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Flush rivet RV-12

Rainier Lamers

Well Known Member
Appologies for posting information on an aircraft that is not a RV-12 here, but I think this may be relevant to some RV-12 builders.

This is just a small note related to experiences with a similar aircraft to the RV12 from a construction and performance point of view. It is a Sling-2 (pic below). The Sling is constructed very similar to the RV using low profile domed pop rivets.
I ordered one factory built but insisted that they try to use counter sunk pop rivets instead (at my risk). We had to prove that the counter sunk rivets where as strong as the normal rivets so the authorities would approve this but that was not a problem. They are.
They started experimenting with various rivet types and dimpling methods and some two weeks ago I received the Sling and what a beauty she had become. The holes left in the middle of the rivet are no issue - just fill them before painting. Very quick. We estimated that cruise would be around 1-1.5 Knots faster compared to the standard issue but it turned out to be about 3 Knots and a noticable reduction in fuel burn if speed is reduced slightly. Unexpected however was the improvement on the low end of the scale with lower and cleaner stall.
So, if anybody may be thinking of doing this to an RV-12, I think it's worth the effort. Speed gain when standing still on the ground is 20 knots :D

The Sling, like the RV-12 is LSA with a Rotax 912ULS, here with a 72" three blade Warp (just for the looks). It's around 80lbs heavier though and slightly larger overall with a sliding canopy and large amounts of bagage storage (which we use to carry test and measurement electronics).

Rainier
CEO MGL Avionics

DSC_4690.jpg
 
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Appologies for posting information on an aircraft that is not a RV-12 here, but I think this may be relevant to some RV-12 builders.

This is just a small note related to experiences with a similar aircraft to the RV12 from a construction and performance point of view. It is a Sling-2 (pic below). The Sling is constructed very similar to the RV using low profile domed pop rivets.
I ordered one factory built but insisted that they try to use counter sunk pop rivets instead (at my risk). We had to prove that the counter sunk rivets where as strong as the normal rivets so the authorities would approve this but that was not a problem. They are.
They started experimenting with various rivet types and dimpling methods and some two weeks ago I received the Sling and what a beauty she had become. The holes left in the middle of the rivet are no issue - just fill them before painting. Very quick. We estimated that cruise would be around 1-1.5 Knots faster compared to the standard issue but it turned out to be about 3 Knots and a noticable reduction in fuel burn if speed is reduced slightly. Unexpected however was the improvement on the low end of the scale with lower and cleaner stall.
So, if anybody may be thinking of doing this to an RV-12, I think it's worth the effort. Speed gain when standing still on the ground is 20 knots :D

The Sling, like the RV-12 is LSA with a Rotax 912ULS, here with a 72" three blade Warp (just for the looks). It's around 80lbs heavier though and slightly larger overall with a sliding canopy and large amounts of bagage storage (which we use to carry test and measurement electronics).

Rainier
CEO MGL Avionics

DSC_4690.jpg


nice looking aircraft !
how about some more photos.
what's in the panel?
 
Sling is similar looking as the Rans S19. IMHO both have better curb appeal but less visibiltiy looking from inside out as the 12. Ill keep the 12.
 
I filled the rivet heads on my -12, the second customer built plane to fly. It added 1.3 OZ to the plane and took about 30 hours for the entire plane. (yes, I kept track :D) and 20 knots on the ground is confirmed. ;)

Mine is just a tad faster than others, but then again the -12 is for cruisin not for racing.
 
Considered it but I knew where I could get some MGL's for cheaps :D

The panel is made in 5 sections so it is easy for us to replace a section when we try out new instruments etc.
The panel shows two Voyagers, MGL's new V6 radio/intercom and a Trig transponder. Also a E-Flap controller - quite nice.

Rainier
CEO MGL Avionics

Dynon?:D:D

Marshall Alexander

CABBCFEF.jpg
 
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What rivets did they use?

Countersunk pop rivets. These where sourced in the UK I believe. If I understand correctly, since the dimpeling increases the hole size (made for standard pop rivets) they needed slightly non-standard rivets to ensure good fit.

