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I need some help in making a decision

S

Smilin' Jack

Well Known Member
I know that I want an IO-360 but the delima is whether fixed pitch or CS.
I know the advantages shorter take off etc but is anyone out there running a Prince prop ( a fixed prop that changes flex in cruise) Bill Durham has one on his RV6 but what about on a 7. and the main question is in regard to CG and weight.
Is going with a fixed prop going to give me headaches in a rearward CG?
I want to stay in the forward half of the acro CG if possible and still be able to take 2-190 lbs folks up. Yes I have worked some of the numbers from the CG that folks have posted and to do this with an aircraft that weighs 1100 lbs I can only carry about 20 gallons on takeoff and assume I burn some by the time I climb up to 4 or 5 thousand feet.

With a fixed prop I lose about 22 lbs of forward weight. I am not to interested in taking off from 700 foot strips and most likely will never do that however I guess if you lose an engine and have to put it down after gliding there with the lost of oil pressure the prop is going to go to low rpm is that not correct? You'd want to pull the prop control back to help with the glide on an engine failure.

I am trying to do this on a budget and not get too carried away with the whole plane. I am not interested in flying instruments but would like to have the ability to get out of weather with the instrumentation on board safely. Can I put a C/S on later or do I have to redue the cowling if I am really interested in going with a C/S

so I need to hear from folks that have a fix pitch whether injected or not really does not matter. I am going to assume with the CS it is not a CG problem but a weight problem in being able to take someone with you and do some acrobatic flying. And with a Fixed Pitch you have a more rearward CG that could really restrict you. Maybe I am being to picky about all this stuff. But my wife said 2 folks doing loops and rolls or no airplane and were too far along with the project to quit now.


What do you think I appreciate it as I am getting ready to order the wings and I think I read that correctly I have to put a deposit on the fuselage too?
I really appreciate your input and thanks for reading this longer post.


Smilin' Jack
HS done
VS done
Putting rudder together for last time.
 
Last edited:
Smilin' Jack said:
so I need to hear from folks that have a fix pitch whether injected or not really does not matter. I am going to assume with the CS it is not a CG problem but a weight problem in being able to take someone with you and do some acrobatic flying. And with a Fixed Pitch you have a more rearward CG that could really restrict you. Maybe I am being to picky about all this stuff. But my wife said 2 folks doing loops and rolls or no airplane and were too far along with the project to quit now.


What do you think I appreciate it as I am getting ready to order the wings and I think I read that correctly I have to put a deposit on the fuselage too?
I really appreciate your input and thanks for reading this longer post.


Smilin' Jack
HS done
VS done
Putting rudder together for last time.
Click to expand...

RV-6, O-320 fixed pitch Sensenich, and the plane can be flown through out the entire loading envelope. Aft CG is only a problem when at gross (well, maybe a little over....) and low fuel. This will not be an issue with the heavy IO-360.

You do not have to place a deposit for the fuselage until you are ready to purchase it. If you are building at a rapid pace it might be a good idea to go ahead and order the fuse when you receive the wings so you won't have down time waiting for the fuse.
 
Yes,

I just got off the phone with Vans, Some how there is a statement on their web site now that you have to have a 25% deposit on the fuselage if you order the wings or vise versa. They are looking in to the pages and removing that statement. They have received a few phone calls about that.

Thanks for the input. With the RV6 and the lighter gross weight you have a problem all the time trying to carry 2 folks and do any acro stuff. It is basically a solo acro aircraft. That is why I went with the 7. But working the weight balance CG stuff for a light front end is the kicker. If I knew for sure that an IO360 swinging a Hartzel fix pitch prop would keep me off the aft CG limit at the ACRO weight limit of 1600 lbs... I will be all set... I just have to wait and see what folks say.

thanks again
Smilin' Jack
 
It's totally your call.

C/S props are nice but not necessary.

My RV-6, with O-320 and 3-blade Catto is limited to about 85 lbs. baggage with min fuel. That's never been a problem. IO-360 would help that.

And as far as density altitude, I've flown out of Flagstaff and even Leadville back when I had a Sensenich wood 2-blade. Take-offs with density altitude up to 13,500' with no problems.
 
About the Prince prop

Smilin' Jack said:
...
I know the advantages shorter take off etc but is anyone out there running a Prince prop ( a fixed prop that changes flex in cruise) Bill Durham has one on his RV6 but what about on a 7. and the main question is in regard to CG and weight.
Is going with a fixed prop going to give me headaches in a rearward CG?...
Click to expand...


My Prince P-Tip prop was about 14 pounds. Mine is a 7A. The aft CG is only a problem with very low fuel and full baggage and heavy passenger.

Catto and Prince both make, IMHO, excellent props. I have used both on my 7A. Lonnie's prop never needed balancing.

As for the flex, Lonnie is correct. It does it. The range of RPM's with the Catto is about 500. (2200 to 2700) With the Prince it was maybe 300. I did not study this, though; the Prince prop was pitched too finely for my airplane. The flexing pitch is a great idea but it does not necessarily get you the performance because there are other factors. Lonnie has some new designs available. Give him a call and discuss it with him.
 
Smilin' Jack said:
Yes,

I just got off the phone with Vans, Some how there is a statement on their web site now that you have to have a 25% deposit on the fuselage if you order the wings or vise versa. They are looking in to the pages and removing that statement. They have received a few phone calls about that.

Smilin' Jack
Click to expand...

Interesting.

Here is a quote from Vans' Kit Options page:

"You may now order a QuickBuild Wing Kit for the RV-7/7A, RV-8/8A, RV-9/9A or RV-10 and have your wings built to QuickBuild status while you work on your empennage or fuselage kit at home. We require that a standard fuselage kit order be placed in conjunction with the QB Wing order with at least a 25% deposit on both kits."
 
