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Lynn Matteson

Joined: 10 Jan 2006
Posts: 2778
Location: Grass Lake, Michigan

Posted: Fri Oct 20, 2006 2:25 pm Post subject: heat muffs and electrolysis

I had a question earlier today (while flying) regarding the use of pot 

scrubbers in a heat muff...if you put a copper scrubber into an 

aluminum heat muff, is there a resulting electrolysis action that takes 

place? Is this a problem? Are stainless scrubbers less immune? (my 

guess is yes)

I realize that my heat muffs (alum) are clamped around the stainless 

steel exhaust pipe, but I have to accept this fact.

How do the pot scrubbers pick up the heat from the exhaust pipe, seeing 

as it does not touch it in very many places...as least not as much as a 

clamped-on finned device (that I built) would?

I'll accept the fact that many of you have tried the scrubbers and they 

work, but I'd like to know the physics of it all.



Lynn

Kitfox IV Speedster...Jabiru 2200

_________________
Lynn
Kitfox IV-Jabiru 2200
N369LM

dave

Joined: 22 Sep 2006
Posts: 1382

Posted: Fri Oct 20, 2006 3:27 pm Post subject: heat muffs and electrolysis

Lynn, 



They slow the air down going through the heated airspace. 

If you don't have them, you will get cooler air coming through.

Dave 

---

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smokey_bear_40220(at)yaho
Guest

Posted: Fri Oct 20, 2006 3:41 pm Post subject: heat muffs and electrolysis

I don't have the time to go into details, but

sometimes turbulence is a good thing.  Maybe someone

else can take over from there?



Kurt S.



--- Lynn Matteson <lynnmatt(at)jps.net> wrote:



 	  Quote: 	
		   How do the pot scrubbers pick up the heat from the

 exhaust pipe, seeing 

 as it does not touch it in very many places...as

 least not as much as a 

 clamped-on finned device (that I built) would?

 I'll accept the fact that many of you have tried the

 scrubbers and they 

 work, but I'd like to know the physics of it all.

 

 Lynn

 Kitfox IV Speedster...Jabiru 2200


	


__________________________________________________

Lynn Matteson

Joined: 10 Jan 2006
Posts: 2778
Location: Grass Lake, Michigan

Posted: Fri Oct 20, 2006 4:51 pm Post subject: heat muffs and electrolysis

I realize that, Dave...that they slow down the air and therefore the 

air heats up. That is why I built some baffles that have fins 

protruding from them, and the fins are offset, thereby making the air 

slow down, go around the fins, picking up heat, etc. My finned baffles 

are in direct contact with the exhaust pipe. Maybe I should have 

explained this when I asked the question. I know the principle of how 

the scrubbers work, what I wanted to know was how do the scrubbers PICK 

UP the heat from the exhaust pipe when they have so very little surface 

area in contact with the pipe. Maybe you guys stuffed the scrubbers in 

your muffs very tightly, thereby creating a lot of conduction heat 

pickup...did you? (those that have tried the scrubbers?)



Lynn



On Friday, October 20, 2006, at 07:25  PM, Dave wrote:



[quote] 



 Lynn,

 They slow the air down going through the heated airspace. If you don't 

 have them, you will get cooler air coming through.

 Dave



 ---

_________________
Lynn
Kitfox IV-Jabiru 2200
N369LM

dave

Joined: 22 Sep 2006
Posts: 1382

Posted: Fri Oct 20, 2006 5:04 pm Post subject: heat muffs and electrolysis

Lynn,  I do not know if conductivity has much to do with it.



The first one i did  , well I found thats air was not cold but cool  - NOT 

HOT.

If was Paul Seehafer that told me to put pot scrubbers in and KApow BATMAN 

I had more heat than i needed.

Springs will  work as well.  Maybe it does conduct but I think the main 

purpose is to slow the air down so that it can get heated on the way by.



I guess when you think of a radiator and the fins from core tubes that 

conductivity does in fact come in to play.