It's difficult to do a picture to show the real finish but it is very near what can be achieved with ordinary countersunk rivets - but it's faster and easier to do. I'm very happy with it, the skin is smooth - no "pimples". This is why I posted this on the RV-12 thread (the RV-12 was a contender for our new development aircraft but it turned out too expensive to have it built for us at the time - and, well, the Sling is a bit of a looker and I'm a sucker for that...).

There have been some questions on the RV-12 thread in the past related to possibily using countersunk rivets and what to expect performance-wise so now we have at least a guide (even if it is not the same aircraft, it is similar enough to be used as a yard stick in my opinion).

Rainier
CEO MGL Avionics
 
Yes I agree - it's not about the speed at all - it's all about the looks.
We used countersunk and filled rivets so there is no rivet head protruding at all - perfectly smooth skin.

Rainier
CEO MGL Avionics

I filled the rivet heads on my -12, the second customer built plane to fly. It added 1.3 OZ to the plane and took about 30 hours for the entire plane. (yes, I kept track :D) and 20 knots on the ground is confirmed. ;)

Mine is just a tad faster than others, but then again the -12 is for cruisin not for racing.
 
Considered it but I knew where I could get some MGL's for cheaps :D

The panel is made in 5 sections so it is easy for us to replace a section when we try out new instruments etc.
The panel shows two Voyagers, MGL's new V6 radio/intercom and a Trig transponder. Also a E-Flap controller - quite nice.

Rainier
CEO MGL Avionics



CABBCFEF.jpg



Looks great.:)

Marshall Alexander
 
Flush rivets

During ww2 the English, trying to save money, tested going to round head rivets on the spitfire, they had a crew of people glue split peas to that spitfire wing and lost about 20 kts of speed and reduced the climb rate by quite a bit. I think that if I were going to build a 12, I would use flush rivets were ever I could......Dave
 
Sorry have to disagree....

Countersunk pop rivets. These where sourced in the UK I believe. If I understand correctly, since the dimpeling increases the hole size (made for standard pop rivets) they needed slightly non-standard rivets to ensure good fit.

It's difficult to do a picture to show the real finish but it is very near what can be achieved with ordinary countersunk rivets - but it's faster and easier to do. I'm very happy with it, the skin is smooth - no "pimples". This is why I posted this on the RV-12 thread (the RV-12 was a contender for our new development aircraft but it turned out too expensive to have it built for us at the time - and, well, the Sling is a bit of a looker and I'm a sucker for that...).

There have been some questions on the RV-12 thread in the past related to possibily using countersunk rivets and what to expect performance-wise so now we have at least a guide (even if it is not the same aircraft, it is similar enough to be used as a yard stick in my opinion).

Rainier
CEO MGL Avionics

Sorry Rainier, I have to take you on on your post and disagree, just to give another perspective AND to make RV12 people aware of thinking to go that route.

1) An Aircraft designed for a certain rivit diameter simply can't be changed to a bigger diameter willy nilly. There are things like Edge Distances that needs to be considered. I have watched from a far a Sling builder going exactly the same route as you and what i see concerns me big time. Have a look here....
http://sling056.wordpress.com/category/general/dimpling/
three_layers.jpg

... There are NO edge distances left on this trim tab hinge :mad:. Being a moving part of a flying surface I am concerned. I have left a message for this person to have this looked at I hope he does! But it prooves my point...
... The rule of thumb is the hole needs to be 1.5x the diameter of the hole away from the edge, this clearly violates that principle ...

2) Secondly I have started offering "Builder Assistance and Training" and I will complete a RV12 in South Africa for less than a comparitive Sling. So I don't know who quoted you, but at least you now know.

3) Last 80Lbs Heavier than RV12 in the LSA class is significant, it means you will have to trade off fuel or bagage or range or passangers, you cant have them all. The RV12 has a sweet spot weight, that can actually combine all those.

So all I want to say is that not everything is always as it seems, there are 2 sides to a story.
Sometimes something that seems easy turns out not to be that simple.

