Rick6a said:
The "facts" according to whom? As I stated in a previous post, I can easily cross midfield at 180 MPH in my FP equipped fast, slippery steed and easily slow down to Vfe before base leg...and rarely need to slip either. You did not believe when I stated it then and I doubt you believe it now. No matter to me. So believe what you will Larry, and let us just stick with...the "facts." Less airspeed on top end you assert? Horseradish.
Click to expand...

You're correct! I still don't believe it, nor do any of the C/S pilot's I know,.... that have read this thread. :D

P.S. --- I agree about the 90 pitch & 2750 rpm thoughts of the other poster.
Means nothing, as it certainly wouldn't be a practical climb prop unless the engine is of high horse power. In fact, we all know that a fixed pitch prop that is purely optomized for speed, will beat a C/S. It will just do everything else, poorly.

L.Adamson
 
Radomir said:
...-- it's kinda hard to spin up a 90" pitch sensenich to 2730 on 180hp...
Click to expand...
I believe the speed numbers. It was the higher RPM on the Sensenich that most likely accounted for the higher speed. The 90 has to be a misprint. Maybe an 80.

I have flown with plenty of constant speed equipped RVs and have never noticed one that was faster in level flight than my fixed pitch equipped airplane.
 
n5lp said:
I believe the speed numbers. It was the higher RPM on the Sensenich that most likely accounted for the higher speed. The 90 has to be a misprint. Maybe an 80.
Click to expand...

When I first got my 8 it had a Prince prop that was a 92 inch pitch. Took off like a pig and cruised like a falcon.
 
N941WR said:
Tony,

There is no problem flying an RV with a FP prop. The CS prop does give you some more options but there are a bunch of RV?s flying with FP props w/o any problem.

Check out Dan C's W&B page, http://rvproject.com/wab/.

Look at the empty weight vs gross weight and add that to your decision making tree. I also suggest you do a search for fixed pitch prop threads. There is a lot of good info out there (once you get past all the ?You must have a CS prop? comments) on speeds, ROC, etc.
Click to expand...


I will, thank you.
 
With 500 hrs in an RV4 with Fixed Pitch I recommend this route. I did fly in a 4 ship with Dave Domier as lead and Bill Collette on his wing and me as #3 and Olie Olsen in an RV3 as #4. In descent Dave pulled power back and suddenly we were 2 2ship formations. Finally the IAC mag says prop overhaul at 500 hours on constant speed and time unlimited on wood props when doing hard core aerobatics. Roger Moore
 
The C/S can be pulled back slowing rpm and saving a bit of fuel in cruise. I owned a FP RV6 and could kick it into a slip to put on the brakes but my passengers didn't appreciate it much.
Although the RV8 200 horse C/S Hartzell does have a cost and weight penalty I prefer it to the performance compromise the fixed pitch had.

It is apples and oranges, to each his own.
 
Wasn't the RV8 designed for the heavier 200hp angle valve engine anyway? I can see building an RV3 or RV4 with a lightweight compy or wood prop, but if one wants a fast cruise metal prop, it seems that the weight penalty is not as great as I had thought for CS. Now it just comes down to a cost/complexity argument.
 
wickedsprint said:
Wasn't the RV8 designed for the heavier 200hp angle valve engine anyway? I can see building an RV3 or RV4 with a lightweight compy or wood prop, but if one wants a fast cruise metal prop, it seems that the weight penalty is not as great as I had thought for CS. Now it just comes down to a cost/complexity argument.
Click to expand...

Based upon my experience and not merely driven by uninformed opinion or perception designed to defend a particular point of view, I really believe the weight argument can sometimes be vastly overblown by some ardent F/P supporters firmly rooted within that camp. The following are my real world numbers:

RV-6A equipped with 0-320 and F/P prop: 1099 lbs. Empty
RV-8 equipped with IO-360 and C/S prop: 1106 lbs. Empty

Both planes are comparably equipped, including leather seats. In the end, we are talking about 7 pounds difference here. SEVEN pounds. That's the approximate weight difference between a Concord (22 lbs.) and an Odyssey (15 lbs.) battery. To me, a far more compelling case can be made for the F/P argument when limiting the discussion to its far more dramatic cost advantage over a C/S choice.
 
