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Honda 1.8L on RV6A Now Flying!

I have watched your progress, very impressed.I know you are busy, but could you e mail me a copy or even rough scetch of your engine mount measurements,just part on engine to mount ,not mount to firewall.THANKS
[email protected]. Tomcatrv4. Tom Hankamp
 
Continued best luck... I've been following your progress for several months. Wish I lived closer so I could come and take first hand look.

It is always encouraging to hear others out there are finding some value or enjoyment with this project. Visitor are always welcome but i know you're too far to just stop by. Thanks for checking in. Charlie.
 
I have watched your progress, very impressed.I know you are busy, but could you e mail me a copy or even rough scetch of your engine mount measurements,just part on engine to mount ,not mount to firewall.THANKS
[email protected]. Tomcatrv4. Tom Hankamp

Sure. Be happy to. Ire-did the plates to have the engine and prop fit the cowling better. Fortunately it's an easy and inexpensive mount design and it is easy to modify.
If there interest I could post it all here.

Unfortunately I'm out of state next week on a working vacation. So nothing to share real soon..
 
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New pics on radiator belly mount mock up

Below is a test fit of the radiator under the belly both from the side and the front. It is bit hard to see but the first pic is from the side and shows a carboard template of how the side of the box that the radiator would be housed in.

Truthfully, it is longer than I think I am comfortable with. Ross if you read this can you share how long your box turned out to be - front to back? I think this is roughly 42 inches total front to back.

o1i.jpg


The next pic is of the radiator positioned under the belly. It is just held up there on cardboard boxes.

o10.jpg
 
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The last post would not take the other pic of the radiator under the belly so let me try it again,.

o1X.jpg


What do you guys think?

Do you think the side view of the cardboard template shows a box that is too long? Personally I am leaning towards shortening it up 4" to 6"

More pics to follow.

Charlie
 
I'll measure mine tomorrow. You can shorten the aft part behind the rad as the air won't separate as it converges.
 
Ross, thanks. Thats very helpful. But it also surprises me..

I think it's because yours has the nice contours and my sides will be straight tapers that mine looks longer comparatively. I measured my cardboard template and it was 48".

Charlie.
 
My rad is about 2/3rds of the way down the duct from the inlet plus it has a guide vane to turn the air upwards and avoid separation.
 
I am sure my tanks are wider than yours so I definitely will be fairing them out of the flow. My tank will also be about 2/3 of the way "in" the box. Since my cowling will protrude down in the airstream a bit my opening overall will be larger. I have to make it wider too. I am leaning towards 4"H x about 18" wide for the inlet and about 5"H x 18" outlet. The outlet will not have a swing ramp to vary the outlet. If it cools too much I may consider adding an adjustable flap up front, but that will be put off for quite some time after much testing.

As far as attachment goes, I am lucky that I have "L" aluminum stiffners in the floor right above the front "walls" above the tank. I probably will use driven rivets there and pulled rivets the rest of the "L" angle where it attaches to the belly. All angle will be 3/4" 0.63" 6061. I plan to use #8 screws/nutplates for the side walls of the box where they attach to the angles at top. The rest of the box will be LP4-3 rivets from Vans.

The tank will be its own section 8" long. The back will be a section and the front another section all 0.32" 2024-t3 aluminum sheet from Vans. Over all it should be about 8.5" tall, 24" wide at the tank, and about 43" long...

Feel free to comment on the plan...

Pic of shorten cardboard mock up.....

o1j.jpg



Charlie
 
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I am leaning towards 4"H x about 18" wide for the inlet and about 5"H x 18" outlet. The outlet will not have a swing ramp to vary the outlet. If it cools too much I may consider adding an adjustable flap up front, but that will be put off for quite some time after much testing.

Feel free to comment on the plan...

Those are very large areas, both inlet and outlet, in particular given the theoretical higher efficiency of a water to air exchanger. And closing the inlet in order to to throttle flow would be bass-ackwards. You want to throttle the exit. "Swing ramp" sounds right.

Before going too much further down this path, are you sure you can't move the exchanger(s) inside the cowl? Most sport airplanes get real slow with something the size of a garden wheelbarrow strapped to the belly. You're a good fabricator; treat it as a challenge. Heck, Eggenfellner did it with the Subaru packages, and I note SARL racers with nicely integrated water cooling.
 
