Shawn's -4 re-build

[ShawnR]

Thanks for the links to your firewall mod Jon. I noted in the photo of you draining the brake lines, the exact same dent in the shelf that I am referring to in mine. (attached)

That will need to be addressed but thinking more about the cut out,...my engine is essentially a zero time engine and has a solid crank. I won't be swapping it out for a constant speed prop. Since the mod will not solve my issue of the fuel pump conflict, probably not a worthwhile mod, for me. Any other reasons to do it?

Thank you

 

[YellerDaisy]

That will need to be addressed but thinking more about the cut out,...my engine is essentially a zero time engine and has a solid crank. I won't be swapping it out for a constant speed prop. Since the mod will not solve my issue of the fuel pump conflict, probably not a worthwhile mod, for me. Any other reasons to do it?

Given that info, probably no reason to do it. In spite of some people's opinion, there are valid and useful reasons and flight conditions where some additional power and/or a C/S prop are of value. It's often difficult for people to consider things from outside of their typical/familiar perspective but obviously one persons 'normal' may be very different than another's. Regardless of all that, if you ever decide to add a C/S prop, you will be pulling the engine (for a different engine/crank) so can make the firewall mod at that time. The mod does offer a little bit more space on the engine side of the firewall and a nice place for oil to collect when spilled (while changing the filter). Other than that, I cannot think of any tangible value to it.

 

[ShawnR]

Oil cooler

Another question that has come up as I work through renos....

When I picked up the engine, the rebuilder told me "You will need an oil cooler". My -4 has never had one. When I checked the application chart on Aircraft Spruce, it refers to aircraft models, ie, Piper PA18. How do I know what oil cooler to buy? I see they are rated by "rows".

I see in the builders manual that it states, essentially, any oil cooler will work. But with confined space, etc., I was hoping for some examples. I have the O-360 in a 1985 RV4 (not sure if cowlings changed since then). What else do I need to consider before choosing an oil cooler?

https://www.aircraftspruce.ca/categories/aircraft_parts/ap/menus/ep/oilcoolers.html

Thanks
Shawn

 

[YellerDaisy]

How do I know what oil cooler to buy? I see they are rated by "rows".

Generally, it comes down to what you can make fit in the available space. You will find wildly varying reports from -4 drivers about CHT and oil temps. My opinion is that this is due to so many variables with the cowling, inlets, baffling, engines, climate, and instrumentation (at least). With my old O-320 and 8 row oil cooler, my oil was always very hot. With my new O-360, 10-row oil cooler (AERO CLASSICS 8000081) and new cowl, baffles, etc... my oil temp rarely exceeds vernatherm temp. I would certainly NOT say that this is the only setup that will work - just the one working for me. I suspect mounting the oil cooler on the firewall would be ideal but I didn't have space for that. I would not recommend mounting it on the baffles behind #4. However; that does work for some folks.

Some photos here and more of the 3d printed oil cooler duct here.

 

[ShawnR]

panel and static port

First off, Merry Christmas everyone!

Happy to report I am back into the shop. My first project to tackle was the instrument conflict mentioned above. After replacing the bulkhead behind the panel (which had been severely modified in the past) with the original design, my carefully designed panel had an instrument conflict. Although not my favourite instrument layout now, the aluminum work turned out ok. And it was an interesting project. For anyone using an EDM350, the diameter of the case is actually around 3.000" so a regular instrument hole is sloppy. The mod allowed me to make the hole a better fit anyways.

The next little project was to be the static ports. As it is, the only static port is on the right side and the tube runs directly to the panel. Someone was over and suggested that the tube should rise in the area of the port for moisture concerns. I also figured I would install one in the left side. Today, I removed a label on the fuselage in that area that read "No static port this side". When I removed the label it appears that a static port is indeed installed there already, but not connected inside. Both ports are of the flush style, installed on the interior of the skin. From doing a bit of research on this forum, it appears to me that a preferred port style is that of a normal rivet head? A bit of a convex shape.... not a flush style. I see Vans and Steinair sells kits for this domed style. Will mess around with rivets or go with one of those.

Edit Post 112 shows a photo of the tunnel and static port plumbing. I rotated the image here. That white fitting is just a termination point, so no rise for moisture, nor connection to the left side. Mmmmmmmm???

 

[Dan 57]

Yep, for any kind of precise instrument readings, you'll need a static left and right, linked by a Tee, their location being given on the plans.