Compare the props, not the airplanes

Rick6a said:
........
RV-6A equipped with 0-320 and F/P prop: 1099 lbs. Empty
RV-8 equipped with IO-360 and C/S prop: 1106 lbs. Empty

Both planes are comparably equipped, including leather seats. In the end, we are talking about 7 pounds difference here. SEVEN pounds. That's the approximate weight difference between a Concord (22 lbs.) and an Odyssey (15 lbs.) battery. To me, a far more compelling case can be made for the F/P argument when limiting the discussion to its far more dramatic cost advantage over a C/S choice.
Click to expand...

From another thread I determined that my Catto weighs about 18 lbs. That's the bar, not airplane empty weight. I think it would cost $2150 if I bought it today.

My recollection is that CS setups weigh more like 60 lbs. Someone correct that number if its wrong. Put the price next to the weight because I also recall there are some unusually light CS setup that cost major bucks.

~40 lbs is a huge difference.

I'm not arguing that everyone should use FP props. They have specific advantages and disadvantages. Weight and cost is an advantage to FP.

I am arguing that anyone who is building should have a very clear reasons for choosing a heavier and more expensive prop. That could be based on the technical merits, or it could be that they just subjectively prefer CS. That's all good because this is about making the owner / builder happy.

Making the choice based on popularity? Not so good, unless following the herd makes the owner/builder happy.

In any event, I doubt anyone is going to dislike their RV because they made a suboptimal prop choice. In the end, this is not about comparing fuel burns, climb rates, takeoff distance, glide distance, useful loads, or cost. IMO the real figure of merit is how satisfied the owner/builder is with the overall airplane. Except in a few cases of specific mission profiles, I doubt the FP/CS choice would swing the overall satisfaction more than a few % either way.
 
Steve Brown said:
In any event, I doubt anyone is going to dislike their RV because they made a suboptimal prop choice.
Click to expand...

I have not run into pilot/builders who have come to dislike their RV's because of not fitting a C/S prop to start with. But I've sure run into a number of them who wished they had installed a C/S after seeing what it's capable of......and what their F/P won't do..

L.Adamson --- RV6A/ Lyc 0360/ Hartzell CS
 
Looks like there is now a composite version of the 7497 BA on Van's for ~10k, supposedly like 18lbs lighter than the alum.

C2YR-1N/N7605-4
 
Don't Believe What?

L.Adamson said:
You're correct! I still don't believe it, nor do any of the C/S pilot's I know,.... that have read this thread. :D

.

L.Adamson
Click to expand...

Larry

It sounds as though you think Rick is being less than truthful about observations made in his own aircraft. Unless I have misunderstood what you don't believe. I can tell you I witnessed exactly what Rick described in his fixed pitch RV 6A!!! Rick and I entered a midfield downwind at 180 MPH and easily slowed to VFE speed by base leg. No slip was required and in fact power was required on final. This was a normal traffic pattern not an extended final. If money was no object I would build with a constant speed prop. I am building an RV 8 on a very tight budget and have no doubt I will enjoy my fixed pitch prop! I have flown many fixed pitch,constant speed,turbo props,and jets and all are fun to fly. I would rather fly than walk no matter what prop I have! ;)

Kevin
 
Wow!

...as a new guy on here and also a new pilot, I am amazed at the heated discussion this topic generates. :) I have enjoyed reading it though. FWIW, I plan to go C/S...but it really has nothing to do with any kind of 'cost-benefit' analysis...but c'mon, we're pilots...flying doesnt make financial sense, we're not doing this b/c it is a good use of money. On top of the fact, I plan to pull out all the stops when it comes to building my 'dream'. but thats just me...
 
