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AX-O's Fastback RV-4

Axel,
Thanks for posting all the updates to your RV4. I think you have the perfect setup now for an RV4. I had an RV4 with a carbureted O-320 and a Catto prop that was the nicest flying RV I’ve had (I’ve had four) - and the most affordable. The best improvement would have been a constant speed prop, but that would have involved making those blood thirsty cuts in the firewall step. I built another RV8 instead. I just installed a Whirlwind 200RV on our new RV8 (my third on an RV), and I also recently installed dual E-Mags.
My question for you is, what benefit have you realized by having the EI Comander? I’m not racing my plane, and don’t plan on any competition aerobatics. Is the standard B curve sufficient? I have an IO-360 with 9:1 pistons and an Av star FI system. Event though I can’t adjust my timing in flight, I don’t know if I need to. Maybe you haven’t flown yours yet, but if you have, please let me know the advantages of the EI Comander.
Thanks
 
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Is the standard A curve sufficient? I have an IO-360 with 9:1 pistons and an Av star FI system. Maybe you haven?t flown yours yet, but if you have, please let me know the advantages of the EI Comander.
Thanks

Thank you, I hope all this work is worth it.

I have not flown yet. will let you know how it goes. I can tell you that it was very easy to send a curve compared to the previous way of doing it.

Hopefully this wont start a thread drift. These types of questions are like asking what kind of primer to use :)
 
What is the advantage of a CS prop for racing? Or did you add it for a different reason? I would have thought that for a race there is only one speed range...balls out!

(Ps...balls out is a reference to the brass balls on a steam engine governor. Nothing to do with anatomy, just in case anyone might be offended ��)
 
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What is the advantage of a CS prop for racing? Or did you add it for a different reason? I would have thought that for a race there is only one speed range...balls out!

I did not do it for racing. I expect to loose 2-3 knots top speed. That been said, One of the things that killed my speed around the track was exiting the pylons with low RPMs. The RPM would drop and i would loose a lot of speed. It would take some time to build the RPMs back up. and by then I was in another turn. So my time around the track may be slightly afected now that the RPM would remain constant.

Not sure I will be racing at Reno with this plane any more. The plane just gets beat up and a non-boosted or non-nitrous RV in the sport class is not guaranteed a spot in the field of 36 now.

I have mixed feelings about this convertion. However, All this may go away once I satrt flying. TBD at this moment.
 
I did not do it for racing. I expect to loose 2-3 knots top speed. That been said, One of the things that killed my speed around the track was exiting the pylons with low RPMs. The RPM would drop and i would loose a lot of speed. It would take some time to build the RPMs back up. and by then I was in another turn. So my time around the track may be slightly afected now that the RPM would remain constant.

Not sure I will be racing at Reno with this plane any more. The plane just gets beat up and a non-boosted or non-nitrous RV in the sport class is not guaranteed a spot in the field of 36 now.

I have mixed feelings about this convertion. However, All this may go away once I satrt flying. TBD at this moment.

I think you will love the constant speed prop!

Skylor
 
I think you will love the constant speed prop!

Skylor

Having gone from planes with, to planes without, I agree. What keeps me away these days is simple: Money. Just can't justify the expense the complexity brings with it, for the amount of flying I do.
 
Flew the plane yesterday for .6 hrs. Will write something up tonight if I get the chance. The plane is way different to fly. Will need some time to get used to it.

With the limited flight time; the plane feels less maneuverable, heavy on the landing flare but it climbs like a bat out of you know what.
 
Very interesting build out. What's the empty/WT.

Cheers, Hans

Hans, I came out at 1,013lb and CG of 69.9 inches. I have not flown much but it does not fell as maneuverable. I know you are big into light and simple. Me too. Not sure this was the right thing to do yet. Will report out once I get some data.
 
Hey Axel,

I admire honesty and that's a porky plane ya have there :)

I still love the very light control forces of my RV4 and the simple combination of FP/160 hp Lyc. I've been flying this very same combo now for 30 years this coming June and never fail to return with a big azz smile.