Forget about the moisture loop or trap, your -4 is a taildragger and this alone prevents moisture accumulation in the lines.

As to the ports themselves, their shape is pretty important. The original Van's solution is the cheapest, lightest, and works pretty well: a large domed pulled rivet is applied, its stem then being driven out.
I helped on a -8 on which we had >15 knots speed errors caused by the original builder installing wrong ports the wrong way... we installed Stein's offering and all is good now.

 

[ShawnR]

Static ports

Thanks Dan

The builder of my -4 put some static ports behind the skin, then made a small hole in the skin. So, about as flush as one can get. I made up a couple of ports yesterday, removed the old hardware and am ready to install them next time someone drops in and can hold the bucking bar. I would just use a washer but there are holes in the skin from the old ports so want to fill those in. The functionality must be something to do with airflow against the skin, hence the rivet being so effective with the small dimple it creates. Guessing......

Moving on.....getting ready to paint the interior. Today, I stripped all of the wiring and things (rudder cables, static line, trim cable, etc) that might be in the way of spraying.

 

[ShawnR]

Paint prep

from post #13

I own a 94 -4 that I completely refurbed and modernized. My interior was painted that same hideous blue, It kept me up at night…I was never so happy when I repainted it. Used a flat gray epoxy primer, turned out great and is very durable. My apologies in advance if you are partial to the blue.

Flyhud

How did you prepare the interior before repainting? I visited our local automotive paint store. They suggested a fine 3M pad to scuff the surface. It does seem to work well for the general areas in good shape. I have areas with scratches and the old paint peeling that I would like to smooth the edges of, but I don't want to use a "too" aggressive sandpaper for fear of scratching the aluminum. What grit sandpaper is good to use for this application? I don't want to use paint stripper for fear of getting it between pieces of aluminum. My other thought was wiping with a lacquer thinner. That might soften the edges of the chipped area.

At the end of the day, anything I do will be better than what it is. I don't want to cause other issues.

 

[ShawnR]

Interior primed

Got the interior primed yesterday. 2 coats of epoxy primer. I wanted the gray look. That certainly changes things. Now the fun part of putting things back together.

 

[ShawnR]

The fun continues. (Not sarcastically...it is way more fun putting things back together than taking them apart!) I assembled a small paint booth to try to control some of the overspray in the shop. It helps a lot.

While doing this, I am looking ahead to the panel and wiring. As much as I have skimmed through some of Robert Nuckoll's aero wiring book (It is loaded with info, but quite a read) I cannot find a guide for choosing the size of wire to feed the fuse panel/cct breakers. There is a lot of information of cross area of wires, etc. but for choosing this main wire, is it as simple as adding up all of the possible electric draws and choosing the wire accordingly? Each fuse is not the actual draw of the instrument/light/radio etc so it would lead to overkill. But short of finding a "rule of thumb", that would be a logical conclusion. Any suggestions/references on choosing this wire size? It will be relatively short (~ 2 feet) so not a lot of loss going on in my installation. I am guessing a 6 gauge would be more than enough, but hoping for some input.

 

[ShawnR]

I realized last night that I was looking at the fuse values and not actual instrument current values. So going through all of the electrical (spec sheets) needs in the aircraft, I came up with a worst case scenario of about 42 amps. 43.13 says a #8 wire would do that but I will probably go with a #6, as mentioned above. I just did it more systematically this time. . It seems #4 is common from what I could find on line.

 

[YellerDaisy]

Looking great!!

42 amps is a lot of juice for a modern, day VFR machine. I would expect that in an older IFR ship and/or fuel injected (redudant pumps and such). I may have your mission mixed up with someone else, apologies if so. These days, with LED lights and EFIS, our machines don't consume much electricity. I can't seem to put my fingers on my electrical spreadsheet at the moment but I have a 40 amp alternator that has a lot of overhead. My electrical bus feed wire is #8.

 

[ShawnR]

Thanks JD. I gave my self 5 amps each for the aux power outlet, dual USB, field circuit, and then radio. So, after that, it just added up. Pretty basic machine as you say. I am surprised too but I went to each spec sheet for each instrument, light, etc. , I found the actual draw or something I could average it out. I did not consider the alternator output. I will need to look to see what size mine is. I had planned on replacing it and have also been reading a bit on overvoltage protection, external regulators, etc. It seems the more I get done, the more I need to learn about!