Yep

If you think this is lively. Just ask these guys whether on not you should prime the inside of the airplane (and how!). :D:eek::D:rolleyes:
 
RV7Ron said:
...as a new guy on here and also a new pilot, I am amazed at the heated discussion this topic generates. :) I have enjoyed reading it though. FWIW, I plan to go C/S...but it really has nothing to do with any kind of 'cost-benefit' analysis...but c'mon, we're pilots...flying doesnt make financial sense, we're not doing this b/c it is a good use of money. On top of the fact, I plan to pull out all the stops when it comes to building my 'dream'. but thats just me...
Click to expand...


Cost-benefit analysis, mmmmm... ok. I gave up on snowmobiles, motorcycles, and just about anything else I was doing as a past time after learning to fly. Nothing else compares. So now all I have to do is fly. I spend all my extra money on flying. That's my story.
 
allbee said:
Cost-benefit analysis, mmmmm... ok. I gave up on snowmobiles, motorcycles, and just about anything else I was doing as a past time after learning to fly. Nothing else compares. So now all I have to do is fly. I spend all my extra money on flying. That's my story.
Click to expand...

Ok, let me rephrase...it makes no sense to anyone who doesnt fly to spend this kind of money on a hobby. I took a first timer up for a flight the other day in a DA20, he loved it and asked me how much a plane like that goes for new. I said about ~$175,000. He said, I could have a new Lamborgini for that! I said, yup maybe so...but it wouldnt be nearly as much fun! As for me, I fly, and it is worth every penny that I sink into it...up to and including a C/S prop! :) Sorry to get off topic a bit
 
Kevin Taylor said:
Larry

It sounds as though you think Rick is being less than truthful about observations made in his own aircraft. Unless I have misunderstood what you don't believe. I can tell you I witnessed exactly what Rick described in his fixed pitch RV 6A!!! Rick and I entered a midfield downwind at 180 MPH and easily slowed to VFE speed by base leg. No slip was required and in fact power was required on final. This was a normal traffic pattern not an extended final. If money was no object I would build with a constant speed prop. I am building an RV 8 on a very tight budget and have no doubt I will enjoy my fixed pitch prop! I have flown many fixed pitch,constant speed,turbo props,and jets and all are fun to fly. I would rather fly than walk no matter what prop I have! ;)
Click to expand...

I don't know what the "normal" traffic pattern is for you guys, but the fact remains.................a C/S prop will slow an aircraft down far faster than an F/P is capable of; unless of course the F/P is much more of a climb prop, or the airplane is plain draggy. As some would say, it's "simple physics"; but then I hate that term.

The argument here, is that Rick's plane can do what a C/S does under the same conditions. Or at least I feel that's what's being claimed. The only way this is possible is pitch or drag as I described above. I'd hate to think that Rick's plane is just plain draggy! :D

L.Adamson --- RV6A
 
Two sides to the same coin

L.Adamson said:
......
The argument here, is that Rick's plane can do what a C/S does under the same conditions. Or at least I feel that's what's being claimed. The only way this is possible is pitch or drag as I described above. I'd hate to think that Rick's plane is just plain draggy! :D

L.Adamson --- RV6A
Click to expand...

It is easier to slow with a CS prop, but the glide range is longer with a FP prop.

Because of the much wider speed range of an RV, this effect is much more noticeable than in the case of a C172 (for example).

Every time I fly I have to manage my speed a little more carefully entering the pattern than if I had a CS.

On the other hand, if the motor quits I'll have about 30% longer glide range.

Is it worth it? Depends on exactly where I am when my motor quits.

In any case, this has not (and will not) kept me from flying airplanes with CS prop. Its just one of the several trade offs to consider when making the build choice.
 
L.Adamson said:
I don't know what the "normal" traffic pattern is for you guys, but the fact remains.................a C/S prop will slow an aircraft down far faster than an F/P is capable of; unless of course the F/P is much more of a climb prop, or the airplane is plain draggy. As some would say, it's "simple physics"; but then I hate that term.

