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A Continental A-65 on a Kolb MkIII? Why not?
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tomd

Joined: 09 Apr 2007
Posts: 7
Location: Scotia, NY

Posted: Sat Apr 14, 2007 5:49 pm Post subject: A Continental A-65 on a Kolb MkIII? Why not?

I am lucky to have access to  a Continental A-65-8 for a very reasonable price, much less than the cost of a  typical Rotax 582, VW conversion, Jabiru and the like. I would like to open a  discussion thread on the use of this engine on the Kolb Mk III Xtra. I realize I  will have to design and build my own engine mount but don't see too many other  challenges I can't live with (the -8 version will not accept a starter or  alternator, so I hand prop). I appreciate any input from the list both for and  against. Thanks.

   [quote][b]

captainron1(at)cox.net
Guest

Posted: Sat Apr 14, 2007 6:50 pm Post subject: A Continental A-65 on a Kolb MkIII? Why not?

Well, it may work out, but a couple of things. It will vibrate a lot more then any of the alternatives and the kolb cage structure maybe marginal for that. I considered putting a O-200 Conti on my M3X. But again it may just be too much for the frame. Ok it is too much for the frame. 

Also 65 hp for that much weight not the best choice. I would buy the motor anyway if the price is real good, but that would be for another project.

jindoguy(at)gmail.com
Guest

Posted: Sat Apr 14, 2007 9:01 pm Post subject: A Continental A-65 on a Kolb MkIII? Why not?

Weight for power, I think is the best reason. You'll have the weight of the heaviest VW conversion with the power of a 582. Not a good trade, in my book.

Why not sell the A65 and either add a bit more to it for a new 582 or get a good used one? 



Rick



On 4/14/07, Tom Deiulio <tpd47(at)earthlink.net (tpd47(at)earthlink.net)> wrote:[quote]        I am lucky to have access to  a Continental A-65-8 for a very reasonable price, much less than the cost of a  typical Rotax 582, VW conversion, Jabiru and the like. I would like to open a  discussion thread on the use of this engine on the Kolb Mk III Xtra. I realize I  will have to design and build my own engine mount but don't see too many other  challenges I can't live with (the -8 version will not accept a starter or  alternator, so I hand prop). I appreciate any input from the list both for and  against. Thanks.

   [quote][b]  http://www.matronics.com/Navigator?Kolb-List http://forums.matronics.com 

when you live at the airport.  [quote][b]

John Hauck

Joined: 09 Jan 2006
Posts: 4639
Location: Titus, Alabama (hauck's holler)

Posted: Sun Apr 15, 2007 5:09 am Post subject: A Continental A-65 on a Kolb MkIII? Why not?

| Weight for power, I think is the best reason. You'll have the weight 

of the

| heaviest VW conversion with the power of a 582.  | Rick

Gang:



Kolbs don't perform well with direct drive engines.  Rick Neilsen and 

John W have had experience with these set ups.



john h

mkIII

_________________
John Hauck
MKIII/912ULS
hauck's holler
Titus, Alabama

slyck(at)frontiernet.net
Guest

Posted: Sun Apr 15, 2007 5:11 am Post subject: A Continental A-65 on a Kolb MkIII? Why not?

I'm a day late because I've been using the digest but here's my  

opinion on the A-65:

The ONLY drawback is the weight.  A sturdy engine mounting would have  

to be

created.  Hard landings (and sudden stops) may overstress the cage  

compression

design limits.

Definitely stay with the -8 (blanked accessory case plate, no pads  

for starter or generator)

Continental also made -8 versions of the C-85 and C-90 that formula  

one racers still use.

A65s prop start very easily.

65 is a conservative rating.  At 2600 rpm it will match any rotax.

Mine used to swing a 74" metal MacCauley and climbed out briskly at  

2300.

They were rated at 2300 redline which was an ultra conservative  

number. They also sold

a  version of the same engine with a few extra oil squirt holes and 4  

ring pistons

rated at 80 hp, obviously called the A-80.  I used the same ones in  

mine.



BB, back working on my Kolb, light snow on the lawn this morning

kfackler(at)ameritech.net
Guest

Posted: Sun Apr 15, 2007 5:13 am Post subject: A Continental A-65 on a Kolb MkIII? Why not?

