IVO Magnum for a good climb

[levansic]

I'm posting this in multiple places to see where the discussion may wind.

I've asked Keith Spreuer for permission to share his setup and performance data with the web forums, and Keith was kind enough to let me do this.

Anyway, Keith recently flew his long-in-progress Subaru-powered Cozy Mk. IV with an IVO Magnum prop, and got some startling performance. For some context, Keith found out that his engine had slipped timing before he acquired it ten years ago, and in the last three weeks, he was able to diagnose this problem and get flying. From Keith's e-mail to Marc's list:

I got it running Saturday and checked the static RPM with the IVO at it's flattest pitch. Three weeks ago it was 4000 RPM now it is 4500 RPM. There is so much thrust I can not hold it with the brakes! The nose dips down like it never did before. So the RPM increase is only due to the timing improvement. The 4500 PRM is about 900 more than I've seen on any of the other props. So I made 3 taxi runs to 75 kts (rotation speed) and stopped to inspect. All was looking good so I flew it. The acceleration to 75 kias was phenomenal at less than 1000 ft of runway. As I accelerated, the RPM increased to about 5300 at lift off so I pulled the nose up to hold 90 kts and keep from going over 5400 RPM (my personal limit and peak HP). The rate of climb was over 2000 fpm!. I did a few other flights and inspected between each. There is not an issue any more with acceleration or rate of climb. I increased the pitch in cruse. The IVO performed very nicely in manual mode. This weekend was very warm here in SoCAL. It was 82 deg at 4500ft. I could not exceed 18" MAP (that's only about 55% pwr) without hitting my coolant temp limit. So I could not test the high speed end too much. It appears that I have plenty of pitch control to not over speed at the high speed end but don't have good data there yet. Now I need to work the cooling system some more.

Keith's site is here.

-- Len

[Marc Zeitlin]

Originally Posted by levansic

....Anyway, Keith recently flew his long-in-progress Subaru-powered Cozy Mk. IV with an IVO Magnum prop, and got some startling performance. For some context, Keith found out that his engine had slipped timing before he acquired it ten years ago, and in the last three weeks, he was able to diagnose this problem and get flying. ....

And just to be clear, the majority of the huge increase in performance Keith has seen is from the fact that his engine is now working correctly, not from the prop. He has not put his original prop back on to see what the difference would be, but if I had to guess, it would not be substantially different than with the IVO.

[John Slade]

if I had to guess, it would not be substantially different than with the IVO.

Don't you just hate having to guess.

I've become increasingly concerned about the stories of Performance Prop blade failures. There seem to be no signs of damage to my prop from running through the exhaust, but then there weren't any warning signs on the props that failed either. Add that to the large number of seagulls we get down here and I think this relatively fragile but totally critical component has to come off. Heck, some of the bugs down here are big enough to cause prop strike concerns

Currently I'm getting 4050 static rpm (2.17 redrive) with 46 MAP on take off. This gets me off in a reasonable distance, solo half tanks, but its a lot like climbing a hill in top gear and is pretty wimpy in climb for full gross take offs. I've been thinking that lots of altitude quickly is really a safety issue - gives you more options in case of an engine out.

I would like to have collected better numbers on cruise before removing this prop, but discretion and all that....The best info I have, which isnt much, is max rpm of 6100 at 11,000'. I didnt get all the required data to make this really useful. I'd have to check my log, but I think I showed 190 kts IAS and the GPS gave me a 235 kts GS. I'd guess that the temp at altitude was around 65F.

So, my 68 inch 3 blade IVO Magnum is on its way. I should have it in a week. A couple of days to install it, then I'm back in phase 1 for 5 hrs. Hopefully it'll be ready to go in time for Rough River.... if I can just make a bit of progress with the repaint job and this damn hurricane doesn't hit too hard....

I'll report back here with first impressions and numbers.

[rv6ejguy]

On the EG33, going from 4000 to 4400 rpm is less than 20 hp difference which could not produce the large increase in performance Keith has noticed.

There is no way that a fixed pitch prop on an auto conversion will allow anywhere near the takeoff and climb performance afforded by a VP prop.

If I set my IVO at cruise pitch before takeoff, the takeoff roll is tripled and climb rate is less than half of what it is when set correctly for power and airspeed.

Two reasons: The engine can't produce rated max power at 4000 rpm and the blade is mostly stalled during the takeoff roll, reducing thrust even more.

John, I think you will notice a big improvement in T/O and climb, top speed may be the same or less. Big question is will you have enough pitch available to absorb the 13BTs power at high altitudes.

I'm very interested to see your results.

[CBarber]

Originally Posted by rv6ejguy

I'm very interested to see your results.

Me too. I was thinking of going ahead and ordering the ground adjustable IVO for $8??.00 and then once we get the rotary running and smooth ad the flight adjustable option. It is nice that the IVO allows this steady upgrade of its product as well as replacable blades. Heck, maybe you can carry a spare in the strake . Just another concession to cash flow .


All the best,

Chris

[Nathan Gifford]

I wonder if those bigger IVO blades (the ones that look like they belong on a C-130) would work better at altitude. I think it was RV6GUY who had it on his plane, but ultimately did not like them.

[rv6ejguy]

Originally Posted by Nathan Gifford

I wonder if those bigger IVO blades (the ones that look like they belong on a C-130) would work better at altitude. I think it was RV6GUY who had it on his plane, but ultimately did not like them.

Big problem with the paddle blades is that they are not produced in a high pitched version, being designed for very low speed operations. I have them in a box if anyone would like to experiment with them. I found them completely useless on my aircraft. They look impressive.

