PA-39 Props

[John Fuller]

My props are around 3,700 SMOH and 6,300 TTSN (42 years!) and the blades have been profiled (shrunk) to the point that they can't be overhauled. The props work great (and have been IRAN'd over the years), but are way overdue for for overhaul/replacement. I can buy blades from Hartzell and overhaul the hubs at known blade cost and unknown hub overhaul cost, or buy new props. From what I can tell, it's either Hartzell Q-Tip props at around $25K, Knots2U props with the D-Twist blades at $20.5K, or stock props from Hartzell. Since I already have the new spinners (and Wow Cowls), I'm assuming I can sell the extra spinners for some amount if I go with Q-Tips, or go with the Knot2U props and deal with the minor machining that may be required to make the spinner backing plates fit, or buy stock props from Hartzell that I think may cost more than the others.

Anybody have any thoughts on the advantages of Q-Tip vs. D-Twist vs. stock? If one has blade erosion advantages over the other, AD differences (I am not aware of any), or real performance/noise differences, I'd like to know. My friendly prop shop can help with the pricing with Hartzell but I'm not sure about Knots2U, nor do I know if the D-Twist props can be purchased directly from Hartzell.

Are there any other prop options (i.e. does Hartzell offer any prop options other than the Q-Tip these days, or stock)? Any news on the MT prop and if it's worth waiting for?

[N3322G]

I went with the D-twist as I was very comfortable with the performance and it was actually less expensive than the stock Hartzell prop. Since it came from Knots2U and they hold the STC, the props came out of 337 status and into STC'd status - not that I plan to sell the plane but eliminates any future questions.

My OPINION only is that Q-tip props would be more difficult to maintain. It is pretty easy to run a file over a standard prop - but q-tips, not so much. They would give you a bit more prop clearance. There are supposed to be quieter but with noise-cancelling headsets - I simply don't care that much.

The MT prop looks sexy to me and the lighter weight is attractive but again, maintenance - are they trashed if they get a big nick or can they be filed - I don't know. Since I am no longer racing and the financial risk would be 100% mine vs sponsor-risk, I do not plan to experiment - I am sufficiently happy with the props we have now.

Hope this helps.

[MULEFLY]

@ John. I have the Qtips... they were on the airplane when I purchased it... so I can't compare to "straight tips". I too have the LoPresti Wow Cowls... and the new spinners... My Qtips have been off once since I owned it and sent to the prop shop... I don't recall how much "stock" I have left.

I have sent repeated emails to the Canadian outfit that was referenced for the MT's... my inquiry was if they had or would have the counter-rotating props in their offering... "no answer".

John at Kts should be able to tell you about spinner clearance on the D's... I purchased my spinners from him. IIRC he was less than 1/2 what LoPresti was asking for them.

All the best!
Jim

[steen]

John,
I have the Knots 2U props on my '66 B CR and could not be more satisfied. Backplate mods were minimal and
the props have performed beautifully for about 10 years now.
The Q tips, by my info, are thinner and have less margin for filing out nicks, etc. than any other prop.
Hope this helps and I recommend the Knots 2U props. By the way, also check out their Arapahoe windshield.....
I absolutely love mine.
Steen

[John Fuller]

Many thanks to all of you for the input on this. Based on this, I'm ordering the Knots2U D-Twist Speed Props - they tell me it's a 4 week delivery.

[N3322G]

FWIW mine shipped exactly on time.