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Hot Tunnel suggestion

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ddddsp1(at)juno.com
Guest

Posted: Sun Jun 25, 2006 9:48 pm Post subject: Hot Tunnel suggestion

I wanted to pass on a suggestion for those looking to keep their RV 10 TUNNEL cool. Take your Black & Decker Wet vac and hook the hose to the blower/discharge air. Then place the hose over one of the heat vents on the firewall simulating hot air blowing into the cabin. Close the vents and see if air is still entering the cabin with the vents shut and the wet vac blowing air into the vent on the firewall side. What we discovered was alot of air was entering the OPPOSITE vent when both were closed. The air was coming in under the hinge on the vent door. When I placed a small aluminum divider between the air vents on the firewall the air ceased leaking into the cabin tunnel. After playing with a few DEFLECTOR designs, I used the inside mounting bolt on the vent box to hold a deflector in place and then also put an 1/8 inch deflector inside the vent box so air could not sneak under the front of the vent door. This should solve the problem with HOT air entering the Tunnel with the vents CLOSED. There still may be a Radiant heat problem but insulation on the firewall and tunnel floor and silicone between the firewall and vent box helps for Radiant heat. 



Dean

40449

 



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zackrv8

Joined: 14 Jan 2006
Posts: 133

Posted: Mon Jun 26, 2006 4:37 am Post subject: Re: Hot Tunnel suggestion

Dean,



  This is exactly what I thought.  I believe the discharge air from both valves (when in the closed position) leaks into the cabin because of the design of the valve.  Your solution should work. 



  Also note in the latest RVator that Vans addresses the HTS (Hot Tunnel Syndrome).



Zack

_________________
RV8 #80125
RV10 # 40512

VHMUM(at)bigpond.com
Guest

Posted: Mon Jun 26, 2006 1:16 pm Post subject: Hot Tunnel suggestion

What a fantastic idea!! Well done.



Chris



Do not archive

---

CJohnston(at)popsound.com
Guest

Posted: Mon Jun 26, 2006 2:50 pm Post subject: Hot Tunnel suggestion

Hey all - 



I'm actually in the process of riveting the tunnel to the firewall, and

I'm trying to assimilate all of the potential fixes to the hot tunnel so

that I can incorporate them into the initial construction...  I'd like

to make a bit of a list of what I've heard from discussions here and at

VAF and see if anyone has anything else.  From what I understand, no one

has pinpointed the exact cause of the "hot tunnel syndrome", referred to

hereafter as HTS .  Maybe it's a single cause, and maybe it's just the

accumulation of many smaller causes.  Whatever the case, there are many

theories, and I'd like to consolidate a bit.  



If I understand this right, there are a couple potential causes:



1. location of exhaust gasses passing by bottom skin?

2. hot air exiting the cowl in a disorderly fashion (heating the skin

under   	the forward fuse)

I admit that I don't fully understand these first two, so if others

could weigh in...



3. heater vent valves not sealing completely

4. generally hot condition (you know, engine running and stuff) in front

of the firewall and the associated heat being conducted to the tunnel



In the spirit of trying to head off the problem, I'm planning to

incorporate some of the suggestions I've heard into the original build,

then fine-tune (or hopefully not have any problems) when flying.  Maybe

it's a case where a bunch of little fixes add up to fixing the overall

problem.  We'll see.



Potential fixes - 



1. different exhaust?  (I still don't understand, but if memory serves,

I think Randy or maybe Vic mentioned that they had the Vetterman exhaust

and the exits are different... maybe I'm making this up?)



2. exhaust coating?  This is my own hair brained idea, but in a previous

life (or when I had one) building race cars, underhood temps were a big

problem for a street/race car.  It's actually really similar to

airplanes - big motor, little space.  Ceramic exhaust coatings helped

reduce the radiated heat in the engine compartment.  Is this a lame

idea?



3. false floor in tunnel?  This seems to be the idea with the biggest

following.  I was thinking (space permitting) of a false floor installed

with some sort of phenolic spacer (instead of highly heat-conductive

aluminum ribs)in the tunnel, combined with insulation.



4. insulate firewall?  I thought I might do this anyway, but it seems

like the mechanical connection of the firewall to the tunnel would

negate any potential benefit from a HTS standpoint.



5. fresh air intake on one side of the heat vent?  



6. gills, or some sort of vent on the bottom of the AC in the tunnel?  



7. phenolic gasket of some sort between the heat valve and the firewall?



Sorry to be so long winded here, but this seems to be a big problem, and

I know that there are some smart people on the list.  There's gotta be a

way to design this problem out of the RV-10.  



I do have a specific question for those already flying who have a hot

tunnel - is the floor under your feet hot also?