Those are very large areas, both inlet and outlet, in particular given the theoretical higher efficiency of a water to air exchanger. And closing the inlet in order to to throttle flow would be bass-ackwards. You want to throttle the exit. "Swing ramp" sounds right.

Before going too much further down this path, are you sure you can't move the exchanger(s) inside the cowl? Most sport airplanes get real slow with something the size of a garden wheelbarrow strapped to the belly. You're a good fabricator; treat it as a challenge. Heck, Eggenfellner did it with the Subaru packages, and I note SARL racers with nicely integrated water cooling.

Dan,

No doubt this will surely add drag to the ship. But honestly that scoop (while a aberration for an RV purist) is actually starting to grow on me...But yes, I have spent hours trying to squeeze it in the cowl and the only way that would be possible would put the radiator sideways to the flow and even then it would be real tight. I know a few of the rotary guys used condenser cores up front and other custom radiators but this engine is tight up front on the right side - just the way it turned out....But yes, I think with some custom work and probably using two small radiators you could pull it off. Or if you build a custom cowl, but I don't want to do that again....

Actually the other concept I seriously considered was laying a thin one inch core flat against the belly. This would greatly reduce the side view (Height?) of the scoop and help a lot in the Looks category. I think a one inch core that was about 24" x 18" would work quite well. There would be some challenges with the tubing, but nothing too tough. Ultimately I went this way because I know several have done it and had very good success with it.

The next post asked about a P-51 style scoop. Yes, absolutely I did consider that. If you mean just a small scoop in the belly with the radiator aft in the fuse..... The only downsides this would be what it does the balance and that far aft with this airframe and the internal ducting for outlet was enough to cause me to pass.....And of course you would still end up with a inlet down in the airstream under the belly so not a whole lot of "gain" and lots of extra work. But yes, I thought of it.
 
Dan,

No doubt this will surely add drag to the ship. But honestly that scoop (while a aberration for an RV purist) is actually starting to grow on me...But yes, I have spent hours trying to squeeze it in the cowl and the only way that would be possible would put the radiator sideways to the flow and even then it would be real tight. I know a few of the rotary guys used condenser cores up front and other custom radiators but this engine is tight up front on the right side - just the way it turned out....But yes, I think with some custom work and probably using two small radiators you could pull it off. Or if you build a custom cowl, but I don't want to do that again....

Actually the other concept I seriously considered was laying a thin one inch core flat against the belly. This would greatly reduce the side view (Height?) of the scoop and help a lot in the Looks category. I think a one inch core that was about 24" x 18" would work quite well. There would be some challenges with the tubing, but nothing too tough. Ultimately I went this way because I know several have done it and had very good success with it.

The next post asked about a P-51 style scoop. Yes, absolutely I did consider that. If you mean just a small scoop in the belly with the radiator aft in the fuse..... The only downsides this would be what it does the balance and that far aft with this airframe and the internal ducting for outlet was enough to cause me to pass.....And of course you would still end up with a inlet down in the airstream under the belly so not a whole lot of "gain" and lots of extra work. But yes, I thought of it.

Ross did some extensive testing on his cooling, I'll look it up, but if memory serves, he had quite low drag. High exit velocity. The heating of the air makes up (some) for the drag across HX. It would be wise to simply improve on his proven work.
 
Ross did some extensive testing on his cooling, I'll look it up, but if memory serves, he had quite low drag. High exit velocity.

Quite low cooling drag (internal flow)...an attempt to prove the Meredeth Effect, i.e. thrust created by an exit velocity higher than freestream. And he did prove it, sort of. The published maximum exit velocity value (from Kitplanes) was 104% of freestream at 80 KIAS.

That's very good, but note that at 80 knots, the actual freestream velocity delivered to the diffuser inlet is much higher than indicated airspeed, due to the huge propeller outflow component. The prop outflow effect can also be seen in measurements of an aircooled installation:

http://www.vansairforce.com/community/showpost.php?p=1177277&postcount=198

Even if the exit velocity was less than 100% of freestream at cruise speeds (and I suspect it was), it is still very likely a lot higher than the average Lycoming cowl. That part is a win, a reduction in drag due to internal flows.

