[rv969wf]

I've bought a lot of books in my lifetime but who is going to pay $1,500 for a book? YES around $1,500 for the "Principles of Engine Cooling" book by Jim Lopresti. LoPresti quoted that if enough people are interested he might bring the price down. Down to what a $1,000 ???? This is nuts in my opinion. The Aug 2006 issue of Sport Aviation on page 144 has an add for this book. Jim mentioned you can't even buy the book right now so why put the dang add in the magazine. Jim has an email address btw: [email protected] He mentioned for anyone interested to write him and he'll see how many people are interested in it. Yes I'd like to have one and would pay maybe $100++ but not $1,500. To print each book alone he said would be around $50 btw. If any of you speed freaks or cooling mod builders are interested in this book it would be nice to show some interest and email Jim and try to get the price down. Anyway I'll quit complaining.

 

[gmcjetpilot]

I've bought a lot of books in my lifetime but who is going to pay $1,500 for a book? YES around $1,500 for the "Principles of Engine Cooling" book by Jim Lopresti. LoPresti quoted that if enough people are interested he might bring the price down. Down to what a $1,000 ???? This is nuts in my opinion. The Aug 2006 issue of Sport Aviation on page 144 has an add for this book. Jim mentioned you can't even buy the book right now so why put the dang add in the magazine. Jim has an email address btw: [email protected] He mentioned for anyone interested to write him and he'll see how many people are interested in it. Yes I'd like to have one and would pay maybe $100++ but not $1,500. To print each book alone he said would be aro
und $50 btw. If any of you speed freaks or cooling mod builders are interested in this book it would be nice to show some interest and email Jim and try to get the price down. Anyway I'll quit complaining.

Alan my friend that is insane. First Roy his dad as you know has passed and was a great designer and incorporated technology. Of course Jim his son is now running "Speed Merchants", makers of after market cowls and other speed mods like gap seals for factory planes. I would save your money. Although a little dated and not glossy, I recommend "Speed with Economy", by Kent Paser. I think it's $20 and worth it. I have a lot of technical books and about $80 was tops.

I talked to Jim LoPresti about buying a part from one of his kits, an oil cooler diffuser. He asked me what I was willing to pay. When I threw out $100 he laughed at me. I think we where way way off by a factor of 5 or 10. I can make my own fiberglass part, thanks. That is why I have an experimental, so I am not at the mercy of vendors, FAA and factory parts.

There is a lot of data out there and a lot of it is free.

 

[Bob Axsom]

Wow!

Alan, as you know I have been working to reduce the cooling drag in my RV-6A by working with aluminum baffling in the lower cowl. So far I haven't run into a heating problem so I will continue the experiment and on the job learning process. I just don't think the book would do me any good at this point. Sometime I would like to learn about the race engine building that you do however.

Bob Axsom

 

[JimWoo50]

Rvator article on cooling drag?

Wasn't there an article in the RVator a number of years ago about two friends in Ohio who both built 6's and had a friendly competition as to who was fastest? If I remember correctly one of the guys modified the inlets in his cowl and gained a few knots.

 

[prporter]

OK, If enough people show an interest in this book, then I will buy a copy, and I will photo copy a book for each of you. $ 79. Any takers?

 

[Nuisance]

The only thing Jim LoPresti is qualified to write about is how to [snip by dr] people into paying huge money for everyday stuff. Check out his landing lights for crying out loud!

jh

 

[Bob Axsom]

Second Issue 2000

Wasn't there an article in the RVator a number of years ago about two friends in Ohio who both built 6's and had a friendly competition as to who was fastest? If I remember correctly one of the guys modified the inlets in his cowl and gained a few knots.

The Article is in the second RVator issue of 2000. The title is "Over 200 mph on 160 HP" and there are definitly some good ideas in there. The 3 mph gain achieved by fairing in the tail tiedown ring is a "must try". The 5 mph increase achieved by running the intake scoop up near the prop is not something you want to do if you have a completely painted nice looking airplane (thousands invested) but that is a lot of speed. It is interesting to note that they refer to Kent Paser's book "Speed with Economy" that George suggested earlier. It seems a lot of us have a copy. In Chapter 4 he goes into his "Engine Cooling Modifications."

