Rans S21 Outbound build French Island. Nic and Mike. Start date 3rd May 2022. Finish date 1st February 2023. Target $ spend to be determined.

[facthunter]

Sensenich are a highly regarded prop manufacturer, I'd stick with a light weight prop and don't do sharp turns on the ground with high revs on the engine. and one wheel nearly locked. Is it fitted with good fitting cooling baffles around the cylinders and an adjustable cowl flap?  Nev

[Mike Gearon]

2 minutes ago, RFguy said:

that's the thing- speed envelope... if you have plenty of power and runway, tune for top end.... no need for a CSU.... . how many ml/nm at 140k TAS  ?  (lph / TAS) 

as for the busted  crank, could be anything. but one needs ot be careful of the situation of having  a heavy weight at both ends of the crank.

520 manual says "Propellers with a Rotational Moment of Inertia of up to 0,8kgm² have been used with no known problems"

whatever that means...

The airmaster https://www.propellor.com/ap533hctf-snr67je     says it's 0.5kg.m2 

But ya dont know about the possible harmonic behaviour without some instrumentation attached.... I'd go with a 3 blade. and put some vibration instrumentation in xyz on the crankcase.

 

Hey, that’s good research! I know in the RV6 I can’t use 2100 to 2300RMP and respect that completely. It’s for good reason they restrict RPM’s. So, any info such as that max .8kgm is helpful.

 

Yes, I think the 3 blade Sensenich carbon fibre is a good option as far as balance and light weight go. Hoping we get a good run and long term reliability. 

[Mike Gearon]

1 hour ago, facthunter said:

Sensenich are a highly regarded prop manufacturer, I'd stick with a light weight prop and don't do sharp turns on the ground with high revs on the engine. and one wheel nearly locked. Is it fitted with good fitting cooling baffles around the cylinders and an adjustable cowl flap?  Nev

We worked extra hard to cool the slow aircraft and now we suddenly have it almost cooling too well. Could need cowl flaps!

 

I never thought about stressing the prop with sharp turns. That’s a really good point. I whiz the RV6 around and will now make sure that’s just inertia and not much prop. I’m very familiar with blade stress on moment arms and have a patent lodged last July 2024 with exactly that problem solved for small scale wind turbines. Those little turbines can still throw blades a half a km or more! I’m building the first prototype and I’ll share when it’s on the tower. 5kw with a 5 meter spread of blades. It’s not that small!

[Mike Gearon]

I didn’t put the pic up. Big day… here.

 

 

[Mike Gearon]

Nic and I fly the S21 with UL520t in the morning then build. Some beautiful flying weather lately.

 

Build 1

 

UL520t is giving us some problems. Engine temps aren’t as well behaved as we first thought after getting the prop sorted and higher flying speeds. Starting to run out of options and will buy the louvers as next step.

 

We also have black smoke and engine cutting out on take off. I’ll video next time. Observed 3 separate puffs of black smoke watching Nic on take off going home yesterday. We know we have that hesitation. Something to do with the FADEC deciding to cut ignition and we are around 2400 2450 at this stage of climb out. Will discuss with local distributor then look to support from Herman in Florida and perhaps UL engineers in Europe. 
 

My take on this is that the FADEC programmers have some parameter that is being exceeded and they cut the ignition. I do know that Nic feeds the throttle in slowly on take off roll to reduce the chances of this problem. We plan on running laptop in aircraft to assess what the turbo is doing and other things we can’t get through the G3X

 

Build 2

 

Prop on last night. Nic is nearly through the avionics. We should be at engine cowl, doors, skylight, windscreen and near finish at some stage. Maybe next few months. It goes frustratingly slowly then seems to leap forward.

[Blueadventures]

Nice Mike.  What was the empty weight of Nic's and a couple of images would be nice of how it looks today.  Yours is coming along nicely; they take a while just need to get over the humps when seems slow and never getting there thoughts; I'd just do some small things to keep it moving. Like the paint job and colours; even though I'm a Blue person.  Cheers