 	  Quote: 	
		   Kolbs don't perform well with direct drive engines.  Rick Neilsen and

 John W have had experience with these set ups.


	


Why is that? Understand, I'm not challenging your comment, I'm just curious.



-Ken Fackler

Kolb Mark II / N722KM

Rochester MI

John Hauck

Joined: 09 Jan 2006
Posts: 4639
Location: Titus, Alabama (hauck's holler)

Posted: Sun Apr 15, 2007 5:30 am Post subject: A Continental A-65 on a Kolb MkIII? Why not?

| Why is that? Understand, I'm not challenging your comment, I'm just 

curious.

|

| -Ken Fackler



Morning Ken:



I don't know.  Probably restricted prop size.



john h

mkIII

_________________
John Hauck
MKIII/912ULS
hauck's holler
Titus, Alabama

jbhart(at)onlyinternet.ne
Guest

Posted: Sun Apr 15, 2007 6:58 am Post subject: A Continental A-65 on a Kolb MkIII? Why not?

Tom,



What is important here is torque delivered to the propeller.  Searching the 

web, I found the following:



The A-65 delivers 148 ft-lbs at 2,300 rpm and the engine weighs in at 170 lbs.



The Rotax 912 delivers 79 hp and 75.9 ft-lbs at 5,500 rpm and weighs 134 

lbs.  By interpolation of Rotax data and with the 2.273 gear box, the Rotax 

will produce 2,300 propeller rpm and 148 ft-lbs of torque at 5,280 engine 

rpm at 84% open throttle. 



The A-65 has a 36 pound or less weight disadvantage.  Some of this could be 

resolved by using a light wood propeller.  



More snow!



Jack B. Hart FF004

Winchester, IN



do not archive

NeilsenRM(at)comcast.net
Guest

Posted: Sun Apr 15, 2007 7:04 am Post subject: A Continental A-65 on a Kolb MkIII? Why not?

Yes I have said many times that direct drive engines don't perform well on 

Kolbs but I guess I need to amend it a bit. Engines that are designed 

correctly for direct drive might do well if they aren't too heavy. 

Continental and Lycoming engines are designed to produce their rated power 

down in the RPM range where it can swing a large efficient prop without 

having the prop tips going supersonic.



I have discussed using  the small Lycoming and Continental engines a few 

times with Kolb and their opinion was NO they are just way too heavy.



Rick Neilsen

Redrive VW powered MKIIIC



---

John Hauck

Joined: 09 Jan 2006
Posts: 4639
Location: Titus, Alabama (hauck's holler)

Posted: Sun Apr 15, 2007 7:16 am Post subject: A Continental A-65 on a Kolb MkIII? Why not?

| The A-65 has a 36 pound or less weight disadvantage.  Some of this 

could be

| resolved by using a light wood propeller.

|

| More snow!

|

| Jack B. Hart FF004



Jack:



Numbers are great!  But.........they do not always equate to the 

"real" world.



Based on flight comparison, that is side by side flying with my mkIII 

and John W's Jabiru powered direct drive 80 hp Kolbra, the Kolbra was 

really puny, except in cruise flight, and the 912 powered mkIII and 

the Jab powered Kolbra were about equal.



Now, side by side performance comparison with John W's new 912ULS 

powered Kolbra and my 912ULS powered mkIII.  John W blew me away in 

take off, climb, and cruise.



Early on there was a Subaru powered mkIII that could barely fly with 

the direct drive configuration.



john h

mkIII

_________________
John Hauck
MKIII/912ULS
hauck's holler
Titus, Alabama

jbhart(at)onlyinternet.ne
Guest

Posted: Sun Apr 15, 2007 9:14 am Post subject: A Continental A-65 on a Kolb MkIII? Why not?

At 10:16 AM 4/15/07 -0500, you wrote:

 	  Quote: 	
		  

.....................................
	


 	  Quote: 	
		  Numbers are great!  But.........they do not always equate to the 

"real" world.
	


 	  Quote: 	
		  

.................................................................
	