Thanks all

cj



#40410

fuse (HTS investigation)

Randy(at)abros.com
Guest

Posted: Mon Jun 26, 2006 2:54 pm Post subject: Hot Tunnel suggestion

1. different exhaust?  (I still don't understand, but if memory serves,

I think Randy or maybe Vic mentioned that they had the Vetterman exhaust

and the exits are different... maybe I'm making this up?)



Just for clarification, I don't have the Vetterman exhaust. I have the

AWI Exhaust.  Randy

Rick S.

Joined: 12 Feb 2006
Posts: 347
Location: Las Vegas

Posted: Mon Jun 26, 2006 3:03 pm Post subject: Hot Tunnel suggestion

CJ,



One note off topic, do as much of your fuel and brake system fabrication while you have easy access to the tunnel. It will save your back and knees a bunch when it comes time to put these in for good.



Rick S.

40185

Wiring

_________________
Rick S.
RV-10
40185

rvbuilder(at)sausen.net
Guest

Posted: Mon Jun 26, 2006 3:25 pm Post subject: Hot Tunnel suggestion

Chris,



  Couple of things.  The way the cabin heat boxes work is that they dump

the hot air from the exhaust muff overboard, at the cabin heat box, when

it is closed to the inside cabin.  This is supposedly so the heat muff

and SCAT tube doesn't overheat.  This effectively provides a nonstop

blast of hot air at the heat boxes and firewall.  There is a few things

you can do for this:



1) Several people have reported good success with using a silicone

gasket between the heat box and the firewall providing a thermal break.

I also did this. You get a silicone gasket with AviaComps heater boxes

if you go that route.  Most people I talk to think it's a bad idea for

Van's stock boxes to be made from aluminum which has opened up a nice

niche for SS boxes.  I sent an email to Don at AviaComp today asking him

if he would make a left cabin heat box in addition to the right side one

he makes.



2) Use some sort of insulating barrier at the firewall, on the inside,

and also in the tunnel.  This is recommended either way.  I used a

ceramic paint additive to reduce radiated heat but I don't know how well

it will work yet.



3) Make sure that no air is sneaking in through the heat boxes.  Recent

post on this.



4) As you said, ceramic coat the exhaust pipes.  John Forsling is

selling pipes for the 540 on the RV-10 and they are ceramic coated,

produce more horses, and are only a couple hundred more than Vettermans.

Forsling and Vetterman used to work together and Forslings exhausts are

usually considered superior, at least by the people I have asked.  If

you are at OSH you can see a set on my engine at Barretts booth.  Keep

in mind that you will have lower performance from a heat muff with a

ceramic coated exhaust.



5) Something I'm thinking about is a way to mix cool air in at the

engine compartment.  Normally I would suggest making a diverter to

bypass the heat muff, but I don't know if heat really is an issue at the

muff.  I honestly don't see why it would be as the SCAT isn't going to

melt unless the muff is made out of aluminum.



Hope that helps,



Michael Sausen

-10 #352 Fuselage



--

johnwcox(at)pacificnw.com
Guest

Posted: Mon Jun 26, 2006 4:29 pm Post subject: Hot Tunnel suggestion

Chris - below are my responses to your worthy query.



John - $00.02



--

pdwalter(at)bigpond.net.a
Guest

Posted: Mon Jun 26, 2006 5:20 pm Post subject: Hot Tunnel suggestion

Are Vans doing anything to address the ongoing tunnel heat problem ?

---

zackrv8

Joined: 14 Jan 2006
Posts: 133

Posted: Mon Jun 26, 2006 5:29 pm Post subject: Re: Hot Tunnel suggestion

 	  pdwalter(at)bigpond.net.a wrote: 	
		  Are Vans doing anything to address the ongoing tunnel heat problem ?

--- 	




Yes!



  Check out the link below....

Zack



http://www.vansaircraft.com/pdf/tunnel_temp.pdf

_________________
RV8 #80125
RV10 # 40512

Tim(at)MyRV10.com
Guest

Posted: Tue Jun 27, 2006 9:36 am Post subject: Hot Tunnel suggestion

With all the tunnel heat discussions lately, I thought I

would write something up, and I incorporated some of Dean's

stuff, along with a nice drawing Bob Condrey sent me, and some photos

I snagged from Scott's Schmidt.  It may be a good read for those

of you who are overly concerned as to the whole "Hot Tunnel"

issue.



http://www.myrv10.com/tips/mods/HotTunnel/index.html



Sorry I haven't been keeping up on the tips as much as I wanted,

but this one is a good one, IMHO.



