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RV-12: Let The Modifications Begin!

Geico266

Well Known Member
Here is the thread to post your modifications made to your compelted and inspected -12. This is AFTER you have recieved the airworthness inspection and flown your hours off in Phase 1. Obviously, we need to be carefull with any modicicatiosn made to any airplane so make sure they are completed using the "aircraft building skills" we learned by building the kits, and have an A&P or knowledgeable builder type inspect your idea and work when completed.

My first mod? In preparation for paint I decided to make covers for the stabilator. I think it cleaned up the ends real nice and gave them a finished look.

RV-12 Sabilator_tip.JPG


If someone would post a "before" picture I would apprciate it. I took one, but it did not turn out.

Other mods I am considering;

1. Coolant temp sensor (to conform with Rotax SB)
2. Fuel boost pump switch.
 
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Mods

Larry - nice modification. Looks a lot nicer and may even fly better - who knows. My guess is that Van's will be watching for the mods that are done post inspection and even might change or modify the kits as a result. It'll be interesting to see the mods made by those of you who know what you're doing.

Thanks for sharing your idea - hope that others will do the same.
 
Hi Larry,
What I have in mind is more of a new version of the RV-12 than a mod. The RV-12 is such a good concept that I think it deserves to be an unquestionable E-AB (I think that?s the term) as well as an E-SLA. The issue here is the 51% rule.

What would it take to make the aircraft a genuine 51% builder project? To build the empennage from scratch? To flush rivet the wings with solid rivet? Solid rivet the centre fuselage? To install an A200-D engine or Jabiru 3300? Steam gauges?

There is so much going for the kit as so far developed. I just love that machine (and metal workers) that turn out complicated parts that fit together so well. It would be great to keep all that, but put back the education element, the multiskilling of yourself that is such a key part of amateur aircraft construction.

To get back to the real world and the nub of your challenge ? I would like to see a 100+ litre (26.4 US gal) tank. Have the tank extend across the fuselage, right behind the seats, tall and narrow, with the optical gauge visible between the seats. In a country like Australia, airports with fuel are few and far between. And you can pay a $50 call out fee. You need enough fuel to fly out and fly back. I would happily give up baggage capacity for fuel capacity. The first thing I did when I had detail on the RV 12 was to check if I could put a couple of 20 litre plastic jerry cans in the baggage compartment. I remember how my Jabiru 2200 flying instructor would load the jerry can when we did a cross-country. That might also solve the problem of access to the rear fuse and sub-baggage compartment floor inspection panels. Still plenty of room for a few soft bags.

Rod
 
Changes

I'm not sure I want to add the weight. With only 480 left after fuel, you are limiting the utility of the aircraft. Also, I'm curious if it changes any liability issues since we all signed a statement that said we built it exactly to plans. Just 2 cents worth.
 
Now I'm no aeronautical engineer, nor do I play one on TV, but isn't balance fairly critical on an all flying stabilator like the RV12 has? Just a thought before adding weight to a control surface. Hate to see anyone hurt. I hear flutter can come on very suddenly and is pretty nasty. And as your tag line says Larry ... But I'll admit, it does look nice.

George
 
I decided I wanted to be able to turn off the fuel pump without pulling the fuse every time. IMHO the fuse holder is not designed to have the fuse inserted and removed constantly and could eventually become weak or break from constant flexing. Anyway, I decided to add a nice little LED rocker switch in the area that has the auto pilot disconnect. It looks pretty good and almost like it came from the factory.

Down side? I'll need to recalculate the "K" factor if I choose to have the pump off most of the time inflight. I plan on only using the boost pump 1,000' AGL or less.

RV-12_pump_switch.JPG


All I need is a label and it should be good to go.
 
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Another maybe - Fuel tank

Like all the early builders, I have never like the fuel tank site-glass. The rest of the tank is fine. I will wait until the snow flies in Iowa, and remove the tank for the "mod". I think it will be 'MY' mod. I believe I will remove the site-glass and move the backing plate up to the surface and 'goooo' it in very well. I have been in contact with a marine fuel tank sender company. They said their units do not leak even if inverted. Their site-glass is durable. I will then be able to turn around IN FLIGHT, and see how much is in the tank. I will also be able to see how much is in it while filling it. Both things appeal to me. The current design site-glass ( to me ) is a leak waiting to happen, sooner or later. ( MY OPINION ) I can cut a hole in the top when I have it off, and 'goooo' the mechanical sender in place. They have been used in the marine industry for years. Simple, and can always be removed if necessary.

John Bender
 
John,

I agree that this fuel tank is leak waiting to happen. And there are so many sources for that leak to occur. This part of the kit leaves me very uneasy. BTW, I'm building the tank as we speak. What a mess.

Art Pennanen
 
John,

I agree that this fuel tank is leak waiting to happen. And there are so many sources for that leak to occur. This part of the kit leaves me very uneasy. BTW, I'm building the tank as we speak. What a mess.

