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Author Topic: K&B 40 for 600 sq in Bipe  (Read 2585 times)

Offline Dennis Toth

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K&B 40 for 600 sq in Bipe
« on: March 17, 2014, 11:25:28 AM »
Guys,
We are having an event in May down here in FL that will include "Unlimite Super 52" which is basically, fly what you brung to the 1952 pattern (they will also have OTS, fun scale and PA). I have a biplane that I built from two Yak 9 kits (I called it YAK YAK) for a club event in the early 90's. At the time I had a K&B 40 in it but never really worked on the engine run. The ship is in pretty good condition so I thought for the old time 52 pattern this would be fun. So, I have two choices - one the original K&B 40, which knowing what we know now would be set to run pretty much a rich 2 cycle on say an 11x4.5 prop 10K ish rpm or an OS 40 4 stroke on say an 11x5.5 at 9500 rpm. I like the sound of a 2 stroke better then the four strokes (the 4's always sounded a little flat for my taste). Nothing special has been done to either engine. Anyone run the K&B 40's lately in a 2-2-2? One last choice is the OS 40FP run as 2-2-2.

Best,        DennisT
« Last Edit: March 17, 2014, 03:55:36 PM by Dennis Toth »
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Eric Viglione

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Re: K&B 40 for 600 sq in Bipe
« Reply #1 on: March 18, 2014, 09:26:08 AM »
Dennis - I guess being a pragmatist, I'd start with a few questions... like:

1) where is the C/G with the K&B now? 2) Are you running the boat anchor K&B muffler or a chip or?? 3) is the tank compartment sealed or can you change tanks easily?

Personally, if it balances with the K&B and you have a metal uniflow, I'd leave it be and run the wet 2/2 run. I have a few and they ran great that way with an 11/5 wood, that if you measured, like all Rev-ups of that vintage, were a lot closer to 4 pitch than 5.

If you went to the OS 4stroke, I'd want tank access and room for a clunk... and hope that you were correcting for a rear CG while you were at it.

The FP40 can be fussy, but either that or the LA46 would be a a no brainer if the CG needs to go the other way, you save over an ounce from the K&B, and can swing the same if not larger props on the same fuel.

Well, that's my .02 for what it's worth.
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Offline bob whitney

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Re: K&B 40 for 600 sq in Bipe
« Reply #2 on: March 18, 2014, 02:40:18 PM »
Dennis, what contest is this
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rad racer

Offline Dennis Toth

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Re: K&B 40 for 600 sq in Bipe
« Reply #3 on: March 18, 2014, 05:08:41 PM »
Bob,
This is a new contest near Indiantown, FL in May. It is going to be a one day contest to start. They plan on PA, OTS, Unlimited Super 52 and Fun Scale. Hopefully we can get some of the Miami guys as well as the Tampa, North FL  and Georgia guys. Once they get the date firm they will make an announcement.

Best,          DennisT
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Offline Air Ministry .

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Re: K&B 40 for 600 sq in Bipe
« Reply #4 on: March 31, 2014, 09:37:23 AM »
K&B can be thirsty , but will haul the coal . wants good cooling , low restriction muffler and NITRO . See ' Finish ' as Nitro is corrosive .  S?P

Actually , one of the Master 11 x 5s works pretty good , at a normal weight . A bit of flywheel in the heavy black prop keeps it steady , on say 65 ft ( 63 lines ) .
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Offline Dennis Toth

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Re: K&B 40 for 600 sq in Bipe
« Reply #5 on: April 01, 2014, 10:21:14 AM »
Started working on cleaning up the ship. This ship was originally built back in 94 for a GSCB biplane event. I had a Yak 9 kit and a wing from a Mustang (same size except the wing tips), so I used the smaller Mustang wing for the lower wing and the Yak 9 for the top.

The ship looked cool but the guys would rib me about it being a Yak that was twice the size and flew twice as bad!

After looking at it without the engine but including the tin tank and aluminum gear/perfect wheels it weighed 36 oz. Since it needed some work around the nose I removed the tank and gear and on a wim weighted it again - 28 oz. With this I think I need to look into a new tank (like a plastic or mold one) and CF gear with new foam wheels. Doing this I think I could save 5-6 oz. That will help this ship a lot.

Anyone know who sells reasonable priced profile CF gear struts?

Best,   DennisT

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Offline Steve Helmick

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Re: K&B 40 for 600 sq in Bipe
« Reply #6 on: April 01, 2014, 09:15:15 PM »
Eliminator Propellers has two versions of their CF Profile LG, unidirectional and with some cross-ply CF. IIRC, it's 1 oz for a pair of legs.  H^^ Steve

Edit: Or maybe it was 1 oz per each leg.
« Last Edit: April 01, 2014, 11:53:58 PM by Steve Helmick »
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Offline Dennis Toth

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Re: K&B 40 for 600 sq in Bipe
« Reply #7 on: April 04, 2014, 07:49:15 AM »
Guys,
I'm making progress with getting this ship back to flying condition. I checked the Aluminum strut and without the wheel it is only around 3/4 oz. The big weight savings will be the using new foam wheels (the original ones were the old perfect tires at 2 1/2 oz each) and a lighter plastic fuel tank (should save another 2 oz ish).