Kind Regards
Rudi
 
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Flush Rivets RV12

Sorry Rainier, I have to take you on on your post and disagree, just to give another perspective AND to make RV12 people aware of thinking to go that route.

1) An Aircraft designed for a certain rivit diameter simply can't be changed to a bigger diameter willy nilly. There are things like Edge Distances that needs to be considered. Rudi


True!
But if you follow all the rules and good engineering practice, it can be accomplished.
 
Pulled Rivets

If you sourced the rivets in the UK, there is a good chance they are Avex rivets. Zenith Aircraft uses Avex and sources them in the UK as well. Murphy aircraft also uses Avex rivets on the Rebel, Elite, and Moose aircraft. Although ACS carries a few Avex rivets, one of bests sources in the US is Hanson Rivet. On their website, they have good charts that list the shear and tensile strength of various manufacturers, including Avex. You'll note there is quite a bit of difference between Pop, Avex, and Cherry Max.

Jerry Folkerts
 
During ww2 the English, trying to save money, tested going to round head rivets on the spitfire, they had a crew of people glue split peas to that spitfire wing and lost about 20 kts of speed and reduced the climb rate by quite a bit. I think that if I were going to build a 12, I would use flush rivets were ever I could......Dave

Considering that the Spitfire is a 300 kt airplane, the speed difference in an RV-12 probably wouldn't be more than 2 or 3 kts.

Keep in mind that the rivet used on the RV-12 is already lower profile than a standard AN470 rivet (that is why they are called LP4-3's, the LP stands for low profile).

BTW, they started removing peas from the test spitfire, and found that they got most of the speed performance back with only about 25% of the airplane flush riveted, so that is how they built them from then on.
 
Time not money

During ww2 the English, trying to save money, tested going to round head rivets on the spitfire, they had a crew of people glue split peas to that spitfire wing and lost about 20 kts of speed and reduced the climb rate by quite a bit. I think that if I were going to build a 12, I would use flush rivets were ever I could......Dave

Sorry Dave this was done to save time in the build not money, there are as we all know a lot less operations in putting in Universal Rivet as opposed to dimpling/ countersinking.

They were able to find areas where they could use universal rivets did not affect the speed or climb too much, so some areas could be built more quickly. The problem with the spit was that it was complex and time consuming to build, about 10000 of them were built in Castle Bromwich near where I live, where they now build Jaguar cars.

We had two big problems at the start of WW2, a lack of aircraft and pilots so speed of building was a real issue.
 
This is exactly right 2-3 knots is the result and one of the reasons (perhaps the main reason) why I started this thread in the first place. We now have a yard stick and in my opinion similar can be expected from the RV.
Just a bit of useful information, nothing else.

Rainier

Considering that the Spitfire is a 300 kt airplane, the speed difference in an RV-12 probably wouldn't be more than 2 or 3 kts.

Keep in mind that the rivet used on the RV-12 is already lower profile than a standard AN470 rivet (that is why they are called LP4-3's, the LP stands for low profile).

BTW, they started removing peas from the test spitfire, and found that they got most of the speed performance back with only about 25% of the airplane flush riveted, so that is how they built them from then on.
 
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Sorry Rainier, I have to take you on on your post and disagree, just to give another perspective AND to make RV12 people aware of thinking to go that route.

1) An Aircraft designed for a certain rivit diameter simply can't be changed to a bigger diameter willy nilly.
Did I say "willy nilly ?" Of course a structural analyses has to be performed. This is a aircraft builders forum. I think that is well understood.
The Sling had to be approved by the aviation authorities for flush rivets after such proof has been submitted.
2) Secondly I have started offering "Builder Assistance and Training" and I will complete a RV12 in South Africa for less than a comparitive Sling. So I don't know who quoted you, but at least you now know.
Perhaps, but I chose the Sling and would do so again. Nothing wrong with the RV-12 at all. It really was a contender (as where several other choices). The Sling won on merit. I liked the '12 because of the removable wings but then I have a Jora with foldable wings and I never had the need to fold them. I only have a single gripe about the '12 - it just does not look as nice as some of its competitors (in my view). In particular since the other RV's do look rather appealing...
3) Last 80Lbs Heavier than RV12 in the LSA class is significant, it means you will have to trade off fuel or bagage or range or passangers, you cant have them all. The RV12 has a sweet spot weight, that can actually combine all those.
Well the Sling is actually a VLA certified to 700Kg MTOW, but available as LSA in identical form - which means it is certified to +7/-5G. That means "Yeehaa !!!". Both my wife and myself are light weight. I have 235Kg usable. That's plenty. So you see - a "sweet spot" is not a fixed point in space Rudi - everybody has a different one.

