Cherokee getting fat

Aaron Coolidge wrote:
: Mine - 1968 180-D - weighs 1400 lbs, the lightest it has ever weighed.
: --

Guess that makes me feel better. I just get a little gunshy when flying it
close to gross since the climb performance *really* goes to crap in the PA-28 when
approaching gross.

The other thing is a resale issue. Since ours was a -140 that's been upgraded
to -180, its legal max gross weight wasn't (appreciably) increased. It's legal only
to 2200 gross TO (2150 landing)... if it were a real -180 it'd be legal to 2400.

-Cory

--

************************************************** ***********************
* Cory Papenfuss *
* Electrical Engineering candidate Ph.D. graduate student *
* Virginia Polytechnic Institute and State University *
************************************************** ***********************

wrote:
Matt Barrow wrote:
: Why in hell did you go for a Tanis heater instead of Reiff?

- Get heat *AT* the head... not at the other end of the jug where it has to go
by cooling fins designed to remove it to get where it's needed.

That's interesting. I've never owned a heater, don't know about Tanis or Reiff,
since I've been flying, I haven't lived in a climate where heating is called
for, but...

I'd think "at the head" is not a particularly important place to have the heat.
Seems to me heating the oil in the crankcase so it can be pumped more quickly
and start lubricating is a better bang for the buck.

.... or maybe the rationale is that heating the head relieves the "choke" of the
cylinder barrel and reduces wear that way? If so, I have to wonder whether the
few degrees rise you're likely to get from an electric heater has any
significant effect on the amount of choke.

Why heat the heads?

Ignorant and looking to learn... Dave

"Dave Butler" wrote in message
news:1119360233.195544@sj-nntpcache-3...
That's interesting. I've never owned a heater, don't know about Tanis or
Reiff, since I've been flying, I haven't lived in a climate where
heating is called for, but...

I'd think "at the head" is not a particularly important place to have
the heat. Seems to me heating the oil in the crankcase so it can be
pumped more quickly and start lubricating is a better bang for the buck.

... or maybe the rationale is that heating the head relieves the "choke"
of the cylinder barrel and reduces wear that way? If so, I have to
wonder whether the few degrees rise you're likely to get from an
electric heater has any significant effect on the amount of choke.

Why heat the heads?

Ignorant and looking to learn... Dave

2 reasons to preheat- Lycoming et-al want you to preheat for damage
issues, i.e. choke and oiling as you mentioned. The second reason for heat
though, is to get the pig to start in the first place.

Also, a full Tanis set-up has a small heater for each cylinder and a pad
on the pan to warm the oil.

Mike Z

wrote in message
...
Matt Barrow wrote:
: Why in hell did you go for a Tanis heater instead of Reiff?

- Get heat *AT* the head... not at the other end of the jug where it has
to go
by cooling fins designed to remove it to get where it's needed.
- We already had spark-plug CHT probes.
- We found an ebay deal.

My thinking is unless you had a good reason not to, Tannis is the better
way
to go. Why do you think differently?

Based on what Aviation Consumer had to say when I was buying a system
(March, 2001 edition). They said there was no advantage to merely heating
the head and that heating the barrel did have advantages.

Aviation Consumer, March 2001, pg. 18

"[Other brand] loses us in claiming that the top of the cylinder is more
critical to heat than the rest of the cylinder."
"As for heating the top of the cylinder being better, we just don't buy
that."
"As for bands versus cylinder head plugs, our view is that [other brand]
overstates the case in saying it's best to heat the head."


Cost - about a factor of three for the Tannis, would have added a couple
thousand $$ to the total cost including installation and paperwork.

Total cost for my Reiff system, including installation was under $1000.

AIUI, Tannis does heat the cylinder with the factory CHT probe. It also
causes problem for the CHT probes that you add for an engine analyzer.

http://www.reiffpreheat.com/FAQ.htm#QA10

FWIW, this if Reiff's take, but then Tannis has there's which is not
supported by third party reviews.

Aviation Consumer, TCM and the shop that did my engine conversion all
advised going with the Reiff.

YMMV.


--
Matt
---------------------
Matthew W. Barrow
Site-Fill Homes, LLC.
Montrose, CO

"Mike in GR" wrote in message
ink.net...