The argument here, is that Rick's plane can do what a C/S does under the same conditions. Or at least I feel that's what's being claimed. The only way this is possible is pitch or drag as I described above. I'd hate to think that Rick's plane is just plain draggy! :D

L.Adamson --- RV6A
Click to expand...

I don't think anyone here is arguing that a fixed pitch prop will slow down an aircraft as fast as a constant speed prop. Clearly it will not! Nobody claimed a fixed pitch prop could perform in every flight regime as well as a constant speed prop. Everyone has a right to their opinion and what is acceptable performance for the money/weight invested in a prop!!!! If your that concerned with drag I'm surprised you have a nosewheel! ;)

Kevin
RV 8 Saving money for a fixed pitch prop. :D
 
Kevin Taylor said:
If your that concerned with drag I'm surprised you have a nosewheel! ;)
Click to expand...

Nosewheels are practical. If I wanted to be macho, I'd ride a Harley to the local bar... :)

L.Adamson

edit...........P/S, I'd go taildragger for an RV8 too. They look better, that way. It could sure use a C/S though. It's the weight and balance thing. Save more for a C/S!
 
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Maybe...but maybe not.

Steve Brown said:
It is easier to slow with a CS prop, but the glide range is longer with a FP prop..... if the motor quits I'll have about 30% longer glide range.
Click to expand...

I have heard that said before but I suspect it may not be true. I would not be surprised if in fact you could glide further with a CS prop.;)

If the engine quits and the prop stops spinning I doubt there would be any meaningful difference in the glide range between a CS and FP prop. Both should have very good glide range with the prop stopped.

If on the other hand (and this is the more common scenario) the prop keeps spinning (driven by the air) then there will always be sufficient oil pressure generated by the engine to drive the prop governor. In other words the pilot can pull the prop controller right out and the prop will go to full coarse. That will feel like you just released the brakes. At full coarse the CS prop may in fact have a coarser pitch than a FP cruise prop. If it does it should present less drag and therefore the aircraft should glide further (all other things being equal).
 
Captain Avgas said:
I have heard that said before but I suspect it may not be true. I would not be surprised if in fact you could glide further with a CS prop.;)

If on the other hand (and this is the more common scenario) the prop keeps spinning (driven by the air) then there will always be sufficient oil pressure generated by the engine to drive the prop governor. In other words the pilot can pull the prop controller right out and the prop will go to full coarse. That will feel like you just released the brakes. At full coarse the CS prop may in fact have a coarser pitch than a FP cruise prop. If it does it should present less drag and therefore the aircraft should glide further (all other things being equal).
Click to expand...

So then, your on final during an emergency landing and you have the prop at full coarse with oil pressure from the engine windmilling, you have the airspeed pegged plus a little for good luck, and just then the spinning motor is slow enough that the oil pressure drops off and the prop goes flat. You just lost that 10 knots that kept you in the air. How do you deal with this?
 
gasman said:
So then, your on final during an emergency landing and you have the prop at full coarse with oil pressure from the engine windmilling, you have the airspeed pegged plus a little for good luck, and just then the spinning motor is slow enough that the oil pressure drops off and the prop goes flat. You just lost that 10 knots that kept you in the air. How do you deal with this?
Click to expand...

From my experience I think you'll find that the windmilling prop will maintain enough engine oil pressure to make the prop governor effective right down to the stall. Slower than that obviously doesn't matter.

My advice to you (and other pilots) would be to test this out in your particular aircraft BEFORE you need to do an engine-out emergency landing.

Personally I have added the "Prop full coarse" as the last item on my engine out check list (in the event that the prop is still windmilling).

Believe me when I say that the difference in glide range between an engine out glide with a CS prop at cruise pitch compared with full coarse is REALLY dramatic. Kill your engine one day by leaning out to idle cut-off (at altitude) and try it out....it feels like you just jettisoned a drag parachute

There may be specific advantages to a FP prop (less cost, less maintenance, less weight) but the extra glide range argument is most likely a myth...if you understand that the prop controller is still functional if the prop is still windmilling. But the truth is that many pilots of CS aircraft don't realise that fact.
 
pierre smith said:
....since there may be a suitable field right under you:)

Regards,
Click to expand...

