Prettner MAGIC build
 

Hi there
Building a Prettner Magic from a funkey glass and foam kit.
MVVS 91 rear exhaust inverted, s-bend header with MVVS pipe on top.
Robart mechanical tri retracts.
will post pics soon.
Cheers
Greg Hede
Australia

RE: Prettner MAGIC build
 

Looking forward to the pics. I've got a 60 size MK version which I just picked up a few months back here in Singapore. Not sure I'll get to it soon before a few Curares to finish off (Mark Rittinger's MinECurare & refurbishing a built MK 60 Curare).

RE: Prettner MAGIC build
 

Progress so far.

RE: Prettner MAGIC build
 

Having built and flown that exact plane I would second think the .91. I had a ST x61 in mine and it was as we like to say ballistic. I think your going to have a ground clearance issue with the prop on that 91.

RE: Prettner MAGIC build
 

I have checked it all out, I'll be using a 12x10 or 12x9 apc and clearance is fine.
Did you have a Magic or Curare, the Magic has a higher thrustline which is easier on prop clearance.
The MVVS 91 is also very light (about 530 grams bare) and genuinely 60 sized, just waiting on the custom header to be made so I can press on with the fuselage.
Thanks for your interest.
Cheers
Greg

RE: Prettner MAGIC build
 

<div style="margin: 0in 0in 0pt">Greg, can that 91 swing 11/8 11/11 props with good results?</div>

RE: Prettner MAGIC build
 

Hi Paul
11x11 would be the best of those, it's not a sreamer 8mm intake and port timing designed for torque, best static rpm with the stock pipe is about 10800/11000 rpm on FAI fuel, I'm going to try some head shims and 15% nitro to see If I can squeeze some more out of it but it didn't like it when I tried 10% on the bench.
When I was experimenting with props on my Speeda/ASP 91ABC/Macs pipe combo I prefered the overall perfomance with the 12'' prop over the 11'', the ASP likes to rev more than the MVVS so I found 12700/13000 static with either the an 11x10 or 12x8 it made the best power but the 12x8 flew better, level flight straightline speed was very similar but vertical on 12x8 was far superior, about the only the place the 11x10 was noticebly faster was the bottom of a full throttle split s where it was really rockin.
Back in the non piped 61 days we couldn't run a 12'' prop because you could only pull 6'' pitch and keep the engine in its power range so it was way to slow so 11x7 or 8's ruled, my initial instinct when I got back into the hobby playing with these things was straight to 11'' props and pull more pitch with the more powerfull modern engines but I'm shifting my thinking to 12'' now and adjust the pitch to the particular airframe/engine characteristics.
I think the Magic will perform really well with the MVVS turning the 12x10 at 11000 on the ground just won't sound like I like em to sound.
I have a Webra 91 P5 for my next Speeda and have had that turning a 12x8 at 14200 on FAI fuel, I think thats pretty close to as strong as a Jett 90 so that will definetly sound right!
I can't believe how many pattern ships I have to build with all those Don fuselages and that Galaxy arrived fron Italy as well, phew!
Cheers
Greg

RE: Prettner MAGIC build
 

<div style="margin: 0in 0in 0pt">Greg, I&rsquo;ll have to take a closer look at the Webra&rsquo;s , 14,200 on 12/8 an no Nitro to boot, good numbers for a modern mill.</div><div style="margin: 0in 0in 0pt"></div><div style="margin: 0in 0in 0pt">So get Building !!!http://www.rcuniverse.com/forum/js/f...eeth_smile.gif</div>

RE: Prettner MAGIC build
 

Finished up the main retract linkages this morning.
Cheers
Greg

RE: Prettner MAGIC build
 

I dunno about those bends in the pushrods for the retracts. They caused nothing but problems in my last plane, basically it acts like a spring under load, and will cause the prushrod to bow out of place instead of lock the gear in.

Just keep an eye on em!