It is the money you spend once but you get to enjoy it for the rest of the life of the plane.
 
Smilin' Jack said:
I know that I want an IO-360 but the delima is whether fixed pitch or CS.
I know the advantages shorter take off etc but is anyone out there running a Prince prop ( a fixed prop that changes flex in cruise) Bill Durham has one on his RV6 but what about on a 7. and the main question is in regard to CG and weight.
Is going with a fixed prop going to give me headaches in a rearward CG?
I want to stay in the forward half of the acro CG if possible and still be able to take 2-190 lbs folks up. Yes I have worked some of the numbers from the CG that folks have posted and to do this with an aircraft that weighs 1100 lbs I can only carry about 20 gallons on takeoff and assume I burn some by the time I climb up to 4 or 5 thousand feet.

With a fixed prop I lose about 22 lbs of forward weight. I am not to interested in taking off from 700 foot strips and most likely will never do that however I guess if you lose an engine and have to put it down after gliding there with the lost of oil pressure the prop is going to go to low rpm is that not correct? You'd want to pull the prop control back to help with the glide on an engine failure.

I am trying to do this on a budget and not get too carried away with the whole plane. I am not interested in flying instruments but would like to have the ability to get out of weather with the instrumentation on board safely. Can I put a C/S on later or do I have to redue the cowling if I am really interested in going with a C/S

so I need to hear from folks that have a fix pitch whether injected or not really does not matter. I am going to assume with the CS it is not a CG problem but a weight problem in being able to take someone with you and do some acrobatic flying. And with a Fixed Pitch you have a more rearward CG that could really restrict you. Maybe I am being to picky about all this stuff. But my wife said 2 folks doing loops and rolls or no airplane and were too far along with the project to quit now.


What do you think I appreciate it as I am getting ready to order the wings and I think I read that correctly I have to put a deposit on the fuselage too?
I really appreciate your input and thanks for reading this longer post.


Smilin' Jack
HS done
VS done
Putting rudder together for last time.
Click to expand...

Hi Jack,

Sabre sells a 22 lb crush plate for the Catto application and it works very well with my 320 setup. Also, on the RV7/7A aircraft the engine mount is two inches longer (Forward) compared to the 360 mount... really makes for a sleek looking aircraft with the longer cowl. :) I love my Catto... smoooothhh! The same could be done with a 360 engine, don't know what the weight would be on the crush plate.
 
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There is no right answer. More nose weight does help with a couple of
200 pounders sitting in the seats. But after two RV's, and flying many
built by others, IMHO, the two options that turn a great airplane into a
greater one is the CS prop which allows you to extract all of the RV's
Total Performance and an autopilot which turns this sport plane into
a fabulous cross country machine. But you don't need either to have a
great airplane. The RV owners I know that started with FP and upgraded to CS were very happy with their decisions.

Good luck!
 
You have a beautiful aircraft Reiley

I guess there would be a difference in the tip up and slider on the cg also. I am just guessing that the slider flying would have a more forward CG since the Crash bar is forward?

Anyone know.
Jack
 
Smilin' Jack said:
You have a beautiful aircraft Reiley

I guess there would be a difference in the tip up and slider on the cg also. I am just guessing that the slider flying would have a more forward CG since the Crash bar is forward?

Anyone know.
Jack
Click to expand...

Not enough to calculate... :)
 
Since your emphasis is acro with some budget constraints, how about losing the injection, go with a carb, and install a CS. FP is a real yawner compared with CS for acceleration (my FP pax are always surprised by the difference), not just take-off, but up and down lines also. You still get 2700 over the top of a loop at low speed. You can carry power going down that will over-rev a FP.

Gross weight usually isn't the problem. Most pilots can diet off the weight difference between FP and CS and be healthier for it, or just carry four gallons less gas. A -7s CG range is much more usable with a CS on a 360. Your bag weight can easily exceed the 100 lb floor limit and still be within CG.

You like driving around in nothing but third gear? Get a FP.:D

John Siebold
 
Smilin' Jack said:
I guess there would be a difference in the tip up and slider on the cg also. I am just guessing that the slider flying would have a more forward CG since the Crash bar is forward?
Click to expand...

But the slider canopy is heavier on the aft end. I think you'll find little if any difference in C/G between the two.
 
Smilin' Jack said:
I know that I want an IO-360 but the delima is whether fixed pitch or CS.
.
Click to expand...

I have had both the 85 inch Sensenich and the BA Hartzell on my RV7. I did have aft CG issues with the Sensenich when fully loaded for OSH but the Saber Mfg 22 lb spacer solved that and smoothed vibration. Comparing the two after the CG issue was solved, I find them both acceptable. The top speed is so close I don't know which was faster. I will keep my BA now, mainly because I like the ease of landing and slowing down with it. It does climb out better but I don't care about that.
 
RV7AV8R said:
It does climb out better but I don't care about that.
Click to expand...

I do, but then I takeoff at 4600' msl to start with, and want to keep climbing fast.........without circling or a back & forth manuver to quickly climb over a 8500' peak just under Class B airspace. C/S's are good for that! Also allows me to drop down the same path at 2000 fpm without a speed increase. :)

L.Adamson --- RV6A, Hartzell C/S
 
Thanks for all the advice and suggestions.
I think I'll try to come up with the money for the CS. The total weight of the AC might be close to 1100 but hopefully we'll be under. I just don't want to be over that number.
Smilin' Jack
HS Done
VS Dome
Rudder Done
working on elevators.
Amateur radio gear sold
Now get the boat sold.....
Trying hard not to touch the retirement accounts :) :) :)
 
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