Dave

---

lcfitt(at)sbcglobal.net
Guest

Posted: Fri Oct 20, 2006 5:47 pm Post subject: heat muffs and electrolysis

In the plastic airplanes, when cooling is an issue, one thing they try is to 

reduce the size of the inlet openings.  This slows down the air through the 

cylinder fins and aids in the cooling.



We have discussed this in the past regarding the ideal inlet vs. outlet 

size - points to the Kitfoxl list.  I noticed this week as we were 

installing the cowl and baffeling on the Lancair IV that the inlet and 

outlets are, for practical purposes, the same size.  I am anticipating 

cooling issues when Brad starts flying.  I guess that is why they often will 

fly in primer for a year or so to make this sort of adjustment less 

painfull.



Frankly, and this is just between us,  for all its speed and mystique, I 

didn't find the airplane very sophisticated.    Lots of little issues that 

are just not found in the Kitfox kit or manual.   One small example, AN365 

nuts everywhere regardless of application.  Easier to put together the kits 

and less inventory, but costly in weight.   Another thing and this might be 

really off base, but the same signals that suggested Skystar's problems 

early on are surfacing at Lancair.  Lots of key people leaving, and very 

little in stock - lots of back orders.  Oh, well,  90% done and 99% to go.



Lowell

---

ddsyverson(at)comcast.net
Guest

Posted: Fri Oct 20, 2006 6:49 pm Post subject: heat muffs and electrolysis

Lynn,



On the heat transfer with the scrubbers - its a multi deal thing....



1) Conduction - some of the heat travels through the metal where the scrubber 

touches the pipe so the scrubber gains some heat which it can then transfer 

to the air because it has additional surface area.

2) Radiation - with the scrubber metal anywhere near the pipe - a lot of heat 

is picked up by the scrubber simply through radiation - try holding your hand 

within a inch of a red hot exhaust pipe - bet it will feel hot even if you 

don't actually touch it - same thing happens with the scrubber metal that is 

not touching the pipe, after which the scrubber metal can then transfer the 

heat to the air mass flowing by.

3) Forced convection - or simply the fact that air picks up heat from the pipe 

and then distributes it within the air/scrubber matrix - the slowing down of 

the air and the mixing/spreading/turbulence of the air flow accomplishes 

this.  



Just Good Old Norwegian Physics......



Dave S   



On Friday 20 October 2006 5:26 pm, Lynn Matteson wrote:

 	  Quote: 	
		   



 I had a question earlier today (while flying) regarding the use of pot

 scrubbers in a heat muff...if you put a copper scrubber into an

 aluminum heat muff, is there a resulting electrolysis action that takes

 place? Is this a problem? Are stainless scrubbers less immune? (my

 guess is yes)

 I realize that my heat muffs (alum) are clamped around the stainless

 steel exhaust pipe, but I have to accept this fact.

 How do the pot scrubbers pick up the heat from the exhaust pipe, seeing

 as it does not touch it in very many places...as least not as much as a

 clamped-on finned device (that I built) would?

 I'll accept the fact that many of you have tried the scrubbers and they

 work, but I'd like to know the physics of it all.



