I'm getting the cart way a head of the horse but the plane I'm trying to buy has a O-360 and a 78" C-214 Mac prop. 78" is on the short side for this plane and I'm told I want at least a 80"...82" would be better. I figure why not go for 84"? The engine builder said I can and should turn this engine up the 2800rpm for takeoff so I think 84" is about as long as I should go. Can a O-360 handle that much prop?

Also, anyone know what plane besides a 182rg uses a B2d32c14/90dhb-8 prop? The longest allowed on the 182 is the -8 which is 82". Think I can find a 90dhb and have it cut to a -6 which would be 84" right??

Edit: I edited the title to more closely match the discussion.

The 182 is limited by ground clearance not the engine, the 0-360 turns a 83in MT just great there are lots of experimental cubs running a 84 in fixed pitch too.

I'm confused......not a challenge, mind you. The Cessna 182 RG is equipped with a Lycoming O-540, not a 360. Apples and oranges when it comes to props.

You can't just pick a prop that you like the size of and bolt it on. The prop has to be approved on the AIRFRAME and engine combination. What model airplane are you looking at?

Go to the Type Certificate Data Sheet first, then Start looking for STCs.

The MTV-15 propeller is approved on the Lyc O-360 in some installations. That is a 210 cm or 83.5 inch prop.

MTV

Experimental so I can use whatever I want as long as it fits. I've been looking at the MTV-15 but for the price I'd rather just find some longer blades for the Mac.

Bushwhacker's O-360 swings a 90" prop.

I can't answer Whee's question (sorry, whee). I hesitate to even ask for fear of possibly passing on bad information, but here I go anyway: Is there a prop to avoid using on an O-360? I recall (I think) hearing that an 82" Borer prop, mounted on an O-360, tends to shed their tips after 500 hours or so. Has any one heard of this or experienced this? Or is this just something I dreamed up?

I'd like to hear an answer to Whee's question as well. I am running an 80" seaplane prop. I am happy with it, but options would be nice.

EDIT: Here's a link to what I remember reading.
http://cessna170.org/forums/viewtopic.php?p=46791

-Nate

You could spin a 100" prop-- IF it was pitched flat enough. Rather than trying to reinvent the wheel, I'd check around & see what everybody else who has that airframe/engine combination runs. Unless it's something pretty damn unique, that shouldn't be too hard. Otherwise, look at similar-use certificated airplanes with that engine- Maule, Husky, etc.

At least 80" is what is recommended 82" is better performance but louder. I haven't talked to anyone running a 84".

Whee,

Okay, you're experimental. That should not imply that you are stupid, however. "Just bolting" a set of blades on a propeller can be suicidal, or at very least, pretty exciting. Experimental or not, you DO NOT want to use any combination of hub/blades/engine that has not had a vibration survey done on it. Without that, you are truly a test pilot, and engines/propellers have been known to completely depart an airplane due to 3rd and 4th order destructive harmonics. That sorta screws up your weight and balance.

Want an example: Years ago, some guys in Fairbanks were running blades from a CS Pawnee prop on their Cessna 170s equipped with Lycoming O360s. As noted earlier by another poster, MOST O-360s have some sort of operating restriction, based on RPM, different with different props. These guys, without any testing, were running the blades at their full length...82 or 84 inches (I've forgotten now the original length). A local A/P mechanic that worked for the University teaching aspiring mechanics knew about these illegal installations, and became concerned that there was no vibration survey.

Being a proactive kinda guy, he went to Hartzell and, based on the fact that there were several of these things out there, convinced them to do a vibration survey on that prop/engine combination. What they found was a destructive harmonic between 2600 and 2700 or so.....perfect.

Hartzell then did a little experimenting, and found that those props, cut off to 80 inch diameter, AND equipped with a Hartzell harmonic damper assembly, passed all vibration tests. The University instructor then got field approvals for all the guys running this combination in FAI, and helped them get the props cut down and locate harmonic dampers. That's how the 80 inch Hartzell came to be approved on the O-360 Lyc. WITH a harmonic damper assy.

Run that kind of setup without a vibration survey, and you are asking for trouble, and potentially a VERY serious outcome. By the way, the harmonic dampers weigh close to 10 pounds themselves, and they are scarce and therefore expensive.

There are props out there that are approved on those engines. Just because you're experimental doesn't imply you can or should ignore the potential for disaster with props that haven't been tested. The O-360 Lyc has known vibration issues to boot.

If you're experimental, why not get with someone like Craig Catto and see what he's got going for that engine?

MTV

X2 on what MTV said.

Prop, control surface and airframe dynamics can be very sensitive to mass, mass distribution, stiffness and contour changes. Generally BC planes are slow enough that airframe flutter is not much of an issue, although the prototype Husky had wing flutter issues before Vd. The way I heard the story was that the test pilot packed up his belongings and never came back to Aviat.