Art Pennanen

Hi Art,

Please stay after school and write the following on the black board 100 times:

"Van's is great and Pro Seal is my friend"

This is the standard punishment for thinking that Van's has done anything but great engineering on all of his aircraft and all parts thereof.

Failed Pro Seal is the only real cause of fuel leaks in all airliners, it is much like computer hard drives "it is not if they will fail but when they will fail. We have just done three "Annual Condition Inspections" on RV-8's two were quick build and one was slow build each had at least one leak due to Pro Seal breaking down. Granted they were very small leaks and on the RV-8 they are in the wing so it is not much of a smell issue, but in the RV-12 the tank is less than 20 inches from our nose, the car gas we should use for the Rotax has a bad smell and it only take a very small leak to make the air stink and the issue of fire a concern.

I will do the tank next week just as Van's has instructed and we (there are two of us doing the tanks together as our last task) will take extra care to get it right. If I had to bet it will not make it a year with out leaking, the tank is made of such light material that it will flex way to much and this causes the Pro Seal to crack and breakdown.

First leak here in Spruce Creek we are going to welded tanks with thicker material and perhaps to an improved shape, but first we have three ready to hatch and two more that should fly early next year, with one on a slower track.

Good luck with your tank.

Best regards,
Vern
 
Failed Pro Seal is the only real cause of fuel leaks in all airliners, it is much like computer hard drives "it is not if they will fail but when they will fail. We have just done three "Annual Condition Inspections" on RV-8's two were quick build and one was slow build each had at least one leak due to Pro Seal breaking down. Granted they were very small leaks and on the RV-8 they are in the wing so it is not much of a smell issue, but in the RV-12 the tank is less than 20 inches from our nose, the car gas we should use for the Rotax has a bad smell and it only take a very small leak to make the air stink and the issue of fire a concern.

I know of many RV's that are more than 10 years old that have never had any leaks (I am sure the major majority have not). The original RV-6A prototype (old blue) is now 21 years old with over 4500 hours...it has never had any tank leaks. Do tank leaks happen? Yes they do on occasion, but nobody should let one negative opinion about prosealed tanks give you the idea that "you should just get over it" and "plan on having your tank(s) leak".

the tank is made of such light material that it will flex way to much and this causes the Pro Seal to crack and breakdown.

Proseal (I assume generic term for fuel tank sealant) doesn't crack, it is a flexible rubber type substance when cured. I don't think slight flexing can cause tank sealant to break down (though I am not quite sure what that means). The Red RV-12 prototype now has passed the 300 hour mark and their has been no sign of tank sealant cracking or breaking down or any signs (or detectable smells) of the tank leaking.
 
Gotta go along with Scott;

Failed Pro Seal is the only real cause of fuel leaks in all airliners, it is much like computer hard drives "it is not if they will fail but when they will fail. We have just done three "Annual Condition Inspections" on RV-8's two were quick build and one was slow build each had at least one leak due to Pro Seal breaking down.

I've been building RV tanks with pro-seal for over 20 years. No reported leaks so far. Just built them per the plans.
 
I've been building RV tanks with pro-seal for over 20 years. No reported leaks so far. Just built them per the plans.

Hi Mel,

I think that you and Scott are under estimating how small a leak or ooze it takes to make the air in an aircraft stink of fuel fumes. I have seen lots of "Quick Build" RV's with small blue stains on them and they are not an issue because they are out in the wings so the owner does not smell anything and the amount of fuel loss is so small that it is of no real concern it just leaves a stain on the aircraft. When the tank is in the cabin with you these kinds of leak will stink.

I sincerely hope it all works fine, it is just my opinion based on my personal experience that there may well be some issues here. I do respect your view that it will not be a problem, I am glad for you that you have had good luck with using tank sealer to fill 1/4 inch corner holes that have no structural support.


Best regards,
Vern
 
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Wait a minute!

I am glad for you that you have had good luck with using tank sealer to fill 1/4 inch corner holes that have no structural support.
Best regards,
Vern
I never said that I filled a 1/4" gap. If you have a gap that large, it should be closed up structurally. Pro-Seal is a great sealant, but it's not a structural member. A 3/32" gap would be maximum for me. I try to keep gaps down to 1/16".
 
I never said that I filled a 1/4" gap. If you have a gap that large, it should be closed up structurally. Pro-Seal is a great sealant, but it's not a structural member. A 3/32" gap would be maximum for me. I try to keep gaps down to 1/16".
Just to add my two cents worth- Vern is right, there are 1/4 inch gaps in the tank corners, that are only closed by a gob of pro seal. It sure doesn't give you a warm fuzzy feeling to know that shortly, I'll be sharing the cockpit with that tank. I love the design and building process of the airplane, so far, but I do think of the tank design as a weak link, particularly, given it's location. Steve
 
Let me clear the air a little. I guess I touched a sore spot when I had negative comments about the fuel tank. I concluded my comments by stating "What a mess". That comment was not a reflection on the design of the tank, but simply the condition of my tanks appearance after a few hours of assembly.
However, I still have concerns with so many penetrations that could be a source of leakage into the cockpit. It would have been nice to have a welded tank with a screw-on top. Fuel fittings could have been welded in and fuel window could have been a tube such as in a Super Cub. The fuel level sender could have electronic through the top cover eliminating most of the leak paths below the top level of the fuel.
Having said all this, what have you who have finished the tank done about the dobs of sealant on the ends of the rivets inside the tank? Is there a concern that these dobs could break of from sloshing fuel and plug the passages through the baffles or the fuel screen? Have you cleaned off the excess sealant around rivet heads on the outside?