Bob Axsom

 

[rv969wf]

Engines and cooling

Hey Bob,,, check your Private Messages, I left you one today. Give me a call sometime and I'll share some things about what I have done on Air Cooled Lycoming engines to make them run cooler so you can go faster with less cooling drag. I have 5 years of documents and testing since 2001 on my RV-6 project. I've done some things that a lot of engine builders / RV builders would not of thought of. Heat dissipation inside and out is the key with an air cooled engine. I will share with you what did and didn't work on my 6 if you want to talk sometime.... One other thing,,,, the LoPresti Book I found out is more for engineers that talk a different language than most of us. Book involves air and water cooled engines both. Thanks......

 

[szicree]

Copyright laws only work when prices are reasonable enough to keep honest people honest. When a publisher/author decides to gouge, folks will ignore the copyright. I hope Lopresti plans on saving that $1500, cuz he'll sell exactly one copy -- the rest of us will get xerox's, e-copies, etc.

$1500!! Gimme a break.

 

[rv969wf]

10-4

A big 10-4 on that comment. I fabricate quite a few things to sell to the average builder and I make my 15-20% markup but good gosh, a book at this price will NEVER SELL, why did he even write the darn thing. Who can afford it?????? The only people that can afford it are the people that hire their work done by someone else to have fast airplanes and are they going to read it? I don't think so.... When I talked to Jim L...today I just about dropped the telephone at the price, heck I even had my credit card out ready to give him my info and order it. I just sat there for awhile and as we visited I decided to just go have a cold one and share this story with everyone....What the heck it's a free world and I didn't want anyone to waste their dime calling to buy this million $$$$BOOK$$$$$

 

[rv6ejguy]

A couple years ago, Jim offered to "help me" with sorting out cooling issues with my Sube. I found out his help was far from free.

He did offer these treats for free however:

Internal airflow is controlled by static pressure---changing directions internally is no big deal?.

Ground cooling is never a design issue?.

?.layed over radiators work just fine and rarely need turning vanes if designed right

All piston powered retractable general aviation planes have 1/3 of their drag due to cooling

So does the P51

P51 does NOT have low cooling drag

Evaporative cooling is for oil cooling only (and they found nothing)

Internal turning never exhibits any losses for my cowls?I trust my measurements ZERO LOSS

Both air and liquid cooled??

Air cooled engines use much less air and have much lower drag by definition?.

Core face area or core volume is meaningless info?

everybody is SOO CHEAP and there never is any press on the special projects?..but I don?t really care..

As far as augmentors, have you ever seen one installed that exhibited any reduction in required pressure cooling? I did not think so..they all have full size inlets and exits so the augmentors are only ornamental?

*******************************************************

Hmmm. It is pretty interesting that his views clash with the designers of actual liquid cooled engine installations and actual flying examples of of air cooled installations not to mention most texts dealing with cooling drag. I guess all the guys are Reno with P51s are idiots too. Maybe Jim can help them turn some air with zero losses and find another 40 knots with a new rad layout. Obviously DG with the #33 Legacy isn't too swift either nor are the radial engined lads with their exhaust augmentors that don't work.

Now if I can just figure out how to turn air with zero losses in those cylinder heads on my flow bench... oh, guess it's giving false info too...

$1500... not for me thanks.

I wish Jim well in cowling sales and Boom Beams.

 

[avpro56]

The only thing Jim LoPresti is qualified to write about is how to [snip by dr] people into paying huge money for everyday stuff. Check out his landing lights for crying out loud!

jh

John, why not tell us how you really feel?

I saw the advertisement for the Lopresti book; but I noticed that no price was listed in the ad. Thinking it was priced high without checking, I attended LoPresti's Oshkosh forum on engine cooling & drag. While Mr. Lopresti was quite informative, most of what I heard was available elsewhere for free or at little cost. He did have some innovative ideas, but nothing that could not be gleaned from another source. Perhaps most interesting, I was unable to verify Mr. Lopresti's qualifications and or credentials other than his last name.

Those contemplating buying this text might consider first listening to a recording of the Oshkosh Forum on cooling drag as presented by Mr. Lopresti.

I had no idea the book was priced at $1,500 until I read this thread. Perhaps Mr. Lopresti should set up shop with the folks at Advanced Pilot Seminars.

 

[gmcjetpilot]

Really interesting

He did offer these treats for free however:

?.layed over radiators work just fine and rarely need turning vanes if designed right

All piston powered retractable general aviation planes have 1/3 of their drag due to cooling

P51 does NOT have low cooling drag

Internal turning never exhibits any losses for my cowls?I trust my measurements ZERO LOSS

Both air and liquid cooled??

