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  #1  
Old 12-27-2017, 02:41 PM
bkervaski's Avatar
bkervaski bkervaski is offline
 
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Location: Birmingham, Alabama
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Default Pg 48-04; Step 1

The RV-14's instructions have been great and I have very few complaints, they did a tremendous job. This is one of those steps I'm not quite understanding "why".

It's calling to undo some rivets and install a blocking plate with some RTV.

Removing the rivets will be challenging based on what's going on in that area but I can manage it no problem. However, beyond that, I'm trying to figure out why we didn't do this when the vents were assembled and also why this modification is being called for.

Any explanation/insight would be appreciated! I may be missing something obvious ...
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Last edited by bkervaski : 12-27-2017 at 03:41 PM.
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  #2  
Old 12-27-2017, 06:14 PM
rvbuilder2002 rvbuilder2002 is offline
 
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Location: Hubbard Oregon
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Quote:
Originally Posted by bkervaski View Post
The RV-14's instructions have been great and I have very few complaints, they did a tremendous job. This is one of those steps I'm not quite understanding "why".

It's calling to undo some rivets and install a blocking plate with some RTV.

Removing the rivets will be challenging based on what's going on in that area but I can manage it no problem. However, beyond that, I'm trying to figure out why we didn't do this when the vents were assembled and also why this modification is being called for.

Any explanation/insight would be appreciated! I may be missing something obvious ...
Removing the rivets is a simple process. Can be done in about 1 minute.

The blocking plate wasn't installed in Section 28 because when the FWF lit was released many people had already built well past Section 28, so doing it this way was a minor compromise in not leaving anyone behind, and to allow for installation variability. If someone decided to do their heat muffs differently and have separate muff feeds to each valve, the block-off isn't required.

The simple answer to "Why install it"..... because the system (if installed as designed and per the construction manual) won't work properly without it.
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  #3  
Old 12-27-2017, 06:19 PM
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bkervaski bkervaski is offline
 
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Quote:
The blocking plate wasn't installed in Section 28 because when the FWF lit was released many people had already built well past Section 28, so doing it this way was a minor compromise in not leaving anyone behind, and to allow for installation variability. If someone decided to do their heat muffs differently and have separate muff feeds to each valve, the block-off isn't required.
Ahh, that makes sense. Thanks!

My “why” wasn’t “why bother” but rather “why now”. I follow the plans to the letter.
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Last edited by bkervaski : 12-27-2017 at 06:24 PM.
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  #4  
Old 12-27-2017, 06:30 PM
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jeffw@sc47 jeffw@sc47 is offline
 
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Location: Simpsonville, SC (SC47)
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Default good question

This looks like a 'Where's Waldo?' puzzler

I shot by this instruction as I went with the Vetterman's exhaust and the muffs came with his kit, so I did not follow the Van's instructions here - lesson learned is that everyone should at the least review Vans' sections even if those parts/elements come from elsewhere. This mod would be pretty hard to do now that I have installed stuff to make access difficult - but doable.

But, I went out and looked closely to the heat muff tube routing and why would it be designed to dam the right cabin heat valve overboard dump? I wasn't able to come up with an answer on my own. It is apparent that with the right cabin heat valve overboard dump blocked off, all of the cabin heat flow would be diverted to the left (pilot's) cabin heat valve where it can still dump overboard to maintain airflow through the system. With all of the cabin heat air being forced to go overboard at one of the two dumps, then I am guessing that the pressure at the pilot's cabin heat vent would be doubled and when that valve is opened the pilot would get a bonus share of heat if the copilot's cabin heat valve remains closed.

This may be only part of Vans' reason for the blocking plate on the right valve. We will have to wait on a explanation from Scott for the rest of the story and if this modification is in any way critical.

AFTER POSTING - I SEE SCOTT'S REPLY.

I do have the system installed like the Van's system with both exhaust muffs flowing into a single branch which supplies both heat valves. Scott - your reply mentions that the system will not work properly if the mod isn't done - unless each heat valve is supplied separately. That suggests that I do need to do the mod. Tell me why the system won't work as originally designed, without making the mod.
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Simpsonville, SC (SC47 - 10nm NW Triple Tree, SC00)
1946 Bellanca Cruisair 14-13-2 (72 YRS OLD 8/15/18)
RV14A (N14ZT), Ser#140195
Start 10/11/14
Dues paid 12/2/18 (USArmy 2/67-2/70)
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!! I SURVIVED RIPON ARRIVAL - KOSH 7/21/2018 !!