 Lynn

 Kitfox IV Speedster...Jabiru 2200

Lynn Matteson

Joined: 10 Jan 2006
Posts: 2778
Location: Grass Lake, Michigan

Posted: Fri Oct 20, 2006 7:08 pm Post subject: heat muffs and electrolysis

I do know that when I worked at the Chrysler wind tunnel about 30 

years a go, that we would test radiators with various numbers of fins 

per inch of core-tube length. The numbers that I recall were 4 and 5 

fins per inch. We, as mechanics and "installers" of the experimental 

radiators, only knew that we were installing rad "x" or rad "y", and 

that they were different. We'd put the rad on the car, in the tunnel, 

then go back to our other mundane chores while the engineers ran the 

tests. What we learned was that

rad "x" ran hotter, but was cheaper to produce because it had less fins 

and that equaled more money in Chrysler's pocket, or a less expensive 

product to sell. And of course, all those fins were in contact with the 

coolant tubes, picked up their heat, and dissipated it into the air 

that passed through. In the variety of fins that I have witnessed over 

the years are: wavy fins, fins with "star"-shaped holes punched through 

them, and fins set at an angle, causing the air to go through the 

radiator at an angle, slowing the air, and thereby picking up more 

heat, and of course, more or less fins per inch of tube length.  But in 

all these cases, the fin was in contact with the cooling tubes drawing 

heat away from the tube, and presenting it to the air for removal. In 

the case of our scrubbers, I just don't see the physical contact with 

the exhaust pipe as the way the heat is picked up. I guess I'll just 

have to accept the fact that the air is slowed down by sheer blockage, 

and it picks up heat that is radiated out from the pipe and let it go 

at that....good enough.



Lynn



On Friday, October 20, 2006, at 09:02  PM, Dave wrote:



 	  Quote: 	
		   



 Lynn,  I do not know if conductivity has much to do with it.



 The first one i did  , well I found thats air was not cold but cool  - 

 NOT HOT.

 If was Paul Seehafer that told me to put pot scrubbers in and KApow 

 BATMAN I had more heat than i needed.

 Springs will  work as well.  Maybe it does conduct but I think the 

 main purpose is to slow the air down so that it can get heated on the 

 way by.



 I guess when you think of a radiator and the fins from core tubes that 

 conductivity does in fact come in to play.

 Dave

_________________
Lynn
Kitfox IV-Jabiru 2200
N369LM

Lynn Matteson

Joined: 10 Jan 2006
Posts: 2778
Location: Grass Lake, Michigan

Posted: Fri Oct 20, 2006 7:18 pm Post subject: heat muffs and electrolysis

Is there a reverse-venturi shape to the outlet, Lowell? The Jabiru 

people say that the best outlet shape has a lip that splays out so as 

the air is leaving the cowl, a slight vacuum is formed helping to pull 

the warmed air from inside the cowl. This may be common knowledge among 

aircraft people, but thought I'd mention it. That, and the old 3:1 

ratio of outlet air to inlet air in area comparison....which is 

probably why you just mentioned anticipating cooling issues.



Lynn

On Friday, October 20, 2006, at 09:46  PM, Lowell Fitt wrote:



 	  Quote: 	
		   



 In the plastic airplanes, when cooling is an issue, one thing they try 

 is to reduce the size of the inlet openings.  This slows down the air 

 through the cylinder fins and aids in the cooling.



 We have discussed this in the past regarding the ideal inlet vs. 

 outlet size - points to the Kitfoxl list.  I noticed this week as we 

 were installing the cowl and baffeling on the Lancair IV that the 

 inlet and outlets are, for practical purposes, the same size.  I am 

 anticipating cooling issues when Brad starts flying.  I guess that is 

 why they often will fly in primer for a year or so to make this sort 

 of adjustment less painfull.



 Frankly, and this is just between us,  for all its speed and mystique, 

 I didn't find the airplane very sophisticated.    Lots of little 

 issues that are just not found in the Kitfox kit or manual.   One 

 small example, AN365 nuts everywhere regardless of application.  

 Easier to put together the kits and less inventory, but costly in 

 weight.   Another thing and this might be really off base, but the 

 same signals that suggested Skystar's problems early on are surfacing 

 at Lancair.  Lots of key people leaving, and very little in stock - 

 lots of back orders.  Oh, well,  90% done and 99% to go.



 Lowell

_________________
Lynn
Kitfox IV-Jabiru 2200
N369LM

Lynn Matteson

Joined: 10 Jan 2006
Posts: 2778
Location: Grass Lake, Michigan

Posted: Fri Oct 20, 2006 7:27 pm Post subject: heat muffs and electrolysis

That works for me, Dave....now how about the possible electrolysis 

thing with the previously-mentioned copper scrubbers? It was mentioned 

that they really worked well, and I wondered if they worked well enough 

to chance risking a possible electrolysis problem due to the 

interaction between the copper scrubbers and (my) aluminum heat muff?