Returning to the context of this thread, Ross wrote that he made no attempt to measure the external aerodynamic drag of the installed belly pod. Further, the system as proposed retains flow through the cowl, another drag cost. I'm suggesting Charlie consider all his options before hanging a wheelbarrow-sized pod on the belly. If the exchanger(s) can't be fitted inside the cowl, then perhaps take a look at the beautiful underwing ducted exchangers we recently saw on an RV-8 in Oz. Simply moving the pod out of the propeller outflow would mean a significant reduction in external drag.
 
I picked up a solid 5-6 knots with my belly scoop over nothing there before (well some other small inlet and outlet ducts feeding from multiple HXs). When viewed from the front, there isn't much frontal area added since the stock exit duct area covers most of the rad duct frontal area. Looks like the momentum recovery offsets most or all of the duct drag in my case.

Cowling mounted can work but the result is more weight forward, poor momentum recovery and often marginal cooling.

I've followed numerous rad layouts and had internally mounted rads on my own plane for years. I spent a lot of time changing it all over to the present layout and couldn't be happier. It's lighter, faster and improved the C of G while cooling much better than previously.

You shouldn't need more than 25 square inches of inlet area with a proper duct shape to cool 180hp in flight. Extra area may be beneficial in ground cooling. With extra inlet area and a movable exit door, your cruise drag penalty is probably slight. Lots of compromises involved here. Certainly you don't want to overheat on an 80-90 degree day with a long ground hold somewhere.

I wouldn't look to Eggenfellner's layout as a good model. Lots of folks had marginal or inadequate climb cooling and had to step climb or cruise climb on hot days.
 
Quite low cooling drag (internal flow)...an attempt to prove the Meredeth Effect, i.e. thrust created by an exit velocity higher than freestream. And he did prove it, sort of. The published maximum exit velocity value (from Kitplanes) was 104% of freestream at 80 KIAS.

That's very good, but note that at 80 knots, the actual freestream velocity delivered to the diffuser inlet is much higher than indicated airspeed, due to the huge propeller outflow component. The prop outflow effect can also be seen in measurements of an aircooled installation:

http://www.vansairforce.com/community/showpost.php?p=1177277&postcount=198

Even if the exit velocity was less than 100% of freestream at cruise speeds (and I suspect it was), it is still very likely a lot higher than the average Lycoming cowl. That part is a win, a reduction in drag due to internal flows.

Returning to the context of this thread, Ross wrote that he made no attempt to measure the external aerodynamic drag of the installed belly pod. Further, the system as proposed retains flow through the cowl, another drag cost. I'm suggesting Charlie consider all his options before hanging a wheelbarrow-sized pod on the belly. If the exchanger(s) can't be fitted inside the cowl, then perhaps take a look at the beautiful underwing ducted exchangers we recently saw on an RV-8 in Oz. Simply moving the pod out of the propeller outflow would mean a significant reduction in external drag.

It's good to consider all options but we who've already done it, have.

Most of my flight testing was done at 100-120 KIAS at around 6000 MSL. Yes, I had no way to quantify where the 5-6 extra knots came from- the magic properties of momentum recovery or the removal of several other ram ducts, NACA ducts and exit ducts.

Prop outflow is significant within a foot or so of the prop and drops off rapidly with distance. You can see a lot of the F1 guys run the carb snorkel within a few inches of the prop and see some very useful gains in MAP. My inlet is almost 40 inches from the prop disc. I did a test at some point to try to determine this figure but not sure if I recorded it. I'll consult my old notes. I only recall it wasn't very significant on my installation in flight.

Several Unlimited P51s experimented with removing the rad duct over the years and found little to no gain in speed. This again suggests that, properly done, a good duct has minimal, if any penalty. They could have fitted wing rads if they were better but other tests on the Spitfire and BF109 post war, showed that the short duct has high inlet separation which means more drag ultimately. No surprise there, though they could have been vastly improved with a guide vane I'd think, judging from what Russell Sherwood and I both saw in testing.

The big minus is that rad ducts on the wings outside the prop arc guarantee overheating on the ground within minutes on a hot day. Simply not practical for a GA airplane.
 
Prop outflow is significant within a foot or so of the prop and drops off rapidly with distance.

Not that simple. Consider an RV at 1800 RPM on the runup pad. Airspeed is zero, yet prop outflow would make it hard to stand upright behind the tail. Stand behind one at 2700 RPM, tied to a truck, if you can.