Last edited by jeffw@sc47 : 12-27-2017 at 06:43 PM.
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  #5  
Old 12-28-2017, 11:46 AM
rvbuilder2002 rvbuilder2002 is offline
 
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Quote:
Originally Posted by jeffw@sc47 View Post
I do have the system installed like the Van's system with both exhaust muffs flowing into a single branch which supplies both heat valves. Scott - your reply mentions that the system will not work properly if the mod isn't done - unless each heat valve is supplied separately. That suggests that I do need to do the mod. Tell me why the system won't work as originally designed, without making the mod.
Parts will never be included in the kit unless they are considered necessary, but I should correct my original statement to say" without it it wont work nearly as well".

The physics of air pressure is such that just like water, it will flow primarily to the path of least resistance.
Pressure Delta (difference) is what makes air flow from one point to another.
If there is no Delta, there is no movement.
If the RV-14 heat system has both heat valves unblocked there is one pressure source (the heat muff circuit) feeding four paths for the air flow (two waste/spill-off paths and two into the cockpit paths).
Regardless of where you want the heated air to go (how you set the heat control valves), it will flow to the path of least resistance. I.E., if the pilot is trying to get heat on only their side and there is no block-off installed on the co-pilot side valve, the flow can choose to go that way and out through the waste flow path instead.
As designed, there is still a small amount of interaction between the left and right heater controls, but it is not a problem..... as long as they are only sharing one waste flow path.

This is just one of many little design details that RV-14 builders are benefiting from with the advanced level of the kit.... and not having to experiment with and resolve on their own once flying.

You're welcome
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  #6  
Old 12-28-2017, 12:24 PM
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bkervaski bkervaski is offline
 
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Quote:
You're welcome
Thanks! It's very much appreciated.
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  #7  
Old 12-28-2017, 01:06 PM
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jeffw@sc47 jeffw@sc47 is offline
 
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Default follow-up question

Scott,

Since I have a lot of stuff installed that makes it hard to get to the co-pilot valve for the mod, would the fix be just as good to install the blocking plate to the pilot's cabin heat valve?
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Jeff Warren
Simpsonville, SC (SC47 - 10nm NW Triple Tree, SC00)
1946 Bellanca Cruisair 14-13-2 (72 YRS OLD 8/15/18)
RV14A (N14ZT), Ser#140195
Start 10/11/14
Dues paid 12/2/18 (USArmy 2/67-2/70)
www.mykitlog.com/jeffw@sc47

!! I SURVIVED RIPON ARRIVAL - KOSH 7/21/2018 !!
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  #8  
Old 12-28-2017, 01:29 PM
rvbuilder2002 rvbuilder2002 is offline
 
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Quote:
Originally Posted by jeffw@sc47 View Post
Scott,

Since I have a lot of stuff installed that makes it hard to get to the co-pilot valve for the mod, would the fix be just as good to install the blocking plate to the pilot's cabin heat valve?
I don't think so but it was never tried there. There is a much longer hose routing to the pilots side which has a higher amount of flow resistance than the short path to the co-pilots side. This would make the block off installed on the pilots side a poorer choice.

I realize that the 14A oil cooler installation limits access to the right side valve but the prototype was upgraded to this configuration later in its life so it is totally doable.

An angle drill with a stubby bit should remove the rivets easily.
Re-riveting will probably be the more difficult part but still doable.
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  #9  
Old 12-28-2017, 02:29 PM
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bkervaski bkervaski is offline
 
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We did it in about 20 minutes, we did have to remove the oil cooler to get an angle for the puller on the inboard rivet.

The very next step is the duct work and having the oil cooler out of the way is helpful (silver lining).
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  #10  
Old 12-28-2017, 03:16 PM
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So for me who is still at chapter 38, I guess it would be a great idea to do this before attaching the engine mount or anything else on the firewall?
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