VansAirForceForums  
Home > VansAirForceForums

- POSTING RULES
- Donate yearly (please).
- Advertise in here!

- Today's Posts | Insert Pics

  #1  
Old 03-21-2016, 04:19 PM
Rdwrv4 Rdwrv4 is offline
 
Join Date: Feb 2012
Location: loves park il.
Posts: 117
Default RV-3 Baby Rocket

Just in the process of painting my 3 and starting a new one. I have alot stuff to use up so some of my choices are dictated by what I have on hand. I would like to get advice on somethings and opinion on other
the Project
1. I want to use a cutdown rocket cowling just cuz it is Sexy and I have one
2 . o-360 conical mount cuz I have one off a super D
3 . balanced shortened elevators off a RV-8 again cuz I have an extra set and they are Identical!!! to the 3 except the spar is .180" deeper and has a much better trim tab and I will make a horizantal to match, the cord on the 8 is too big
4. Canopy off a panther or what Todd has that might be better. I want the volumous feel of a razorback canopy that terminates close to the longerons.
5. I have a hartzell off a RV8 but the extra 80lbs, CG issues and complexity is making me lean towards a 3 bladed Catto and I have one of those too
6. tilt back seat 2" at upper longerons and have hatrack shelf storage behind head ,I like this cuz it will offer accessable storage in flight and shelf floor will stiffen fuselage
7. hanging rudder pedals like RV4 without the firewall buckets this will allow pedals to come forward 2" more
8 1" upper longerons will be straight from tailpost to firewall but will have to twist them to allow the skins to lay flat. width at seat increases by a little less than 1/2" due to the wide Rocket cowl although the shortened cowling makes a little smaller firewall than the stock rocket.
9. build the last turtleneck bulkhead in 2 pieces so I can reach in and buck rivets, I ran out of little friends to do this, inspection cover on the belly just aft of the elevator reversing bar so I do not have to climb through baggage compartment.
10. 2 piece aft belly skin to make it much easier to fit.
11. early wingtips and wheel pants cuz I have them I like the way they look too if I had later ones I would like them too I think, free is beautiful
12. small instrument panel sitting on top of longerons , helps ease of entry
13. RV4 gear legs cuz they're two inches longer than 3 I think I found a cheap set
14. Fuselage floor should stay the same except the front forward lower longerons will be 96° angle to account for firewall shape. I may have to widen lower firewall as much as 1 1/2 inch but hoping not too won't know until I cut cowling down


Structural concerns
1 parallel valve O-360 weighs 30lbs more but Catto Prop is light so I will change the the perimeter tubing size on the engine mount from .035 to .049
2. The forward fuselage sides are no longer vertical but more curved and trapazoided out 10° so this is not as strong not sure what to do about this yet. All firewall angles will be 1" instead of 3/4" and I can hang the rudder pedals off of them. the steel firewall engine mount attach gussets will be .063 and slightly larger. and will attach with Hi-shear fasteners where convient.
One area of concern is the fuselage spar opening will be 1/4 to 1/2 inch wider and may interfere with the -3 bolts on the spar

Ideas and Input would be appreciated and spare parts would be loved. I really enjoyed building my last 3 so I hope this won't be frustrating but very enjoyable
thx Robin

Last edited by Rdwrv4 : 03-21-2016 at 04:24 PM.
Reply With Quote
  #2  
Old 03-21-2016, 05:41 PM
David Paule David Paule is offline
 
Join Date: Dec 2009
Location: Boulder, CO
Posts: 3,486
Default

With the longer gear legs, don't forget that where they hit the ground, they need to be in the right location with respect to the CG.

Dave
Reply With Quote
  #3  
Old 03-21-2016, 06:00 PM
JonJay's Avatar
JonJay JonJay is offline
 
Join Date: Jan 2007
Location: Battleground
Posts: 3,856
Default

Sounds fun! I would look at the other rocket mods, especially to the empennage. A well sorted 150HP RV3 as you know can go past VNE in level flight.
__________________
Smart People do Stupid things all the time. I know, I've seen me do'em.

RV6 - Builder/Flying
Bucker Jungmann
Fiat G.46 -(restoration in progress, if I have enough life left in me)
RV1 - Proud Pilot.
Reply With Quote
  #4  
Old 03-21-2016, 07:00 PM
Rdwrv4 Rdwrv4 is offline
 
Join Date: Feb 2012
Location: loves park il.
Posts: 117
Default

the -4 gear legs are only 2 " longer and in the landing attitude move the axles back less then 1/2 " but building my own mount and will place wheels in the correct position, I am a little concerned about the extra stiffness being hard on the mount.
Quote:
Originally Posted by David Paule View Post
Withhe longer gear legs, don't forget that where they hit the ground, they need to be in the right location with respect to the CG.

