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3W Bearcat with Moki 300

Old 04-03-2016, 11:34 AM
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My little Bearcat has had her maiden flight today after all reworks and overhaul.

Very little to say about it - a very calm and able Flyer. Pretty fast even on 40% throttle, giving the brand new Moki 300 some time for breaking in. Set the 4-blade SL- Prop (30" dia) to 18" pitch, revving roughly 4000 on the ground.
Take off weight 24,5 kg. Really no problem at all, no feeling of being too heavy at any time. CG at 205 mm (wet).

Very neutral and gentle on all controls, with power to spare. Made two flights - both ending in a very soft 3-point landing - a fine day today.

Sorry no inflight pics, but a video to upload soon.
Enjoy
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Old 04-03-2016, 04:20 PM
  #152  
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Hi Detlef,

It really looks great. Both our planes are almost the exact configurations and flying characteristics. Take off weights about the same as well. I really like your tail wheel. At some point I may change mine out. The painted landing gear also looks really nice.... Rob
Old 04-04-2016, 07:46 AM
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Hi Rob,

thank you.

I only wish I had the scale main retracts already installed. The only thing that is really missing is the strong tall upright parking silhouette with the long legs.
Maybe coming up with that one day.

The outer paint scheme is from the previous owner.
If I find the time one day I will paint her black, or VERY dark blackish blue.
But not this season, I am too happy to have her in nice flying condition by beginning of the season....

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Last edited by Detlef Kunkel; 04-04-2016 at 07:56 AM.
Old 05-09-2016, 02:58 AM
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yesterday, flight no 5.

My son Leon at the controls, his statement after the flight was not so very good for me.

He liked the BC a little bit too much. I doubt if I will get it back

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Old 05-09-2016, 03:49 AM
  #155  
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Almost completed Rare Bear
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Last edited by Billy J; 05-09-2016 at 03:52 AM.
Old 06-27-2016, 03:07 AM
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just wanted to share my first experiences after 15 flights with the BC.

I was not too happy with the old style solo blades 30" (4-blade prop). The pitch was set to 21" turning 3600 on the ground, but the engine was over-revving in flight easily, even in a shallow dive.
( the rev limiter on the 300 starts at 5800 cutting off the ignition half second-wise). I did not like that too much.

So I made a new blade with sufficient basic pitch & twist, and that was a fine success at once. Turning still 3600 on the ground, the engine is doing 5500 now in the air. Speed is 250 km/h then. Perfect match for both Bearcat and the engine.

(For those who are interested; the new blades will be available soon from SL Propeller.)

Dislikes:
Suffering from the pretty high speed were ailerons and flaps.
I did reinforce all tail and tail surfaces before, but did not throw away the old weak hinges of the wing. I made brass bearing bushings to reduce the heavy play in the old bearings, and thought it might be enough to prevent the ailerons and flaps from starting to shake or flutter. OK, they were NOT fluttering, but broke the tiny hinge material nevertheless. Lesson learned (again) : never underestimate the load on such surfaces travelling at such Speed !!
Should have heard on myself.

Landing was without further damage, and the BC is nearly airworthy again after replacing the old hinges.


Old hinges, broken and repaired, but simply too weak for the Moki 300:





Last pic shows ailerons and flaps being abjusted while curing.
The surfaces could be positioned much better that they were before, really fitting in the airfoil like they should.

What else can I say? I like the BC with the 300 in the nose, a big fun to fly it.
...and my son Leon is waiting impatiently to get the TX back in his hands
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Last edited by Detlef Kunkel; 06-27-2016 at 03:12 AM.
Old 06-27-2016, 12:00 PM
  #157  
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I almost lost my Bearcat to Aileron flutter last year. One hinge actaully broke as well. I ending up balancing each aileron and strengthening hinges as you did. No more issues. I was a little disappointed in 3W's choice of hinge design. I haven't had any issues with flaps, but seeing what you did, I may go back and strengthen those as well. As for the prop blades, I use the 30" CFK Hamilton style blades from SL-Propeller. I pitched them to around 3500 rpm and seems to work well with my 300. It's a pitch of about 20. Sven is great to seal with as well. I'll have to keep an eye our for the newer blade. ... Rob
Old 06-27-2016, 09:32 PM
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Rob,


try the new blades . They will be available in a few weeks. The difference is really big. Sven is already busy making the moulds..


Yes, you are right. The hinge material is fine for a 1,6 m Trainer with a .40 Methanol engine, but is totally wrong in the fast BC.
Old 07-16-2016, 11:26 PM
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One of the last weaknesses are the main retarcts. I did not want to spend much time here as I am going to modify the BC to scale mains. But the cylinders are so small, I always struggle to get the gear fully up in flight. I had enough of that and made new bigger cylinders ( from 23 pistont diameter to 28. more is not possible as the pic Shows.
I guess this Problem is sorted out now.
BTW the design with the offset cylinder is made because I did not want to weaken the rib where the cyl. is going through. Like this I did not need to change anything in the wing.





Got a parcel from Sven (SL) last week.
Installing and adjusting the new blades in the jig takes me nearly one hour, but a precise adjustment is worth the time.
The prop looks fantastic I think.
Looks like rain today, otherwise I would be on the flying field today and see what the BC does now.


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Last edited by Detlef Kunkel; 07-16-2016 at 11:30 PM.
Old 07-17-2016, 06:40 AM
  #160  
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Wow... The new blades looks great. I'll have to contact Sven and order a set. What length are they? I went to the SL website but I can't find those blades. I assume if i just email Sven he'll know what I'm looking for? Rob
Old 07-17-2016, 09:23 AM
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Rob,
Diameter is roughly 29,5 inches.