Tim - N104CD - Flying

10flyer(at)verizon.net
Guest

Posted: Fri Jun 30, 2006 12:55 pm Post subject: Hot Tunnel suggestion

Hey guys, just back in town after a week long trip and am catching up on the 

tunnel heat issue. I have been actively addressing the issuue myself as it 

is warming up down here in SoCal. I think the ideas regarding the heat boxes 

on the firewall are all good ones, but I'm starting from the inside. If I 

recall correctly, the folks with the Vetterman (two exhaust pipes) have a 

little more heat issue than those of us with the other style ( one pipe). 

Judging by the discolored metal of my unpainted belly (90 hrs flying) 

directly aft of the lower cowl, I'm banking that a lot of this heat is 

radiating up through the tunnel from below. It seems it would only be worse 

for the guys with two pipes protruding out the bottom. I actually believe 

that it is all of the engine compt. heat venting out that big hole 

underneath as well as the exhaust. In addition, if the vents were leaking 

badly (I still believe this is part of the problem) wouldn't you be feeling 

heat coming out of the openings in the cabin....I don't in mine.  Bottom 

line, I have insulated the firewall and floor in the tunnel all the way to 

the back seats and also firesleeved my tunnel fuel lines to try to insulate 

them a bit ( Having a little bit of a fuel vapor problem and pump cavitation 

at idle). I hope to fly in the next few days. If I don't see an improvement 

then I will be disconnecting the scats to the heat vents and routing them 

overboard for a flight to see if that helps. Maybe they should just be 

disconnected in the Summer time!!! Mark

jesse(at)itecusa.org
Guest

Posted: Fri Jun 30, 2006 6:16 pm Post subject: Hot Tunnel suggestion

While on this subject, I thought I would pipe in here, since I have seen

something interesting between N256H and N415EC.  First of all, those of us

with 2 pipes may actually have less tunnel heat problems, since the two

pipes are not centering the exhaust directly under the tunnel.  That may

make some difference, but I am not sure.  We have had very little trouble

with tunnel heat (that we have noticed) in over 200 hrs on N256H.  Secondly,

N415EC has longer pipes sticking out the bottom than N256H.  I haven't

talked to Van's, but is it possible that they lengthened the pipes to help

get the exhaust further out of the cowl so it wouldn't cook the belly as

much?  I haven't measured the difference in length, but it seems to be about

4-6 inches longer in kit 40415 than kit 40241.  I really should measure to

make sure it isn't just an optical illusion.



Right now we are on a marathon to get N415EC flying in time for Oshkosh.

The FWF is completed, wiring is mostly done, and now we are installing

controls.  It will be tight, but we are hoping that we might fly late next

week.  Then it will be 40 hours of neighborhood flying before Osh (unless we

get an extremely lazy DAR who doesn't notice "experimental" written all over

the TMX-IO-540 and fuel servo.



Just a couple of thoughts.



Do not archive.



Jesse Saint

I-TEC, Inc.

jesse(at)itecusa.org

www.itecusa.org

W: 352-465-4545

C: 352-427-0285



--

Tim(at)MyRV10.com
Guest

Posted: Fri Jun 30, 2006 6:46 pm Post subject: Hot Tunnel suggestion

Jesse Saint wrote:

 	  Quote: 	
		   

 

 While on this subject, I thought I would pipe in here, since I have seen

 something interesting between N256H and N415EC.  First of all, those of us

 with 2 pipes may actually have less tunnel heat problems, since the two

 pipes are not centering the exhaust directly under the tunnel.  That may

 make some difference, but I am not sure.  We have had very little trouble

 with tunnel heat (that we have noticed) in over 200 hrs on N256H.  Secondly,

 N415EC has longer pipes sticking out the bottom than N256H.  I haven't

 talked to Van's, but is it possible that they lengthened the pipes to help

 get the exhaust further out of the cowl so it wouldn't cook the belly as

 much?  I haven't measured the difference in length, but it seems to be about

 4-6 inches longer in kit 40415 than kit 40241.  I really should measure to

 make sure it isn't just an optical illusion.

 


	


I had heard, at one point, that at least one builder got either

extensions, or had his lengthened.  Perhaps they made a change

along the way like you suggest.  That wouldn't be a bad thing to

help the problem, and might be quieter too.  We'll have to

see how they measure between the various ones at OSH, and then maybe

compare to what you measure on 40415.

[quote] Right now we are on a marathon to get N415EC flying in time for Oshkosh.

 The FWF is completed, wiring is mostly done, and now we are installing

 controls.  It will be tight, but we are hoping that we might fly late next

 week.  Then it will be 40 hours of neighborhood flying before Osh (unless we

 get an extremely lazy DAR who doesn't notice "experimental" written all over

 the TMX-IO-540 and fuel servo.

 

 Just a couple of thoughts.

 

 Do not archive.

 

 Jesse Saint

 I-TEC, Inc.

 jesse(at)itecusa.org

 www.itecusa.org

 W: 352-465-4545

 C: 352-427-0285

 

 --

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