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01-23-2012, 11:15 AM
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Join Date: Jan 2005
Location: South Africa, Johannesburg
Posts: 1,313
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Quote:
Originally Posted by joedallas
True!
But if you follow all the rules and good engineering practice, it can be accomplished.
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Joe what methods have you been using on your flush RV12? Rudi
__________________
Rudi Greyling, South Africa, RV 'ZULU 7' Flying & RV 'ZULU 10' Flying
"Science, freedom, beauty, adventure...what more could you ask of life? Aviation offers it all" - Charles A. Lindbergh
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01-23-2012, 11:15 AM
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Senior Curmudgeon
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Join Date: Sep 2005
Location: Dayton Airpark, NV A34
Posts: 15,420
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Please read;
http://www.vansairforce.net/rules.htm
Excerpt:
The Posting Rules in Greater Detail
1. Civility: First and Foremost.
This is intentionally vague, and gives the moderators a LOT of discretion. If any one of them is rubbed the wrong way with a post, it's toast. If you can't be civil at all times, don't participate. We don't tolerate uncivil behavior here
Thanks,
__________________
Mike Starkey
VAF 909
Rv-10, N210LM.
Flying as of 12/4/2010
Phase 1 done, 2/4/2011 
Sold after 240+ wonderful hours of flight.
"Flying the airplane is more important than radioing your plight to a person on the ground incapable of understanding or doing anything about it."
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01-23-2012, 07:08 PM
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Join Date: Jan 2006
Posts: 905
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An interesting thread. Certainly worthy of discussion if one is considering flush rivets. Don't understand why it gets out of hand , but sometimes it does. The key in my opinion is to remember we all love airplanes, and want to make them just as perfect as we can. There are many ways to get there, and discussing these are both educational and informative. When we close our minds to other's points of view the discussion loses it's value.
Dick Seiders
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01-23-2012, 11:51 PM
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Join Date: May 2007
Location: Somerset West
Posts: 1,033
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OK, to summarize (based on a similar aircraft to the RV-12 that is normally constructed using low profile domed pop rivets, converted to flush rivets using countersunk pop rivets):
a) Speed: 2-3 knots can be expected (or a consequent lower fuel burn if lower speed is maintained).
b) Stall: Lower stall speed and/or cleaner stall can be expected.
c) Visual impact: Great improvement but this may be subjective to the individuals personal values. Some may value this a lot, others might not.
We know that going this route will significantly add to the build time. We know that we have to ensure structural integrity of the airframe will be maintained to current (or better) standards - if required, professional advice should be obtained.
We do know that the reference aircraft is not a RV-12, is slightly heavier and slightly larger but falls into a similar speed category (give or take a few knots) so the final result on the RV-12 is not guaranteed and hence may differ.
My personal take is that it will be similar. Reason: The RV-12 is slightly faster than the reference aircraft (if both are constructed with domed rivets). This means it should benifit slighty more. However, it has slightly fewer rivets as far as I can tell so that should even things out.
We will know the exact result once we have a RV-12 built this way and the owner reports back. I'll be most interested...
Is that about right so far ?
Rainier
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01-24-2012, 04:08 AM
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Join Date: Jan 2005
Location: South Africa, Johannesburg
Posts: 1,313
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Much Better!
__________________
Rudi Greyling, South Africa, RV 'ZULU 7' Flying & RV 'ZULU 10' Flying
"Science, freedom, beauty, adventure...what more could you ask of life? Aviation offers it all" - Charles A. Lindbergh
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01-24-2012, 02:38 PM
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Join Date: Aug 2010
Location: Marshall TX (KASL)
Posts: 1,783
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Lets do a little simple arithmetic.
Say it takes 100 hours of extra build time for the flush riveting. This is probably low.
Lets say the result is a 3 kt speed increase (probably WAY high).
For a 400nm trip, "flushing" saves about 6 minutes. (say 110kt vs 113 kt).
One must therefore make one thousand such trips to break even on time saved when flying vs. extra time spent in building.
That means breakeven does not occur until the plane reaches more than 3500 hrs total time.
Aesthetics might be a reason and justification, but not speed unless we are kidding ourselves! But hey, I've spent a lot of time on aesthetics on my plane, and part of the great thing about building is that we can have the result that we want and be proud of our workmanship! There was a -12 at OSH in 2010 that had all of the rivets filled before painting. Took lots of time and effort to do that, looked beautiful.
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01-24-2012, 04:05 PM
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Join Date: Feb 2005
Location: Huskerland, USA
Posts: 5,862
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Quote:
Originally Posted by Bill_H
There was a -12 at OSH in 2010 that had all of the rivets filled before painting. Took lots of time and effort to do that, looked beautiful.
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Thanks! That was mine.
I have had several calls in the past month about what I used to fill the rivets. It is certainly no secret and I would like to share. Mine was he second customer built plane to fly. There were several of us that waited for kits to be released, so we had plenty of time to do extra things. Filling the rivets was one of them. I experimented with several methods and materials to fill the rivets. A long story short this is what worked the best. No need for flush rivets, just fill the pulled ones. I kept tract of the amount of material I used and it added 1.3 oz. to the plane. Took about 30 hours of additional work, but well worth the effort IMHO.
