Old Man Emu thinks about building his own

[old man emu]

I've got several CAD programs, but I find that eMachineshop works in a similar way to the way I learned to draw plans. It does not have all the bells and whistles of the high range CAD programs ,but I can draw simple stuff with it and then export it in *.dxf format for use in CAM software.

 

OME

 

 

[old man emu]

This plane building can be dangerous to your health!

 

The other day I nearly got involved in fisticuffs with a bloke over the layout of my instrument panel. I've decided that I'm going to install an altimeter, an airspeed indicator, a bat & ball, a combined oil temp/pressure guage and a tach in the instrument panel. The first three instruments are going to be 3-1/4" diamter and the last two, 2-1/4". I was going to place the big ones in a nice triangular pattern in the centre of the panel, and the small ones below and to the left and right of the panel. It would look pretty.

 

Well .... This bloke went off a treat and begged me not to lay them out like that. He said the ASI, ALT and B&B had to be on the left hand side of the panel and the engine instruments on the right hand side. Considering that the plane is a single seater and the panel is 24" across, I figured even my worn out old eyes would be able to see all the instruments in one glance. Still he kept on. "You'll never know when you might suddenly fly into IMC" Given that I'm a fair weather flier at best, I figured that at the first sign if IMC, I'd turn and run. Besides, Who's building this plane anyway?

 

I'm glad it didn't come to blows. He's 91 year old and a quarter of my weight. I couldn't bear the horror of the beating he'd give me.

 

So what do you think. Am I right to stick to my guns, or is he right to stick to convention?

 

OME

 

 

[Bubbleboy]

OME...its a loaded gun really. You are flying it so do whats right for you. Bear in mind who may test fly it but a single seater shouldnt cause too much issue. I have made a cardboard mock instrument panel and have been playing with different scenarios. Some folk have emailed me and told me its all wrong but I listen and make my own decision.

 

 

Scotty

 

 

[robinsm]

Single seater, keep the important ones in front of you in the centre (especially with a 24" panel). Save your self the beating and nod wisely, and then do your own thing.

 

Cheers

 

Maynard

 

 

[cherk]

This plane building can be dangerous to your health!OME

fun isn't it ..........these dilemae! suggest for least eye ergo........grouped in natural eye scan etc. etc, sequence ...blah blah but you likely knew that!!

 

 

[pudestcon]

Do your own thing OME, what you describe sounds ok to me, especially being a single seater.

 

Here's my layout for extra food for thought, for you.

 

Pud

 

 

 

[old man emu]

I'll see if I can get a drawing done this weekend.

 

OME

 

 

[old man emu]

Well I've got the drawing done. I think it's pretty neat.

 

 

If anyone wants .dxf files for the large and small instruments to add to their drawings, just give me a Co-eee.

 

OME

 

 

[sain]

Nice and simple OME. no fuel guage I take it? or battery voltage/ammeter?

 

 

[old man emu]

The fuel guage will be a sight tube, or a cork attached to a stick through the fuel cap. I suppose I could fit an ammeter and an hour meter. I might hide the hourmeter under the engine cowls. I will probably need a power outlet for the radio, too. Darn modern do-dads!

 

OME

 

 

[fly_tornado]

GPS mount?

 

 

[old man emu]

GPS mount?

GPS mount???? Isn't that a polo pony for a student at Kings?

 

OME

 

 

[old man emu]

Strewth! 3-1/2 months since I wrote anything here. What's been going on?

 

I finally got up the nerve to attack my good CAD program, Rhino. After a few hours of messing about, I started to get the gist of it, so I went back to Square 1 with the wing rib. This time I also went back to basics and just place points on the worksheet for every station point given on the rib drawings. Then I joined them all up and got the outline of the rib. After that it was easy to place the spar holes and lightening holes. I'm satisfied with what I've got there. The next step is to do the drawings for the fuselage trusses. This will give me the lengths and angles for the tubing. After that I have to decide how they will be manufactured.

 

There are tow ways to prepare the tubing for assembly. The first is the old "hands on" method where I measure and cut the tubes and then grind and file the bird mouths to fit everything together. This of course will take a long time and will result in a degree of material wasteage.

 

The second method is to send the drawings away to a CNC company and have them do all the cutting and shaping (as well as supplying the materials). Then they just ship the pieces to me and I arrange for everything to be welded up. There's a fellow I know who has just got his fuselage tubing for a Breezy from this mob: www.cartesiantube.com

 

They are a Canadian company. I've been given an estimate of between $3000 and $6000 for the supply, and cutting. And then there's the freight cost.

