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04-21-2019, 11:52 AM
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Join Date: Aug 2007
Location: Friendswood, Tx
Posts: 390
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My friend just bought an rv6 with a -7 tail on it. We are removing the 200hp, io-360, contant speed prop combo and returning it to the seller. We are building an 0-360 a1d narrow deck engine and prince prop setup for the plane. Can someone with a -7 tail post the w&b numbers for their plane? Hopefully i can get one with a constant speed prop and one with a fixed pitch for comparison. I am trying to work out the position on the battery, elt, etc as we go. My rv6 has a stock .020” metal tail, 0320, whirlwind c/s prop, glass panel, autopilot, flightline interior and 9 lbs dive weight on the alternator. It weighs 1105lbs with a cg index of 71.9”. It is still tail heavy with a pax or bags. I sure don’t need any more weight in the tail.
Left 516
Rgt 511
Tw 78
Total 1105 at 71.9”
I really appreciate the responses.
__________________
Rv-6
0-320/180+hp
10-1 pistons
Lycon port/polish
Dual pmags
EI Commander
Whirlwind 200rv prop
IFR Glass panel
Trutrak Vizion 385 Autopilot
Flightline Interior
Almost rv14 seat mod/cable locking
Electric seat back adjuster
Last edited by titanhank : 04-21-2019 at 12:05 PM.
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04-21-2019, 07:38 PM
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Join Date: Mar 2009
Location: Plano, TX
Posts: 2,089
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I just weighed my 6A yesterday. I have an RV-7 tail, wide-deck O-360, Heavy prestolite starter, Catto Prop, flightline Carpet, Classic aero seats. Battery is PC680 mounted on the firewall. ELT is under the baggage floor.
Empty weight is 1068, CG is 72.4"
I will probably add a steel crushplate to help with the CG a bit, that should get the CG to about 71.6". I don't have much baggage allowance at the moment. That Catto prop is just so light...
Quote:
Originally Posted by titanhank
My friend just bought an rv6 with a -7 tail on it. We are removing the 200hp, io-360, contant speed prop combo and returning it to the seller. We are building an 0-360 a1d narrow deck engine and prince prop setup for the plane. Can someone with a -7 tail post the w&b numbers for their plane? Hopefully i can get one with a constant speed prop and one with a fixed pitch for comparison. I am trying to work out the position on the battery, elt, etc as we go. My rv6 has a stock .020” metal tail, 0320, whirlwind c/s prop, glass panel, autopilot, flightline interior and 9 lbs dive weight on the alternator. It weighs 1105lbs with a cg index of 71.9”. It is still tail heavy with a pax or bags. I sure don’t need any more weight in the tail.
Left 516
Rgt 511
Tw 78
Total 1105 at 71.9”
I really appreciate the responses.
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__________________
Colin P.
RV-6A #20603
Complete 5/10/19
PP SEL / A&P
I donate every year on my B-Day (in Dec), but donated early in Sep'19.
Last edited by WingsOnWheels : 04-21-2019 at 07:46 PM.
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04-21-2019, 08:23 PM
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Join Date: Jul 2018
Location: CA
Posts: 227
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Quote:
Originally Posted by Snowflake
Having flown my original rudder -6 for about 10 years now, i'd ask why you'd bother changing the rudder if you didn't have to...
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I agree. The only time it's an issue is slow in a crosswnd.
So up the approach speed and decrease flaps as well as leaving the throttle in a bit.....
__________________
20 dues paid member since 2018
RV6A
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05-02-2019, 06:32 AM
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Join Date: Feb 2019
Location: Atlanta Georgia
Posts: 34
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We have been looking at buying a 6 or 7 already built and flying as well. It is fairly easy to tell if it has the larger rudder, but is there a way to tell if the skin is .02not .016? Did later 6 kits ship with thicker skin but smaller tail? Or are all smaller tails .016?TIA
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05-02-2019, 07:25 AM
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Join Date: Jan 2005
Location: Peshtigo, Wisconsin
Posts: 768
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Personally, and I may be prejudiced, but I think the 6/6A with the standard empennage is the best looking RV design out there. As stated above, compensate for x-wind approaches and the size of the VS/rudder is a non issue.
__________________
Jeff Orear
RV6A N782P
Peshtigo, WI
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05-02-2019, 10:20 AM
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Join Date: Jan 2005
Location: Charlottesville, Virginia
Posts: 1,230
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Thin
Quote:
Originally Posted by circuitbreaker8747
We have been looking at buying a 6 or 7 already built and flying as well. It is fairly easy to tell if it has the larger rudder, but is there a way to tell if the skin is .02not .016? Did later 6 kits ship with thicker skin but smaller tail? Or are all smaller tails .016?TIA
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I do not know of a simple test to tell.
Obviously the .016 is thinner....if you could see/feel a sample of both before touching or feeling a rudder you might be able to tell. The main thing to look for on the rudder in a pre-purchase is cracks at the rivets. If they are caused from VS spar misalignment, the cracks would be worse down low and get better higher.
Cracks are not deal killers...just different repairs. Although the misaligned VS issue can lead to more repairs than just re-skinning. Plus may be indicitive of the quality of construction.
Originally the -6's came with the small rudder and .-16 skins.