1. Material used was Superfill (Aircraft Spruce)
2. Dispenser was a syringe filled with the Superfill and a #16 x 1" farm needle with the point ground off. (aviation department in any farm store)
3. Fill the rivet hole from the bottom up and leave it just a tad over filled, allow to cure for 2-3 days.
4. When the syringe starts to stiffen in about an hour up throw it out and start over with new material.
5. Remove excess cured Superfill with a 90 degree die grinder and a 2" fine sanding wheel, low 50 PSI. Just barely tap the rivet top to shine the top and remove the excess material. Repeat 10,000 times.
Hope it helps.
__________________
RV-7 : In the hangar
RV-10 : In the hangar
RV-12 : Built and sold
RV-44 : 4 place helicopter on order.
Last edited by Geico266 : 01-25-2012 at 05:42 AM.
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01-24-2012, 07:18 PM
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Join Date: Jul 2008
Location: kansas
Posts: 330
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I used Larrys named product and procedure to fill all my rivets on the outside and have also filled those visible inside the cockpit after installing the full interior package and to me it has a much improved appearance.I am painting the interior also.
Some of you awaiting Skyview and need something to do would be pleased with the look I am sure.
Thanks for the info Larry.
__________________
Larry Vandegrift
ULPower 260is
Last edited by skydiverlv : 01-25-2012 at 02:46 AM.
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01-24-2012, 08:57 PM
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Join Date: Oct 2010
Location: La Feria Texas
Posts: 3,822
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Great idea, I was about to post the same thing. At least we will feel we are making some sort of progress rather than just stalling.
Quote:
Originally Posted by skydiverlv
I used Larrys named product and prodedure to fill all my rivets on the outside and have also filled those visible inside the cockpit after installing the full interior package and to me it has a much improved appearance.I am painting the interior also.
Some of you awaiting Skyview and need something to do would be pleased with the look I am sure.
Thanks for the info Larry.
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01-25-2012, 12:04 AM
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Join Date: May 2007
Location: Somerset West
Posts: 1,033
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Well, when we decided for the flush riveting, speed certainly was not the reason. We estimated 1.5 knots and as you point out - that is not worth it. We got closer to 3 knots but final judgement is not out yet due to an interesting thing that is happening - I need to play with this a bit more. The "reference aircraft" is now showing strong tendencies to "ride the step" and hold higher than expected speeds. I know some say this is rubbish but I can demonstrate it reliably. Not sure what the exact cause is but basically, you force the speed higher (say to about 125 knots) by dipping the nose a bit after just overshooting your target altitude on climb, then get level and bring back the power to cruise. She will now hold 120 knots indicated at a density alititude of around 3000 ft (our current typical conditions here at a lowish AGL). So there is more to this thing than first meets the eye.
For Rudi: This was done at an all up weight of 500Kg, with a 72" three blade ground adjustable Warp pitched for 5800 RPM on full bore power, straight and level. The 120 knots indicated results from 5500 RPM at approximately 20 liters/hour fuel burn (I have not calibrated my flow sender to perfection yet but it is more or less there). Advancing the throttle to full power however does not appreciably increase speed - perhaps to about 123-124 knots but that is about it. This may be a problem in case LSA certification is done in the USA with the 120 knots limit, not sure (we have a higher LSA speed limit here).
But as mentioned, when we started the speed was not a factor at all. The only factor was the aesthetics of the aircraft. It allready has very pretty lines but I felt the rivets spoilt it. I felt strongly about this and asked the factory to consider flushing it - which, to my surprise they agreed to despite the additional hassles of certifying the changes to an aircraft that had been finished and was a hot seller.
The result was worth the extra cost for sure (in my opinion Rudi) and I would definitely do this again just for the looks, even if the speed would not change at all.
I am quite convinced a similar affect (aesthetics) would be had on the RV-12 and obviously there is at least one project on the go to do just that so I am definitely not alone here.
As builder or owner, pride comes into it. Look at a well made RV-7 (as example). There is one in the hanger next to mine. It's beautiful even if it is not flying - a work of art. I wanted no less.
I am hoping to find some time to build an aircraft myself soon and I have not decided which one - but one thing is for sure. If it happens to be a kit that has pop rivets, I would not even dream of not flushing it unless it is a classic design where the "rivet look" is part of the image...
Rainier
Quote:
Originally Posted by Bill_H
Lets do a little simple arithmetic.
Say it takes 100 hours of extra build time for the flush riveting. This is probably low.
Lets say the result is a 3 kt speed increase (probably WAY high).
For a 400nm trip, "flushing" saves about 6 minutes. (say 110kt vs 113 kt).
One must therefore make one thousand such trips to break even on time saved when flying vs. extra time spent in building.
That means breakeven does not occur until the plane reaches more than 3500 hrs total time.
Aesthetics might be a reason and justification, but not speed unless we are kidding ourselves! But hey, I've spent a lot of time on aesthetics on my plane, and part of the great thing about building is that we can have the result that we want and be proud of our workmanship! There was a -12 at OSH in 2010 that had all of the rivets filled before painting. Took lots of time and effort to do that, looked beautiful.
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Last edited by Rainier Lamers : 01-25-2012 at 12:20 AM.
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