"Dave Butler" wrote in message
news:1119360233.195544@sj-nntpcache-3...
That's interesting. I've never owned a heater, don't know about Tanis or
Reiff, since I've been flying, I haven't lived in a climate where
heating is called for, but...

I'd think "at the head" is not a particularly important place to have
the heat. Seems to me heating the oil in the crankcase so it can be
pumped more quickly and start lubricating is a better bang for the buck.

... or maybe the rationale is that heating the head relieves the "choke"
of the cylinder barrel and reduces wear that way? If so, I have to
wonder whether the few degrees rise you're likely to get from an
electric heater has any significant effect on the amount of choke.

Why heat the heads?

Ignorant and looking to learn... Dave

(See the URL summary in previous post)


2 reasons to preheat- Lycoming et-al want you to preheat for damage
issues, i.e. choke and oiling as you mentioned. The second reason for heat
though, is to get the pig to start in the first place.

Also, a full Tanis set-up has a small heater for each cylinder and a pad
on the pan to warm the oil.

Tannis (AIUI) does not head the head which has the CHT probe, or did they
develop a plug that can co-locate the CHT probe AND the heater element? I
don't think they had one in 2001.

wrote in message
...
Matt Barrow wrote:
: Why in hell did you go for a Tanis heater instead of Reiff?

- Get heat *AT* the head... not at the other end of the jug where it has
to go
by cooling fins designed to remove it to get where it's needed.

That's not only a myth, but flat out wrong.

http://www.reiffpreheat.com/FAQ.htm#QA11

: Matt Barrow wrote:
: : Why in hell did you go for a Tanis heater instead of Reiff?
:
: - Get heat *AT* the head... not at the other end of the jug where it has
: to go
: by cooling fins designed to remove it to get where it's needed.

: That's not only a myth, but flat out wrong.

: http://www.reiffpreheat.com/FAQ.htm#QA11

I can see I stirred up a hornet's nest here. I don't care all that much
either way... I looked into it awhile back and decided that with appropriate
workarounds, Tannis provides better performance where it matters. In response to your
previous messages:

- Tannis does have workarounds for the CHT probe. I think they've got a combo
thermocouple and heater element, but I just use the spark-plug probes. They've also
got the extra-kludgy valve cover gasket heater... ick!

- Cost... yeah, that makes a difference. I got mine used.

- My statement regarding heat AT the head was poorly worded, but my point still
stands. I was not talking about interfering with cylinder cooling
(http://www.reiffpreheat.com/FAQ.htm#QA11)... rather the argument that heat flows well
the other way. If you read their rebuttal (http://www.reiffpreheat.com/FAQ.htm#QA10)
carefully, you see:

"Our testing of our system and the other brand showed that the cylinder temperature
measured at the top end of the cylinder mid-way between their element and ours was the
same with both systems. Not surprising since both are 50 watt heaters. They did a
test too, but they skewed the results in their favor by measuring the temp about 1
inch away from their heating element."

No surprise there... if you look at the cylinder, a point midway between the
CHT probe and the base of the cylinder barrel has almost the same amount of barrel
travel. Heat *will* flow in all directions from the source, but if you heat in the
center of the head, it'll get more heat *IN* the head than if you heat from the bottom
of the jug. The head is where the choke is, where the highest thermal load is once it
starts (read: uneven expansion initially).

Don't get me wrong... both products have issues, and they both are flinging
crap at the other to try to say that theirs is better. Aside from the expense and
complication of heating *all* cylinders (including ones with CHT probes), the Tannis
is a better engineered solution.... put heat where it's necessary. If you could seal
off and insulate the cowling extremely well so little heat is lost, everything inside
would eventually get toasty. In a finite time with imperfect insulation, I'd rather
put the heat where it's necessary.

Flame on...
-Cory



--

************************************************** ***********************
* Cory Papenfuss *
* Electrical Engineering candidate Ph.D. graduate student *
* Virginia Polytechnic Institute and State University *
************************************************** ***********************

Dave Butler wrote:
: That's interesting. I've never owned a heater, don't know about Tanis or Reiff,
: since I've been flying, I haven't lived in a climate where heating is called
: for, but...

Generally, the freezing point is about where it's considered a good idea to
preheat. Some people say 40, some 20.

