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Prop/Engine "Sag"Question

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Deems Davis

Joined: 09 Jan 2006
Posts: 925

Posted: Sat Feb 03, 2007 10:28 am Post subject: Prop/Engine "Sag"Question

For those who have finished your plane or previous planes. I'm 

interested in your real life experience regarding whether you've 

experienced or noticed any sag in your engine since initially mounting 

it. I've heard that after a hundred or two hundred hours that the engine 

will settle on the mounts which results in the prop dropping ( 1/8", 

3/16", 1/4" , ?????). Is this a real phenomena or an urban airport myth? 

If its real, how much 'sag' have you experienced? I'm leery of adding a 

'fudge factor' not knowing exactly what it should be, and 1/8" tolerance 

isn't what I'd like to achieve. Am I striving for the holy grail?  It 

seems like there ought to be a better way to ensure things fit after 

flying for a while I'm in the process of installing my cowl and would 

like to have it and the spinner mate evenly when it's all said and done.



Thanks for any information received



Deems Davis # 406

Finishing - ( A Misnomer ! )

http://deemsrv10.com/

pitts_pilot(at)bellsouth.
Guest

Posted: Sat Feb 03, 2007 10:45 am Post subject: Prop/Engine "Sag"Question

Deems Davis wrote:



 	  Quote: 	
		   



 For those who have finished your plane or previous planes. I'm 

 interested in your real life experience regarding whether you've 

 experienced or noticed any sag in your engine since initially mounting 

 it. I've heard that after a hundred or two hundred hours that the 

 engine will settle on the mounts which results in the prop dropping ( 

 1/8", 3/16", 1/4" , ?????). Is this a real phenomena or an urban 

 airport myth?


	


Yup, it's real.



 	  Quote: 	
		   If its real, how much 'sag' have you experienced? I'm leery of adding 

 a 'fudge factor' not knowing exactly what it should be, and 1/8" 

 tolerance isn't what I'd like to achieve. Am I striving for the holy 

 grail?  It seems like there ought to be a better way to ensure things 

 fit after flying for a while I'm in the process of installing my cowl 

 and would like to have it and the spinner mate evenly when it's all 

 said and done. 


	


Lot's of variables in how much sag ...... the specific mount (the rubber 

hardness can change drastically between 'models') makes a difference as 

well as engine/prop weight and heat ....... but the sag can be taken 

care of by adding washers under the mounts.

Linn ......aerobatic mounts don't sag a whole lot!!!

do not archive



 	  Quote: 	
		  



 Thanks for any information received



 Deems Davis # 406

 Finishing - ( A Misnomer ! )

 http://deemsrv10.com/

jesse(at)saintaviation.co
Guest

Posted: Sat Feb 03, 2007 10:53 am Post subject: Prop/Engine "Sag"Question

I have looked at this.  If there is any sag in N256H, it is 1/8" or less.

It is not enough to be very noticeable after 300 hours.  YMMV, but this is

what I have seen.  I would recommend rigging it up about 1/8" or 1/16" to

allow for it, but even at this you have to look closely to notice this

difference.



Jesse Saint

Saint Aviation, Inc.

jesse(at)saintaviation.com

www.saintaviation.com

Cell: 352-427-0285

Fax: 815-377-3694



--

Tim Olson

Joined: 25 Jan 2007
Posts: 2882

Posted: Sat Feb 03, 2007 11:18 am Post subject: Prop/Engine "Sag"Question

One thing to keep in mind is that none of the planes flying are all

that old, when compared with how many years those engine mounts

will be installed.  It's certainly not an *average* number of

hours that people like some of us are putting on, so when someone

says "in a couple hundred hours", for many homebuilts that's going

to mean 5 years.



2 things to consider:



A) You can always just not mount it as high to compensate, but just

plan on replacing your rubber mounts every 3 or 4 years.



B) I would definitely leave at least the recommended gap between the

cowl face and the prop hub/spinner.  That's one area I wouldn't want

to see rub.



Tim Olson - RV-10 N104CD - Flying

do not archive

Jesse Saint wrote:

[quote] 

 

 I have looked at this.  If there is any sag in N256H, it is 1/8" or less.

