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SHIPCHIEF

Well Known Member
I've decided to upgrade the propeller on the RV-4 from the Sensenich aluminum unit (with 2600 RPM red line) to the new Sensenich Composite Adjustable Pitch propeller.
The old style 12" spinner is not offered for the prop, just the 13" spinner, which I ordered. The 4" spacer is not offered either. The spacer is said to be available from Saber Engineering, so I'll be calling them tomorrow.
My question is: will 1/2" increased radius on the spinner be an issue, besides cosmetics? :confused:
 
Good Call...

SHIPCHIEF said:
My question is: will 1/2" increased radius on the spinner be an issue, besides cosmetics? :confused:
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Scott,

Not a huge deal and won't affect anything aerodynamic. However, you won't like it when the rest of the airplane looks symmetrical. Easy fix, order a 12" spinner from Aircraft spruce or Van's and cut to fit, or put a WTB 12" spinner in the classifieds. The new sensy prop should fit inside a standard spinner (I helped install one on a Nine), if not go with a slightly longer one from AS. You won't regret it.
Also, you will love the Saber extension, high quality product. The best part about the change is the new prop, great improvement in both weight, technology and smoothness/lack of harmonics ridiculous rpm restrictions. Win Win :)

V/R
Smokey
 
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As Smokyray says, a regular unfinished 12" spinner kit should be able to be cut to fit this prop just fine. The blade roots are round, more like a CS prop's blades, and don't require nearly as big of an opening in the sides of the spinner. The only things weird about how a spinner fits with this prop, are that there are two extra steel dowel pins that stick out from the spacer thru the rear spinner bulkhead and into the prop hub, that normal props don't have, thus you'll have to drill those two extra holes into the rear bulkhead of a fresh spinner kit. Also, the front bulkhead fastens onto the front of the Sensenich hub with just two #10 screws, so you'll have to be a little creative in how you're going to fit and attach a front bulkhead if you use one at all.

Note: Those two extra dowel pins that engage the hub makes the special spacer from Saber a requirement if you need a 4" spacer instead of the standard 2.25" spacer that comes with the full prop kit from Sensenich. Ordinary prop spacers don't have these two pins, and they're a requirement for the Sensenich hub. Also, many spacers meant for wood props have drive lug extensions on all 6 bolt holes built into them, or steel ones pressed in, to engage the holes in the back of a wood prop. My original spacer had these, and there's no recesses in the new prop's hub to accommodate them, hence the two dowel pins 180 degrees apart, in between two bolt holes to give a positive rotational lockup between the spacer and the prop hub itself.

You're going to like this prop a lot.

I'm loving my new prop. It's very smooth. Total weight difference was that the entire assembly added 3 lbs over my old Aymar-Demuth and all its mounting hardware and spinner, and I need more weight up front anyway. It performed beautiful on the trip from Texas to Oshkosh and back. I'm able to hit the full 2700 rpm at cruise altitude at WOT, plus now have 2300 static rpms and a much more stronger and solid takeoff and initial climb... currently using the #5 pitch pin setting. Top speed at cruising altitudes is still 195-200 mph TAS (195 with full tanks, loaded to max gross, it creeps up to ~200 mph as the fuel burns down to below half tanks and the plane gets lighter and the CG shifts more aft) exactly the same top cruise speeds I got with the old Aymar-Demuth wood prop.
 
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You know what they say... buy once, cry once! :p

My credit card account is still crying in agony, and will be for quite some time to go.

I really wasn't in a position to spend this much $ on a prop right now either, but I needed a new prop fast, it was one of a few alternate choices with quick delivery, so I did it anyway.

It was also the most expensive of those choices too... literally double what I could've gotten a really nice brand new wood prop for (which would have been perfectly fine for 95+% of my flying), but the allure of the high-tech carbon fiber blades and being ground adjustable with the easy to use pitch pins were factors that were too irresistible. :cool:
 
On the price, "I feel your pain" :rolleyes:
I've already ordered the 13" spinner with the prop, so Marilyn will be flying behind it initially.
I just talked to Sam at Saber Manufacturing for the 4" spacer and the bolts, now I wait for the bank account to recover, then maybe I'll start collecting 12" spinner parts....But my RV-8 is next in line for my attention.
 
SHIPCHIEF said:
On the price, "I feel your pain" :rolleyes:
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Just keep telling yourself it's less than half the cost of a CS prop conversion :D
That's what I'm doing. The Sensy really is an excellent prop. The 13" carbon fiber spinner will work just fine on the older RV-4, it just won't look as pretty against an older 12" cowl.

BTW, on a -4, I'd start with the #5 pitch pin despite that the install manuall says start with #4, even if you've only got 150hp. If you've got a 160hp O-320, especially on a lightweight -4 then you might even want to try the #6 pitch pin. The #4 pitch pin was very much a "climb" prop setting for my 1016 lb RV-6 (gave me 2400 rpm static).
 