Hi there Pierre. It's good to hear again from the man that did the 250' engine-out turnback after take-off in his RV6A (and posted the video on Youtube) thus effectively killing off the great VansAirforce Turnback thread (stopped all the naysayers in their tracks !!!!):D

Of course as you and I both know once we have actually reached that "suitable field" we can always throw the prop to full fine if the fan is still windmilling to cut speed as required. Going suddenly from full coarse to full fine should just about put you through the windshield.:p
 
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I have a FP prop. If magically I could change it to a CS prop at no cost I would do it now. When you fly with other RVs and you have to have them throttle back so you can maintain their climb rate you will understand.

Always fly by yourself and in most cases the FP is just fine...but never as good as a CS prop. Fact.
 
N941WR said:
Funny, but I have never seen that happen with a FP prop.
Click to expand...

Oh come on! It turns out is was just a bad zerk. That could happen to anyone, even on a fixed pitch prop...
.
.
.
er, well not that.

But it's a small price (plus some money) to pay to actually be able to:
- climb
- slow down
- fly aerobatics
- have a plane that is in CG
- have a cool blue knob
- dozens of other things that fixed pitch planes can't

George

TOTALLY in jest :D
 
grjtucson said:
Oh come on! It turns out is was just a bad zerk. That could happen to anyone, even on a fixed pitch prop...
.
.
.
er, well not that.
Click to expand...
Now, that was funny!

grjtucson said:
But it's a small price (plus some money) to pay to actually be able to:
- have a cool blue knob
Click to expand...
And that was so true. Probably the only realy justification I have read to date.

L.Adamson said:
Of course. I see most of the threads! At least changing a zerk fitting will be easier than removing the spinner, loosening six bolts, to change the prop pitch each time.... :D

L.Adamson
Click to expand...
I think that is probably a good tradeoff, for me at least. If I could add a CS prop to my engine, which I can't, I would lose close to 40 - 60 lbs of useful load. That is not a compromise I want to make.

The Sensenich adjustable prop sounds like a really good tradeoff for my engine/airframe. Still, leaving it set to cruise will still probably leave me with a max climb rate of oh, around 1400 FPM, maybe more. While increasing my cruise 10 to 15 MPH, I hope.

To me, having a high useful load is more important than extracting every last ounce of climb performance out of my plane. In my current case, my prop is a climb pitch, which goes up like crazy but limits my cruise to 165 MPH

With a ground adjustable prop I can tune its pitch for the conditions I find myself in. Total time to change pitch, oh about 10 minutes, maybe less.

All in all, adding that GAP would reduce my useful load by 7 lbs. So, let's see, that will leave me with a 753 lb useful load I can live with that and that is while staying with Van's GW of 1750.
 
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N941WR said:
I think that is probably a good tradeoff, for me at least. If I could add a CS prop to my engine, which I can't, I would lose close to 40 - 60 lbs of useful load. That is not a compromise I want to make.
Click to expand...
Are you comparing the heaviest CS alum prop to your light FP Catto?

I think the BA Hartzel in composite is 40lbs right? That's only a 20 lb diff for a serious performance increase

What's the weight diff for fp metal cs CS metal?? Apples to apples/
 
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Just to be picky!

wickedsprint said:
I think the BA Hartzel in composite is 40lbs right? That's only a 20 lb diff for a serious performance increase
What's the weight diff for fp metal cs CS metal?? Apples to apples/
Click to expand...
If we're going for "apples to apples" you need to throw in the weight of the governor and extra cable.
 
I have a metal FP (Sensenich) and if I were to upgrade to Whirlwind, I'd lose a pound or two.. yes, even if I include weight of governor and cable... worst case, I'd break even weight-wise...

Can we now put this weight discussion to rest once and for all??
 
Van on Constant vs Fixed

I noticed the following quote on the Hartzell website that seemed interesting to me:

"Any time you?re talking about performance you?re talking about a constant-speed prop. The constant-speed Hartzell prop dramatically increases the take-off and climb performance of the RVs ? and provides optimum cruise as well. You can?t get both in a fixed-pitch prop."