Air cooled engines use much less air and have much lower drag by definition?.

Core face area or core volume is meaningless info?

As far as augmentors, have you ever seen one installed that exhibited any reduction in required pressure cooling? I did not think so..they all have full size inlets and exits so the augmentors are only ornamental?
-----------------------------------
Turbo Subaru RV6A flying
Twin Turbo Subaru RV10 building
Race engine builder, fabricator, turbo junkie, technical writer, mad scientist since 1978

I have not got a chance to see the book. I gather the info you mention was in conversation? Is this what Jim LoPresti said? I don't get some of the comments? Can you explain them?

I do want to talk about water cooling since you are way more experienced with water cooled engines in planes, Subaru in particular, than I think anyone on these here forums.


" P51 does NOT have low cooling drag"

Really I have always heard how low the drag was? I have no strong opinion. I do think an air cooled Lyc in a RV is lower drag than any water cooled installation to date. That may change but not yet. Do you have some facts or can you elaborate on what he was saying? I know the P51 was not perfect and they can and do overheat. What do you think he was talking about?



" Air cooled engines use much less air and have much lower drag by definition?."

I can't believe that is true in general, but I do think it's true with today's small water cooled engine installations, which by default are Subaru and Mazda alternative engines. I don't know about Rotax's water cooling. Since they are 115hp max we'll forget them for now. Adapting water cooling to an airframe optimized for air cooled engines is always going to be a compromise. I know you are working on that. How is it going?


I would like your opinion on COOL JUGS in California. I talked to them the other day. They got their Piper/O360 cooled with 3.5 inches of water (air pressure). An air cooled Lyc needs up to 9 inches of H2O across the fins to cool.

I like the KISS method of air cooling, which is lighter (no glycol-water to carry around, pumps, hoses radiators), simpler and cheaper. However with that said, water cooling should allow a Lyc to run super high compression (12:1 CR) and get better efficiency (lower fuel burn) and/or power. The "NEW" Cool Jugs may be out in about a year for $17,000. We shall see.

If "Cool Jugs" ARE SUCCESFUL, it changes the equation around, where a small radiator with lower pressure requirements than a stock air cooled Lyc, would make the water cooling drag less. They have only one plane flying with the original designed COOL JUGS. They claimed they picked up speed even with an over-sized scoop and radiator. I recall 7 mph. The new design cylinders will have better combustion chambers and HC pistons (12:1 CR) which can run on 92 octan and not detonate. We shall see.

I am pro air cooling, but this may change if water cooled Lycomings show their full promise. On the other hand at $17,000, plus $1000 for a custom radiator/houses, I'll probably stay with air cooling. I think there is room for both, but it will take some changes in the methods and design used in a typical Subaru and Mazda. I think Cool Jugs may have a good design. We shall see, when there are 20 planes flying with the cool jugs for a few years.



"Core face area or core volume is meaningless info?"

Don't get it. I think if you have a smaller radiator, requiring less air than a larger one, the smaller radiator would have less drag? But it brings up a question about the relation of the cooling system as a whole and the radiator size.

"Cool Jugs" I think have better water flow and pumping which allows the use of a smaller radiator. You might disagree, but Subaru's and Mazda's both have cooling problems in planes. The recent Eggenfellner RV-9A test Van showed water temp was an issue. We can digress into how terriable Lycoming cooling is, but if it's baffled properly with an oil cooler sized and installed properly, cooling is not a big deal. However the Lyc driver does need CHT awareness and may have to lower the nose climbing out heavy on a very hot day. Since we all know 400F is the real max CHT for long engine life.

I speculate that the Cool Jug, with the higher pressure, high flow water pump, along with good water passage design, in parallel, allows it to be very efficient. This allows it to run a smaller radiator. Now you tell me is a 12" by 9" core, by 3" deep not a small radiator? I don't know, but I can see how to hide that inside the cowl with some ducting.

Do you reject the idea that a car cooling systems are not ideal for aircraft? I know the Mazda guys do have serial flow thru the case and do have steam pocket issues.


Here are some Cool Jug pictures. Look at the size of the water pump:

Just one of those big hoses can be $150!



"As far as augmentors, have you ever seen one installed that exhibited any reduction in required pressure cooling?"...." I did not think so..they all have full size inlets and exits so the augmentors are only ornamental?"