Dave
Reply With Quote
  #5  
Old 03-21-2016, 07:21 PM
Michael White's Avatar
Michael White Michael White is offline
 
Join Date: Jan 2005
Location: Cartersville, Georgia KVPC
Posts: 918
Default

Robin,
Add the gussets at the lower corners of the firewall/forward fuselage area ala the RV-8.

Dave P is right...you will need to maintain, at a minimum, the same relationship of the wheel axles to the wing LE, and preferably 2 inches forward of that per Rocket guys Mark F and Vince F to help prevent nose-overs. Because of the longer legs of the RV-4, you will need to change the socket geometry at the engine mount (spread them out). Since you're going to beef up the mount, this will be an easy change...just get the geometry right before welding.

As you know from our last email exchange, I have a full set of Rocket drawings. I could be willing to part with them. Let me know if you're interested, and we can work out a deal.

Sounds like a cool project. Good luck with it and keep us in the loop as you make progress.
__________________
Moose
VAF #136
N424LZ Reserved
Reply With Quote
  #6  
Old 03-22-2016, 09:18 AM
smokyray's Avatar
smokyray smokyray is offline
 
Join Date: Jan 2005
Location: TX32
Posts: 1,708
Default No substitute...

Quote:
Originally Posted by Rdwrv4 View Post
Just in the process of painting my 3 and starting a new one. I have alot stuff to use up so some of my choices are dictated by what I have on hand. I would like to get advice on somethings and opinion on other
the Project
1. I want to use a cutdown rocket cowling just cuz it is Sexy and I have one
2 . o-360 conical mount cuz I have one off a super D
3 . balanced shortened elevators off a RV-8 again cuz I have an extra set and they are Identical!!! to the 3 except the spar is .180" deeper and has a much better trim tab and I will make a horizantal to match, the cord on the 8 is too big
4. Canopy off a panther or what Todd has that might be better. I want the volumous feel of a razorback canopy that terminates close to the longerons.
5. I have a hartzell off a RV8 but the extra 80lbs, CG issues and complexity is making me lean towards a 3 bladed Catto and I have one of those too
6. tilt back seat 2" at upper longerons and have hatrack shelf storage behind head ,I like this cuz it will offer accessable storage in flight and shelf floor will stiffen fuselage
7. hanging rudder pedals like RV4 without the firewall buckets this will allow pedals to come forward 2" more
8 1" upper longerons will be straight from tailpost to firewall but will have to twist them to allow the skins to lay flat. width at seat increases by a little less than 1/2" due to the wide Rocket cowl although the shortened cowling makes a little smaller firewall than the stock rocket.
9. build the last turtleneck bulkhead in 2 pieces so I can reach in and buck rivets, I ran out of little friends to do this, inspection cover on the belly just aft of the elevator reversing bar so I do not have to climb through baggage compartment.
10. 2 piece aft belly skin to make it much easier to fit.
11. early wingtips and wheel pants cuz I have them I like the way they look too if I had later ones I would like them too I think, free is beautiful
12. small instrument panel sitting on top of longerons , helps ease of entry
13. RV4 gear legs cuz they're two inches longer than 3 I think I found a cheap set
14. Fuselage floor should stay the same except the front forward lower longerons will be 96° angle to account for firewall shape. I may have to widen lower firewall as much as 1 1/2 inch but hoping not too won't know until I cut cowling down


Structural concerns
1 parallel valve O-360 weighs 30lbs more but Catto Prop is light so I will change the the perimeter tubing size on the engine mount from .035 to .049
2. The forward fuselage sides are no longer vertical but more curved and trapazoided out 10° so this is not as strong not sure what to do about this yet. All firewall angles will be 1" instead of 3/4" and I can hang the rudder pedals off of them. the steel firewall engine mount attach gussets will be .063 and slightly larger. and will attach with Hi-shear fasteners where convient.
One area of concern is the fuselage spar opening will be 1/4 to 1/2 inch wider and may interfere with the -3 bolts on the spar

Ideas and Input would be appreciated and spare parts would be loved. I really enjoyed building my last 3 so I hope this won't be frustrating but very enjoyable
thx Robin
Robin,
Here's a link that might add some light to your thinking...remember that the aerobatic gross weight G loading and VNE of the original RV3 are easily challenged with the mods you list.
The Matronics thread below discusses the same issue including counterbalancing the RV3 elevator.