Lynn

On Friday, October 20, 2006, at 10:03  PM, Dave and Diane wrote:



 	  Quote: 	
		   

 <ddsyverson(at)comcast.net>



 Lynn,



 On the heat transfer with the scrubbers - its a multi deal thing....



 1) Conduction - some of the heat travels through the metal where the 

 scrubber

 touches the pipe so the scrubber gains some heat which it can then 

 transfer

 to the air because it has additional surface area.

 2) Radiation - with the scrubber metal anywhere near the pipe - a lot 

 of heat

 is picked up by the scrubber simply through radiation - try holding 

 your hand

 within a inch of a red hot exhaust pipe - bet it will feel hot even if 

 you

 don't actually touch it - same thing happens with the scrubber metal 

 that is

 not touching the pipe, after which the scrubber metal can then 

 transfer the

 heat to the air mass flowing by.

 3) Forced convection - or simply the fact that air picks up heat from 

 the pipe

 and then distributes it within the air/scrubber matrix - the slowing 

 down of

 the air and the mixing/spreading/turbulence of the air flow 

 accomplishes

 this.



 Just Good Old Norwegian Physics......



 Dave S

_________________
Lynn
Kitfox IV-Jabiru 2200
N369LM

lcfitt(at)sbcglobal.net
Guest

Posted: Fri Oct 20, 2006 8:03 pm Post subject: heat muffs and electrolysis

Guy and Lynn,



No cowl flap, but there is sort of a tunnel - exhaust in each - on each side 

where the cowl extends below the fuselage contour a bit.  Nice thing about 

this project for me is that I am labor only.  Issues?  I just wait for the 

heads-up from Brad.  I give opinion, but the decisions are his.  Yes! 

Through every part of the project I have been very happy my airplane is a 

Kitfox.



Lowell



Do Not Archive



---

smokey_bear_40220(at)yaho
Guest

Posted: Fri Oct 20, 2006 10:13 pm Post subject: heat muffs and electrolysis

The old WW-I Jenny had a radiator where the water only

went around the outer ring.  The entire center was

only conductor.  Seems the heat would transfer a long

ways from the contacted surface.



I think in the case of the scrubbers, they not only

slow the air down but mix it so that more air has a

chance to contact heated surfaces.  As was mentioned,

radiation has more time to work too.



My air coming from my oil cooler only rises about 10

degrees in temperature.  I planned to use it for cabin

heat.  Looks like I'll have to lower the airspeed thru

the cooler to get much heat out of it in winter. 

Scrubbers aren't adjustable enough.  



Kurt S.  S-5



--- Lynn Matteson <lynnmatt(at)jps.net> wrote:



 	  Quote: 	
		   I realize that, Dave...that they slow down the air

 and therefore the 

 air heats up. That is why I built some baffles that

 have fins 

 protruding from them, and the fins are offset,

 thereby making the air 

 slow down, go around the fins, picking up heat, etc.

 My finned baffles 

 are in direct contact with the exhaust pipe. Maybe I

 should have 

 explained this when I asked the question. I know the

 principle of how 

 the scrubbers work, what I wanted to know was how do

 the scrubbers PICK 

 UP the heat from the exhaust pipe when they have so

 very little surface 

 area in contact with the pipe. Maybe you guys

 stuffed the scrubbers in 

 your muffs very tightly, thereby creating a lot of

 conduction heat 

 pickup...did you? (those that have tried the

 scrubbers?)

 

 Lynn


	


__________________________________________________

dave

Joined: 22 Sep 2006
Posts: 1382

Posted: Sat Oct 21, 2006 2:02 am Post subject: heat muffs and electrolysis

Lynn  ,  I am not familiar with  metal interaction between copper/brass 

with Aluminum  at all.

That being said for pot scrubbers  you would think that copper would be a 

better conductor than Stainless Steel.