 

[ShawnR]

To wrap up some of the previous posts....

Static ports are done
Rudder pedals are reinstalled (waiting on a few pieces of hardware )
Master brake cylinder is plumbed on inlet side. I replaced the plastic plumbing fittings with some hydraulic fittings. When the shop made my lines up, they put those fittings on so I had to change over. I like them much better though. You can see them in one of the photos. Local shop so nice.
I assembled the FlyLED's control module for the Strobe/Nav lights. I will give them a kudos. Nice PC board to work with. Well documented kit. Good support.
I decided to take the advice and sentiment expressed in previous posts and ditched the little rocker switches for more robust toggle switches. Thanks for the input there.

I am starting to work on the wiring. I will be putting a shelf behind the instrument panel to support the fuse blocks, grounding blocks, light control module, etc. I looked at options like on the floor for the control module, firewall for the fuse blocks, etc. but I like the shelf, and it be will be nice to install and for maintenance.

But, thinking about the wiring, how does one make the actual physical connections for the communications pins? I don't have much to connect, but the engine monitor can connect to the GPS RS232 lines to calculate fuel necessary, and the AV30's connect to the GPS for course information. The pins don't look large enough to put two wires into them. I think my system is too simple for the junction boxes I see in larger systems. So is it a matter of stripping the wire back from the pin and joining it there? I think Stein calls it "window stripping"? That is about the best video that I have found but hoping someone can confirm this is what I need to do for the communications lines. Or do I use a terminal block outside of any connector? I would be concerned about losing shielding but maybe those lines are not sensitive to interference? Any suggestions?

 

[sf3543]

To wrap up some of the previous posts....

Static ports are done
Rudder pedals are reinstalled (waiting on a few pieces of hardware )
Master brake cylinder is plumbed on inlet side. I replaced the plastic plumbing fittings with some hydraulic fittings. When the shop made my lines up, they put those fittings on so I had to change over. I like them much better though. You can see them in one of the photos. Local shop so nice.
I assembled the FlyLED's control module for the Strobe/Nav lights. I will give them a kudos. Nice PC board to work with. Well documented kit. Good support.
I decided to take the advice and sentiment expressed in previous posts and ditched the little rocker switches for more robust toggle switches. Thanks for the input there.

I am starting to work on the wiring. I will be putting a shelf behind the instrument panel to support the fuse blocks, grounding blocks, light control module, etc. I looked at options like on the floor for the control module, firewall for the fuse blocks, etc. but I like the shelf, and it be will be nice to install and for maintenance.

But, thinking about the wiring, how does one make the actual physical connections for the communications pins? I don't have much to connect, but the engine monitor can connect to the GPS RS232 lines to calculate fuel necessary, and the AV30's connect to the GPS for course information. The pins don't look large enough to put two wires into them. I think my system is too simple for the junction boxes I see in larger systems. So is it a matter of stripping the wire back from the pin and joining it there? I think Stein calls it "window stripping"? That is about the best video that I have found but hoping someone can confirm this is what I need to do for the communications lines. Or do I use a terminal block outside of any connector? I would be concerned about losing shielding but maybe those lines are not sensitive to interference? Any suggestions?

I would at least place the fuse blocks in a position where you can get at them to change a fuse Without removing the top skin. Maybe up side down on the bottom of the shelf so you can at least reach under the panel to get at them.

 

[ShawnR]

I have been toying with this, as well as putting the shelf on a hinge of some sort. But my reasoning for it being as shown is that, at 60 years of age, I would rather undo the screws and lift the cover off than contort myself under the panel and work upside down. Not sure if I will regret this or not. Depends on how many times I have to take the skin off or not.

 

[Roadjunkie1]

I have been toying with this, as well as putting the shelf on a hinge of some sort. But my reasoning for it being as shown is that, at 60 years of age, I would rather undo the screws and lift the cover off than contort myself under the panel and work upside down. Not sure if I will regret this or not. Depends on how many times I have to take the skin off or not.

Well, I, for one would not put it under the top forward skin. There are a TON of screws that would have to be removed every time you had a fuse issue. PITA. Looks like there is plenty of room under your starboard switch panel. That said, in all the flying I have done, I have never had to rest a breaker. I would still think about putting it in a more accessible place. If you do blow a fuse, you know it's going to be somewhere that isn't near your home base. There you are, out on the ramp in the rain......... Just a thought.