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Considering Sensenich composite prop

My RV-6 has the short cowl, a wooden Sensenich prop with a 4 inch extension, and a dynamic balancer that weighs about 14 pounds (can't remember the brand).
Two questions:

If the CG works out, would it be beneficial to keep the dynamic balancer installed?

Would the existing 4 inch spacer work for the new prop?
 
Chasbo said:
My RV-6 has the short cowl, a wooden Sensenich prop with a 4 inch extension, and a dynamic balancer that weighs about 14 pounds (can't remember the brand).
Two questions:

If the CG works out, would it be beneficial to keep the dynamic balancer installed?

Would the existing 4 inch spacer work for the new prop?
Click to expand...

Keep the balance ring, an RV-6 with O-320 needs the weight up front. I kept my Landoll inertia ring (11 lbs). Mark Landoll made both harmonic balancers, and plain steel flywheel rings... he retired and went out of business a year or two ago.

Your existing spacer for a wood prop will not work with the Sensenich ground adjustable prop. The hub for this prop has two extra holes in it for the special stainless steel dowel pins to fit into it from the spacer instead of having recesses counter-sunk into it for the lugs/prop bushings to engage into like a wood prop or normal aluminum prop does. Saber Manufacturing makes a special 4" spacer that you'd need to substitute in place of the 2.25" spacer normally supplied with this prop. You'd need to order the prop without the normal spacer and bolts, and buy the special 4" spacer and bolt kit instead, I think you have to order those directly from Saber. If you want a black with red tips prop, you can get it from Vans. If you want other colors (mine is white with red tips) it's probably best just to order direct from Sensenich themselves. That's what I did.
 
Just a follow up:
The spinner arrived yesterday, the prop today. Sensenich had a production delay, so it took about 20 days longer than anticipated.
I just got home from work about an hour and a half ago. I read the instructions from Saber, and Sensenich while I ate my dinner, then got to work. The pieces were all there, and they all fit. Marilyn and I assembled it on the kitchen counter, and set the pitch with pin #5. That took about a half an hour, reading the instructions and going slow.
I'm starting my 'days off' so tomorrow morning, out to the airport we go!
 
You'll also find that the 13" spinner doesn't look bad at all on a 12" nosed older RV-4.

My hangar mate just bought an older RV-4 and put his Whirlwind 200GA composite ground adjustable prop with 4" spacer and 13" spinner on it. His spinner looks to be manufactured by the exact same subcontractor as the spinners for the Sensenich composite GA props. His has the same exact same style of hand-written part number markings and orange and green stripes on the rear bulkhead as mine does. In fact the only real difference I could tell between his spinner kit and mine is the way the front bulkhead attaches to the front half of his prop hub. He's got 4 screw holes in his as opposed to only 2 for the Sensenich.

You're going to love this prop. It's a winner IMHO.
 
Marilyn & I went to the airport and spent the afternoon assembling the Sensenich carbon fiber adjustable pitch prop onto her RV-4. Everything went great. Pre-assembling it on the kitchen counter paid off.
The tracking was nearly perfect, the full power test went fine. I set the blades with pitch tool #5, and the 160 HP Lycoming indicated 2200 RPM full power static. Temp 26 C, Altitude 466 ft MSL. Full Rich.
I ordered the prop in -4 which is 68" diameter, the RV-4 has short gear. Sensenich must have built the prop shorter vs cutting back the tip, it still has the full scimitar tip shape.
 
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Marilyn & I went to the airport and spent the afternoon assembling the Sensenich carbon fiber adjustable pitch prop onto her RV-4. Everything went great. Pre-assembling it on the kitchen counter paid off.
The tracking was nearly perfect, the full power test went fine. I set the blades with pitch tool #5, and the 160 HP Lycoming indicated 2200 RPM full power static. Temp 26 C, Altitude 466 ft MSL. Full Rich.
I ordered the prop in -4 which is 68" diameter, the RV-4 has short gear. They must have built it shorter vs cutting back the tip, it still has the full scimitar tip shape.
 
Can't wait to hear the flight report :D

BTW, my hangar mate's WW prop is 72" and he's also got the short gear on his RV-4. He lifted the tail up with the prop vertical and even with the tail held very high up in the air, I still had a couple fingers clearance between the tip and the hangar floor. If you get it nosed over that far, you're already in the process of wrecking the plane and a prop strike is the least of your worries.
 
I selected 68" diameter because (I believe) that's the original recommendation from VANs. Sensenich offers reduced diameter to 68, so I tried it.
My son has a 68 diameter Ted Hendrixson on his 160 HP RV-4, it's awesome. I was also thinking about the late Paul Lipps, and his calculations on tip drag re: the longer the prop blade, the greater torque tip drag imposes on the engine. I suspect some take off thrust will be lost in exchange for some improved top end speed?
Further, If an RV-4 tail is high enough to snag the prop, it might also be descending, like after a bounce. That would include squat on the gear. RV-4s have fairly soft gear.
So we'll try it out and get back to the group.
 
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