So all I want to say is that not everything is always as it seems, there are 2 sides to a story.
No. Every builder has his own side. And that is just the way it is supposed to be. That means there are many sides.
Sometimes something that seems easy turns out not to be that simple.

And sometimes it is...

Rainier
 
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This is a pretty general rule and it holds true in most structural cases (depending on material properties). For this particular application the rule can be bent (I'm specifically refering to the trim tab hinge of the Sling that Rudi comments on). The reason is simple: The material on the edge in this case does not distort at all due to the rivet and there is more than ample strength available considering the many rivets here and the very low forces than can be expected on the smallish trim tab. In fact, the main reason for the many rivets is not related to the strength needed here but rather to ensure a flush fit of the thin hinge. This is one of the (very few) places the rule can be "adapted" without fear of negative consequence.

But please: I started the thread so give just a bit of feedback for consideration to RV-12 builders for the very simple reason that exactly this has been discussed here and on other forums and this is pretty much the closest we can get to a real answer until somebody does this to an RV-12 and reports back.
It is painfully obvious to any serious builder that every single rivet replacement location needs to be analyzed as to suitability and possible issues. Having said this, in most cases (by far) there simply is no issue except for the additional effort required by the builder.

When this was done to the Sling, we had no idea on how this would turn out. There where even opinions that stated (with quite some conviction and reasoning) that the Sling would now be slower and the stall would be worse. Luckily however, this turned out not to be the case and it is a winner in all respects. The aircraft is now "slower" and "faster" and looks much better than before close-up. This is undeniable.

Rainier

Actually, the edge distance rule of thumb is 2D (two times rivet diam. from hole center to material edge).
 
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I have just become aware of a builders log with some good comments and lots of pictures related to building a flush riveted Sling. I think this may certainly be of interest to any RV-12 builder wanting to go this route or just looking in for interest sake.

Rainier

http://sling056.wordpress.com
 
So why all the flush riviting effort on a sling and comparing it to a RV12 if it does not compare to a 600KG RV12? If one break the 600KG Sport Pilot barrier you can just as well compare it to the next category like a RV7 which is designed as flush and has a useful load of 700+lbs ie 317+KG. That seems like a better choice??? :confused: Whoa!

Sling missed its mark, it is not a good enough sport plane to compete against a RV12 in its class, and it is also not a good enough of a PPL plane to compete against a RV7 in its class.

RV12 builders should not change the diameter of the rivets willy nilly before contacting Vans, so the reference to a Sling site on a RV12 forum is of little value since they changed to larger diameter rivets.
 
What is your beef Rudi ?
Who cares about the weight ?
Why are you ranting like this about an aircraft you have no interest in ?

This thread is about flush rivets on an RV-12 and what that could do. This is not about the Sling. This is about the RV-12 which is a fine aircraft. That is not under question. This is the RV forum. Keep your comments for the Sling forum, I'm sure they will be appreciated there :rolleyes:.

Your negative rantings about the Sling are well known in South Africa. That's fine, I don't mind and neither do some 65 that have recently ordered one in this country alone. Opinion is good. You have yours, I have mine.

Please Rudi, if you have a specific reason why it would be stupid for a RV-12 builder to look at flush rivets - inform us, I'd really want to know. The points you mention have nothing to do with this at all. :confused:

Yes, of course it is a good idea to get guidance from Van's before proceeding. That does not mean it cannot be discussed beforehand surely ?
This is experimantal aviation. Anything goes, even stupid ideas. You need stupid ideas so you can identify good ideas. Make sense ?