I am going to disagree (a lot), and I think AJ and others (the entire aerospace industry) have found that exhaust augmentors work great. I agree that if you increase the exit air velocity and efficiency and don't reduce the inlets or modulate the size of the exit, e.g., cowl flaps, using exhaust augmentation is not gaining you much, but augmentor exhaust nozzles are used on every thing from a C-310 to low-bypass turbofan engines to increase thrust or cooling.

There are stacks of studies and books showing the principles of exhaust augmentation, nozzles and Coandă effect. This is based in physics and Bernoulli's principles, to dismiss it as useless is just "W", wrong, but it does have to be done properly. "Augmentation" is how modern jet engines work, high velocity air in a core of low flow air, promoting greater flow. Its also used in rockets. This area is well understood as is lift on a wing, it works.

Exhaust augmentation has been used in many plans, two GA planes that come to mind are C-310 and P-23 twins, commercial piston planes (military, airliners) many.

So may be his book is over priced? You think?

 

[keen9a]

George, I think someone must have turned of your sarcasm sensor. I don't think anyone here believes any of the nonsense from Jim that rv6ejguy posted.

 

[gmcjetpilot]

Now YOU tell me

George, I think someone must have turned of your sarcasm sensor. I don't think anyone here believes any of the nonsense from Jim that rv6ejguy posted.

I see that now. never MIND!

I do want RV6ejguys opinion on this stuff and cool jugs, cheers. I think Jim was right about water cooling Vs air cooling, as it applies to RV's today with water cooling. I don't think it has to be that way of course. I'm curious what RV6ejguy thinks of the P51 and why he thinks it works. I have my thoughts but he knows that stuff better than I do. Can the P51 be applied to the RV? I think that is what he is doing and I am interested, that's all.

 

[rv6ejguy]

George, I think someone must have turned of your sarcasm sensor. I don't think anyone here believes any of the nonsense from Jim that rv6ejguy posted.

Believe it or not, these are copied and pasted from several unsolicted E-mails Jim sent me a few years back. Maybe Jim just wasn't himself that week. I don't know the man. You know what they say- you will meet two types of engineers...

 

[Andy_RR]

G'day People! New to this board, for posting at least. I have been keeping tabs on all the hot tips for when I finally get to build my RV-8 - hopefully starting in late 2007. Thanks to you all for a great resource!

Air cooled engines use much less air and have much lower drag by definition?.

Just to let you know there is a bit of science to this:

Heat transfer is directly proportional to the temperature differential between the cylinder head (in this case) and the cooling medium (air, or liquid).

If, as in liquid cooling, you split the heat rejection into two phases (metal - liquid, then liquid - ambient air) you have to split the temperature differential between the each phase. The metal can't get hotter and the ambient air can't get cooler. The one that is really getting rid of your heat (the liquid - ambient air phase) is then operating at a lower temperature differential.

Now if you can only heat the ambient cooling air up to a lesser amount, you have to make up the difference by using more air to dump the same amount of heat. Pumping more air through your radiator costs you power - drag power!

Hope that makes some sense!

Andrew Rabbitt

 

[rv6ejguy]

Unfortunately many people assume (including myself some time ago) that because air cooled engines operate at higher temperatures and Delta T is higher that they are always more efficient than liquid cooled engines. My extensive studies into this shows that this is not always true. While your point about exchanging heat via an extra step in liquid cooled engines is valid, the big thing forgotten here is the fact that modern radiators are way more efficient per unit area and volume in rejecting heat compared to air cooled fins and may offer comparable or less drag in the process. This is especially valid if one considers the superiority of the rad duct dynamics possible with liquid cooled installations vs. the low efficiency and high losses in most air cooled installations.

3 view studies of various WW2 fighters, both air and liquid cooled show that in every case, air cooled installations have higher inlet areas and higher frontal areas per unit hp. This does not prove how much air is being flowed to cool each engine of course but it does show that the designers deemed these high inlet areas to be required.

Of interest is the work done on Reno racers, particularly Rare Bear with its R3350 and revised cowling and spinner. Inlet area is very small for the 4000+ hp. Since this aircraft is racing at 5000 feet where the air is relatively dense and copious amounts of ADI and spray bar water are being used, it serves to reason that inlet area can be reduced despite the very high hp. Can't argue with what they have done as they hold the piston speed record. There is no doubt that the original inlet designs of the P47, F4U and F8F were far from optimal with no spinner being fitted. I have often wondered why.

Likewise, racers like Strega and Voodoo have totally redesigned radiator scoops and are producing about double the stock hp. Again ADI and spray bar water is used to a high degree in cooling these engines. At Reno, the P51s have won their share of the races on less hp and less cubic inches so both concepts are equally viable in my view.

