go with carbon rod, make sure it doesn't go over any sharp metal edges. It's not very strong sideways. If someone made me use a carbon rod for an Oly II, I'd use the biggest one I could fit. I'd prefer to have the warnings music wire used to give me.
Dec 01, 2019, 11:19 PM
I fly, therefore, I crash!!!
SteveT.'s Avatar
Thread OP
Unfortunately I can't go with 1/4" rod as I built the wings stock using 1/4" width spars. That said, I am building it as an electrified version, so it should not be stressed like one launched on a high start. I will just order some K&S 7/32 music wire from Brodak.

That said, I did find some .2187" ejector pins here..

Last edited by SteveT.; Dec 01, 2019 at 11:28 PM.
Dec 02, 2019, 01:23 AM
Registered User
I guess I was remembering the wrong wing.

I've used Dixie pins for pins that were too big for music wire.

Maybe the ejector pins are good enough. I'm used to winch launching.
Dec 02, 2019, 05:08 AM
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whacker's Avatar

Ask your local supplier about the Drill Rod and how it was heat treated

The Link you provided offers up this detail

Precision made of superior quality, H13 type, thermal, shock-resisting hotwork die steel
Hot-forged heads provide uniform grain flow, higher tensile strength
Core hardness 40-45 HRC
Outside diameter nitrided to 65-74 HRC hardness and finished to minimize wear
Heads annealed for easy machining
Centerless ground D diameter

seesm similar to Royal RHX or ?

There is a 3 page discussion here on wing rod materials, some have used them others offering up info on their experiences either from use, or what they googled

WING Rod Info

Anyone selling steel rod would likely be able to supply some info on the strength, hardness, tempering etc of the material, just ask.

I have bought drill rod material here locally that is so hard that a file won't mark it.

That doesn't mean it's no good though, as there may have been some special surface treatment , and the inner core is softer to allow for give and toughness.

Take the advice of some and ORDER some of the Royal Pins, available from a number of suppliers, you can't go wrong, just be prepared to cut them to length.
Style RHX will work fine, can be cut with a abrasive cut off wheel and is available in various lengths.

Hopefully your able to work out a Source, and let us know how your experience is with your new OLY II, and the wing rod material you find

in the waughs river valley
Last edited by whacker; Dec 02, 2019 at 05:23 AM.
Dec 02, 2019, 06:39 AM
Sonoran Laser Art
Ace Hardware by me has a K&S display with all different sizes sold individually. There website also has it.
Dec 02, 2019, 07:40 AM
allanp's Avatar
As Lincoln said,"Dixie Pin"
Dec 08, 2019, 12:58 PM
Everything is broken
JimZinVT's Avatar
Are Dixie Pins available longer than 6"? That's all I see on the site.
I used a piece of drill rod as a heavier option for the wing rod in my Ahi (stock one is a carbon tube). It bent on the first hard landing.
Dec 08, 2019, 02:57 PM
I fly, therefore, I crash!!!
SteveT.'s Avatar
Thread OP
As it turned out, my LHS actually has decided to start re-stocking some of the 'basics, and I found they did have the 7/32" K&S music wire in stock, so, I picked up a piece of that. Hopefully, since I am going electric on this plane, it will be enough.

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Dec 08, 2019, 02:59 PM
Registered User
If you click on the "headed inch pins", you will find some 10 inch pins. Checking backwards, I find what I think are numbers for some 10 inch pins on the in stock page. Also, they're far from the only source of ejector pins, as a quick internet search reveals. McMaster Carr sells ejector pins, but it looks like the ones much bigger than 1/4 inch are nitrided. Also, the nitrided prices are reasonable, but the others are significantly higher. I think the nitrided ones may actually be weaker, although perhaps strong enough. I don't know what the nitriding does to the failure mode. MSC Industrial Supply is another source.

I think your drill rod must not have been hardened yet.
Last edited by lincoln; Dec 08, 2019 at 03:02 PM. Reason: to clarify who I was responding to
Dec 08, 2019, 03:01 PM
I fly, therefore, I crash!!!
SteveT.'s Avatar
Thread OP
Hardening a drill rod (and please excuse the obvious pun), is not that hard. There are videos on YouTube showing how to do it.

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Dec 08, 2019, 03:02 PM
Registered User
Steve T.
That music wire will be fine for an Oly II. It's enough for careful winch launching on days that aren't gusty, so for electric it might be just right.

If you harden drill rod, will it fail by bending or snapping? The former is obviously preferable. Music wire is great stuff.
Last edited by lincoln; Dec 08, 2019 at 03:04 PM. Reason: acknowledging new post

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