Hobbsy

My Feedback: (102)

I've had a Webra .50 with a Dykes ring for about 5 years, it has been flown about 4 times on a US Aircore Colt 40. I ran it today to make sure it is broken in enough to convert to Diesel operation.
Fuel==Fox 5% nitro/20% castor
Prop==Graupner 10.5x6
RPM max===13,750 for about 30 seconds then starts to sag
RPM max sustained 13,650 1 click rich from above rpm
2nd prop, Graupner 12x5==surprising rpm of 12,500.

Are these numbers typical? Thanks, Dave

proptop

My Feedback: (8)

Those numbers sound good to me...considering the props and fuel...
Don't know if mine will correlate though?
Mine (2) are ABN and with a Nelson muffler I get 13,600 with one engine, and 13,800 with the other using an APC 10X8 on 15% Powermaster.

Hobbsy

My Feedback: (102)

Thanks Prop, I knew someone else had to have one, sounds close enough to me. That ugly looking pipe is a Mac's muffled tuned pipe, (.90) sized and does not change the engine performance, just quietens it.

TimC

Hobbsy, I'll tach mine tomorrow with a 12x5 and 5% nitro. I don't have a 10.5x6. I can't remember if mine is ringed or abn. I'll pull off the muffler and have a look-see.

TimC

Hobbsy, I forgot to do it yesterday. Here is the results with 5% nitro. This can of fuel might have had a small amount of 15% dumped in to save space. I checked and mine is the ringless version of the Webra .50. It peaked out at 12,760 with a 12x5 APC. I was running an 11x6 on 15% and didn't re-adjust the low speed needle for the 12x5 and 5%. Transition was awful with the 12x5. The low speed needle is very sensitive on this Webra.

Hobbsy

My Feedback: (102)

Thankyou much, mine sounds like it is good to go then. A Diesel head will be here in a few days, I have a H9 Sopwith Camel comming for it.

TimC

When I put the 11x7 back on, I checked it for peak with 15%. It peaked at 13,680. Are those Camels pretty tricky to fly?

Hobbsy

My Feedback: (102)

According to my friend Bobby at Apex Hobbies it is a gentle flyer.

proptop

My Feedback: (8)

With the Webra .50 in the Camel, you will have enough power, but you're gonna need a LOT of nose weight. The kit comes with a 1 pound lead "mini" brick...but I think you will need even more? (Minnflyer did a nice write-up...and I have an old O.S. .90FS for mine )

speedster 1919

My Feedback: (3)

Hobbsy---When you put a diesel head on an engine does it add more weight ? Webra's are very light engines but I can recommend the perfect engine if that plane needs so much dead weight up front. Are you ready------------TAH DAH

speedster 1919

My Feedback: (3)

WEBRA T4 60 four stroke

Hobbsy

My Feedback: (102)

Speeds, I have a Webra T4-.91 (really an .87), it turns an APC 14x6 at 10,000 rpm on 5% nitro fuel.

DarZeelon

Tim,


This number seems very ambitious...
You need a strong .61 engine to spin an APC 11x7 at 13.7K and a pipe would make it easier.


My own experience (with a customer's Webra .50GT) says otherwise.

A Bolly 10.5x7 prop, which is considerably lighter than an 11x7, held the engine back into the 11,500 RPM.
This was on FAI fuel, but the difference should not be that large.

He had to exchange the prop to 10.5x6, or an MA 10x7, to allow the engine to 'sing' at over 14K.

Allowing the engine to get into the fat part of its torque and HP curves is important, since if it is kept back on the ground and unloads considerably in flight, the needle setting may be much too lean.

This engine seems to have a very pronounced 'crescendo' in its power curves, below which it has an equally pronounced 'torque pit'...


Editted to correct nitro and RPM numbers from the customer.

RVman

Dar my 50 GT (ABN) tached at 13600 on 11-6 APC pn a stock muffler, i don't know why that load (10.5-7) is killing the engine you used. I normally run a 12-4 around 14K also on stock muffler.

DarZeelon

Tom,


Maybe some nitro just 'bumps' the engine, so to speak, over that low torque 'obstacle'...

I had corrected the previous post; the guy does not use any nitro in his fuel...

RVman

Yeah it could be the nitro, i use 10-15%, it doesn't need it all, but i want the same fuel for my saito...

TimC

Dar, 11x7 was a brain fade on my part. The prop I'm using on my .50 is an 11x6. There are too many numbers in this world.