Prop outflow as an incremental addition to freestream drops off with increasing airframe velocity, or decreased power.

My inlet is almost 40 inches from the prop disc. I did a test at some point to try to determine this figure but not sure if I recorded it. I'll consult my old notes. I only recall it wasn't very significant on my installation in flight.

It would not be at cruise settings. Was the 104% at 80 measured with climb power, level at steady low power, or with engine at idle, in a glide?

The big minus is that rad ducts on the wings outside the prop arc guarantee overheating on the ground within minutes on a hot day. Simply not practical for a GA airplane.

Interesting point. Was Geoff Braddock having that problem?

http://www.vansairforce.com/community/showthread.php?t=145250

BTW...

This is pretty much the recipe I'd use today if I was doing another RV using an alternative engine.
 
Not that simple. Consider an RV at 1800 RPM on the runup pad. Airspeed is zero, yet prop outflow would make it hard to stand upright behind the tail. Stand behind one at 2700 RPM, tied to a truck, if you can.

Prop outflow as an incremental addition to freestream drops off with increasing airframe velocity, or decreased power.

It would not be at cruise settings. Was the 104% at 80 measured with climb power, level at steady low power, or with engine at idle, in a glide?

Interesting point. Was Geoff Braddock having that problem?

http://www.vansairforce.com/community/showthread.php?t=145250

BTW...

Indeed, full throttle on the ground on my plane produces a couple inches of pressure at the cowl cheeks, no dispute there. In flight, a different story. Confirmation by measurement. If I get a chance, I'll instrument again and fly if I can't find my old data.

Now, if we look at something like Strega which has had hundreds of mods done to make it faster, including a massively revised scoop, radiator and cooling system trying to find every knot through drag reduction, you think they wouldn't have gone to wing mounted rads if they thought they would have gone faster?

My data was taken at steady state, straight and level, stabilizing for a couple minutes in most cases. Trying to measure for my purposes in the climb would have thrown more variables into the mix.

Looks like Geoff's installation would have some of the rad face in the prop blast. Certainly if rads our mounted outboard of this, you'd only have still air conduction on the ground and essentially zero cooling. No delta, no flow, no cooling.
 
Folks,

I have not firm up the exact inlet and outlet dimensions. The main difference between Ross' set up and what I am dealing with is the center section of my cowling bottom does extend down below the fuse belly some. Right now I am looking at 4"H x 18" inlet which I know is a lot more than what Ross recommends. But....about 40% is covered by the cowling belly. I will need to stay at the 18" width of the inlet due to the bottom cowling bump, but Ross' research and experience gives me encouragement that I should be able to get the height of the inlet down to 3" or so. I will create another cardboard mock up soon.
 
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I have not firm up the exact inlet and outlet dimensions. The main difference between Ross' set up and what I am dealing with is the center section of my cowling bottom does extend down below the fuse belly some. Right now I am looking at 4"H x 18" inlet which I know is a lot more than what Ross recommends. But....about 40% is covered by the cowling belly. I will need to stay at the 18" width of the inlet due to the bottom cowling bump, but Ross' research and experience gives me encouragement that I should be able to get the height of the inlet down to 3" or so. I will create another cardboard mock up soon.

Adding frontal area because you already added frontal area? Brother Charlie, think outside The Box.

If the center of the cowl hangs low, perhaps you could use two inlets, one on each side of the hanging cowl section.

Perhaps two inlets and two exits....two separate ducts systems. The narrowed width of each heat exchanger could proportionally shorten the inlet and exit diffusers. Conceptually it would be a little like the underwing exchangers, except being inboard on the fuselage, you are not so constrained in overall length. And I'd try to move them rearward some. You want the inlet in a high pressure area and the exit in a low pressure area.

There is also an aesthetic aspect. None of this need look like a wheelbarrow.

http://www.vansairforce.com/community/showpost.php?p=745120&postcount=129
 
Dan,

I honestly don't know what causes you to feel the need to ridicule and nitpick my project - calling it a wheel barrow. I can think of many reasons what causes this behavior but I am not a psychiatrist.

It is rude and most important it is unwanted. I have asked you to stop and even others have asked you to stop. Yet it continues.

I have already had a moderator delete one of your post hoping you would get the hint.

There are too many good people who for reasons of their own, are interested in my project and your unwelcome parental behavior stinks. So regardless of your reasons - stop.