Dick Van Grunsven
President
Vans Aircraft Inc.
 
Neither Choice is Bad

Funny how everyone gets so exercised about this subject.

I am NOT an expert. So take my thoughts on the matter with a grain of salt.

Arguing the weight difference between LIKE-MATERIALS propeller installations on the RV-8 is almost meaningless. For instance, the weight difference between an aluminum Fixed Pitch and an aluminum Constant Speed installation is minimal when you consider that with equipment (FP spacer or CS drive), you are talking about a 15 pound difference for the two most common selections: The excellent FP Sensi is about 40 lbs installed. The Hartzell CS is about 55-58 lbs. The RV8 ain't going to care much either way. If those 15 to 18 pounds are that critical, you either crammed way too much into that bird or you need to skip eating pizza for a few weeks, Porky.

Performance with EITHER type of prop is EXCEPTIONAL. So if you are a new builder/buyer wondering which to get, it has more to do with your bank account than some VAST performance difference or weight management regime. The CS definitely has a wider range of performance advantages...but is not a VAST range of differences. Its it worth the $$$. Heck yeah if you can afford it. H*** no if you can't. More on this later.

The CS will definitely provide a wider range of performance choices in all categories except maybe top speed. BUT the FP will provide PLENTY of performance on a reduced budget and you only have to choose which way you want to compromise that performance...but the compromise still kicks the snot out of anything you have flown before unless you fly jets or WWII fighters. We ain't talking about Luscombes and Cubs and C-140s. ANY RV on ANY Prop is silly fast, silly light, and silly fun to fly. PERIOD.

The be totally redundant here: The main difference other than price, is that the CS allows you to tailor the prop to your needs at nearly every rpm & power setting. You do not have to compromise as you do with a FP.

Sometimes this is a huge advantage.

Sometimes it don't mean squat.

Sometimes that "compromise" is compromising with the wife to keep married when she sees the extra $$$ you just spent on the CS.


All I can say on this is that with a CS you will not have to play with re-pitching the FP over and over until you get the performance you want or expect at (cruise, climb, pattern, redline - pick one). The CS really does allow a level of control you do not get with a FP. But the FP isn't a BAD choice either. Anyone saying otherwise is silly. So forgetting the last 14 or so pages...really, you can not go wrong EITHER WAY.

Other thoughts...

Fighting over 5 to 10 knots of top speed is irrelevant in the real world. Who gives a crap? 90% of your flying will be at cruise or economy cruise. No one flies at max power in choppy weather, or while locally sight seeing. Generally the speed demon flyers are after a trophy, or want bragging rights, or like being beat to death by turbulance, or like seeing 15 GPH on the flow meter instead of 8.5. So chasing an ever increasing top speed in an d of itself is a fools game unless you plan on racing. In which case there is no help for you. lol. Been there. Went broke. loved it.

SO:

Consider how you will fly the plane or think you will, and make the choice based on that. If you got the cash, you really will love the CS prop. Landings are definitely shorter, cruise may or may not be more economical at a given speed/rpm/power setting (in that you can tailor it to what you want to acheive at the moment) and climb may be faster. It seems to me that pattern speed "may" be easier to deal with. I know several guys with FS that have to retard throttle a lot sooner than I do just to slow down to pattern but that could just be a matter of style. Point is CS allows you to CHOOSE.

BUT...having flowing behind a FP for 30 years, I'd never have known what I was missing other than the normal grumbling about what pitch to stick with. Had I hung a FP on the RV-8 last summer, I'd still be thinking Holy-Ho-Chi-Min-Batman! This sucker rocks! And thats my point. All this rambling comes down to this. Either way, the plane is going to amaze you. Anything after that is just icing on the cake. Do I think the CS is a better over all choice, especially after flying all manner of aircraft for 30 years without one? YES. A Hands Down Resounding, YES, IDUBIDEBLY, SPARKY, IT IS.