Your airplane is looking MUCH better than the pictures you posted after you acquired her.....Keep up the good work!

 

[sf3543]

Well, I, for one would not put it under the top forward skin. There are a TON of screws that would have to be removed every time you had a fuse issue. PITA. Looks like there is plenty of room under your starboard switch panel. That said, in all the flying I have done, I have never had to rest a breaker. I would still think about putting it in a more accessible place. If you do blow a fuse, you know it's going to be somewhere that isn't near your home base. There you are, out on the ramp in the rain......... Just a thought.

Your airplane is looking MUCH better than the pictures you posted after you acquired her.....Keep up the good work!

I have been toying with this, as well as putting the shelf on a hinge of some sort. But my reasoning for it being as shown is that, at 60 years of age, I would rather undo the screws and lift the cover off than contort myself under the panel and work upside down. Not sure if I will regret this or not. Depends on how many times I have to take the skin off or not.

Well, I, for one would not put it under the top forward skin. There are a TON of screws that would have to be removed every time you had a fuse issue. PITA. Looks like there is plenty of room under your starboard switch panel. That said, in all the flying I have done, I have never had to rest a breaker. I would still think about putting it in a more accessible place. If you do blow a fuse, you know it's going to be somewhere that isn't near your home base. There you are, out on the ramp in the rain......... Just a thought.

Your airplane is looking MUCH better than the pictures you posted after you acquired her.....Keep up the good work!

I placed mine on the front of the electronics tray angled down. It’s easy to reach under the panel and change them by feel. I keep a diagram of which fuse is in each slot so I can remember which is which.

 

[Flyhud]

Great progress! I would keep the eqipment shelf as small as possible, the larger it is the more you will inhibit access to the center tunnel and the rudder pedals, brake cylinders etc. I also placed a row of breakers (non essential equipment) on the shelf facing down so they can be accessed simply by reaching underneath the panel. I’ve attached a few photos of my installation that may help with ideas. To make wiring easier, I built a jig which replicated the position of the panel and the equipment shelf in the airplane so I could do a majority of the wiring on the workbench.

 

[ShawnR]

I decided to consolidate suggestions with my initial thoughts. I made the shelf that swings down with just 2 screws, should I need/want to get at the panel via the pilot seat. Or access it from the top which will make initial wiring much easier. Removing the hinge pin also allows me to slide it left or right for maintenance issues, but the pedals and brake components are pretty accessible without moving it anyways.

Thanks for the input!

 

[jull_under]

I decided to consolidate suggestions with my initial thoughts. I made the shelf that swings down with just 2 screws, should I need/want to get at the panel via the pilot seat. Or access it from the top which will make initial wiring much easier. Removing the hinge pin also allows me to slide it left or right for maintenance issues, but the pedals and brake components are pretty accessible without moving it anyways.

Thanks for the input!

Shawn-
This is a great idea.
Any concerns about vibration. I'm wondering if the additional vibration (if any) using a piano hinge will affect the any electronics where they require you to install on a "solid" structure.

 

[Dan 57]

concerns about vibration

Thought the same... 2 stiffening angles, or other idea, will help. Still, I like that hinge idea, wish my whole panel was hinged...

 

[ShawnR]

Thanks guys. Yes, there are 2 j-channel stiffeners underneath. And with the front edge being screwed to the bulkhead, I think it is rigid enough. Hoping so anyways...

 

[ShawnR]

I have been moving along with the wiring. Which prompts a question....

The wiring to the strobes in the wings is a shielded wire. To make the connections at the wing roots and maintain the shielding, what connectors are you all using? The DB series? I have some DB15's coming from Steinair that I ordered on speculation so that does work out well. Or does a slight break in the shielding for the purpose of a connection not cause an issue? It will be continued through the connector (Molex maybe?) to the wing wiring. Wings won't be going on for a while, so I have time, but I would rather have connectors in place before I head to the airport. Suggestions? FlyLED's lights.

Thanks

 

[PaulvS]

I have been moving along with the wiring. Which prompts a question....