John and Kolbers,



So what is the real world? The point is if you use a 4,000 foot hard surface 

runway why not use a low torque, light weight, high rev'ing engine with a 

small propeller?  You can get to and from with the same cruise and the same 

gph rate. 



The point is that if one can run identical propellers at the same setting, 

the performance of the A-65 minus the 36 pound weight increase will be equal 

to the 912 up to the point of 84% open throttle.  The propeller does not 

care if it is gear or pulley or direct driven.



One of the great things about this list is that people are flying engines 

other than Rotax.  This shows the skill of builders and the strength of 

Homer Kolbs and Dennis Souder's efforts that Kolbs are not limited to Rotax 

engines.  What is important is the fact that we safely fly over and under 

weight Kolb knock offs with a variety of engines, reduction units, and 

propellers.  That is what "experimental" is all about.



If Tom can get his A-65 safely mounted, his MkIII should fly very well.  Not 

everyone wants or can afford a Rotax.  This does not mean that Rotax is a 

bad engine, it isn't.  It just means that viable alternative engines are 

available.



Jack B. Hart FF004

Winchester, IN



do not archive

John Hauck

Joined: 09 Jan 2006
Posts: 4639
Location: Titus, Alabama (hauck's holler)

Posted: Sun Apr 15, 2007 10:28 am Post subject: A Continental A-65 on a Kolb MkIII? Why not?

| One of the great things about this list is that people are flying 

engines

| other than Rotax.  This shows the skill of builders and the strength 

of

| Homer Kolbs and Dennis Souder's efforts that Kolbs are not limited 

to Rotax

| engines.  What is important is the fact that we safely fly over and 

under

| weight Kolb knock offs with a variety of engines, reduction units, 

and

| propellers.  That is what "experimental" is all about.

 |

| Jack B. Hart FF004



Hi Jack:



I'm sorry.  I left the most important part out of my last post, which 

turned out to be a comparison between John W and my airplanes.  My 

intention was not to push Rotax, although I will not hesitate to tell 

you how much I like the engine I fly with.



What I wanted to say was Kolbs do not fly well with direct drive 

engines.  They do much better with engines, not necessarily Rotax, 

that are equipped with reduction drives.  Kolbs are super STOL type 

aircraft.  If you power them other than a reduction drive, you take 

away from this capability.  The first aircraft that comes to mind that 

flies with a reduction drive is the old Helio Curior, a super STOL 

aircraft.  Part of that spetacular package is the powerful engine that 

turn a big prop through a reduction drive to slow it down.



Kolbs were not designed to fly off 4,000 ft paved runways.  Rather 

more at home on air strips like my little strip, Gantt International 

Airport, that started off life in the cow pasture on 600 feet of 

unimproved rough sod.  Kolbs will land on sand bars in the Tallapoosa 

River in Alabama or the Sag River in the Arctic North Slope of Alaska. 

Kolbs fly well when they are loaded up to their max gross weight. 

Some of us even push that a bit and they still fly well.  I was not 

knocking anyone who was experimenting with their Kolb or other 

homebuilt.  I have done and still do a lot of experimenting with my 

airplane, and airplanes I have built in the past.



I will say that flying with an engine that is not reliable, 

underpowered, and barely flying on the edge, is hazardous to ones 

health.  I for one do not like that kind of flight and would much 

rather have an aircraft that is more comfortable to fly and well above 

the danger zone.



I know you are terribly interested in low weight and low fuel burn. 

I'd love to have the low fuel burn, but get a lot more enjoyment out 

of performance than economy.



When I share my experiences, I am also sharing my desires.  I think 

that is natural for a person to do that.  Don't get me wrong.  I am 

not trying to convince you or anyone else to build, equip, and fly 

like me.  If you want to, great!  Then we can comfortably fly 

together.



Take care,



john h

mkIII



Winds are 23 mph gusting to 33.  Not conducive to good flight testing.

_________________
John Hauck
MKIII/912ULS
hauck's holler
Titus, Alabama

JetPilot

Joined: 10 Jan 2006
Posts: 1246

Posted: Sun Apr 15, 2007 11:04 am Post subject: Re: A Continental A-65 on a Kolb MkIII? Why not?

 	  jbhart(at)onlyinternet.ne wrote: 	
		  



The point is that if one can run identical propellers at the same setting, 

the performance of the A-65 minus the 36 pound weight increase will be equal 

to the 912 up to the point of 84% open throttle.  The propeller does not 

care if it is gear or pulley or direct driven.