 

I'm wondering if there is an Australian company that could do it cheaper overall.

 

Old Man Emu

 

 

[sain]

well, there are plenty of cnc mobs around. have you tried the yellow pages for your area?

 

 

[drifter45]

Hello OME, what are you planning to use for an engine? I'm interested as I've had a thing for the Gere Sport ever since I saw the Shaws radial version.

 

cheers John

 

 

[old man emu]

I'm looking at a Corvair 6 cylinder, like BubbleBoy is going to put into his Pietenpol. I am goign to have a good look at them when I go to Oshkosh next year.

 

OME

 

 

[drifter45]

That should swing a decent size prop compared to direct drive Jab or VW. I'd thought about a VW with redrive. I'm got plans for a FFP Dakota Hawk so I can take herself flying out of the wind but I have'nt given up the biplane lust.

 

cheers John

 

 

[old man emu]

The main reason I'm going for the Corvair is that a 6 cylinder is a smoother running engine than a 4 cylinder, simply because there are two more power strokes per revolution. Also, the engine was designed to go to higher revs in a car, so even at take-off revs, the engine will just be woking lazily.

 

Bubbleboy is the expert on the Corvair.

 

Old Man Emu

 

 

[old man emu]

10:15pm and I've just completed drawing the fuselage trusses. My eyeballs are facing each other and my tiny brain is overheating. I'm going to have a cup of coffee, play some Solitaire and go to bed. A good few days' work.

 

OME

 

 

[old man emu]

One of our members was good enough to translate my wing rib drawing into CNC machine code and then cut me half a dozen ribs. We decided to use el cheapo 3-ply from Bunnings as these ribs are going to be used to practise building a wing. There are enough to make a 4 foot section of wing, and I will be playing about with strut attachment and internal bracing methods. If I get them right, I'll test out a method for covering the leading edge with fibreglass.

 

 

OME

 

 

[sain]

Hi OME,

 

Looks like a nice job on the CNC cut. Is it still a RAF 15 profile your using? It looks just a little bit different to my eyes, although it is hard to compare. I was trying to compare it to the one from the UIUC Airfoil data site:

 

I'm also curious if your doing your test wing section full scale, or if you've shrunk things down a bit. Any chance you could enlighten me?

 

 

[old man emu]

That profile is a US27. I could not get the official data for the shape, so I just followed the information that was published originally. I has taken a fair bit of mucking about with the CAD to get the shape right.

 

What I plan to do is assemble one complete bay of the upper wing. That's 4ft. I'll be able to experiment with attaching the internal bracing and probably the design of the aileron system brackets. Also, I can try out the interplane strut attachment and the wing root attachment design. These items in the original plans reflect the state of art at the time they were published, but I am going to see if I can employ improved designs from the Pitts ariplane.

 

I've already had some discussions about the design of the wing rib cutouts and look like increasing the radius of the cuts in the section between the main and rear spar holes to 1/2" to disperse the stress points. I maight even do some testing to destruction to see what the rib will take, but I don't think the current set of ribs will be suitable for that as they are not cut from the final material (5-ply marine grade 1/4"). Also they were not laid out on the sheet of ply in the way that I want. When they finally get cut, I am going to have them laid out at 45 degrees to the grain so that every ply will be contributing something to the strength of the rib, not like these ribs where only the middle ply is taking the most load.

 

I hope to keep the final weight of the ribs down. These practice ones weigh in at 72gms each.

 

OME

 

 

[sain]

Oh.. that explains it. It does look a lot more like the usa-27 airfoil.

 

There is some data available here: http://www.ae.illinois.edu/m-selig/ads/coord_database.html and there are .dxf files of the raf-15 profile here: http://isoar.ca/~andrewm/rc/airfoils/200.html if your still looking for it.

 

 

[Guernsey]

Good on ya OME, this is the stuff I like to see on this Forum.

 

Your choice of a six cylinder engine could also give you a better choice of props (harmonics and that sort of thing).

 

Alan.

 

 

[old man emu]

This is going to be a steady as she goes project. At the moment I am studying all the pieces and how to make what is required. When I eventually just want to be able to order this and that from here and there so that when I am ready to start I have most of the components on hand and will be able to get stuck in full time. I expect that if everything is on hand, I could realistically hope for a completion date 6 to 9 months afer starrting.

 

OME