Come my way someday and lets give the birds a workout with some ACM and see where the chips fall.

It's been a while since we've flown together and you'll get hangar space and a place to sleep as well.

Cheers, Hans
 
I admire honesty and that's a porky plane ya have there :)

Hans

Thanks for the offer.

I spoke to a few RV-4 folk with constant speed props and they are in the 1050s for weight. So I am not doing bad compared to them. I do like taking my hand off the stick and turning the auto pilot on, I also enjoy the nice creature comforts for my self and my wife. Different missions, different aircraft requirements.

Break

Engine shop is not calling me back or answering my emails thus far.

On to flight testing and completing the Phase I.
 
"I also enjoy the nice creature comforts for my self and my wife. Different missions, different aircraft requirements".

You're right on Axel, and I wish you successful mission completion.

My offer to come out and visit us stands nonetheless. The mountains here are incredible to enjoy from the seat of an RV4

Hans
 
1080#

The first RV4 I owned weighed in at 1,080 pounds with an O-360 and Hartzell prop. And it was bare bones. And it went like snot. Of the three (3) RV's I've owned, it was my favorite.

Don't sweat the empty weight.
 
Just curious what the others were

The first RV4 I owned weighed in at 1,080 pounds with an O-360 and Hartzell prop. And it was bare bones. And it went like snot. Of the three (3) RV's I've owned, it was my favorite.

Don't sweat the empty weight.

I?ve thought about converting to a C/S prop on my -4 but Axel?s comments about the changes in how the airplane feels confirms why I am reluctant to do it.

What were the other 2 RVs that you use for comparison?

Cm
 
Just a thought on control system feel. CG was a bigger factor than weight on my RV6. We had a relatively heavy six but the control response was very light. It was so light that despite being in limits we decided to move the CG forward. This may a big difference in the perceived feel of the aircraft. The airplane seemed heavier overall but the trade off in a heavier feel in pitch was much better formation flight and landing characteristics.
G
 
Bringing back the thread drift. Will have more on flying qualities soon. Hope to fly this weekend. I will be evaluating different cgs also.
 
Hans, I came out at 1,013lb and CG of 69.9 inches. I have not flown much but it does not fell as maneuverable. I know you are big into light and simple. Me too. Not sure this was the right thing to do yet. Will report out once I get some data.

I'm sure the majority of the difference you are feeling is due to the CG. That is a huge weight increase at the very front. So static long stab will go way up, force per G as well. That corresponds to what you are describing, especially the flare. Just get the wife in the back and it will feel like it used to. Or make a lead tailwheel. :D
 
It's been a long time since I have posted progress with the plane. In true Dilemma fashion, is not done.

I sold my 340 and decided to build a 360 so I could learn the inner workings of an engine since I was lacking that knowledge. I was fortunate enough to have a good friend (Dayton) help me with the task. he flew in a few times to give me a hand. Paul also flew in once to check things out.

I wanted a vanilla engine so I built an IOX-360, 9 to 1 compression, electronic ignitions, FM-150L from Don and cold air sump.

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Engine put together and ready to go in.
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Dang..... the width is going to be a problem. The 360 is half inch wider on both sides (inch total). Will need to address some issues later.
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Started experimenting with fiberglass and RTV to see if I could wrap my cylinders. results showed it was fairly easy to do if you sandwiched the materials between plastic sheets.
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Time to start wrapping the cylinders. Mark the shape of your piece on the plastic, put RTV on one plastic sheet, put the fiberglass on top, put another sheet of plastic on top, squeegee it evenly, cut it as required, pull one side of the plastic and stick it on the engine. Leave the other side of plastic on until the RTV dries. That leaves a nice finish on the outside.

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Time to start wrapping the cylinders. Mark the shape of your piece on the plastic, put RTV on one plastic sheet, put the fiberglass on top, put another sheet of plastic on top, squeegee it evenly, cut it as required, pull one side of the plastic and stick it on the engine. Leave the other side of plastic on until the RTV dries. That leaves a nice finish on the outside.