In this application I have not idea if one would be better than another  (SS 

versus Copper )

I found this it matters

"1)  University of Sherbrooke, Sherbrooke, Canada

Abstract  The surface pitting of copper conductors recovered from fire 

debris has been reproduced by laboratory tests. The results of these tests 

demonstrate that molten aluminum that comes in contact with copper 

conductors drastically reduces the melting point of copper by alloying. "

Dave

---

Lynn Matteson

Joined: 10 Jan 2006
Posts: 2778
Location: Grass Lake, Michigan

Posted: Sat Oct 21, 2006 4:55 am Post subject: heat muffs and electrolysis

It's raining here today...a perfect day to change my tailwheel spring 

to the new 3-leaf, and to install some scrubbers in one heat muff for a 

trial test...I can't wait...wish I had an airplane wind tunnel so I 

didn't have to wait for good weather to test. : )



What, Kurt, you don't think snipping out some of those strands of 

scrubber "wire" is an adjustment? : )



Lynn

do not archive

On Saturday, October 21, 2006, at 02:12  AM, kurt schrader wrote:



 	  Quote: 	
		   

 <smokey_bear_40220(at)yahoo.com>



 The old WW-I Jenny had a radiator where the water only

 went around the outer ring.  The entire center was

 only conductor.  Seems the heat would transfer a long

 ways from the contacted surface.



 I think in the case of the scrubbers, they not only

 slow the air down but mix it so that more air has a

 chance to contact heated surfaces.  As was mentioned,

 radiation has more time to work too.



 My air coming from my oil cooler only rises about 10

 degrees in temperature.  I planned to use it for cabin

 heat.  Looks like I'll have to lower the airspeed thru

 the cooler to get much heat out of it in winter.

 Scrubbers aren't adjustable enough.  



 Kurt S.  S-5



 --- Lynn Matteson <lynnmatt(at)jps.net> wrote:



> I realize that, Dave...that they slow down the air

> and therefore the

> air heats up. That is why I built some baffles that

> have fins

> protruding from them, and the fins are offset,

> thereby making the air

> slow down, go around the fins, picking up heat, etc.

> My finned baffles

> are in direct contact with the exhaust pipe. Maybe I

> should have

> explained this when I asked the question. I know the

> principle of how

> the scrubbers work, what I wanted to know was how do

> the scrubbers PICK

> UP the heat from the exhaust pipe when they have so

> very little surface

> area in contact with the pipe. Maybe you guys

> stuffed the scrubbers in

> your muffs very tightly, thereby creating a lot of

> conduction heat

> pickup...did you? (those that have tried the

> scrubbers?)

>

> Lynn



 __________________________________________________

_________________
Lynn
Kitfox IV-Jabiru 2200
N369LM

Lynn Matteson

Joined: 10 Jan 2006
Posts: 2778
Location: Grass Lake, Michigan

Posted: Sat Oct 21, 2006 5:20 am Post subject: heat muffs and electrolysis

Without knowing any more than I do about electricity/electrolysis, I 

think I'll forego looking for the copper scrubbers and use the steel(?) 

ones that I bought yesterday for the first test. It would be nice to 

test copper in one muff and SS in the other, though....what the hell, 

I'm sure a short test like this would not cause enough of a problem as 

to bring the plane down. Far from that, perhaps a little pitting where 

the copper contacted the aluminum is all that I can imagine...we'll 

see. As soon as the west coast wakes up, I've got an electrical 

engineer friend "on retainer" that might be able to shed some light on 

this.



Lynn

do not archive



On Saturday, October 21, 2006, at 06:01  AM, Dave wrote:



 	  Quote: 	
		   



 Lynn  ,  I am not familiar with  metal interaction between 

 copper/brass with Aluminum  at all.

 That being said for pot scrubbers  you would think that copper would 

 be a better conductor than Stainless Steel.