An O-360 is turning 2700 rpm whether it's on a cub or an RV-3. For certified installations, prop to engine and engine to airframe surveys are required.

While certification is a pain in the arse, the airworthiness regulations are pretty good guidelines to consider for experimental aircraft. 80% of the regulations in Part 23 were born out of reaction to incidents and accidents in the field. I have learned a lot working in aircraft certification, and if you are going to be tweaking a plane, the regs are very worthwhile to familiarize yourself with.

Propeller departure from an aircraft could potentially overpower the horizontal stab if you are going slow and loaded aft, then you are in for a wild "last" ride.

mtv wrote:If you're experimental, why not get with someone like Craig Catto and see what he's got going for that engine?

MTV

Craig's building a variety of props for the Lyc O-360. For the STOL guys, I believe the longest is 86x38 on a stock configuration and 86x40 on the 205hp stroked version (IO-375). FWIW... I think his 86" prop won Valdez on a Super Cub with a Lyc 360. Talk to him. He's GREAT!

I've talked to Craig before about making me a prop for a different plane but on this one I want to stay with a CS prop.

I agree with and understand what MTV and Scolopax are saying. Here is where I am at: I won't put a hartzell on it and I have yet to find a Mac prop that is approved for an undampened O360. Both to prop shop that overhauled this prop and the engine builder were not concerned about using a C214 on a undampened O360. I personally am undecided at the moment but I know that this point if I change props the only two options I'd consider is an MTV-15 or a 80" Whirlwind.

Not sure how many but I know there is a fair number of guys running this engine/prop combo but almost all are much shorter length so not comparable.

mtv wrote:........That's how the 80 inch Hartzell came to be approved on the O-360 Lyc. WITH a harmonic damper assy........

Almost all the 360-powered C170's I've seen with c/s props have the Hartzell. I've seen very few fixed pitch props (maybe none) on 360-powered 170's. What c/s prop was used on this application before the approval work you described?

whee wrote:I'm getting the cart way a head of the horse but the plane I'm trying to buy....

No offense, but if it was me I'd get the airplane bought before I worried about re-engineering it. Kinda like picking out honeymoon spots before the bride-to-be even says yes.

Your right hotrod but I can do nothing more till my plane sells.

May I offer a simpleton's view on this whole subject.

Your on this board because you may, possibly, eventually venture to a rough, unimproved strip? So if you put the longest possible prop on your aircraft, limiting the ground clearance. The mere act of taxing over a gopher hole mound may give you the pleasure of a prop strike. I don't say this lightly, it happened on my Soloy 207 on a dirt strip, taxiing over ruts in the runway. The conversion runs a 93" 3 bladed prop, with absolutely the legal limit on ground clearance. Ground clearance is as important, or perhaps more important than big tires, cause they ain't gonna roll if there is no power and the cost of a mistake is huge.

Getting old and slow here - while reading Dogpilots post it finally dawned on me that ya might want to consider prop clearance with a blown tire!

Trim

Does the extra diameter really even make sense at full RPM (takeoff)? Sonic speed would be right near 79" or 80" at 2600 rpm or so. Just curious what a person is looking to improve...unless you are looking for cruise performance (lower rpm)?

Cool calc from P.Ponk on blade length and tip speed: http://www.pponk.com/HTML%20PAGES/propcalc.html

"To produce maximum thrust at full power your tip speed should fall between .88 and .92 mach."

whee wrote:I've talked to Craig before about making me a prop for a different plane but on this one I want to stay with a CS prop.

I agree with and understand what MTV and Scolopax are saying. Here is where I am at: I won't put a hartzell on it and I have yet to find a Mac prop that is approved for an undampened O360. Both to prop shop that overhauled this prop and the engine builder were not concerned about using a C214 on a undampened O360. I personally am undecided at the moment but I know that this point if I change props the only two options I'd consider is an MTV-15 or a 80" Whirlwind.

Not sure how many but I know there is a fair number of guys running this engine/prop combo but almost all are much shorter length so not comparable.

Does Whirlwind use a MacCauley hub?? (edit - checked it - no, they make their own)
They do some really nice blades which I have heard great things about. I'd have their 210 if I had my time again.
Want to buy my 82" Mac??

mountainmatt wrote:Cool calc from P.Ponk on blade length and tip speed: http://www.pponk.com/HTML%20PAGES/propcalc.html

"To produce maximum thrust at full power your tip speed should fall between .88 and .92 mach."

Given it a try for your plane? That calculator suggests a pretty massive prop, it may develop maximum thrust but everyone in a 5 mile radius is going to know you're taking off.