The wiring to the strobes in the wings is a shielded wire. To make the connections at the wing roots and maintain the shielding, what connectors are you all using? The DB series? I have some DB15's coming from Steinair that I ordered on speculation so that does work out well. Or does a slight break in the shielding for the purpose of a connection not cause an issue? It will be continued through the connector (Molex maybe?) to the wing wiring. Wings won't be going on for a while, so I have time, but I would rather have connectors in place before I head to the airport. Suggestions? FlyLED's lights.

Thanks

I didn't use pluggable connectors in the wing roots for the flyleds and instead ran the wiring from the wings into the fuselage to be spliced under the seat floor. Once the wings are on there is no intention to ever remove them and if becomes necessary to do so then the lighting wires would just be cut.
I don't believe that a DB type connector is ideal for a reliable connection in the wing root, which is somewhat exposed to the environment. A sealed Deutsche type connector would be a better option, if you really want to have a connector there.

 

[ShawnR]

Thanks Paul. I would rather not be doing those connections to the controller board at the airport, but you make good points. I don't ever plan on pulling the wings again, and if I do, the wing lighting wires will be a small concern.

Panel wiring (or rather, general wiring) is moving along. But moving, so that is a good thing....

 

[steve murray]

Hey Shawn
I am in the process (long process) of building a 30+ year old RV4 kit. I am currently working on the fuselage structure.

Would you be willing to take a bunch of your fuselage structure from all different angles, inside and out?

There are very few RV4 build logs with pictures still available and I found these pictures are hugely helpful in understanding the "less than detailed" plans. I would like pictures of everything but definitely would especially like to see where panels have been added for storage, avionics shelves , pass throughs around or through spar (404) bulkhead, routing for fuel lines, etc... If you could temporarily upload a bunch of photos to a google album and I could download them I would appreciate it immensely.

Thanks for your consideration.

 

[Roadjunkie1]

Thanks Paul. I would rather not be doing those connections to the controller board at the airport, but you make good points. I don't ever plan on pulling the wings again, and if I do, the wing lighting wires will be a small concern.

Panel wiring (or rather, general wiring) is moving along. But moving, so that is a good thing....

If it hasn't been said already, label ALL your wires, both at the beginning and the end. It will make things MUCH easier when trying to chase down an electrical problem!

 

[PaulvS]

Thanks Paul. I would rather not be doing those connections to the controller board at the airport, but you make good points. I don't ever plan on pulling the wings again, and if I do, the wing lighting wires will be a small concern.

Panel wiring (or rather, general wiring) is moving along. But moving, so that is a good thing....

Hi Shawn
The location of your flyleds controller presents another option, which is to use a crimp Dsub connector at the controller instead of the solder connector that comes in the kit. The wires in the wings would be made long enough and with a service loop so as to reach the controller. The wires can be terminated with the crimped-on pins before going to the airport. At the airport the remaining step would be to push the pins into the Dsub connector.

 

[ShawnR]

If it hasn't been said already, label ALL your wires, both at the beginning and the end

Thanks Mike. Yes, I have been trying to label them all. I had a label maker so I am using it and putting clear heat shrink over it. It does not do the heat shrink labels. If I had a lot more to do, I think I would go with the Rhino series of printers and heat shrink tubing. That makes labeling look pretty easy!

 

[ShawnR]

Hi Shawn
The location of your flyleds controller presents another option, which is to use a crimp Dsub connector at the controller instead of the solder connector that comes in the kit. The wires in the wings would be made long enough and with a service loop so as to reach the controller. The wires can be terminated with the crimped-on pins before going to the airport. At the airport the remaining step would be to push the pins into the Dsub connector.

I think that is the answer! Thanks for pointing that option out. I had not considered that one but will make the task at the airport much better than soldering.

 

[ShawnR]

I have been working away on the wiring. As suggested earlier, I built a fixture to hold the panel on the workbench, and did most of the instrument wiring on that. This worked out well. But then the panel went into the plane for the next phase. The swing down panel did complicate things a bit, but I think it will be worth it long term. I will probably switch the screws holding it up for some quarter turn fasteners of some sort. Almost done though. Next will be putting the engine mount back on and getting it back on its gear. I had to change the battery mounting. The battery that came with the plane (Odyssey 925) did not fit the original brackets. I was convinced to change batteries to save more than 10 lbs and now have an Odyssey 680, much more reasonable. It is the same as the one in the 9A too so I have consistency. This meant changing the hold down method and my buddy came up with a nice bracket for that. Will post a photo of that later. Another feat this past month was the updating of the AV30's firmware. In doing that, I found one internal battery showed as a "Failure", from being discharged while waiting for installation for the last year. But after cycling a few times (connecting and removing power), the battery started taking a charge and passed the subsequent endurance tests. uAvionics support was good through this process.