The blades are brand new, so they are not on the HP yet. But they are available. I guess you are the second customer then
Old 07-18-2016, 07:28 PM
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Excellent looking mods Detlef, you guys have some great looking Cats!
By chance when you build your scale gear will you do a build thread here or on a diff forum? Sure
would like to compare notes with you as I am starting gear for a 1/3.7 scale Cat...

Thanks,
John
Old 07-19-2016, 01:39 AM
  #163  
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Hi Detlef,
Great to catch up with you at Flying legends,, yes keep me posted in the new scale Bearcat Gear,,
Here is a quick shot of our 2 3w cats at F.L.

Cheers GB
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Old 08-12-2016, 04:27 AM
  #164  
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Hi Deflef,

I just received my new set of blades from Sven at SL-Propeller. These are really nice. I attached a photo showing the standard Hamilton Blade for comparison. Have you flown your Bearcat with the new blades? I was also curious to what your static RPM's are with the Moki 300. Rob

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Old 08-17-2016, 12:04 AM
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Hi Rob,
I set the blades to 20-21 " of pitch. The Moki 300 revvs 3500 on the ground and 5500 at 250km/h (155 mph)

Be VERY sure to re- tighten all bolts after the first few minutes of engine run BEFORE the first flight, and again after each of the first flights.
The hub gets quite warm on the Moki, and the new blades are settling quickly at those high temperatures.


I did not care enough and had all blades loose after just 2 flights. Dont make the same mistake.
While settling down, there is also a certain danger of a misadjustment of the pitch of each single blade. So check this also after the first few flights.

After a while, this tendency is gone and the blades are settled completely.

Performance and of course the looks of the new blades are really nice on the BC

Please report your experience!

Detlef

Last edited by Detlef Kunkel; 08-17-2016 at 03:07 AM.
Old 09-19-2016, 01:43 PM
  #166  
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Well, it all finally came together and I'm ready to start building my Moki 300 powered 3W Rare Bear. I can't tell you how happy I am to have this thread as a resource for my build. Rob and Detlef, you have already been a big help!

Now, I have a couple of questions. I put my bear together on the bench and took some angle measurements and frankly, I was pretty surprised. This is what I found:

Main Wing = 0 degrees
Horizontal stab = +1
Fire wall = + 5 (!)
Front of cowl = +3

The wing/stab looks about right but the firewall and cowl are way off. I would expect to find both of them somewhere around zero degrees. So my question to Rob and Detlef is What did you guys find and how did you deal with your thrust angles?

Here's how I handled the scale articulating gear. They started out as Century Jet gear but almost nothing is left after I completely re-manufactured. They really did start out as total junk but after 6 weeks of machine work I really think they're up to the task now:
https://www.youtube.com/watch?v=W63aCcBwOrw


This 300cc powered Rare Bear with those fat SL blades pitched to about 23 inches is going to be insane!

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Last edited by mitchilito; 09-20-2016 at 01:35 PM.
Old 09-20-2016, 04:50 AM
  #167  
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Mitch,
What color scheme are you thinking?
paul
Old 09-20-2016, 01:29 PM
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Paul, I'm going with the old white and gold scheme (with 4 bladed prop). I tell myself that someday I'll update to the newest purple/burnt orange - but to pull that off right really requires a new, longer cowling and other changes. Who knows, maybe it'll happen some day. In the mean time I want to fly the stuffing out of it.
Old 09-20-2016, 01:53 PM
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Originally Posted by mitchilito
- but to pull that off right really requires a new, longer cowling and other changes.
So does the white and gold scheme for that matter. Rare Bear hasn't had a stock looking cowl since it was the old yellow and blue "Able Cat", and even then I'm not sure how close it was to stock since it was wrapped around a -3350 instead of a -2800.
Old 09-21-2016, 01:08 PM
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You are correct about that, Chad and you have convinced me to make a scale cowl. And since I'm doing that I might as well go with the purple and burnt orange paint scheme!

This means I'll have to get rid of the gun bumps and oil cooler scoops in the wing too. All this will add a couple of months to the build but why half-step it now? I never did like the non scale look of the 3W Rare Bear version.

I've decided to add a couple pics of my landing gear. The first picture you see is a pic of the gear as received from Century. I can't imagine in a million years why they would ever design all that funky geometry into their gear. It had no purpose whatsoever! Other two pics are my gear. Basically the only things left stock are the strut and the main housing.

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Last edited by mitchilito; 09-03-2017 at 03:25 AM.
Old 09-22-2016, 03:16 AM
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Mitch, looking forward to your build
Good luck with it
Old 09-22-2016, 04:38 PM
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Hey Mitch, It's great the thread keeps going. Can't wait to see your progress. Regarding thrust line, I did some digging on it and found that most just centered and no down pitch at all. That's what i did and it trims out just fine. Just a reminder, I'd make sure you add some support on those aileron hinges.. I had issues with mine and some flutter.
Old 09-23-2016, 03:53 PM
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Hey, thanks for the input, Rob. I'm glad you're not mad I hijacked your thread!! :-)
I plan to add kevlar cloth to either side of the existing hinges then extending onto the spar. I think that will be sufficient and I won't have to pull the existing hinges like Detlef did.

I plan to order a SL prop like you guys have. Where do you get them?

Thanks,
Mitch
Old 09-24-2016, 03:43 AM
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Mitch,

Here is the site you need for the prop. http://www.sl-propeller.de
Old 09-24-2016, 01:46 PM
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Thanks Greg!

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