P-Tip Propellers

Theres at least one Lazair flyer who has installed a set
of p tip's from Prince Props

  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 .


Shannon, ready to advance the thrust levers and get those p tips to gobble some air




 
 
 
 
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.