: I'd think "at the head" is not a particularly important place to have the heat.
: Seems to me heating the oil in the crankcase so it can be pumped more quickly
: and start lubricating is a better bang for the buck.

That's important, although with multiweight oils it's less so.

: ... or maybe the rationale is that heating the head relieves the "choke" of the
: cylinder barrel and reduces wear that way? If so, I have to wonder whether the
: few degrees rise you're likely to get from an electric heater has any
: significant effect on the amount of choke.

: Why heat the heads?

: Ignorant and looking to learn... Dave

You got it... there was an article (Mike Busch on avweb?) on the clearance of
the dissimilar metals (pistons and cylinders). There's a point (temperature) where
there is *negative* clearance (i.e. scuffing). If one can warm the thing from 0F to
+40F, you've already gotten past it. Also, the heat loading is uneven due to the
mass. It takes a (relatively) long time for the cylinders and heads to heat up
compared to the lightweight pistons in very close proximity to the fire.

-Cory

--

************************************************** ***********************
* Cory Papenfuss *
* Electrical Engineering candidate Ph.D. graduate student *
* Virginia Polytechnic Institute and State University *
************************************************** ***********************

Aaron Coolidge wrote:
: Hi Cory, I think that if you have airflow the head is an efficient heat
: dissipator. If you have no airflow, the metal components of the cylinder
: will eventually get to thermal equilibrium regardless of the position of
: the heating elements.
Correct, but remember this. There *are* heat leaks somewhere or else it would
get hotter and hotter. That means that there's heat flow. AUIU, once the convective
air is blocked, the prop/cranks is the biggest heat sink of all... sucks heat right
out of the case. There *will* be a thermal gradient under the hood... hottest places
at the elements, and coldest at the heat sinks.

I have a reiff system; my plane is kept outside in
: Southeastern MA; I do not have a cowling cover (but the fiberglass
: cowling is a good insulator and I use cowl plugs). I find a 30 deg F rise
: at the cyl head on the coldest days that we experience. I measured 30degF
: at the #1 cyl head with my trusty Omega handheld thermocouple with 0 degF
: ambient. I am satisfied.
Agreed... I generally run the same setup... no cover, but cowl plugs. I
haven't put a thermocouple on them, but at 20F the heads are quite warm to the
touch... I'd say 40-50. Sounds like the same 30 degree rise. With better insulation,
things would be even better.

: I got the Reiff because I can't stand tanis' web site! I was impressed with
: Reiff's after-sale service, as well. When I messed up gluing the heater
: to the oil sump they sent me a new batch of glue. The glue is just metal-
: filled epoxy (think J-B Weld), but I wanted to use their "special" stuff
: anyway.
: --
: Aaron C.

I got mine used, so it was cheaper and didn't have support no matter what.
I'm not saying Reiff sucks. It's much better than leaving one cylinder without heat
IMO. I'm just saying that aside from that issue with the Tannis, Reiff bands will
probably perform "up to and possibly including" tannis performance...

-Cory
--

************************************************** ***********************
* Cory Papenfuss *
* Electrical Engineering candidate Ph.D. graduate student *
* Virginia Polytechnic Institute and State University *
************************************************** ***********************

"Mike in GR" wrote in message
ink.net...


"Dave Butler" wrote in message
news:1119360233.195544@sj-nntpcache-3...
That's interesting. I've never owned a heater, don't know about Tanis or
Reiff, since I've been flying, I haven't lived in a climate where
heating is called for, but...

I'd think "at the head" is not a particularly important place to have
the heat. Seems to me heating the oil in the crankcase so it can be
pumped more quickly and start lubricating is a better bang for the buck.

... or maybe the rationale is that heating the head relieves the "choke"
of the cylinder barrel and reduces wear that way? If so, I have to
wonder whether the few degrees rise you're likely to get from an
electric heater has any significant effect on the amount of choke.

Why heat the heads?

Ignorant and looking to learn... Dave

2 reasons to preheat- Lycoming et-al want you to preheat for damage
issues, i.e. choke and oiling as you mentioned. The second reason for heat
though, is to get the pig to start in the first place.

Also, a full Tanis set-up has a small heater for each cylinder and a pad
on the pan to warm the oil.


As does Reiff, and it has a thermostat that Tanis doesn't.