When Van's found the large rudder from the new-9 worked better on the -7 they also sent larger VS and rudders to the -6 builders....so some later -6 kits have the -7 larger rudders. This is what I think, I may be wrong but close.
FYI--all the rudders work well if built and installed correctly.
__________________
Bob Martin
RV-6, 0-360 Hartzell C/S, Tip up, 1200+TT
James extended cowl/plenum, induction, -8VS and Rudder. TSFlightline hoses. Oregon Aero leather seats.
D100-KMD150-660-TT ADI2- AS air/oil seperator. Vetterman exhaust with turndown tips.
Louisa, Virginia KLKU N94TB
Last edited by Bob Martin : 05-02-2019 at 12:41 PM.
Reason: removed P factor bad info-Thanks Jon
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05-02-2019, 10:54 AM
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Join Date: Jan 2007
Location: Battleground
Posts: 4,348
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Cracks in .016 skins are caused by improper construction technique. Period.
The “big engine” theory was the first “guess” back in the day, but there are way too many of us flying with 180HP and no cracks. If prop wash “beating against the tail” or “vibration” was the cause, it would just be a matter of time before all .016 tails had cracks, regardless of engine size. Cracks typically develop in the first few hundred hours or less and it doesn’t matter what the engine is.
A search on this topic will reveal many discussions, all leading to stress induced by improper construction.
It is very easy to look for this. Lay a straight edge on the control surface. It should lay flat all the way from the spar to the trailing edge radius. If it doesn’t, it wasn’t built right.
This is true for .016 and .020 skins. .020 are just more tolerant of build error.
__________________
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.
Last edited by JonJay : 05-02-2019 at 10:58 AM.
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05-02-2019, 06:39 PM
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Join Date: May 2006
Location: Pocahontas MS
Posts: 3,884
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Jon, while I'm sure I don't have your level of experience, I have a hard time accepting putting a sharp period on your statement and blaming it all on builder error. I'm currently looking at a very well built -6 that easily passes the 'straightedge test', but has multiple cracks in the trailing edge of an elevator, the trailing edge of the rudder, and significantly, multiple cracks around the *leading edge end* of the skin stiffeners. This with <500 hrs on the airframe.
When I look around the rest of the airframe (and most other aluminum a/c structures) I see ribs and other secondary structural elements carried all the way to the primary element (spar, etc), and tied to the web and/or lapped onto the mating structure's flange, with a rivet through all three pieces. Another difference between the control surfaces and the stabilizers, wings, etc is that the two sides are *not* tied to each other by a rib, but can move independently because of the 'untied' skin stiffeners. That combo seems to allow the skin to flex a lot more (relative to other structure's action) around the end rivets of each stiffener. Additionally, there's that longstanding recommendation from Van's to use proseal or other sealant to tie the two sides of the control surface together at the stiffener pairs.
I'd love to have a structures guy weigh in.
Charlie
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05-02-2019, 09:37 PM
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Join Date: Jan 2007
Location: Battleground
Posts: 4,348
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That?s fair Charlie.
There may be, and probably are, more than one factor involved.
If the stiffeners where not tied together with RTV (per the instructions of that period, if the holes where de-burred too aggressively leaving a sharp edge, etc....
I shouldn?t be so emphatic about the induced stress issue. Over the years, the bulk of the Vans ?brain trust? has settled on that being the most probable cause.
I have one small crack that developed mid span on one rudder stiffener. It showed itself within the first 10 hours. 800 hours with no other cracks. I assume I did not properly dress the hole. It isn?t in the typical place where I have seen cracks. The 6 you are looking at has cracks ? in all the right places. ?
__________________
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.
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05-02-2019, 11:09 PM
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Join Date: Jul 2005
Location: Hubbard Oregon
Posts: 9,035
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Quote:
Originally Posted by JonJay
There may be, and probably are, more than one factor involved.
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I agree.
There are many factors that can have an influence on control surface skin cracking. A strong indicator of this is that there are a lot of RV's with a good amount of accumulated flight time that have not had cracks. This is a strong indicator that it is more than just the design not being what it should be. It is true that the control surface design could be more robust. This was done with the RV-10 and 14 but at a rather substantial penalty of additional weight.
Some common causes -
Undesirable level of engine/prop induced airframe vibration
Leading edges that wren't fully formed/rolled to the level they should have been (this puts an excessive preload on the skin just aft of the spar causing cracking to occur at the fwd most rivet)
Trailing edges not fully formed causing a preload in the skin that induces cracking at the aft most rivet.
Lack of the recommended sealant to connect the upper and lower stiffener each other.
Poor prep technique (deburring and/or dimpling... either excessive or inadequate) on the skin rivet holes (those aft holes are a bugger because of the close proximity of the other half of the skin).
I am sure there are others but I am not thinking of them right now.
Add a small influence of a couple or three of these together and you can have a significant enough influence to cause a crack.
__________________
Opinions, information and comments are my own unless stated otherwise. They do not necessarily represent the direction/opinions of my employer.
Scott McDaniels
Van's Aircraft Engineering Prototype Shop Manager
Hubbard, Oregon
RV-6A (aka "Junkyard Special ")
Last edited by rvbuilder2002 : 05-02-2019 at 11:11 PM.
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