 It is not enough to be very noticeable after 300 hours.  YMMV, but this is

 what I have seen.  I would recommend rigging it up about 1/8" or 1/16" to

 allow for it, but even at this you have to look closely to notice this

 difference.

 

 Jesse Saint

 Saint Aviation, Inc.

 jesse(at)saintaviation.com

 www.saintaviation.com

 Cell: 352-427-0285

 Fax: 815-377-3694

 

 --

carl.froehlich(at)cox.net
Guest

Posted: Sat Feb 03, 2007 1:11 pm Post subject: Prop/Engine "Sag"Question

I assumed 3/16" sag on my RV-8A.  After 300 hours, no sag.



Carl Froehlich



--

zackrv8

Joined: 14 Jan 2006
Posts: 133

Posted: Sat Feb 03, 2007 1:42 pm Post subject: Re: Prop/Engine

Deems,



  I mounted my spinner bulkhead flush with the top of the cowl on my RV8.  I have the regular motor mount rubber (non aerobatic).  After 1000 hours and many aerobatic flights up to 4 G's, I have no sag.



  Of course, my 4 cylinder doesn't weigh as much as the 6 cylinder engines.  I plan on mounting my RV10 spinner flush.



Zack



 	  Deems Davis wrote: 	
		  For those who have finished your plane or previous planes. I'm 

interested in your real life experience regarding whether you've 

experienced or noticed any sag in your engine since initially mounting 

it. I've heard that after a hundred or two hundred hours that the engine 

will settle on the mounts which results in the prop dropping ( 1/8", 

3/16", 1/4" , ?????). Is this a real phenomena or an urban airport myth? 

If its real, how much 'sag' have you experienced? I'm leery of adding a 

'fudge factor' not knowing exactly what it should be, and 1/8" tolerance 

isn't what I'd like to achieve. Am I striving for the holy grail?  It 

seems like there ought to be a better way to ensure things fit after 

flying for a while I'm in the process of installing my cowl and would 

like to have it and the spinner mate evenly when it's all said and done.



Thanks for any information received



Deems Davis # 406

Finishing - ( A Misnomer ! )

http://deemsrv10.com/

_________________
RV8 #80125
RV10 # 40512

tadsargent(at)bellsouth.n
Guest

Posted: Sat Feb 03, 2007 3:13 pm Post subject: Prop/Engine "Sag"Question

Deems, my 7A has had a 360 on the nose for 2 years and 200 hours flying 

time.  I have negligible sag.  Make it look good now.  You will never notice 

it again when you get flying.

Tad Sargent



---

Deems Davis

Joined: 09 Jan 2006
Posts: 925

Posted: Sat Feb 03, 2007 4:17 pm Post subject: Prop/Engine "Sag"Question

Wow, This list is great! I also posted the same question on VAF. While 

there's some difference of opinion, the majority of the real life 

responses indicated little or no noticeable sag after several hunderd 

(1600) hours and many years. The other piece of useful information was 

that if some sag does occur and you want to take it out. a couple of 

properly sized washers at the annual condition inspection would take 

care of the problem. So. I've decided to make it fit flush now, and 

adjust if and when it gets noticable and annoying.

THANKS again for all who have replied.



Deems Davis # 406

Finishing - ( A Misnomer ! )

http://deemsrv10.com/

Now if getting the seam tight and straight between the cowl and fuse was 

just as easy..................................

kdbelue(at)charter.net
Guest

Posted: Sat Feb 03, 2007 4:39 pm Post subject: Prop/Engine "Sag"Question

After 5 years and over 700 hrs, my spinner has sagged about 3/16". I had 

always thought I would put some washers in to raise it, but when I tried to 

there were interference problems with the airscoop. Every plane is 

different - I just left mine the way it is because there wasn't enough room 

to modify the front of my airbox. If you start out with the spinner flush 

with the cowl it will still look good even if it sags 1/8".



Kevin Belue

RV-6A flying

RV10 finish



---

bpattonsoa(at)yahoo.com
Guest

Posted: Sat Feb 03, 2007 5:47 pm Post subject: Prop/Engine "Sag"Question

450 hours in an RV-6A.  It was a myth until around 250-300 hours.  It has now sagged about 3/16 to 1/4.  

 Seems to have stopped, but who can tell.  Next big annual I plan on putting washers on the bottom mounts.

