This not a rhetorical question. Why is the most high tech prop in 2020 made of wood and glue? Does not sound like many are doing the "field repairs" or that is not the problem people have with them (or maybe they're not complaining). Why doesn't everyone with this kind of budget and desire for weight savings have composite? They make boat propellers out of it.

frstnflt wrote:This not a rhetorical question. Why is the most high tech prop in 2020 made of wood and glue? Does not sound like many are doing the "field repairs" or that is not the problem people have with them (or maybe they're not complaining). Why doesn't everyone with this kind of budget and desire for weight savings have composite? They make boat propellers out of it.

There are a lot of interesting things going in material science these days... one of the most interesting, in my view, is compressed wood.... it appears that you can make incredibly strong structures that are very light... from wood. Who'd a thunk it?

The Stearman was the strongest airplane built in WWII. I know I'm going out on a limb here... nomex on. The wings were wood and the airplane was stressed for +9G and -11G (Ask yourselves why it was stronger in negative G?). Nature is an amazing engineer.

I've had several MT's... four blade, three blade and two blade. I like MT... especially with nickel leading edges!

my two cents.
gunny

frstnflt wrote:This not a rhetorical question. Why is the most high tech prop in 2020 made of wood and glue? Does not sound like many are doing the "field repairs" or that is not the problem people have with them (or maybe they're not complaining). Why doesn't everyone with this kind of budget and desire for weight savings have composite? They make boat propellers out of it.

Really? Let’s see, Components:

Wood core, wood being the “original composite”
Carbon fiber sheath
Painted surface
Nickel leading edge.

Now, look up the definition of the word “composite”

MTV

I am still open to a newer generation prop but really not sure I want to mess with a field approval.

D.

mtv wrote:

frstnflt wrote:This not a rhetorical question. Why is the most high tech prop in 2020 made of wood and glue? Does not sound like many are doing the "field repairs" or that is not the problem people have with them (or maybe they're not complaining). Why doesn't everyone with this kind of budget and desire for weight savings have composite? They make boat propellers out of it.

Really? Let’s see, Components:

Wood core, wood being the “original composite”
Carbon fiber sheath
Painted surface
Nickel leading edge.

Now, look up the definition of the word “composite”

MTV

By a loose definition a metal prop with paint and other coatings is also composite. I know there is a reason wood is still used other than tradition which is why I asked the question. You do not know or you are sore about someone else trolling you. It was a respectful question inviting someone with knowledge of material science or aeronautical engineering to educate the community.

Now, look up the definition of the word "rhetorical"

I'm not necessarily an MT fanboy, but I am a fanboy of composite propellers because all other sectors of aerospace have been relying on composites for decades. I use it at work extensively and what you can do with composites is amazing.

Why is the most high tech prop in 2020 made of wood and glue?

I am not sure on MT's choice of wood core because I don't work for them. At work, usually the core of any composite is mainly for transmitting shear through the structure or holding the shape, not for the actual strength. In terms of building a composite propeller, having a core of a lightweight material is what gives the propeller it's shape. This could've simply been foam, but then you get about zero structural gain from it. For a little more weight, I imagine wood gives more structure, easy to shape into the airfoil, and heritage people trust. If it were foam, people like you might ask why the most advanced prop on the market is made of "styrofoam and glue" instead of "wood and glue" - by the way you forgot the key ingredient there, carbon. Carbon fiber floorboards and other flat sheets are usually honeycomb aluminum or foam core with a very thin face sheet of carbon fiber. This allows the heavier CF to only be where the stresses need to be taken care of, and the other lighter material just gives structural depth.

Does not sound like many are doing the "field repairs" or that is not the problem people have with them (or maybe they're not complaining).

There's a couple in this thread. Not sure why someone would complain about the field repairs, not much different from filing a metal prop except no performance is lost from epoxy repairs. (Maybe a slight imbalance but filing does that as well).

Why doesn't everyone with this kind of budget and desire for weight savings have composite?

You're guessing that people who have $15k to spend on a prop aren't buying composite props when there is one available. I would lean towards guessing that they are. Sure does seem like all the totally built out C180/185, Huskies, Scouts, 170's, etc are mostly running composite props now. Money is a key requirement, but your question suggests people are avoiding them for reasons other than money.

Thank you all for posting this is a very informative thread

My reason: Hartzell never got back to me after I talked to their rep and said I wanted a prop. I replaced my McCauley C58 about a year and a half ago and put feelers out to both Hartzell (Trailblazer, which is all carbon fiber and resin, I assume meeting your definition of composite) and MT (Flight Resources). Flight Resources responded same day (which was a Sunday and Christmas Eve) and Hartzell never called me back. I would have considered either prop based on positive reviews of both, but if Hartzell is slow to respond before they have my money I can't imagine how they respond after they have it. Case closed for me.
As an aside, not only does wood have good strength/weight ratios, it also is very good at damping vibrations.

Finally got it back. 10 weeks and $9,000 later, it looks great with the shiny new nickel leading edges. Finishing annual, so it'll be another day or so before I get to try it out.

Hey Pierre, are you sure that chain is strong enough for the job? Looks like you should use a few more sections.

Good to see you got it back, keep us posted.

Kurt

Is that long scat hose a water supply for the humidifier feature on your cabin heat?

Did a lot of research before I bought my MT. I could not be happier with John at Flight Resources or the performance of my MT prop. Your mileage may vary but I'm loyal to companies which take care of me. Beauty is in the eye of the beholder.

Pierre thanks for posting - great paint scheme!

Good news. The prop rebuild appears to have made a significant improvement in performance.