	




This is not quite true,  if he uses a metal prop that was designed to cruise and be efficient at 100 MPH, it might not do very well in a slower cruising Kolb.  A wood prop would probably be even worse, and less efficient.  36 pounds is not that much extra,  IF IT HOLDS TRUE when all is said and done.  



What would worry me is the prop, having lower power with heavy weight will make it a poorly performing airplane.  Having lower power, high weight, with an inefficient prop will make the plane almost not worth flying.



Mike

_________________
"NO FEAR" - If you have no fear you did not go as fast as you could have !!!

Kolb MK-III Xtra, 912-S

d-m-hague(at)comcast.net
Guest

Posted: Sun Apr 15, 2007 11:33 am Post subject: A Continental A-65 on a Kolb MkIII? Why not?

At 02:27 PM 4/15/2007, John Hauck wrote:



 	  Quote: 	
		  What I wanted to say was Kolbs do not fly well with direct drive

engines.  They do much better with engines, not necessarily Rotax,

that are equipped with reduction drives...


	


There's nothing magical about the presence (or absence) of a reduction drive.

If you have two engines of the same horsepower and same weight, but one has 

a direct drive prop turning at, say, 2500 rpm, and the other one has a 2:1 

reduction with the engine turning 5000 rpm, the performance will be identical.



That said, one way to get more power out of a given engine is to turn it 

faster.  This was less feasible in the 1930's and 1940's when the A-65, for 

example, was designed, but modern metallurgy has come a long way, so we can 

cruise nowadays at rpm's that would have been way above redline in an older 

engine.  This is why a 65hp Rotax engine weighs considerably less than a 

65hp Continental.  However, turning a small prop fast is less efficient, so 

we have reduction drives.  If the reduction drive assembly weighs less then 

the bare engine's weight difference, you get better performance.



Sign... my Ultrastar sits in my fabric garage, as the rain and winds batter 

my half rebuilt trailer...



                                 -Dana

--

--

My software never has bugs. It just develops random features.

by0ung(at)brigham.net
Guest

Posted: Sun Apr 15, 2007 1:11 pm Post subject: A Continental A-65 on a Kolb MkIII? Why not?

Gang:



Kolbs don't perform well with direct drive engines.  Rick Neilsen and 

John W have had experience with these set ups.



john h

mkIII



John I think the problems that have been noticed by rick and john w  is

direct drive on high revving engines requiring a small diameter prop.   The

a65 would be a slow turning engine and could turn a much larger diameter

prop and would work well that way,   the big disadvantage would be hp to

weight ratio.



Boyd

John Hauck

Joined: 09 Jan 2006
Posts: 4639
Location: Titus, Alabama (hauck's holler)

Posted: Sun Apr 15, 2007 1:22 pm Post subject: A Continental A-65 on a Kolb MkIII? Why not?

The

| a65 would be a slow turning engine and could turn a much larger 

diameter

| prop and would work well that way,   the big disadvantage would be 

hp to

| weight ratio.

|

| Boyd

On a Kolb the prop diameter would be limited.



Agree the VW was designed to turn more rpm.  But the Jab is an 

aircraft engine from the get go, not a converted auto engine.



john h

mkIII

_________________
John Hauck
MKIII/912ULS
hauck's holler
Titus, Alabama

NeilsenRM(at)comcast.net
Guest

Posted: Sun Apr 15, 2007 2:45 pm Post subject: A Continental A-65 on a Kolb MkIII? Why not?

John



The Jabiru engine is a aircraft engine but it runs at a higher RPM than most 

aircraft engines. Stuart at Power Fin once commented that they, Jabiru, just 

didn't understand props. Aircraft engines need to turn their rated power in 

the very low 2000 range to be able to efficiently handle a 70-72 inch prop 

which is almost necessary to fly a big Kolb very well. Granted with enough 

power you can get the same thrust but then you have more weight and use more 

fuel.