It is not my intention to start a flush rivet war between two aircraft :D. This is getting just a tad silly. If you do not mind, I'd like to withdraw my troops.

OK, can we start again ?

Rainier

So why all the flush riviting effort on a sling and comparing it to a RV12 if it does not compare to a 600KG RV12? If one break the 600KG Sport Pilot barrier you can just as well compare it to the next category like a RV7 which is designed as flush and has a useful load of 700+lbs ie 317+KG. That seems like a better choice??? :confused: Whoa!

Sling missed its mark, it is not a good enough sport plane to compete against a RV12 in its class, and it is also not a good enough of a PPL plane to compete against a RV7 in its class.

RV12 builders should not change the diameter of the rivets willy nilly before contacting Vans, so the reference to a Sling site on a RV12 forum is of little value since they changed to larger diameter rivets.
 
Sorry Rainier I did not try and get personal, my beef is this:

You cannot come onto a RV12 forum compare the Sling to RV12 and suggest how great it is and not expect some push back? And using flush riveting as a vehicle.

You made some bland statements about costs and carrying capability in your statements etc which is 1/2 true.

I just corrected you, or offered a different opinion. I know the 2 aircraft very very well, while very few people on this forum know the Sling. So for me just to sit back and not challenge you on your statements would be wrong to my kin.

Changing rivet diameter is not a simple tasks, if you happy to fly an aircraft with those edge distances on your trim tab so be it, I wont. You said "At my Risk" well it is exactly that. I would warn my own kin, ie RV guys before going down that route.

Once again you bring up numbers...65 vs 600 hmmm let me think about it. Maybe RV12 builders should go have a close look at that site and they will see what a wonderful little kit the RV12 actually is. The myriad of miss-aligned holes that builder experienced is evidence. The RV12 is simply fantastic. Very few 1st time builders actually know this and appreciate it.

Is there merit in flush RV12, maybe, but not like this method!

If you stayed to flush rivet facts without pushing the Sling vs RV12 comparison it would have been a different story, but you didn't and I'll stand up to defend cause I know both well.

Regards
Rudi
 
Honestly Rudi,
I think it is you that is pushing the comparison which has no place here.
Yes, I'm using the Sling as example - simply because it is there and flush riveting has been done. As pointed out - the two aircraft ARE very similar which follows from my original post'd details that metion things like engine etc. A couple of knots this way or that, a couple of KG's this way or that. Does make no difference. Which is why it is a yard stick, something that can be used.
I really don't think this is "pushing the Sling". I'm not the maker or the Sling and I have no financial interest in the company that does.
I am however interested in a flush riveted RV-12 (in case that is not clear by now).

Anyway, if you don't mind, I'll be withdrawing from this part of the thread and will only continue discussing anything that is relevant to the original thread title.

Rainier


Sorry Rainier I did not try and get personal, my beef is this:

You cannot come onto a RV12 forum compare the Sling to RV12 and suggest how great it is and not expect some push back? And using flush riveting as a vehicle.

You made some bland statements about costs and carrying capability in your statements etc which is 1/2 true.

I just corrected you, or offered a different opinion. I know the 2 aircraft very very well, while very few people on this forum know the Sling. So for me just to sit back and not challenge you on your statements would be wrong to my kin.

Changing rivet diameter is not a simple tasks, if you happy to fly an aircraft with those edge distances on your trim tab so be it, I wont. You said "At my Risk" well it is exactly that. I would warn my own kin, ie RV guys before going down that route.

Once again you bring up numbers...65 vs 600 hmmm let me think about it. Maybe RV12 builders should go have a close look at that site and they will see what a wonderful little kit the RV12 actually is. The myriad of miss-aligned holes that builder experienced is evidence. The RV12 is simply fantastic. Very few 1st time builders actually know this and appreciate it.

Is there merit in flush RV12, maybe, but not like this method!

If you stayed to flush rivet facts without pushing the Sling vs RV12 comparison it would have been a different story, but you didn't and I'll stand up to defend cause I know both well.