Charlie
 
I thought it might be help or of interest at least to most people, what the cowl bump and its relation to the belly inlet looked like so here is a pic.

Notice on the cardboard template there is a line at the bottom marking where a 3"height would take the inlet as compared to the template itself which is 4". Based on Ross' real world experience I am leaning towards making it 3".

o12.jpg
 
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Here is a pic of the radiator submersed in water where I pressurized it to 15 lbs. It passed with no bubbles.

o1B.jpg
 
I honestly don't know what causes you to feel the need to ridicule and nitpick my project - calling it a wheel barrow.

Put that chip back in your pocket Charlie. You asked for comments. It's unreasonable to expect nothing but "Wow, that's great!"

I've been dead serious. The proposed inlet and exit areas are excessive, throttling the inlet would be a technical error, the additional frontal area adds external drag, and it's not going to be pretty. I don't believe in being critical without proposing solutions, so I've linked photos of other liquid cooled aircraft, proposed ideas, and explored details. You're under no obligation to consider any of these things, but they are legitimate commentary.
 
On the inlet sizing question, assuming you have the rest of the duct/ diffuser shape and rad sizing correct, experiments by Russell Sherwood have shown that he can cool 230hp with less than 15 square inches of inlet area. He said he'd go down to 12.5 if there was another iteration in the future. It does look like ground cooling is impacted somewhat by reducing the inlet size so be careful there.

On my installation, the main rad inlet is a lot bigger than that primarily because I couldn't get my hand and wrench in to access the bolts which attach the splitter to the rad and would have had great difficulty in laying in the glass and resin if it had been smaller. As you shrink the inlet, the diffuser shape and guide vane placement become more critical to make it all work efficiently so that is a consideration too.

The penalty of a slightly oversize inlet is minimal from what we know as long as you can throttle the exit.

This all being said, none of us want to re-do a rad scoop design which doesn't cool adequately in the climb or on the ground so we tend to fudge the rad and inlet sizes upwards.
 
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Put that chip back in your pocket Charlie. You asked for comments. It's unreasonable to expect nothing but "Wow, that's greaD

Dan,. You missed it completely. Your parental dismissive comments are unwelcome.

I have always welcome constructive comments that are respectful. And when they come from some one who has real world experience like Ross, it has value. When it comes from someone who works at putting others down to make themselves (think they) sound smart it's arrogance. Stop it. Move on to somewhere else.
 
On the inlet sizing question, assuming you have the rest of the duct/ diffuser shape and rad sizing correct, experiments by Russell Sherwood have shown that he can cool 230hp with less than 15 square inches of inlet area. He said he'd go down to 12.5 if there was another iteration in the future. It does look like ground cooling is impacted somewhat by reducing the inlet size so be careful there.

On my installation, the main rad inlet is a lot bigger than that primarily because I couldn't get my hand and wrench in to access the bolts which attach the splitter to the rad and would have had great difficulty in laying in the glass and resin if it had been smaller. As you shrink the inlet, the diffuser shape and guide vane placement become more critical to make it all work efficiently so that is a consideration too.

The penalty of a slightly oversize inlet is minimal from what we know as long as you can throttle the exit.

This all being said, none of us want to re-do a rad scoop design which doesn't cool adequately in the climb or on the ground so we tend to fudge the rad and inlet sizes upwards.

Ross the real world experience and research is super helpful. I am incorporating these concepts (generally) in my design. I'm still in the cardboard template stage. The radiator will be at or larger than yours, even though I will be at lower HP.

In case some folks have not noticed I'm not driven to win style points and while I appreciate and value learning from others who have actual been there experience, I,'m also not driven to spend lots hours to achieve perfect efficiency. Others who have gone before me like you and Dave Anders, my hats off to you!. And thank you very much for sharing your lessons leard.

My scoop will be aluminum sheet. It's what I'm comfortable working with. It will be simple. It will be attached by screws and easily removable if needed.

It won't be perfect. It will work well. I'll continue to share my progress as long as there is interest.

Charlie.
 
Put that chip back in your pocket Charlie. You asked for comments. It's unreasonable to expect nothing but "Wow, that's great"

Dan,. You missed it completely. Your parental dismissive comments are unwelcome.

