Most of us know Shannon Whitaker  by his frequent posts on the Lazair News Letter's Forum  through our recent email exchanges I have learned that he has a wealth of knowledge when it comes to the Lazair and its no wonder he was very fortunate to grow up around them when he a young,he had no choice, seeing that his father was a Lazair distributer starting way back in 1981 and had sold ,built and flown every model except for the police ss model,  they are still to this day hard core Lazair lovers.Shannon has recently installed P-tip propellers from Lonnie prince's company Prince P props and has been kind enough to share his experience with Lazairforce.
      If there is one area of improvement in performance that can be exploited easily it would be in the rotation to thrust converters on the business end of the power plants,the props, although reasonably effective, leave a lot of room for improvement, the challenge though is to design a propeller that is effecient at small diameters and high rpm, a difficult task that requires some unique thinking .

 
 
 
 

By Shannon Whitaker  a Cupped tip on the P-Tip prop (hence the name p-tip) is what makes them work really well. The cupped tip is carved right out of the wood and is not a seperate piece. What happens is centrifugal force makes the prop flex at top r.p.m.. This in effect makes the prop grab more air at top engine speed. What a concept, a rather ingenious idea if you ask me. The Prince Props were specifically made for the Rotax 185's by computer design and weigh less than the doubled carbon bi-props. The Prince Prop company is owned by Lonnie Prince who happens to be a Lazair owner and enthusiast. . 1. The prop hub will have to be heated to remove it from the crankshaft and the use of a small flywheel puller will be needed also. A small propane torch is all you need to heat the prop hub.  2. The original prop hubs will have to be drilled out with two new holes. You can use the Prince Prop crush plates as guides or as templates to drill the two new holes in the correct location. I used a drill press to make new holes. 3. The same type of original Lazair bolts can be used to bolt the Prince props to the prop hub. The only difference is that a shorter bolt of the same type and grade will be needed. The prince props have a thinner cross section than the stacked carbon props thus they need a slightly shorter bolt.  4. I used the same Torque value as the carbon props to tighten down the Prince props. I also used loc-tite on the prop bolts.  5. The prop spinners will have to be modified with a slightly larger cut out to accomodate the wider prop. I would advise people to remove their prop spinners completely unless they have had a new spinner backing plate made from turned T-6 Billet. The original Lazair spinner backing plates are defective and should be used as a pattern for having new backing plates made. I can give you a pretty fair evaluation of the prince-props. The increase in performance isn't a drastic change but I feel that they are an improvement over the carbon props. A stock (lightweight, i.e. no parachute or fangled gear) Series III Lazair with a nose pod (Mike McKusick's pod) will maintain altitude on one engine with the p-props. Climb performance increases by 100-200'/min (depending on how strong your engines are) and the noise level decreases by 10-15%. The engines will slow down 1,000 rpm because of the increased pitch (34x10) and you will pick up 5-10 MPH cruise speed @ 4,500-4,800 rpm with a nose fairing. A Lazair without a nose fairing will not see any great increase in cruise speed because of the great amount of frontal drag. Also, your ground run will be approximately 50' feet shorter  with the prince props.  Drawbacks, You have slight increased vibration at certain rpms with the prince props and they cost $250 each ($25 crush plates not included) with an approximate 2-3 month delivery time. In Addition, your stock prop hub can be used by drilling two additional holes to accomodate the 4-bolt pattern of the P-Tips. The props that I have are a very lightweight birch and weigh several ounces less that the Carbon-Bi props. They are painted with a very nice looking grey enamel or epoxy? coating and are a beautiful piece of work. Your stock Lazair prop spinners can be used by slightly enlarging the Bi-prop cut-out provided that you have a new spinner hub plate made from Turned T-6 Billet. The original Lazair Spinner hub plates should be removed because of cracks that will develop around the prop hub area.

Check and compare top:Prince P lower: conventional twin nylon if you look closely at the tips you can see the pronounced curved tips (check shadow upper right) mounted on the test stand

Close up of test mount,

 

The prince p going through the motions on the test stand....or a new Idea for a patio fan complete with mosquito fogger.