BUT living with the compromises you make when choosing a FP is not like the difference between dating a Victoria Secrets Super Model and Rosan Barr after a month long binge of cheese cake and pizza. Its more like the VS model and, say, a Playboy Bunny. Some like em skinny, some healthier...but if you complain about either, you are a raving idiot!
 
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F/P for me

new to forum...complete wings on slow build RV8.

Going FP wood all the way. I love the way a wood prop looks, I love that it is cheap and if I don't like it I can try a different one. I also like that it is dirt simple.

I've been fortunate to fly a bunch of really cool planes but never have I flown any plane as smooth and comfortable as those behind a good wood prop.

I sold my plans built BD-4 to finance this RV8 project saving the engine, prop, and instruments for the RV8. So to that end any of you die hard C/S supporters want my prop (Hartzel Hub: HC-C2YK-1BF Blades: F7666A-2 74" ) 600 hrs TT... $4000 OBO please let me know.

Ken
 
CS / FP Looks Like A Draw

No clear winner here. Gain here loose some there. Get what turns you on and enjoy a great plane. I had no choice. It came with a FP sesi 85" P.
 
prop confusion..

OK, I'm confused about this "slowing down in the pattern" talk.

Disclaimer: I'm a student pilot (55 hrs in a DA20), so what do I know?

The DA20 is a slick little plane (flies better IMHO than the C150 I started out with). It has a serious cruise prop in that level cruise RPM is never more than about 2500.

Taking off, I'm lucky to see 2100 RPM.

My instructor and I take off with a DA of sometimes more than 8k ft. No problem that I can see except for longer take off rolls. Yeah, climbs a bit anemic - maybe 500 fpm.

As far as slowing down, I chop the throttle abeam the numbers to 1300, drop half flaps and trim up the nose to 70 kts. The speed reduction happens quickly near as I can tell. By the time I'm on final with full flaps I'm doing maybe 60 kt or a little less.

Am I missing something? Seems like when the nose goes up the speed goes down (quickly) with the power off. Do RV's not do this?

Maybe some of you more experienced pilots can explain why I have no trouble slowing down.:eek:

Dave
-9A finish kit planning on a FP prop
 
turbo said:
No clear winner here. Gain here loose some there. Get what turns you on and enjoy a great plane. I had no choice. It came with a FP sesi 85" P.
Click to expand...

Out here in the wild & mountainous west.... :)

We takeoff & then head right up over the mountains. An F/P on an R/V can't do that...

Then we head down the mountain pass and through the canyon at a 2000 fpm decsent & right into the airport pattern. An F/P on an R/V can't do that either.... :D

L.Adamson --- RV6A Hartzell C/S
 
Daver,

The RV you are building has a cruise speed significantly higher than the plane you are training in. Like more than double its flap extension speed.

With a FP RV if you pulled the power abeam the numbers, you would have to make a three to five mile pattern before the plane would slow down enough to lower the flaps.

With a CS prop, when you pull the power and bring the prop back, the blades present a flat face to the direction of flight, which works like an airbrake and slows the plane down fairly fast.
 
props

Thanks Bill!

Yeah, the DA20 only cruises about 125 kts. I think my -9A will be faster.

I usually slow the Diamond down alittle before I enter the pattern because there's usually a Cessna or a Piper ahead of me doing 100 kts or less.

So is slowing down the -9 with a FP prop a big problem?

I hope not:eek:

Dave
 
Daver said:
...So is slowing down the -9 with a FP prop a big problem?

I hope not:eek:

Dave
Click to expand...

Not at all. You just have to throttle back a few miles out. You can't drop the flaps until you get to 90 mph and once I hit that number I put in all the flaps abeam the numbers and trim it for 65 mph solo / 70 mph with two on board and fly the entire pattern at that speed and full flaps.

There are some tricks to, you can do a high speed "brake" (step turn) which bleeds off speed fast. Or, you can simply cross control the plane, sticking the tail out. This causes some drag and will help you slow it down.