You're under no obligation to consider them, but they remain legitimate commentary...and not written for you alone.

Stop it. Move on to somewhere else.

Request declined. You post as you wish, as will I, both within a reasonable interpretation of the VAF rules. Please note that personal comments are generally not acceptable.
 
...

arrogance noun
ar?​ro?​gance | \ ˈer-ə-gən(t)s , ˈa-rə-\
Definition of arrogance
: an attitude of superiority manifested in an overbearing manner or in presumptuous claims or assumptions
 
Hey Dan, I would have figured the post was pointed in a different direction....
But hey, what do Lower Slobovians know?
 
Kinda hard to post on a public forum asking what others think, then get mad when people give you well reasoned input with examples. I for one appreciate the discussion and think it should be perpetually available for future builders.
 
Comments even constructive critical ones have always been welcome. But there is no excuse for comments that are demeaning. To put this another way, most people can be constructive even in critque without feeling the need to be parental or rude.

Let's hope future comments are in the spirit that is so we'll stated by Bob Collins in his open letter on the VAF rules page.

If you have not read it please do so and use it as the VAF leadership has requested.

Charlie.
 
Comment

I see no personal attack, only the definition of a word.

If, however, you feel it applies, consider it ?legitimate commentary?...

Make it a great day.
 
New TB mount

Attached is a pic of the new adapter I had made up that repositioned the TB so it will fill well in the cowl. There were several factors that caused me to chose this. One being the location of the exit of the turbo, second my desire to try to get "straight on" air flow to the intercooler, and of course the challenge of obtaining a smooth travel for the throttle cable. Given these factors this seemed to be the best choice.

o1Q.jpg
 
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Charlie

I really enjoy following your progress. You get a lot done in short order. It's amassing what people accomplish these days. When I was a kid the talk of the neighborhood was a guy building a row boat in his basement.

Keep up excellent work. Hope to see you flying soon...
 
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Jim,

Thanks. It is a labor of love for sure. Your signature line shows you have a lot of experience and my hat is off to you! Truthfully my day job really gets in the way but fortunately I retire soon, and then I plan to burn the midnight oil.

The honda on an RV6A airframe is certainly not for everyone, but I enjoy it and I am optimistic that it will work out. What is most value to me has been those who have forged the path before me by installing an alternative engine in a plane and seeing it fly. I have learned a lot from those who are willing to share their success and failures (which is really hard for some people for obvious reasons).

Glad there are a few out there who enjoy what is happening here.

Good flying to you.

Charlie
 
I'm doing my annual now and will also install my twin Shorai batteries while I have it all apart.

I measured my oil cooler and it's about 8 X 8 X 2 inches.
I also use a Mocal oil thermostat to feed or bypass the cooler. Helps with the warmup in cooler weather.
 
Ross,

Thank for checking that out and posting. I am convinced it is important to have an oil cooler if using a turbo.

Charlie
 
Rough in test fit of intercooler routes

I am doing some initial testing to try to find the best location for the intercooler. It is important to know that the intercooler orientationn as seen in this pic probably not going to end up as you see it in this pic. But I thought it would be interesting for some to see the beginning stages of where and how the intercooler will be plumbed. I also have two intercoolers and may use the other one and may even modify them as needed.

I am trying to get it so it will be "straight on" to the air that will be routed to it in cat hose. Which means it may be vertical. Of course this will also depend on how well this interfaces with the tubing that comes from the turbo.

One thing that is important to know when looking at this is that the exhaust will be where the orange line is. I noted that because many would ask why I did not consider this location for the intercooler.

Others may wonder why I don't put it forward on the left side of the cowling. One reason is that it would be a long haul for the charged air to get there and then back to the TB. The other is that it would be tough to get "straight on" flow to cool it.

Lots more testing fitting to happen before final decisions are made.


o1a.jpg
 
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Sheetmetal break examples

Many of you will already know this and may have additional helpful hints to add, please do so...

As I begin to fabricate the aluminum sheet box (Belly scoop) for the radiator mount, I wanted to do some testing to get the right radius of bend. I will have to keep it fairly sharp due to the bottom of the radiator is square and the metal will be tight up against it.

I made my own break with a couple of pieces of straight and flat wood with a simple hardware store hinge. I use a 1/8" angle steel with 1.5" x 1.5" sides as the "break" to clamp down on the metal to keep it secure while it is being bent.

