old man emu

I'm going to walk away from balsa. There's a lot of work in shaping it and keeping the same profile from one end to the other. I reckon it would take a couple of days to finish off the shaping. Once the shaping is done, you've got to fix the balsa to the tube, and the result I've seen are pretty yuk.

I can save time, effort and have a better looking end product if I do it the way I've outlined here. I'd say that I could have all my streamlining finsihed in one day.

OME

Wouldn't the foam idea make the struts much thicker thereby increasing drag? Bill

I've done the drawings so that the widest part of the fairing is only 1/4" thicker than the tube (1/8" on each side). That's not too much considering the benefits of streamling. Also, the streamlining is designed as a symmetrical aerofoil so the flow of air around the fairing will not break up and cause the eddy on the downwind side thaat you et with a cylindrical tube.

DJP

Yes, there are tables which give the corresponding streamlined tubing size for a given round tube size, but as you say, the streamlined tube is heavier and more expensive than round tube. The idea is to reduce drag without a substantial increase in weight.

Cost is a big factor in the completion of a building project. If I had boundless amounts of money to throw at a plane, I'd go out and buy a factory built one. But since that is not the case, I'm looking at every way I can reduce costs and still be able to produce a quality plane at the end.

OME

can you see that image?

OME

Somebody has to experiment with streamlining struts.

OME

OK

Here it is in two parts.

Old Man Emu

Scratched up No 6 - Part 1.pdf

Scratched up No 6 - Part 2.pdf

Scratched up No 6 - Part 1.pdf

Scratched up No 6 - Part 2.pdf

Scratched up No 6 - Part 1.pdf

Scratched up No 6 - Part 2.pdf

OK. I took the dog out for a walk this morning and used the time to work on the ins and outs of making these fairings.

I'll test some of my theories today and if all goes well, "Making Streamlined Tube Fairings" will be the topic of the next "What has Old Man Emu Scratched up?"

OME

I wonder if they teach those spelling helpers such as: 'i' before 'e', except after 'c' ? Had to recite that one to Old Ma Emu this morning because she thought 'piece' looked odd when she wrote it down.

What about '-ise' and '-ice' ? The way I remember it is that, if the word is a verb, it has '-is-' in it, and, if it is a noun, it has '-ice' ( to practise a skill, or a 'practice' as in a type of behaviour.) And I notice (don't ya luv English spelling?) that the spell checker in this program only recognizes one spelling for the homophone 'practise/practice and doesn't like the 'u' in behaviour. Damned spellchecker! Probably assembled by some humourless B.

Old Man Emu

Here's a drawing of a high aspect ration streamlining with the tube show. The tube is supposed to be 3/4". Using the length and width, the aspect ratio is 4.3.

I noticed when reading one source that a cylinder has a coefficient of drag of 1, and a streamlined tube has a coefficient of drag of about 0.45.

OME

It amazes me that when one begins the study of another language in a classroom situation, the syllabus always places great emphasis on the conjugation and declension of verbs and nouns to ensure that the what is said or written is correct in terms of case and number. However, the English syllabus ignores these building blocks of our own language.

I do not want to suggest that I am a White Supremist, but if English is to be the language of international commerce and relations, then we should see to it that persons for whom English is their first language are kept to a high standard compared to those for whom it is a second or third language.

OME

OK. Just back from Bunnings (well I had to leave ... the cleaners wanted to lock up and go home!)

Aluminium Weather Flash: 10M x 150mm x 0.7mm $33.90

SUNPAL PVC roll 0.8mm thick , 1 metre wide, $27.30 per metre.

I haven't priced Lexan. I don't think the flashing would be stiff enough to bear up to hangar rash.

I'll have a go at drawing a shape to see how wide a strip I would have to cut to form the piece.

OME

My greatest hate: plural verbs with subjects which are in the singular and vice versa. And for the life of me, I can't bring an example to mind right now. I suppose I'll have to turn on ABC Local and wait for one.

OME

Wow! What a lot of ideas!

Gnarly:

Cutting a 42" block of foam with a hot wire is easy as. It's done all the time by blokes who make radio controlled planes, and they are doing it with much thinner aerofoil shapes than would be needed for tube streamlining.

Litespeed:

Using aluminium flashing sounds good, too. I might be forced to pop down to Bunnings today to check it out. Could you post a sketch of how you would set uo the metal tubing and dowel piece to get the shape? I was wondering if it would be possible to use the foam core to shape the flashing over.