One other point to make with turbo auto engines, with power retained at altitude, it is a huge compromise to use a fixed pitch prop. Not the same as a Lyc or Cont at all. Ever wonder why cert turbos almost always have VP or C/S props? To have enough pitch to run high cruise power at 12,000- 24,000 feet will almost certainly mean way too much for t/o and climb.

[Dust]

I love it when 2 + 2 is 4. john seemed to be getting great climb performance out of his rotary fixed pitch prop, but, now it seems as though the excitement has worn off - he wants/needs better take off roll and climb.

Rv6jguy has been saying that all auto conversions need an adjustable prop for good performance.

It appeared to me, an uninterested continental trying to be user, that the rotary did not need the adj prop and the sube did.

it now appears that both do. Makes the decision between the two more difficult.

items now down to

Sube - can be turboed easier than a rotary (that is what turintine(sp) feels
Sube - probably more fuel efficient

Rotary - tougher because of fewer moving parts.
Rotary - cheeper

Just rehashing info for all to consider, not trying to insult - just standin at the side considering what i have read

[Kumaros]

Originally Posted by rv6ejguy

Big problem with the paddle blades is that they are not produced in a high pitched version, being designed for very low speed operations. I have them in a box if anyone would like to experiment with them. I found them completely useless on my aircraft. They look impressive.

Color me stupid, but isn't pitch a double variable in IVO props?
Once variable through the incorporated "blade twisting" torque mechanism;
Twice variable through the way the blades are clamped in the hub.
I mean, can't one choose initial flatter or steeper pitch by clamping the blade stumps accordingly?
As for having them for an experiment, yes I would love to do the initial test phase with a prop optimized for low speed operations. How much would you want for those blades?
Kumaros
It's all Greek to me

[rv6ejguy]

IVO makes two pitches of blades for the Magnum 30-90 inches and 45-105. The blades are clamped by two 1/2 inch bolts each, perpendicular to the flat root face between 2 knurled 1/2 inch aluminum plates so they are not adjustable in this way, only by warping the blades via the torsion rods.

Make me an offer on the blades. Used for a half hour of flying, mint. These would not absorb more than 100 hp at 2300 prop rpm though once I was above 90 knots. They are the 76 inch diameter. Might be good for ground testing or an airboat.

I basically said before that an atmo rotary would be lame in t/o and climb with a fixed pitch prop in a loaded Cozy. A turbo rotary might be acceptable because it makes about 50% more torque at 4000-4500 than an atmo one. You will be lucky to get 4000 rpm on takeoff with an atmo rotary using a FP prop without screaming the crap out of it in cruise at altitude. Just my 22 cents. As John says- I could be wrong.

[Kumaros]

Thank you for clearing up my misconceptions about IVO props. I thought the blade roots orientation was arbitrary, thus enabling one more mode of pitch adjustment.
Anyway, since the testbed for my proposed turbodiesel will be some sort of airboat, it seems your blades would be ideal during that phase. I'd gladly pay half of the current catalog price plus shipping.
Kumaros
It's all Greek to me

[karoliina]

Some have cs props in ultralights (=sportplanes) here. The climb performance
difference is huge. We have a ground adjustable prop in our Star and
we have adjusted it back and forth to get acceptable performance in both
climb and travel. For safety reasons we have had to draw the compromise
towards climb performance and we are stll far away from our flight club's
wt9 Dynamic which departs like a rocket from a short field and is still
about 60 km/h faster in cruise (which is due to better aerodynamics in
addition to the pitch of its cs prop). With two on board our plane would not
make it from 300 m grass field. With cs or vp prop that would not be
a problem at all. I would not consider a Cozy without cs prop for a second
if performance is the only variable that would be concidered.

[John Slade]

lame in t/o and climb with a fixed pitch prop in a loaded Cozy.

This is the reason for the IVO, if you don't count my concerns about the Performance prop holding together, and wanting to have a spare prop anyway.

Solo with 1/2 fuel she flys just fine, but once I loaded her up to plans gross I wasn't comfortable with the take-off and climb. Looking at a take-off distance chart I may still be within what's normal for a Cozy - high gross on a hot day extends the roll considerably - but on my 3000' it seemed like the end of the runway was coming up awfully fast. Certainly it would be hard to stop in the distance remaining.

With a long runway and a cold climate the fixed pitch may still be the best way to go. It depends on how well the IVO performs at cruise. We shall see.

John (sanding, sanding and sanding some more)

[rv6ejguy]

Originally Posted by Kumaros

Thank you for clearing up my misconceptions about IVO props. I thought the blade roots orientation was arbitrary, thus enabling one more mode of pitch adjustment.
Anyway, since the testbed for my proposed turbodiesel will be some sort of airboat, it seems your blades would be ideal during that phase. I'd gladly pay half of the current catalog price plus shipping.
Kumaros
It's all Greek to me

I'll look up what these are worth, sounds fair to me. How do you usually ship things? We use Fedex but could be kinda pricey. I'll check on rates. Just to clarify, these are the three blades only, no hub.

[Kumaros]

Originally Posted by rv6ejguy

I'll look up what these are worth, sounds fair to me. How do you usually ship things? We use Fedex but could be kinda pricey. I'll check on rates. Just to clarify, these are the three blades only, no hub.

It's OK, I'll buy a hub and three Magnum blades anyway, I'll use yours during the test phase on a makeshift airboat. FedEx lowest priority, to lower shipping costs as much as possible, would be perfectly acceptable. Add up the cost of the blades and shipping costs and let me know how I can transfer the funds, Paypall maybe?
Kumaros
It's all Greek to me