It is best just to plan ahead and slow down a few miles out. Some of the CS guys will blast into the pattern and use the prop to slow them down. That works but because of those 100 mph Cessnas I like to enter the patern going slow so I don't run anyone over.

PS. You will figure out what works for you when you get to that point. Make sure you are good with slips. They are really easy in the -9, just don't go below 70 mph. That will give you a good safety margin.
 
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slowing down

Thanks again Bill!

This forum has been a great asset for newbies like me.

I just need to take my check check ride & finish the plane!

Dave
-9A finish kit
 
Energy Management

We expend a lot of energy in the climb segment of the flight. I have always been interested in how much of that energy can be reclaimed in the descent. Even in a Cessna 172 I have found it pretty exhilarating throttling back a bit and starting a long descent many 10s of miles out. There is increased airspeed and decreased fuel consumption. You don't get it all back, but it is fun to see how much you can get back.

This is one of the charms of glider flight. It is all energy management. In a contest flight this is the whole deal, sort of. There are compromises in the final climb. If you climb too high before the final glide you will need to fly faster than the optimum speed to reach the finish line at the proper altitude and you will be throwing energy away. If you don't climb high enough, maybe you will not make the finish line, and that is not good. Most people choose to climb a bit too high and throw some energy away, but that energy is pretty much from vertical air currents that you don't have to directly pay for and that aren't from burning carbon fuels.

Now in our RVs all the energy is from the carbon fuels so I am even less interested in wasting it. The constant speed prop is a good speed brake, but if we plan our flight to use that capability we are flushing energy right down the old toilet. I think it is fun to fly so as to not need to needlessly destroy energy! It may take a bit more planning, but it is very possible to not need the braking capability of spoilers or speed brakes or constant speed props and it is more efficient.

Oh, I don't drive a Prius, but I do get irritated when hangar owners at my local airport leave the lights on 24/7 just because they aren't directly billed for the energy.
 
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This whole discussion among you RV guys just cracks me up! The RV-8 has a usefull speed range from 60 -200+ knots. How in the world can you expect to extract maximum HP from the engine at any speed in that range without a C/S prop? You can't... It is impossible. It's like driving a car with only one gear... It's possible to make it move, but the overall performance is extremely limited. Sure, Cubs get along fine with a fixed pitch prop, but they ony have one speed for climb, cruise and landing - 60 MPH; not too hard to match a prop for that!

Before buying the -8 that's in my hangar currently, my buddy looked at a bunch of potential RV's. I shot down every one with a fixed pitch prop, or we factored in the cost to "properly" equip the airplane with a C/S. It simply boggles the mind that someone would build an RV, then hamstring its takeoff and climb performance with a fixed prop.
 
200+ kts in an -8?

I had no idea:eek:

I don't think my 150 HP -9A will do near that....

All the -9 performance specs on Van's site are with a FP prop, no?

Dave
-9A finish kit
 
well boggle your mind cause I'm putting a FP wood prop on my -8 and can't wait! I even sold my Hartzel C/S from my BD-4 to help pay for other stuff. Why? Cause its MY plane and I WANT it that way. Nothing beats the smoothness of a good wood prop and they are inexpensive enough I can buy a whole bunch of different kinds for the price of a C/S. Plus its simple to fly. THe aircraft I fly during my day job is complicated enough..I want something that is fun, simple and affordable and looks really nice. To me thats a wood prop...I wouldn't put a C/S on my -8 if you gave me the top-o-line prop for FREE!!! Any questions?
 
wood prop

Ken,

A wood prop is exactly what I'm planning for my -9A also.

Van discusses the pros & cons of different props in the build manual which I've studied intently.

He also discusses the CS vs FP issues.

All in all, I've decided a wood cruise prop will work well for me.

Like I've heard from another poster on this forum "build the plane YOU want, not what others want" ......or something like that.

BTW, Van's specs show no difference in gross weight climb performance between the CS equipped -7 or -8 and the FP prop equipped -9 with the 160 HP engine.

Dave
-9A finish kit
 
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