I know nothing about engines. Why do you snap cylinders and how much of a cylinder do you wrap? Just half?
 
I’m curious about this too. Will you use standard inter-cylinder baffle material, or something else to seal the gaps between cylinders? I assume that it will seal the fin areas better than aluminum sheet, but how is it going to hold up in use? When it comes time to do cylinder work will it come off easily? Has this been done before, or are you blazing a new trail? Good luck. Cant wait to see the final installation.
 
I’m curious about this too. Will you use standard inter-cylinder baffle material, or something else to seal the gaps between cylinders? I assume that it will seal the fin areas better than aluminum sheet, but how is it going to hold up in use? When it comes time to do cylinder work will it come off easily? Has this been done before, or are you blazing a new trail? Good luck. Cant wait to see the final installation.

Done before, flown 10 years, holds up fine, stays put, peels easily if desired. Think of it as a gasket which doesn't allow leakage out the side of the aluminum wraps. We want the air to go all the way to the wrap exit at 6 o'clock. Most don't; a lot of the flow goes out the sides and never makes it down the intended exit.

Install note: be sure to use a tiny strip of silicone between the silicone/glass wrap and the aluminum wrap. Don't want air passing down through the space between them.

In some locations it is also an extension, i.e. forces the air in between fins earlier so the turbulent flow has a longer path. The space between the cylindrical section of the cylinders is a good example. Normally those fins just get free air cooling. There is no need for an aluminum wrap over the silicone/glass, as the deltaP pushes the wrap against the cylinder.

There is some experimentation going on. For example, Bill Lane seems to have his wrapped so thoroughly that he is not getting any significant pressure rise in the lower cowl by shrinking the cowl exit...the baffles are now the system throttle. There is also some merit in a future experiment, which will be shaped inlets where the air enters the fin space, and diverging exits at 6 o'clock. In theory it might reduce pressure loss across the baffles.

Is this stuff really necessary? Strictly speaking, no. It's optimization.

Back to Ax.
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Wrapping the fins is nothing new. It is there to force the air through the fins and minimize spillage (wasted efficiency). Just like having a nice O-ring between parts to seal. If done right and in conjunction with the inlet and exit area, you can get very aggressive with the wrapping. In this case, I am just doing under the aluminum baffles and may modify as flight test goes on. Some portion above the cylinders too. Not sure how things will hold up to use. Got 10ish hours on the motor right now. None of this is required and Lycoming have been flying without this FOREVER. This is experimentation and validation of other people's experiments.

Below is a picture from Dave Anders. He told me his CHTs run in the 330s at cruise and he wanted to wrap the cylinders even more. Look at the pic closely, especially between the pushrod tubes.
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It doesn’t look like the cylinder base fins are getting any cooling at all. If this is the case, why don’t we just point cooling airflow at the cylinder head only? Reduce cooling inlet and exit accordingly.
 
It doesn’t look like the cylinder base fins are getting any cooling at all. If this is the case, why don’t we just point cooling airflow at the cylinder head only? Reduce cooling inlet and exit accordingly.

The above picture has openings to cool the base of the cylinders and mine does too. You should try an experiment and report back.
 
Next it was time for the baffles. I used the Van's baffles and modified them as required for fit. Also made a mod to the #2 and 4 cylinder baffle to allow air to flow past over the blockage on the fins. I made the hole in front of the #2 cylinder in such a way that I can enlarge it as flight testing goes on to tune the airflow. The pieces were received an RTV seal for final install. Pics are of the process and do not show final install.

#2 baffle
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#4 Baffle
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More baffle experimenting. I wanted to help the air intake diffuser to calmly expand the flow. I made damns at the base of the cylinder heads to help with the geometry. In the pics below I was already starting to figure out how the diffuser was going to attach. I laid one layer of fiberglass to keep the carbon fiber diffuser from touching the aluminum.