This afternoon. 90F. 4500' lake. Winds calm. Local AWOS put density altitude at 7800 (I calculated a bit lower). Just me onboard plus gear and 32 gallons, so about 2800 lbs.

On the step in 15 seconds. Off the water in 30 to 33 seconds. Climb to 8500' MSL nonstop at 500 FPM.

This is not only back to prior performance, but better. I used to figure on 40 seconds under similar conditions.

I am now convinced that the extensive blistering/wrinkling on the prop reduced thrust. I plan to write to MT to see if they found any manufacturing defect, or if I need to change anything about how I operate. I hope to avoid the major expense and downtime in another 800 hours.

Pierre

Photo shot from the deck as I write this post.

Fantastic Pierre!

Kurt

After arriving in Alaska from Colorado I noticed that a couple dents on my MT leading edges (stainless) that had been filled with epoxy, were no longer filled with epoxy. I assume this is because I was flying through lots of rain on the flight up. I went to their website to look into re-doing the epoxy. Learned a lot from reading the field repair guidelines. Turns out I don't have to fill them since there's no hole/crack in the stainless, just a dent. Honestly I didn't realize there was so much that could be repaired "by hand". I may still fill them to round out the blade profile which theoretically helps performance.

https://www.mt-propeller.com/pdf/sls/sl32r5.pdf

Just checking in here to remind readers if you have ANY questions or concerns related to ANY MT Prop, please call me or Larry directly. My number is 715-56-eight-3-nine-80. Larry is 612-six19-five782.

Remember, we stock exchange blades for our most popular models so you can get a quick O/H turn time AND get the new nickel leading edge upgrade as part of your O/H if you want that.

The MT approved prop shops continue to see too many MT props brought in for repairs that could have been done by the OWNER. They are not going to turn away business, so they accept them and do the requested repairs.

There are nearly 30 MT approved repair shops in USA. Do what I do when I need one O/H...I call several of the shops with my prop model and s/n and ask for a quote and turn time. Shipping cost is about the same anywhere in USA. I select the shop that provides me a price and turn time I am happy with (most often that is Tiffin Aire in Tiffin OH).

Here is a DRAFT of a video clip I made to see how much impact the MT could take and then show how to do the repair yourself using supplies and tools at home. When I shot the Nickel-Cobalt leading edge of the MT prop with a .22 Long Rifle held 2" away from the surface, the bullets simply ricocheted off leaving only a lead smudge on the surface.
https://www.youtube.com/watch?v=BTw22TgTjnE&t=31s

Foam Core Composite or Natural (wood/epoxy) Composite:
MT builds blades with both methods (and metal blades too). The Hartzell Trailblazer uses the Foam Core construction method (ACS). With ACS, the carbon fiber shell is the load carrying member of the design....the foam is a place holder and fills the void in the core. If this shell is damaged, the structural integrity is compromised and repair is not possible.

With a natural (wood) composite, the wood/epoxy composite core is the load carrying member...the carbon fiber shell is simply there to add stiffness and protect the core from moisture and impact damage. The beauty of spruce wood is that it has no life limits, damage does not cause a stress riser and it is light, strong and has the best dampening characteristics (ever seen a wood tuning fork?). I watched a demo at the MT Factory where they drilled five 3/8" holes clean through a 83" 2-blade MT prop and spun it up to 3000 RPM in a test cell without any adverse vibration or failure. The German Air Force routinely flew home in WWII with wood props that were riddled with shrapnel and bullet holes. Allied welded steel blades that were damaged like that required immediate shut-down of that engine to avoid catastrophic failure due to vibration.

If you want an MT Prop, but prefer a foam core or forged aluminum blade, just let me know and we can have it built that way for you....but one must wonder why military's around the world with unlimited funds are converting to composite props. Missionary planes (Cessna 206) are also finding the MT with Nickel edges the preferred prop used in some of the most rugged and remote areas of the world because damage is field reparable and they have demonstrated they still operate safely even when 4" of the tips have been sheared off.

Thank you VERY MUCH for your support!!

Like!!!!

Thanks for the excellent write up John. I have had 3 MT props over the years and with one exception all have been 100 percent trouble free. The only exception was a leaking seal that MT took care of no charge, no leaks on this prop after almost 300 hours after reseal. Silky smoooooth!

Kurt

Great piece information, John. I have found so many "myths" out there regarding composite props in general, and MT props specifically, yet as you noted, lots of operators are moving to composite props.

The repair information is excellent information, particularly the discussion of foam core vs wood core props. Before we bought our first composite prop (an MT 83 inch on a Husky), I spoke to the Chief of Maintenance of an air taxi outfit that was running composite propellers on BE-1900s, with lots of gravel runway ops. I expressed a concern over damage to blades, and his response was that the damage these props exhibit in day to day ops are easy to repair, and safe.

Aluminum props, on the other hand, tend to take a lot of blade damage to leading edges, and frequent dressing out of blades is required. And, one rock ding can make an aluminum prop unairworthy or worse. Those nickel leading edges are really tough, as you noted.....though I don't think I'll pull out my six shooter to prove the point.

I have been really pleased with the MT Ultra prop you folks sold me for my current plane, a Cessna 175 with a Lycoming O-360. I was not at all surprised by it's low end performance, because that's what I've come to expect from MT props. What did surprise me was the addition of ~ 5 mph cruise speed compared to my previous Hartzell 80 inch prop. The Ultra is definitely a winner!

Anyway, thanks for more great information on a great series of propellers. I'm glad to see you and Larry are still leading the way on these props.

MTV