Pud:

We all know about your hot balls

OME

I had a long think about using foam.

Firstly I would have to design and cut metal (aluminium) cutting templates. The biggest problem here is determining the size of the major axis to get a good looking shape, and where the metal tube would sit along the major axis.

Then I thought about how I would go about cutting the shape from foam. The limiting factor here is the length of the hot-wire bow. The longest piece of tubing I'd need is 40 inches long, so that is a manageable length with a 12V DC power supply.

The next thing is to work out how to produce the lengthwise hole that the metal tubing would fit into. The length of the foam piece is too much to drill out, unless I could lay my hands on a fence post auger, and could set up some way to hold everything rigid while I line bored.

The alternative is to produce one length of cut-to- shape foam about 42" long and use it as a mold to lay fibreglass over. There is also the possibility of using the 42" length as a former for the heated Lexan sheet method described here http://www.homebuiltairplanes.com/forums/light-stuff-area/4669-lexan-strut-fairings.html

Alternatively, I could just ditch the whole foam former idea and simply heat Lexan. However, I don't know how good a shape this would produce.

Old Man Emu

Couldn't you knock some up out of high density foam? Either CNC cut or just a simple hot wire cut, trim to length, sand, coat....

OME

That Canadian site can supply at $5.32 per foot plus freight.

OME

The plans of the plane I want to build call for the interplane struts to be constructed from 3/4" round tube, then streamlined with a balsa fairing. Since balsa is not cheap, I thought I would use streamlined 4130 tubing, but that stuff doesn't have the strength of round tube.

As I was looking around for a way out, I came across a mob which sells plastic streamlined fairing. Only problem is that the mob is in Canada. www.ultralightnews.ca

Has anyone heard of this stuff in Australia?

Old Man Emu

The last of the "Knock, Knocks"

OME

Scratched up No 5.doc

Scratched up No 5.doc

Scratched up No 5.doc

Paul McBride is a bloke who is worth listening to. We often give him a call when we have an odd engine problem. It pays to go to Oshkosh and meet people!

OME

If you own, fly or know an owner of a C172R or C172S please arrange for an inspection of the STAINLESS STEEL rudder cables. These cables are showing the same rapid wear that the aileron cables are showing, but there is no AD for the rudder cables as yet.

You will have to access the rear of the airplane behind the luggage section wall and check the cables as they pass through the fairlead. You will also have to check the cable in the vicinity of the pulley under the floor of the cabin. Best if you can get a little apprentice to go into the rear of teh plane. That's who found our bad cables.

We have replaced three sets of cables in the past month and are keeping a watch on the cables of another plane.

Old Man Emu

I use What's New (24 Hours).

OME

Thanks for the positive comments, Sue & Tomo.

Moderators:

The following is not meant to be an advertisement, but I think Maj deserves further explanations.

QED Hardware was originally set up to provide advice and supply hardware to homebuilders. It is part of a CASA approved service facity. As such, its overheads are very low and I try to make sure that my prices are well below the major suppliers. I don't stock pilot equipment or bulky items like tubing and timber. However, I do stock a range of hardware products from nuts and bolts to hydraulic fittings. Even grease nipples!

I try to use Australia Post for delivery all the time, and try for the cheapest postage rate. In my pricing and delivery I always work on the principle of charging the customer the price I would like to pay if I was buying the stuff.

As for the advice, the owner of the whole organisation is a LAME with over 40 years' experience. He has built his own airplane (a Pitts) and occasionally gets the time and energy to work on a GeeBee Sporster. We service Jabirus, the usual Cessnas and Pipers, Maules, Stearmans, Long EZEs, Cozys, Stinsons, Airedales (not the dog), and an assortment of other homebuilt airplanes. So our technical advice department is pretty strong. We also try to put through an apprentice every three to four years. (Our last one now works for Mike Goulian on the US airshow circuit)

Hope that gives you an idea of our organisation.

OME

I'm considering the position.

OME

Just getting away from the incident for a moment, but I think this comment could have been better thought out:"Recreational pilots are all trained in emergency landings because the engines on recreational planes are more prone to stoppage"

I bet Jabiru and Rotax loove to hear that sort of comment from a leader of an organisation which uses their products.OME

OME

OK,

I'll get in a supply of both -52 and -52A for you homeless drifters.

OME