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PostPosted: Wed Nov 04, 2009 9:14 pm
by BlackRain
I have been looking around at the various posts regarding engines for the lazair. What would kind of improvements can one expect from the p tip props? Is it worth it to get the props or look for more power with a different engine with more hp? Information regarding putting redrives on as well. Any thoughts and suggestions are appreciated.


PostPosted: Thu Nov 05, 2009 12:33 am
by lazairiii
As Shannon stated, you either need to look at the JPX and rebuild them (hard to find) Tyler can give you more details on these, or stick with the Rotax 185's with P-Tips (tried and true). I'm 170#'s and I get a huge boost with the P-tips. If you opt to keep the Rotax's, send them out and I'll rebuild them so you will have max compression, new gaskets, seals, rings, carbs rebuilt, etc.


PostPosted: Thu Nov 05, 2009 8:43 am
by BlackRain
Thanks George... appreciate the input. What thrust gains did you make after installing the P tips on your 185's?


PostPosted: Thu Nov 05, 2009 9:32 am
by bdiedenhofen
One thing to keep in mind with the Lazair is that it flies great as a "low and slow" airplane. Modifying it to create more performance is sometimes detrimental to the concept behind the plane. If you want a plane that climbs fast, cruises fast and delivers big plane performance you're really better off with something else. My bird climbs at about 300 to 400 ft/minute depending on the day. I weigh 180lbs and I have a pod (which makes a big difference in terms of performance). I can cruise at 45mph, but it's way more fun to just float around at 30mph and see the sights. I've got the bi props and the airplane - series III - is absolutely perfect just as it is in my opinion. If I ever need to replace an engine, it'll be another R185. Shannon reports good improvement in climb with the P tip, and if I ever break a prop and can't find a replacement I'll invest in a P tip too. I just find they're a little expensive considering that the bi props are sufficient enough. I suppose that for float use, the P tip might be a better way to go. At one time there were a number of folks modifying to redrives. This would be a good alternative for float use as well as you would get more pull to get off the water. However, cruise speed will no doubt be slower.
One guys opinion,
Brian D

PostPosted: Fri Nov 06, 2009 8:58 am
by Shannon
This question is asked often. I think most guys want to be really sure there is a definite improvement in performance with P-tips before they spend big bucks. I can understand that. I also understand that guys hear what they want to hear and often rationalize things in a way that makes them feel good despite the facts. Read the section on P-tips here : The information there is basically good with the exception that the props are made from Hard Rock maple and the price has gone up a good bit.

Personally I'll never fly with carbon fiber Bi-props again if possible. The increase in performance though not large is a definite improvement over the Bi-props. It's just an estimation but performance (thrust) will increase by 20% +/- on a good set of engines. Run-out junk engines will not turn the P-tips up to speed so no miracles in that case. Depending on all the variable factors a particular guy could see as much as 100'min +/- climb rate increase and 5mph in cruise speed gain. WOW-WHOOPIE that doesn't sound like much for the money right ? That small bit of extra performance could mean the difference in making it to a safe landing area single engine however. I can tell you that because I had the occasion to do it single engine. Some light guys with light planes may even be able to maintain altitude with a P-tip single engine.

Ultraflight stated an approximate 17% gain in thrust with the "ground adjustable" single blade prop they developed. Unfortunately that prop proved to be defective and nearly all of them were recalled and sent back to the factory. A few stayed out there however. Here's a pic below of one on a junk plane that was for sale years back. So there's your proof right from the factory that the Rotax 185 is capable of delivering more thrust with a better prop. Read Tech Update 8.11 and June 82' Lettair

Lastly I like the way the P-tips look. They just look "right" for the plane with the curved tips. They sound awesome in the air and are a good degree quieter than the buzzy Bi-props. Finally no longer do you have to waste time answering the annoying question of "WHY does it have two props on each engine". Now you get to answer the new cool question of "WHY do the props have curved tips" which is a welcome change.

PostPosted: Fri Nov 06, 2009 9:30 am
by Shannon
I tell you those things are simply just a work of art.

PostPosted: Fri Nov 06, 2009 9:48 am
by Shannon
Side View

PostPosted: Fri Nov 06, 2009 10:29 am
by Shannon
BlackRain @ Nov 4 2009, 08:14 PM wrote: I have been looking around at the various posts regarding engines for the lazair. What would kind of improvements can one expect from the p tip props? Is it worth it to get the props or look for more power with a different engine with more hp? Information regarding putting redrives on as well. Any thoughts and suggestions are appreciated.


Craig you could go with different engines but it wouldn't be cool to install more powerful and/or heavier engines on an "unbeefed" stock Series II. It's not really cool to even put bigger-heavier engines (JPX's for example) on an un-beefed stock Series III in my opinion. We actually did just that in 84' and didn't think it was Kosher for a number of good reasons. The stock airframe (wing engine mounts) for example is just not strong enough for rough ground and bouncy landings with heavier engines. Ultraflight obviously came to the same conclusion and produced the Elite which is nothing more than an upgraded beefed-up Series III.

Personally I would only consider putting on more powerful engines if I completely upgraded the wings and fuselage. The upgrades for me would include things like Series III wide stance gear (A-frame), 4'- .020 D-cell skin doublers, Jury strut upgrade, upgraded engine mounts, box stiffeners, wing attach doublers, ect ect ect....... Man that's a lot of work, time, and money. It also takes great dedication, learning, patience, skill, drive, guidance, and enthusiasm (which most guys seem to lack). I've personally done all of these things so I know exactly what it takes firsthand. I'm not guessing.

You can forget Re-drives for 185s, none available. Also to re-engine a Lazair (with Solo's or F-36's for example) it will cost a bundle.

Pic: Stock Series III with JPX's

PostPosted: Fri Nov 06, 2009 11:19 am
by Shannon
Unbeefed modified Series II with JPX's installed. Note how the seat has been pushed as far aft as possible to correct gross center of gravity error. Things are pushed back so far in fact that the wing struts are canted back to meet the fuselage wing attach fittings. This has led to decreased diehedral which reduces stability. To make matters worse the wingtips have been removed which destroys slow speed handling and stability. This plane (owner unknown) if not scrapped could very well kill someone who does not understand the dangers. With WOT application this plane will blow right past VNE like right now !

PostPosted: Fri Nov 06, 2009 11:26 am
by Shannon
This unbeefed Series II was modified with extended length ailerons and Hirth F-36 motors. Apparently the airplane did not fly correctly as the last owner again reconfigured the airplane to a wild "push-pull" highly modified configuration. As it always happens the plane ended up a chopped up piece of garbage and was scrapped (thankfully). Really sad as this plane (as owned by the previous owner) was a nice little basically stock Series II with 185s, floats, and custom enclosed trailer.