You will see in the pic below (I apologize it is quite big, there is detail in it that I wanted to make sure was fairly easily recognized) there are 3 test pieces with various radius curves. You get a more gradual bend if you set the "break" bar back from the hinge. It is hard to see in the pic but if you look close at the right side at the end, you will see a line labeled as "1/4" and another "1/2". Below you will see the results of the test. The sharpest was done at zero, the next at 1/4" offset and the last at 1/2" offset.

Also notice the bottom board is longer than "tilt" board - This is important so when you bend the sheet you can go past 90 degrees without hitting the clamps.

o1d.jpg
 
i made a welded 26 gallon tank for my 12 and i made the bends for the flanges and short bends. for .062'' 5052 the book says 3/16'' radius [i think]. i took 3/16'' steel bar stock 11/2'' wide and with a bench grinder and belt sander i did a pretty decent job of rounding the edge. i set this bar back at least the thickness of the sheet metal from the edge where the brake bends. 5052 is a little softer but even with 2024 and 6061 i get real nice bends, no indication along the bend that the sheet metal has been weakened. i use this bar for all my bending.
 
Bob, Thanks for sharing. Your set up sounds better. If I would have had that thick of a piece that was long enough I would have done the same.

If you have a pic of that rounded edge feel free to post it here.

Charlie.
 
It is easy to make inserts of varying radii to use in a traditional (sharp nosed)
or home made bending break.

Just cut a few strips of thin (~ .020) material about 2" wide.
Bend one with the brake to about 120 deg (or as far as it will go) and then keep progressively adding another under the previous bent one. Each one will have a bigger radius than the last.

You can then nest as many as you need to get the radius you desire , and with the set back adjusted properly the bend you make will be totally symmetrical.
 
Scott weird you mentioned that. The general concept ran through my mind but I had never done that or seen it done.

Thanks for sharing, I sure people will try it. I will.

Charlie
 
pulled rivets

As I venture towards the fabrication of the radiator belly scoop I am revisiting my supply of pulled rivets.

While driven rivets are certainly stronger, there are a wide variety of pulled rivets to consider.

I personally like the LP pulled (blind rivets that Vans sells, but I know there are a lot more rivets on the market and it can get confusing. I am certainly no expert but I thought I would share some of my observations.

One thing that is often noticed is that some rivets are sometimes labeled as "non-structural". There are design features that dictate that label including body alloy, shaft alloy, head shape, and stem shaft retention. The one feature that seems to stand out more than others though is the length of the remaining portion of the stem shaft. Does it break off at the "top" of the head, or considerably lower in the bottom of the body.

The best example of this is when you look at the Cherry "N" rivet verses the Cherry "Q" rivet. The Cherry "N" stem breaks off low in the finished body and does not transcend the line where the two parent metals are mated. Hence it provides no extra value in shear tension. On the other hand the Cherry "Q" stem is designed to break off up high towards the "top" of the head of the rivet after being pulled. This results in the stem shaft transcending across seam where the two metals are joined and offer additional strength for the rivet especially in shear.

This is why you will see that the Cherry "N" rivets and the "Q" rivets have virtually the same strength rating in tension, but the "Q" is almost double in strength in shear.

Here is a quick test I did comparing the AVEX 1610-0410 rivets with the LP4-3 rivets that vans sells.

The strength of the AVEX 1610 series is well advertized but I have not been able to find the strength of the LP rivets. (Scott if you are reading is that something you can share?)

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beginning of the belly scoop

I thought I would share some pics of the beginning of the fabrication of the belly scoop. It will be mostly 0.032 - 2024-T3 sheet aluminum. Something I am comfortable working with.

The angle aluminum 0.63 6061-T6 angle that will be rivets to the bottom of the belly of the plane.

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And a pic of the side panel that will be screwed into the angle aluminum at the top. (the blue color on the aluminum sheet a the protective plastic coating).

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The strength of the AVEX 1610 series is well advertized but I have not been able to find the strength of the LP rivets.

Charlie - The LP4-3 rivets on my RV-12 are manufactured by Gesipa and are the PolyGrip - MultiGrip series. According to factory specifications from the Gesipa catalog .... Shear =162 lbs. Tensile = 236 lbs.

Have been following your progress and really enjoy reading about your build.

Happy building,
 
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