Regards
Rudi
 
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Thanks,
 
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
 
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
 
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.
 
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.

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.
 
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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.
 
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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.

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.
 
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

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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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.

Not a bad time to figerglass the wing tip close out also. There is a lot you can do to improve the looks and performance of the -12.

Keep us posted of your progress guys!
 
Flush Rivets

Joe what methods have you been using on your flush RV12? Rudi

My web site shows each time I time made an alteration from the plans.
I have an engineering back ground and very comfortable with all my deviations.
This is not an endorsement to follow my alterations; this should only be preformed if you know what all the loads applied to each occurrence of the deviations.
 
Larry I have a couple of questions:
Did you have trouble putting rivet hole filler on the sides and underbelly, did the stuff want to run back out?
I have lost my information on wing tip finishing, can you give me a link or hint as to where to go for this information?

Not a bad time to figerglass the wing tip close out also. There is a lot you can do to improve the looks and performance of the -12.

Keep us posted of your progress guys!
 
Lets do a little simple arithmetic.
For a 400nm trip, "flushing" saves about 6 minutes. (say 110kt vs 113 kt).

Now, for some reason the term 'flushing' amuses me and should be the term used in future for this subject. :)

We decided in the end to leave the rivets au naturel but would have filled them if we had time before painting, purely for the aethetics.

Flushing through the use of countersunk rivets on an RV-12 is really not worth the effort (in my humble opinion) for an aircraft in this speed range.
 
Flush Rivets Re-think

One more Thing
3500 Hrs x 3 mph = Free 10500 miles @ 20 MPG = 525 Gallons @ $4.00 = $2100 for 100 Hrs Work = $21 Dollars per hour of work + or -. Times the number of times the 12 add's 3500 hrs to it's total time.

Pluss
Aesthetics and ease of waxing.
And I think 100 hours may be a little high but close.

Re-think

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.
 
Lots of figuring going on here when the undisputed correct answer of why someone would want to flush rivet the 12 is simply "...because I want to".
 
Your calc, my numbers

Hey Joe, I like the way you are thinking. For me the numbers are different:

1000 hours (I don't care if someone else gets the benefit after that)
$9 per gallon here in the UK
30 hours effort expended using Superfil - I excluded having to do one wing twice (that's another story) ;-)
For me that comes to ?10 or $15 per hour, which isn't bad for a hobby.

And my real purpose was for polishing. This is the second black pop-rivet plane I have owned. I don't polish too often, but you only need to do it once or twice to fill the rivet holes with white polish - which looks daft on a black plane ;-)

Cheers...Keith
 
Ryan is exactly point on. Do it if you want to, but don't expect any economic benefits. 3 Kts difference simply won't happen - I really doubt if it would even be measurable. (I think Vans wrote about this in an RVATOR). The calculation was to just show how, if everything is outrageously optimistic, that the benefits are still nil. And, filling the rivets is not the same as using flush rivets. Don't confuse the two, the time investments will be very different.
BTW to get really nitpicky about it, you might want to do a Net Present Value calculation. You are doing 100 hours of work "now" for a stream of money to be paid back over many years, and the value of that future money is less.
But Ryan has the correct answer - bragging rights! We all want a plane that is slightly different and gets some oohs and ahs...
 
Fulsh Rivets Re-Think for Speed

Bill with all due respect
2.60 knots is not 3 knots and at 120 Knots --138mph I think 3 mph is a real number.

And not to mention the color difference

Black is faster by keeping the air near the surface warmer; it reduces the viscosity of the air in the boundary layer. This reduces drag, ....but then again it depends on the type of paint , carbon based paints are faster than metallic , lead based paints..

It’s all to do with thermodynamics and metallurgy...


I am not Building Lsa

I'm a Old dragracer and I do mean old.

I may be wrong but I am doing this because I think I'm right.
and I have more time then money.

Ryan is exactly point on. Do it if you want to, but don't expect any economic benefits. 3 Kts difference simply won't happen - I really doubt if it would even be measurable. But Ryan has the correct answer - bragging rights! We all want a plane that is slightly different and gets some oohs and ahs...
 
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