http://www.matronics.com/archive/arc....digest.vol-ab

V/R
Smokey

Last edited by smokyray : 03-23-2016 at 11:31 AM.
Reply With Quote
  #7  
Old 03-22-2016, 09:23 AM
SHIPCHIEF SHIPCHIEF is offline
 
Join Date: Mar 2008
Location: Seattle
Posts: 1,366
Default Angle of Gear Legs

I have a Thorp T-18, and fly my wife's RV-4.
The T-18 has short stiff gear legs and the RV-4 legs feel like wobbly spaghetti to me.
I think you could re-angle the RV-3 mount with those RV-4 legs and be OK. Of course, the new angle will raise the front of the plane a little more when on the ground...
I built an RV-8, I really love the landing gear's behavior, but not the space taken up by the gear towers.
I sure like working on the RV-4 better than the -8, everything is so accessible and easily serviced. An RV-3 must be even better!
Keep us posted on your RV-3 Rocket project!
__________________
Scott Emery
http://gallery.eaa326.org/v/members/semery/
EAA 668340, chapter 326 & IAC chapter 67
RV-8 N89SE first flight 12/26/2013
Yak55M, and the wife has an RV-4
There is nothing-absolute nothing-half so much worth doing as simply messing around with Aeroplanes
(with apologies to Ratty)
Reply With Quote
  #8  
Old 03-24-2016, 08:59 AM
dacronwall's Avatar
dacronwall dacronwall is offline
 
Join Date: Oct 2013
Location: Palo Alto,CA
Posts: 85
Default Baby Rocket

My RV-3 was originally built and flown with an IO-360 and CS prop. It does add weight, but it can be done....and the performance....get the heck out!
Dave
__________________
My RV-3 is more fun on accident than your Cessna is on purpose
Reply With Quote
  #9  
Old 04-12-2016, 07:13 PM
Rdwrv4 Rdwrv4 is offline
 
Join Date: Feb 2012
Location: loves park il.
Posts: 117
Default Baby Rocket update

OK firstly, upon examining the Rocket Cowl in hand I discovered no a chance of putting it over a 360 with a RV3 mount. So I acquired a RV4 mount with long legs. it is a little longer than the -3 by about 4 inches. I think I can make that work but it will require repitching the gear sockets.
So CS prop and 360 apx 100lbs extra up front. Weight in rear needed! , I weighed both the RV-3 tail and RV-8 tail . FYI weights are as follows. (Done with bathroom scales ,weighed myself with and without each part) elevators 2.6lbs vs 6.4lbs each. Rudder 3.4lbs vs 7.6lbs Vertical 6 lbs vs 7.8lbs Horizontal 12.8lbs vs 17.8 lbs total difference 15lbs. That sounds about right considering the moments. Big concern is the larger surfaces may look out of proportion. No one I have asked has expressed any aerodynamic concerns. Using The -8 parts makes it much easier for me to build cuz I have them. Anybody know of any aerodynamic concerns? I will use the last two RV-8 bulkheads and deck at the rear all that should fit harmoniously. The angles of the stringers and Longerons are almost the same.
Reply With Quote
  #10  
Old 04-12-2016, 07:41 PM
David Paule David Paule is offline
 
Join Date: Dec 2009
Location: Boulder, CO
Posts: 3,486
Default

The extra horsepower is destabilizing, so adding tail area helps.

You could do a basic static stability analysis following any of the older texts out there to get an idea if the CG limits ought to change, and if so, to where. Perkins & Hage's book is excellent and there are others available too, that basically contain all the information you'd need. That and a calculator and you're in business.

Flutter could potentially be an issue with the larger surfaces and their mass balance weights, which all add mass inertia, to the standard tail cone. My thinking is that for some of the flutter modes the stiffness of the fuselage is a contributing factor, and if the inertia goes up and the stiffness doesn't change, the natural frequency goes down - which is in the wrong direction for you.

Is this an issue? Heck, I surely don't know. But it's a factor worth studying. Here, though, I don't have a reference to suggest.

Also, added weight in the nose and tail can significantly change the spin characteristics, and not necessarily in a good way. Just so you know. I think that the added tail area might be beneficial here but this is out of my expertise and can't really say.

Dave

Last edited by David Paule : 04-12-2016 at 07:45 PM.
Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump


All times are GMT -6. The time now is 04:12 PM.


The VAFForums come to you courtesy Delta Romeo, LLC. By viewing and participating in them you agree to build your plane using standardized methods and practices and to fly it safely and in accordance with the laws governing the country you are located in.