I finished removing the old film around the nose and will go with paint in the engine area, completed fillets on the rear and some film cleanup. Have some crueling edges on the old film, anyone have a way to hold them down so new finish will go on smooth? I was thinking thin CA?

After the film is stablize the next step is to refinish the repaired areas then shorten the gear struts about 1" (they were for a much larger ship so they look a little wide on this span). Then I can install the tank and engine and bench trim.

Best,        DennisT
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Offline Dennis Toth

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Re: K&B 40 for 600 sq in Bipe
« Reply #8 on: April 12, 2014, 09:28:31 PM »
Got the paint touch up on today and will do the clear coat tomorrow. Also got out the K&B 40 out and loosened up. The motor was a little stiff (been sitting for at least 8 years) seems I was running it last on Sig 50/50 fuel and although a bit stiff not frozen. I put a small prime of 100 % synthetic and several drops of after run oil. Pulled it through several times then took my heat gun and warmed the case and cylinder. After working it through and several applications of the heat gun it was smooth and lose. Ready to put into the ship once the clear is done. Attached is a photo taken by Charles, before the cleanup.

Best,     DennisT
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Offline Dennis Toth

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Re: K&B 40 for 600 sq in Bipe
« Reply #9 on: April 17, 2014, 05:10:53 PM »
Check the engine con rod for free movement on the wrist pin, all good no sticking or crude. Also checked the ball bearing for smoothness and rust. All good on the bearings also. The D ring seems to have a very good seal, should hand crank.

Once the weather clears will put the KBS Clear coat on and add motor and tank.

Best,      DennisT
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Offline Dennis Toth

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Re: K&B 40 for 600 sq in Bipe
« Reply #10 on: April 19, 2014, 04:06:58 PM »
Got the KBS clear coat on today. Used a foam brush like they said. Went down smooth looks like glass. Did a test over the MonoKote trim also, seems good. KBS instructions says it needs to cure for 24 hours before polishing out. It becomes fully cured in 4 days. I will get everything ready to bolt on and be ready for next weekend (if I get the muffler).

Best,       DennisT
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Offline Dennis Toth

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Re: K&B 40 for 600 sq in Bipe
« Reply #11 on: April 21, 2014, 09:37:25 PM »
Clear coat is cured, this is the KBS diamond clear just brushed on and it leveled as they said it would. The K&B 40 engine is set with the 0.275 venturi and a K&B NVA. It looks good bolted in the nose. For now I have a Smith uniflow tank, its a little heavy I will build a lighter tank but to get it the air this will do. Next, need to shorten the gear and get ready to do the bench checks. Still need to figure out the proper point for the CG. Right now its near the LE of the bottom wing which is at about the 15% behind the LE of the top wing. I will do some research on where others have positioned the CG on bipes.

Best,     DennisT
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Offline Dennis Toth

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Re: K&B 40 for 600 sq in Bipe
« Reply #12 on: April 26, 2014, 11:35:44 AM »
Guys,
The K&B 40 was the right choose for the Bipe. I am running it on a narrow blade 11x5, launching at 9700 rpm, 0.275" venturi, OS FP25 muffler, 4.9 lap time on 60' lines. Setting was right at the 2 -4 point. Bipe came in at 46 1/2 oz.

I like this engine, starting was great - pulled it through two times for a prime, 3 flips forward, 3 flips backward, attached battery, one spinner flip and away we go. It runs very smooth and solid.

Best,        DennisT
« Last Edit: April 27, 2014, 04:49:34 PM by Dennis Toth »
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Offline Dennis Toth

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Re: K&B 40 for 600 sq in Bipe
« Reply #13 on: June 07, 2014, 06:04:33 PM »
Well, Uncle Mike was right, this motor works very well on the APC 11x5. Today I flew the K&B 40 in the Bipe and tried several props. The original base prop was a Zinger 11x5 with narrow blades and rounded tips. This pulled OK and the motor was pretty happy at just about any needle setting from lean 4 cycle to 2 cycle. I then tried a Zinger 11x4 with slight undercamber in a rich 2 cycle. Then the APC 11x5. It was very surprising how obvious the performance jump was with the APC. The base prop was close, just didn't have quite the pull through that the APC has. The undercamber again was OK but the APC was just stronger. I don't know what other props would be similar to the APC that might be a little lighter weight, maybe one of the wood scimitars?

Best,        DennisT
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