  

 Bruce Patton

 ---

dasduck(at)comcast.net
Guest

Posted: Sun Feb 04, 2007 9:02 am Post subject: Prop/Engine "Sag"Question

Deems,  

I allowed for sag in my O-360 wood prop RV-6 which it did, about 3/16”.  

After 500hrs I changed to a Hartzell heavy prop and it sagged some more, so I re-aligned with the washers between the engine flanges and the ‘pucks’.  

   

There are various thicknesses of those washers and it is an easy, effective way to improve the alignment of the spinner to the cowl.  

Allow for a small amount of sag, and if it sags a bit more than you allowed for, shim it.  

Don  



 RV-6  980hrs  

         

  

From: owner-rv10-list-server(at)matronics.com [mailto:owner-rv10-list-server(at)matronics.com] On Behalf Of Bruce Patton

 Sent: Saturday, February 03, 2007 5:47 PM

 To: rv10-list(at)matronics.com

 Subject: Re: RV10-List: Prop/Engine "Sag"Question  

  

       

450 hours in an RV-6A.  It was a myth until around 250-300 hours.  It has now sagged about 3/16 to 1/4.    

    

Seems to have stopped, but who can tell.  Next big annual I plan on putting washers on the bottom mounts.  

    

   

    

Bruce   

  

   	  Quote: 	
		   	


     --  Release Date: 2/3/2007 

  

--

 2/3/2007

     [quote][b]

billderou(at)yahoo.com
Guest

Posted: Sun Feb 04, 2007 10:15 am Post subject: Prop/Engine "Sag"Question

Another approach which may slow the aging process is to use stiffer pucks on the upper forward and the lower aft mounts such as Piper recommends for the 260 Commanche. For the Commanche, Lord recommends a mix of -34 and -35 pucks which I installed and are rare. No sag yet but I only have 70 hours on my RV-10.

   

  Perhaps Van should be asked to get another opinion. I know he has offered stiffer pucks for aerobatic applications in the past.

   

  Bill DeRouchey

  billderou(at)yahoo.com (billderou(at)yahoo.com)

  N939SB, flying

   

  



don wentz <dasduck(at)comcast.net> wrote:

  [quote]      v\:* {behavior:url(#default#VML);}  o\:* {behavior:url(#default#VML);}  w\:*  {behavior:url(#default#VML);}  .shape {behavior:url(#default#VML);}                Deems,<?xml:namespace prefix  = o ns = "urn:schemas-microsoft-com:office:office" />

  I allowed for sag in my O-360 wood prop RV-6 which it did, about 3/16”.

  After 500hrs I changed to a Hartzell heavy prop and it sagged some more, so I re-aligned with the washers between the engine flanges and the ‘pucks’.

   

  There are various thicknesses of those washers and it is an easy, effective way to improve the  alignment of the spinner to the cowl.

  Allow for a small amount of sag, and if it sags a bit more than you allowed for, shim it.

  Don

  

RV-6  980hrs

   

         

  From: owner-rv10-list-server(at)matronics.com [mailto:owner-rv10-list-server(at)matronics.com] On Behalf Of Bruce Patton

Sent: Saturday, February 03, 2007 5:47 PM

To: rv10-list(at)matronics.com

Subject: Re: Prop/Engine "Sag"Question



   

      450 hours in an RV-6A.  It was a myth until around  250-300 hours.  It has now sagged about 3/16 to 1/4.  



    Seems to have stopped, but who can tell.  Next big annual I plan on putting washers on the bottom mounts.



     



    Bruce 

 	  Quote: 	
		   	


-- Release Date: 2/3/2007 

  [quote][b]

Ray.R.Doerr(at)sprint.com
Guest

Posted: Mon Feb 05, 2007 11:11 am Post subject: Prop/Engine "Sag"Question

I've heard the 4 bagger guys say 1/4" so I added to that since the 6 cylinder sits out there even further.  I setup my Cowl for 3/16" and now with 210 hours on it, it has settled about 1/4", so I would say use 1/4" as your starting point, not 3/16" and you should be good.  I am now going to shim behind my mounts with a steel washer to get it bang on.

Thank You

Ray Doerr

40250

N519RV

--

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