RE: Prettner MAGIC build
 

There pretty rigid, I think you have problems if you try to do the whole pushrod in wire but with carbon tube in the middle you can stall the servo by holding the gear leg and the pushrod hardly moves.
Cheers
Greg

RE: Prettner MAGIC build
 

Actually I had both, the Curare flew better but the Magic was faster

RE: Prettner MAGIC build
 

Yeah the Magic has a much thinner wing section so should be faster.
Hanno was trying variable pitch props to control down line speed with probably an engine more tuned to torque than horsepower so maybe he thought he needed more airframe speed because he had more control over the power source.
Anyhow, I couldn't give a toss about any of that because these things are sport models these days and I just want to remenber and fly them as super fast locked in the groove classics.
cheers
Greg

RE: Prettner MAGIC build
 

I think the fact that the magic was over 11 lbs made him review the given amount of power. He also thought he could get away with (and did) because of the dense air at sea level in Acapulco.

RE: Prettner MAGIC build
 

Hey JNred, where did you buy that kit from the Magic ?

RE: Prettner MAGIC build
 

Steve
Long time out of production I picked it up on ebay here locally.
Cheers

RE: Prettner MAGIC build
 

I dont think anyone has done a magic build before. Thanks !!!
Your building and pictures make me want to get up and start sanding my plane! Really nice work on everything.


DM

RE: Prettner MAGIC build
 

Its been a while since I touched this thing but done a little bit in the last couple of weeks.
After a lot of bench testing I've decided to give the OS91 ducted fan motor a try, it turns an APC 11x7 at 17,000 with a MVVS muffled pipe (same rpm as a Macs but much quieter).
Made the rudder and elevators which were missing from the kit and hinged them, faired in the bottom the wing and made and fitted the servo tray.
Cheers
Greg

RE: Prettner MAGIC build
 

At 17,000 it should sound awesome. Of course fuel consumption has got to be HIGH!!

RE: Prettner MAGIC build
 

Greg,

I was wondering about that engine - an OS 91 VR DF I take it?

Serious power... What type of fuel are you using to get those numbers? I've been interested in the OS 46 VX - the slightly newer baby brother.

Will you be able to pass the header into the fuse top despite the rear intake carb?

David

RE: Prettner MAGIC build
 

David
Yes 91VRDF, using 18% Klotz KL100/10% Nitro.
Tried 20 and 30 Nitro and didn't make a lot of difference.
There is plenty of room for the header to get past the carb but the header I had made for the MVVS91 wont't work I have to get another one made, unfortunatly the header will end up a tad long for peak RPM according to my testing but still should be good and may even be a little more forgivig to operate.
I haven't had to chop or modify the airframe at all get this thing in so if its no good in the air I can swap back to the MVVS91 easily.
Cheers
Greg

RE: Prettner MAGIC build
 

David, I hadbought an OSmax 46 vf-dfwhich is the predecessor of the newer 46 VX-DF and there's not enough crankshaft sticking out for a propellor on both. Strickly ducted fan use only. I was bummed. http://www.rcuniverse.com/forum/js/f.../sad_smile.gif So I resold it on ebay. Would require some type of adapter to lengthen the crankshaft, if it could be done at all without vibration. IDon't think it's really possible to run standard propellors on it.

I have a NIP Hartori Magic 40 header and finally got an OS 40 VF. Now I just needbuilt up wood plansfor a 40 Magic.

Bryan

RE: Prettner MAGIC build
 

Tru Turn makes a special adapter nut to allow you to run props on the .46VX

RE: Prettner MAGIC build
 

Bryan, Jeff,

thanks for the info.

Do the TT adapters accommodate a spinner backplate as well as a thick APC prop hub?

David

RE: Prettner MAGIC build
 

David

yes, i have the 46vf-df with short shaft, the adapter nut protrudes thru the washer an nearly bottoms out in the recess on the apc props. 10x8-11x6 with no problems.