Even the big WWII engines (Merlin and some of the big radial engines) used 

reduction drives to efficiently power the huge props they used. Big slow 

turning props produce much more thrust than a small fast turning prop.



Rick Neilsen

Redrive VW powered MKIIIC



---

slyck(at)frontiernet.net
Guest

Posted: Sun Apr 15, 2007 4:32 pm Post subject: A Continental A-65 on a Kolb MkIII? Why not?

I guess we won't know until someone actually does it.  



Since it wouldn't be on a type certificated airplane there would be  

some weight saving options:

clunky mags replaced with electronic ignition

lighter exhaust system

fuel injection (Lar has a spare ready)



A few advantages:  no oil cooler, no filter, no water/radiator.

No hoses to leak except fuel



The A-65 was approved for several diameter props, metal and wood.

I can't see any reason not to use a light composite.

Unless I'm missing something, a Warpdrive prop spun by any engine,  

redrive or not,

at 23-2600 rpm should yield the same gittup and go.

Sensenich made the most efficient wood.



Parts are still available but I would have that old crankshaft  

magnafluxed.

You may have to enclose the engine to get the right air cooling effect

or try to duplicate the J3 Cub scoopers.



Use oil drilled con rods for the higher RPMs

A-50, A-65, A-75, C-75 (not the same engine folks), C-85 all used the  

same stroke crank.

Some tapered, some flanged.  -A rare few were hollow nosed for prop  

control (erk!)



Replace or remachine the oil pump, they were marginal to start with

Good luck, BB

ceengland(at)bellsouth.ne
Guest

Posted: Sun Apr 15, 2007 4:38 pm Post subject: A Continental A-65 on a Kolb MkIII? Why not?

John Hauck wrote:

 	  Quote: 	
		   

 

  The

 | a65 would be a slow turning engine and could turn a much larger 

 diameter

 | prop and would work well that way,   the big disadvantage would be 

 hp to

 | weight ratio.

 |

 | Boyd

 

 

 On a Kolb the prop diameter would be limited.

 

 Agree the VW was designed to turn more rpm.  But the Jab is an 

 aircraft engine from the get go, not a converted auto engine.

 

 john h

 mkIII




	


Can I take a shot at this?



Here's one of the better explanations I've seen:



http://www.geocities.com/vjaqua/



Click on 'Propellers'.



Vance Jaqua was a pretty smart guy & could explain things where non-tech 

people could understand tech subjects.



It really is all about prop diameter ('disk loading', or 'mass flow'). 

The Jab or direct drive Sub turns *the prop* too fast (typically 

3000-3400 rpm) at rated power to turn a 6' diameter prop like the Rotax; 

it must use a smaller dia prop so its efficiency, at low speed is poorer 

than a typical a/c engine or a geared Rotax, engine.



The link above has a chart showing various efficiency curves of hp per 

sq ft of prop area for various speeds. If you think about the two 

extremes, 160 hp can lift a 2 seat helicopter straight up by having a 

25-30 ft diameter 'propeller'(a 160hp C-172 staggers into the air), & 

there aren't any low speed a/c using a pure jet, because of the tiny 

disk area per hp.



If a geared Rotax and a direct drive Continental have the same HP at the 

same *prop* rpm, they will have the same torque at the prop and they can 

swing the same diameter/pitch prop. The only performance difference 

would be due to difference in weight.



Charlie

d-m-hague(at)comcast.net
Guest

Posted: Sun Apr 15, 2007 6:21 pm Post subject: A Continental A-65 on a Kolb MkIII? Why not?

At 08:32 PM 4/15/2007, robert bean wrote:



 	  Quote: 	
		  Since it wouldn't be on a type certificated airplane there would be

some weight saving options:

clunky mags replaced with electronic ignition

lighter exhaust system

fuel injection...



You may have to enclose the engine to get the right air cooling effect

or try to duplicate the J3 Cub scoopers.


	


Hmmm, there's a thought... cooling could be an issue in a pusher 

installation like a Kolb, especially on the ground.



Somehow, though, the idea of a fuel injected, electronic ignition A-65 just 

seems wrong... 



-Dana



do not archive

--

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My software never has bugs. It just develops random features.

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