Justin's Raven

Aircraft Projects Underway or Completed

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justin.schoeman
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Re: Justin's Raven

Postby justin.schoeman » Sun Dec 06, 2009 6:09 pm

Leak tested the fuel tank today. Seems to have many pinhole leaks. Some through rivets, some through welds (of course no leaks in my stuff - fuel cap, level sender flange, and fuel strainer (-) ).

Need to look into the best way to fix these leaks...

Also made attempt #2 at a trim control. I would like to move the trim control to the center console, so that it can be used from both seats. I really like the crank handle use in the Piper Tri-Pacer, so I tried something similar here. Unfortunately, I could not find lead screws anywhere, so I used a stock metric thread. That means you have to spin the crank 50 times to go from full down to full up! Actually not a major issue, as the trim stays near the middle most times anyway. If I can find a proper leadscrew though, I will use that.
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The trim cable goes right through the middle of everything, and gets clamped in the center piece. Still need to add steel cable guides to the top and bottom plates.
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Re: Justin's Raven

Postby justin.schoeman » Wed Mar 10, 2010 10:32 pm

A long, long time since I updated this thread. And unfortunately that is a reflection of the amount of work I have done :( .

Had an absolutely AWSOME holiday up in Pemba, and Tekomaji. Fishing, snorkeling, swimming, partying... After that it was difficult to get back into the swing of work ;-) .

Done a thousand small jobs. Made the one-way valve for the fuel system. Made most of the tools and jigs for assembling the engine... Lots of bits and pieces, but no visible progress...

Spent this week swearing at myself. If I ever mention filling rivets again, please just shoot me. It does look a lot better, but wow, it is a huge pain.
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Re: Justin's Raven

Postby justin.schoeman » Wed Mar 17, 2010 3:11 pm

Just reallised that I nearly made a horrible mistake. I was planning on installing a ram air inlet for the airbox to try and get a little more performance. A little bit of maths shows that at best, I would get around 0.4PSI boost at the carb intake, which is small, but usable.

Then I had a look at the fuel pressure, and the gravity feed system will give me at most 0.3PSI. All well and good, until you realise that the carb float bowl is vented to the air inlet - so the float bowl would pressurise to 0.4PSI, with fuel delivered at 0.3 PSI... I can see a minor problem developing!

There are a number of possible workarounds, like requiring the use of the boost pump (and using carb heat if the boost pump fails). Or venting the tank to the air box. But all these options seem unnecesarilly complicated, so it seems ram air is out for now...
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Re: Justin's Raven

Postby German » Wed Mar 17, 2010 9:37 pm

Should not be a problem on a pump delivered fuel system like Rotax or am I wrong?
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Re: Justin's Raven

Postby justin.schoeman » Wed Mar 17, 2010 11:13 pm

German wrote:Should not be a problem on a pump delivered fuel system like Rotax or am I wrong?
Shouldn't be a problem. No way ram air pressure is going to override a fuel pump vhpy .

I was seriously considering using the Revmaster combined oil/fuel pump - but in the end I decided against adding more complexity just for a few more HP.

That is not the only complication with ram air though - you need to make sure that the carb can run on ram air. I know Jabiru says that their Bing carb mustn't have ram air. Don't know about Rotax though...
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Re: Justin's Raven

Postby justin.schoeman » Thu Mar 18, 2010 3:27 pm

justin.schoeman wrote:
German wrote:Should not be a problem on a pump delivered fuel system like Rotax or am I wrong?
Shouldn't be a problem. No way ram air pressure is going to override a fuel pump vhpy .

I was seriously considering using the Revmaster combined oil/fuel pump - but in the end I decided against adding more complexity just for a few more HP.

That is not the only complication with ram air though - you need to make sure that the carb can run on ram air. I know Jabiru says that their Bing carb mustn't have ram air. Don't know about Rotax though...
Almost forgot - I think the Bing on the Rotax 914 is used on a blow through turbo? If it can handle that, it shouldn't have any problems with ram air?
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Re: Justin's Raven

Postby justin.schoeman » Fri Mar 19, 2010 11:15 pm

Ran into another snag with the engine. Unfortunately, I trusted the engineers measurements of the prop hub and crank, and did not check, until I started working through the pre-assembly checks. What is supposed to be a min .002" interference fit, now slides over 5mm without any pressure.

