I ran a really quick and dirty calculation based on some information in Marks' Handbook of Mechanical Engineering and determined that round wires on a Hatz traveling at 90 mph at sea level would exert a drag of 68 lbs, versus equivalent streamlined wires drag of only 8 lbs! This is significant since the extra drag equates to a horsepower requirement of 14 horsepower!! For a typical Lycoming or Continental, that's 1.1 gph!!!

Incidentally, there is a great NACA Technical Paper (#279)that the info in Marks' is based on. This report is available on the NASA Report Server in PDF format at:
http://naca.larc.nasa.gov/reports/1928/naca-tn-279/naca-tn-279.pdf

Hope this helps;

Jim Phillips
S/N 201

Thanks for the good info.

Michael
N838CB

Round wire has been streamlined by use of model airplane balsa TE and metal foil tape. You will need to put roll threads as sharp cuts could lead to failure.

Contact Wassbiplane@tds.com as he has tested wire and his own fittings.

Randy

All wires start out as round. The wires are individually made to length by passing the part to be streamlined through a series of sheels that flatten out the cross section until they are left witht the desired lenticular cross section. Then the wires are ground and finally polished to remove any stress concentrations. All this working actually improves the strength of the wires over stainless stock of the same alloy. Finally, the threads are rolled (not cut) on the end. Since the wires are individually made, they are very expensive. These wires are the most heavily stressed part of the airplane. This is no place to scrimp and save money. There are only a couple of places in the world that make these wires.

This process was invented by the Brittish at the Roayal Aircraft Establishment at Farnborough during World War I. I believe the SE-5 was the first plane to employ the wires. The wires were one of the contributors to the SE-5's superlative performance.

Jim

Keep the good ideas flowing. The rest of us will jump in when we can! Chuck Brownlow

I have been fortunate to fly a Hatz with the cables and also several with streamlined flying wires. You want the flying wires! It felt like I was pushing a billboard through the sky with the cables. It was very noticeable. I can distinctly remember thinking, as I was flying, that it didn't matter what the cost I was going to get the streamlined wires for my Hatz.

Just my opinion.

Bill

Does some one know of a source for stream line wires other than A.S.& S.?

Note: I am leaning towards getting a built 320 from Don's Dream Machines in GA. His 320's do better than 160 HP. However at the same time I have compared the weight of a 320 with the 360, not much difference. How do you thing a Hatz would handel the 360? With all the aluminum we have used, my Hatz will be on the heavy side.

Note N838CB is going to be painted with a gloss black fuselage and gold wings and all polished stainless steel cockpit complements. Vertical stab and wings will have a large gold
star. These are Vanderbilt University colors. We are going to take this plane to OSk. and I want it to stand out. What do you think? Do judges favor certain colors on Biplanes?

Michael
N838CB

Is Steen Aero still taking orders for Brunton streamlined wires? As far as I know, Brunton is the only company left making streamline wires after Mcwhyte quit. Is this true?

Mark T

Randy

The Pelican is absoluely right (as usual) about the terminology. I assumed Michael was refering to all the wires on the plane, so I didn't make any effort to differentiate between them, since I was referring to the drag of the entire wire package (flying wires, Landing wires and roll wires). I did ignore the tail brace wires since nearly everyone uses round wires there anyway. It's really amazing how much extra power it takes to move the round wires through the air versus the streamlined wires. I'll try to be more careful with terminology in the future.

Jim

But a related, "backwards" question comes to mind.

If I understand the numbers correctly, it means that it takes 14 extra horsepower to move the draggy round wires at the same SPEED (emphasis added)as the streamlined wires? If so, that seems to underscore the obvious point that for a given setup, a large increase in power has a proportionally small effect on performance.

But how about holding power constant (say at 75%, as a discussion point), and then comparing the resulting speed using round wires to the streamlined wires? How much speed would you really lose?

Just curious!

regards, Terry

Nobody builds a Hatz Biplane with the idea of going fast, but it would kind of gall you if your buddy's Hatz consistently leaves you in his slipstream. Drag reduction is almost like a free ride. The best thing about it is it never hurts you in some other part of the flight envelope like a bigger engine will.

Jim

And thanks again for the simple, clear explanation!

Agree completely about drag reduction being good for performance in any way you look at it. The big compromise here (for poor boys like me) may just be cost. One could ask "If I could save around two grand, would I be willing to cruise at 86 mph rather than 90 mph? Would I be willing to climb at 280 fpm rather than 300 fpm?"

Certainly not arguing for the round wires, as I agree they're a second-rate solution. But two grand will buy a lot of gas or whatever...

regards as ever, Terry

Michael

I'm sorry I missed the part of your question about the round portion of the roll wires. This is the part where the wires cross and then pass inside the fuselage. Unlike the flying and landing wire attach points which are offset to allow the wires to cross without interference, the roll wire pulls on the centersection and the attachemtn lugs on the fuselage structure are symetrical. Flat wires would interfere with each other at the crossing point. Of course, there is no need to have a streamlined section once the wire passes through the fuselage decking. For these two reasons, the wires are round for the last 16".

Jim