I don't think blanket statements like the one from Jim are valid as this is a general statement based on likely invalid assumptions. I'd rather say that we don't know. Certainly an opposed air cooled engine offers much lower frontal area per unit hp than radial concepts so this negates that advantage liquid cooled engines might have. Probably the only way to really answer this question is a test in the same airframe with equal hp engines, one liquid and one air cooled. Employ the latest lessons learned for optimized cooling layout and see which one is faster.

In the meantime, both systems work. Maybe when some of the RV10s get completed with various liquid cooled engines, we can draw some conclusions about this matter. I frankly doubt if we'll see any stunning advantage of one over the other especially in RVs where the airframe is designed around an air cooled engine and more difficult to optimise for a liquid cooled one.

 

[Mike S]

In the meantime, both systems work. Maybe when some of the RV10s get completed with various liquid cooled engines, we can draw some conclusions about this matter. I frankly doubt if we'll see any stunning advantage of one over the other especially in RVs where the airframe is designed around an air cooled engine and more difficult to optimise for a liquid cooled one.

Very well said

Mike

 

[Andy_RR]

...the fact that modern radiators are way more efficient per unit area and volume in rejecting heat compared to air cooled fins and may offer comparable or less drag in the process.

I'm not convinced that this can be taken as fact, at least in terms of per-unit-area. Volume is irrelevant, except potentially for packaging constraints, because ultimately, it's the mass flow of air and its temperature rise you require to pass through your heat exchanger that determines your heat rejection. If you limit your temperature delta you then need to either slow the air down more or push more of it through. Both represent increased pressure drops and hence drag.

I think the comparison with WW2 fighters is misleading you too, since at that time you were largely stuck with radial engines (= large frontal areas). The Argus As10 (fitted to the Fiesler Storch) was heading in the correct direction in terms of aerodynamic potential, albeit at much lower capacities and power levels and by the Germans!

Perhaps, it's fair to say that there's not much in it these days and even that the liquid-cooled boys of yesteryear were superior. I'd counter that by admitting you do get more design flexibility with a liquid-cooled application whilst insisting that the ultimate cooling capability (aerodynamically-speaking) still lives in the air-cooled camp

The argument is more about what is possible, rather that what has been already done.

 

[rv6ejguy]

Your point is very valid about the layout of air cooled cylinders. Engines like the Gypsy Major and Ranger plus other inline types as the Italians and French had in various designs cut the frontal area considerably compared to radials but did not allow for large displacement grow easily. They all showed considerable promise is small, lightweight airframes developed by all the powers in the WW2 era.

I'm always at odds with people saying that volume has no bearing on heat rejection. As face area for rads is limited in aircraft due to frontal area concerns, extra depth to the heat exchangers is the only way to increase heat rejection once face area is set. With extra depth comes more drag of course, plus poor performance in ground and climb scenerios, plus diminishing relative heat rejection but my flow bench studies show that pressure drop (drag) is not proportional to HE depth. The huge advantage of radiators lies in a good duct design where we have the length to efficiently diverge the flow, wet the entire rad face, (slow it down as you correctly point out) and then re-converge the flow, hopefully to add the heat, recover some of the pressure lost and exit the cooling air at or near the free stream velocity.

This is the big compromise in liquid cooled installations, face area vs. depth/ volume. Taxi conditions and climbing have far different dynamics than cruising. We'd like to have the large area, thin core rad for the former condition and a small face area in cruise. Can't do that, so we are left to compromise and use a variable geometry exit or inlet to throttle the flow. The P51 could not taxi for long but was fine in flight. This compromise would not be acceptable for a GA application. This fact makes VG rad doors essential for our applications if low drag in cruise is to be realised.

Heat rejection is dependent on a thin column of turbulent flow (coolant) exposed to maximum surface area finning. The rad wins hands down in this race. There are many interelated mechanisms at work here and nobody to my knowledge has quantified the whole process on a liquid cooled engine, only separate parts of the picture. This is the basis for installing temperature and pressure probes in our RV10 rad duct so that in flight performance can be measured.

I think we can learn a lot from past designs but as you state, we should be looking forward to what can be done in the future. Certainly work done by Reg Clarke and a Velocity owner up here in Canada have proven in flight that very small inlets (low mass flow) on properly designed rad ducts can efficiently cool Subaru and Chevy installations.