Art Pennanen
 
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My OPINION some more

I don't feel the little dobs on the end of the rivets are of any concern. The stuff stick together pretty well. I plan to cover up the window, and install a marine mechanical sender. I am not overly worried about the corners, even thou there is a fairly big gap to fill. If we put enough on in those corners, I think they will be fine. The window has been my only real concern. Lots more places along there to potentially leak ( MY OPINION ). Time will tell us how this all plays out. I mainly want a mechanical gauge to turn around and look at just to feel more comfortable the electric one is working well. Also see when filling, from the outside.

John Bender
 
Fuel tank leak in red RV12 demo ride

I got a demo ride in the red RV12 at this year's Sun&Fun. After doing several steep turns, you could smell the fuel. That would been bad news on a long trip.If I can find someone to weld up a tank, I think that's the way I'll go.
 
I got a demo ride in the red RV12 at this year's Sun&Fun. After doing several steep turns, you could smell the fuel. That would been bad news on a long trip.If I can find someone to weld up a tank, I think that's the way I'll go.

It was right after Sun & Fun that all RV-12 builders were told not to install the sight window in their tanks because the window failed during the trip to Sun & Fun (so no surprise you smelled fuel).

If someone takes a demo ride this weekend while it is at the Copperstate fly-in I don't think the passenger will even be able to tell the tank is in the cockpit unless someone tells them.
 
It was right after Sun & Fun that all RV-12 builders were told not to install the sight window in their tanks because the window failed during the trip to Sun & Fun (so no surprise you smelled fuel).

If someone takes a demo ride this weekend while it is at the Copperstate fly-in I don't think the passenger will even be able to tell the tank is in the cockpit unless someone tells them.

Hi Scott,

I am not sure which story is correct Scott, above you said that there was a failure of the window indicating that it was producing the leak and smell, but when Van's sent us the notice it said the following:

"Dear RV-12 builder,
During a recent inspection of Van?s prototype RV-12, it was
discovered that the fuel tank sight window, T-1210, was ?crazing?.
While this window has been in service for a year, Van?s is
investigating alternative materials that will better resist the harsh
environment inside the fuel tank. If you have not installed your T-
1210 sight window, Van?s recommends that you do not install it at this
time. Van?s is currently researching alternative materials and will
make new sight windows available as soon as we have procured that
material."

I would not thing that what we normally think of as "Crazing" would cause leakage and smell. So that begs the question of what are the facts regarding the window? If it was not leaking where did the fuel smell come from and if it was the window leaking then the people who are flying with the old window should know if there was in fact a failure that produced a leak.

Best regards,
Vern
 
Hi Scott,

I am not sure which story is correct Scott, above you said that there was a failure of the window indicating that it was producing the leak and smell, but when Van's sent us the notice it said the following:

"Dear RV-12 builder,
During a recent inspection of Van?s prototype RV-12, it was
discovered that the fuel tank sight window, T-1210, was ?crazing?.
While this window has been in service for a year, Van?s is
investigating alternative materials that will better resist the harsh
environment inside the fuel tank. If you have not installed your T-
1210 sight window, Van?s recommends that you do not install it at this
time. Van?s is currently researching alternative materials and will
make new sight windows available as soon as we have procured that
material."

I would not thing that what we normally think of as "Crazing" would cause leakage and smell. So that begs the question of what are the facts regarding the window? If it was not leaking where did the fuel smell come from and if it was the window leaking then the people who are flying with the old window should know if there was in fact a failure that produced a leak.

Best regards,
Vern

Depends on whether you understand what crazing is.
Here is one definition I found...

"this is a term generally used when describing a defect of an item. Crazing is the same as cracking, except that crazing is often very small, almost undetectable cracking."

My personal definition fits this..."tiny random cracking that may or may not be through the entire thickness of a material"

It is easy to see (for me at least) that if the site window had crazing (as reported to all RV-12 builders), and any of the tiny cracks allowed fuel to the outside, it would be detectable in the cockpit.
 
It was right after Sun & Fun that all RV-12 builders were told not to install the sight window in their tanks because the window failed during the trip to Sun & Fun (so no surprise you smelled fuel).


The notification was several weeks after Sun-n-Fun. Did Van's know about a fuel tank problem in April, but wait until June to notify builders?
 
The notification was several weeks after Sun-n-Fun. Did Van's know about a fuel tank problem in April, but wait until June to notify builders?

I have no idea what the time line was.

The airplane was transported to and from S & F on a truck so a couple weeks passed while it was being transported home.
 
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