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Made new inlet diffusers plugs out of foam. Carved them to fit the baffles and cowl. Once done, I used quick-dry wall putty to fill out and smooth the surface. Also covered the mold with a few coats of epoxy resin. Used a torch to get the air bubbles off the molds and smooth everything. This worked out very well.

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The finished part (sorry for not being clear)...

I've had the idea that epoxy-impregnated fiberglass gets wonky above 200F.
 
I've had the idea that epoxy-impregnated fiberglass gets wonky above 200F.

Dan Addressed this already. In my case I have used standard West Systems epoxy vice high temp. The first few times it gets hot and cools down it smells strong and chemical-like. Parts are also not as strong if you push on it with your finger (flex a little more than when cold). as time goes on (keep cycling temps) the smell goes away and the part does not show any difference in flex. The hottest these part will ever be is after shut down when the hot air raises and has no where to go. At that point there are no loads acting on the part. When you are flying (loading the parts), air is coming in and cooling these parts.

Some people will read that I am not using high temp epoxy and will loose their minds and that is OK. I like to do experiments and base my designs on the lessons learned. After 6 years of using this method and hundreds of hours, I say this works just fine (for me).

Those are very some shapely diffusers. I bow to Axel the Artisan!
Thanks Dan, that means a lot. I remember my Aerospace professor saying...."become the air molecule, flow through/around the part" or something to that effect.

Nice work! Will engine movement inside the cowl be any problem?

This is a mold. Not the finished part. The final part will have neoprene hose to tie up the cowl ring to the diffuser.
 
That is a very good looking cowl ring----reminds me of the ones Dave Anders make a long time ago. Internal profile is a lot better than many that are just straight "pipes".
 
I like what I see.

Only comment that I can think of is that Dave Anders has an "Angle Valve" engine. The angle valve engines have better oil flow to the valves and if memory serves me correctly, there are oil squirters on the bottom of the pistons so there should be more heat removed from the cylinders in the oil than what most of us have on the parallel valve engines.

Watching the temperatures on the first few test flights will help make sure that enough heat is removed from the engine.

Please post your test data when flying this setup.
 
The Lycoming M1B engine that was delivered to me late last year had very good cylinder fin casting, with all the cooling passages cleaned up. The blockage area between the fins as shown in AXO picture are no longer there. Maybe the high end Thunderbolt engine work paid off with better casting quality. At least for my engine, I may not need to do the Dan Horton cooling mod like this.
 

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I like what I see.

Only comment that I can think of is that Dave Anders has an "Angle Valve" engine. The angle valve engines have better oil flow to the valves and if memory serves me correctly, there are oil squirters on the bottom of the pistons so there should be more heat removed from the cylinders in the oil than what most of us have on the parallel valve engines.

Watching the temperatures on the first few test flights will help make sure that enough heat is removed from the engine.

Please post your test data when flying this setup.

And - - the angle valve has intake induced swirl that yields faster combustion burn needing less spark advance and lower heat rejection. The higher fin density is far superior to the parallel valve. Thus, the angle valve cooling air can be throttled down a lot more than a parallel valve and still have cooler internals.

Some familiar looking stuff there Axel - -looking cooler and faster . . . .

Axel, if you are using a felt prop seal, I have some input on that. And pictures.
 
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Certainly is...

And - - the angle valve has intake induced swirl that yields faster combustion burn needing less spark advance and lower heat rejection. The higher fin density is far superior to the parallel valve. Thus, the angle valve cooling air can be throttled down a lot more than a parallel valve and still have cooler internals.

Some familiar looking stuff there Axel - -looking cooler and faster . . . .

Axel, if you are using a felt prop seal, I have some input on that. And and pictures.

BillL did something quite similar several years ago. Works great on our RV-7A.



 
Lets vacuum these things up. Used left over carbon fiber from my Formula 1 race plane.

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Vacuum off the next day
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