 In this application I have not idea if one would be better than 

 another  (SS versus Copper )

 I found this it matters

 "1)  University of Sherbrooke, Sherbrooke, Canada

 Abstract  The surface pitting of copper conductors recovered from fire 

 debris has been reproduced by laboratory tests. The results of these 

 tests demonstrate that molten aluminum that comes in contact with 

 copper conductors drastically reduces the melting point of copper by 

 alloying. "

 Dave

_________________
Lynn
Kitfox IV-Jabiru 2200
N369LM

pwmac(at)sisna.com
Guest

Posted: Sat Oct 21, 2006 6:09 am Post subject: heat muffs and electrolysis

Aluminum and copper or brass are close in the electromotive chart. 

Steel is not a good used with Al. My 84 172 had stainless pads in the 

air intakes to keep out the bugs. Never saw any corrosion, but there 

was no heat at the leading edge intakes. If the muffler is stainless 

then use stainless pads If the thing is Al then use copper or brass. 

If the shroud is Al and the muffler is stainless or other steel you 

already have a corrosion issue that wont be exacerbated by any kind of pad.

Hope this helps, Paul

===================

At 04:01 AM 10/21/2006, you wrote:

[quote]



Lynn  ,  I am not familiar with  metal interaction between 

copper/brass with Aluminum  at all.

That being said for pot scrubbers  you would think that copper would 

be a better conductor than Stainless Steel.

In this application I have not idea if one would be better than 

another  (SS versus Copper )

I found this it matters

"1)  University of Sherbrooke, Sherbrooke, Canada

Abstract  The surface pitting of copper conductors recovered from 

fire debris has been reproduced by laboratory tests. The results of 

these tests demonstrate that molten aluminum that comes in contact 

with copper conductors drastically reduces the melting point of 

copper by alloying. "

Dave

---

Float Flyr

Joined: 19 Jul 2006
Posts: 2704
Location: Campbellton, Newfoundland

Posted: Sat Oct 21, 2006 7:32 am Post subject: heat muffs and electrolysis

I think most (not all) the dissimilar metal corrosion will occur on the

softer metal.  E.g. Aluminium in contact with steel given sufficient heat

and moisture the aluminium will corrode more than the steel.  The pot

scrubbers are stainless steel as is the muffler.  It is ,no doubt, not the

same kind of stainless steel but they are probably close enough together

that wear and corrosion should be minimal..... Check it every twenty or so

years. 



Noel



[quote] --

_________________
Noel Loveys
Kitfox III-A
Aerocet 1100 Floats

Float Flyr

Joined: 19 Jul 2006
Posts: 2704
Location: Campbellton, Newfoundland

Posted: Sat Oct 21, 2006 7:34 am Post subject: heat muffs and electrolysis

They also work as heating fins ... They help to transmit heat from the

muffler into the air inside the muff.



Noel



[quote] --

_________________
Noel Loveys
Kitfox III-A
Aerocet 1100 Floats

dave

Joined: 22 Sep 2006
Posts: 1382

Posted: Sat Oct 21, 2006 7:47 am Post subject: heat muffs and electrolysis

If we worrying about metal interaction in a heater we need to focus on 

better things in life ... Like flying --  i got 2 hours in this am so far 





Dave



---

Float Flyr

Joined: 19 Jul 2006
Posts: 2704
Location: Campbellton, Newfoundland

Posted: Sat Oct 21, 2006 7:53 am Post subject: heat muffs and electrolysis

I see there is some question as to whether or not the pot scrubbers actually

transfer heat or just slow down the airflow so more heat can be absorbed

directly into the air from the muffler.



I have thought up a little experiment for you to try.  This is a simple do

it at home test that the XYL (Mrs) can help you with.  Put a pot scrubber in

a cast iron skillet and let it warm up for say five minutes then remove the

scrubber from the pan and insert a meat thermometer into it.  It the

temperature on the thermometer rises then the scrubber will have absorbed

some of the heat from the skillet.  I advise you not to try to handle the

pot scrubber with your bare hands.  Let it sit for a minute or two then

touch it with your fingers.... It should still be warm.



Do not use any oils or spices in this recipe. 



Bonne Appetite



Noel



[quote] --

_________________
Noel Loveys
Kitfox III-A
Aerocet 1100 Floats

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