By all indications, the hub was cold pressed onto the crank, galling the bore in the hub. It is amazing that people take short-cuts like this on an engine they intend to fly behind - and that on the crank, which is probably the weakest point on a big bore VW...

Seems like I am going to be waiting another month for more spares...
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Re: Justin's Raven

Postby justin.schoeman » Wed Apr 07, 2010 10:15 pm

Life has been obscenely busy again... Working 12 hours a day, 7 days a week. (**)

Fortunately, I managed to take some of the long weekend off to get the plane prepped (I am taking it to Skyworx on Saturday for painting).

Among the bits and pieces I finished - complete with cr@ppy cell phone camera shots are:
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Nylon mounting plate for headset jacks. A simple nylon sheet, backed with an aluminium L for a local ground, as well as cable support. The nylon plate gets bolted into a hole in the baggage compartment floor, and isolates the jacks from the fuselage, to prevent ground loops.
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'Rubber' boots for the nose wheel steering push rods. This is an interesting composite that I had never heard of before reading about it in Kitplanes. Basically take some heavy fiberglass cloth, and thoroughly rub red (high temperature) silicon in (until the back side of the cloth is thoroughly wetted). Then lay it over a bold, with a decent overlap.

Once it cures, you end up with a very flexible, incredibly tough 'rubber' boot.

I initially made the mold too short (misjudged how close the end fittings come to the firewall, so I had to add an extension to the top. Looks ugly, but won't be visible ;-) .
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And the servo mount. The third iteration thereof. Difficult to make something that can take 5kg of force pushing on the servo, and distribute it evenly through the base plate, but still provide vibration isolation. This one seems to do the job, although it needs more testing.

Will hopefully pick up the last (they damn well better be the last!!!) engine spares when I am in the US, and assemble the motor when I get back.

I always say the plane is 3 months from flying, but this time I mean it!
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Re: Justin's Raven

Postby justin.schoeman » Mon May 17, 2010 8:33 pm

Got the plane back from Skyworx on Saturday, and it is beauuuuuutiful :D . Solid white for now, but a friend will airbrush some designs once it is flying.

The paint makes an amazing difference. Changes a somewhat industrial looking chunk of aluminium, into a sleek and shining aircraft. And the interior makes me drool. Can't wait to get it flying!

And to top it off, the last engine parts are finally on SA soil - just waiting for local delivery now.
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Re: Justin's Raven

Postby Sox » Mon May 17, 2010 11:55 pm

justin.schoeman wrote:Got the plane back from Skyworx on Saturday, and it is beauuuuuutiful :D
Justin, I passed you on the Krugersdorp highway on Saturday morning towing your new baby - looked great - enjoy!
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Re: Justin's Raven

Postby Scotsman » Tue May 18, 2010 7:29 pm

Hi Justin, how much did the paint job cost if you don't mind me asking? Did you have the interior sprayed as well?
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Re: Justin's Raven

Postby justin.schoeman » Tue May 18, 2010 11:23 pm

It cost R13k for the job. Solid white outside, and two different hammertone grays on the inside.

Probably about 1.3x the cost to DIY, but the finish is amazing, and weight is negligible.
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Re: Justin's Raven

Postby Tailspin » Fri May 21, 2010 8:32 am

Justin

This is excellent Dude !!!! !!!!
I really cannot wait to see her in Person. (^^) (^^) (^^)
Well done Keep at it ## ## ##
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Re: Justin's Raven

Postby Scotsman » Fri May 21, 2010 6:52 pm

Really not a bad price on the paint job. I will definitely be using Kevin when I get to that stage.
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Re: Justin's Raven

Postby justin.schoeman » Mon May 31, 2010 4:56 pm

Some interior photos... Spent the weekend preparing templates for the side panels, carpets and fabric. Also finished the foam for the seats (excuse the dirty footprints...).

Once I have treated all the foam and fabrics with flame retardant, I can put it all together, and have a nice pretty interior :D .

[The interior colours are a bit washed out in the photos - it is a bit darker than what the photos look like (especially the panel).]
Attachments
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Luggage shelf
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Panel
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Seats
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OT: Time for a 'birthday' party for the cruiser... (On the way to the shops to buy parts for the Raven - so it is not entirely OT!)
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