I should be able to remove the panel from the plane by disconnecting just connectors when I am done...should I want to make changes in the future......if I did things right.....

 

[ShawnR]

I arrived at the point where I started applying power to circuits. Woo Woo! I also did some configurations on the AV30's but have a lot to do. Being very customizable leads to time spent with the manual and after flying to set up all the fields and where you want them. The biggest things were getting the lower one to power up as a heading indicator and talking to the GPS. Relatively easy to do with the manual in hand. Kind of cool to punch a new waypoint into the little portable Garmin, and have the HI spin around to the new heading with course indicator. (Little things in life make me happy... )

Moving on. We had a very mild winter, as most did, but after 3 days of snow, we are back into serious shop time! Just when one thought we might be flying early this year, Mrs Nature said don't think so!

 

[Dan 57]

Shawn
and now you have enough space left for that glove box

 

[ShawnR]

Not really....with the brace for the radio there, and where I located the master fuse block, I kinda messed that up. No wonder some guys build more than one. The second one would be better, I am sure. At least, in my case.

 

[ShawnR]

I noticed today that the rod bearings that form the hinge for the rudder do not appear to go as far into the nutplate as I would like. Does anyone know the thread length on this part?

Bearing, Rod End, 3/16" x 3/8"

store.vansaircraft.com

The specs give the diameter but not the thread length. The drawing (30-4) shows several threads showing past the nut plate, as would be expected. Perhaps if the rod end gets bottomed out, I might have enough threads. As I type, maybe that will be the resolve. I see on a thread regarding a 14? I think ...that someone mentions a longer version of that rod end. My plans do not comment on this. Anyone recall issues in this area?

 

[fixnflyguy]

I noticed today that the rod bearings that form the hinge for the rudder do not appear to go as far into the nutplate as I would like. Does anyone know the thread length on this part?

Bearing, Rod End, 3/16" x 3/8"

store.vansaircraft.com

The specs give the diameter but not the thread length. The drawing (30-4) shows several threads showing past the nut plate, as would be expected. Perhaps if the rod end gets bottomed out, I might have enough threads. As I type, maybe that will be the resolve. I see on a thread regarding a 14? I think ...that someone mentions a longer version of that rod end. My plans do not comment on this. Anyone recall issues in this area?

Any amount of threads beyond the nutplate are just along for the ride. 1 thread past gives you assurance of 100% engagement. Is your hinge line correct, or is the rudder/ vertical fin too far apart? I'd take a look at it all. As long as it's able to have a functional jam nut and 1 thread you should be fine.

 

[ShawnR]

Thanks Bill. From the pic and the specs on vans site, it looks like that thread is only about 7/8" long so it probably just needs to be seated a little further moving the rudder in. Interestingly, I looked in the manual about installing the rudder, and I could not find much. A very short paragraph to attach it but no mention of distance to Vertical Stabilizer. As I have read, this era of the plans left a lot up to the builder. I have threads showing behind the jam nut. Not sure how that will affect anything else though, ie, clearances/interference. Will see. I noted it as I was trying to fish the tail light wire through to the tail cone. I guess the rudder will need to come off anyways to do that and to fit the new bottom for the light. That might become next winters project now. If I can get this plane in the air this year, I certainly will have no need for lighting.

 

[ShawnR]

I don't have any decent photos in my phone but we are still making progress on this project. Fuselage wiring is done, engine mount is on, landing gear back on, brakes relined and reinstalled, new brake lines installed. The rudder will need to come off to address the fasteners discussed above. Deferred for now. Engine should be going on this week. Then all of the engine wiring, baffles, new oil cooler install (never had one so finding a place for it, etc)........the more I get done and closer I get, the farther completion seems to be....

 

[ShawnR]

Plane is back on its own legs. Engine is on. Even after installing the Vans fitting into the fuel pump, I had a conflict directly with the firewall. So had to modify it. But I am happy with the result.

 

[ShawnR]

With winter brings me back to working on the -4. Today's project is the carb heat muff. I have found a few threads with images o the topic, but not a lot of images.. A friend saw mine and felt it was way too big. I was wondering what most have in their 4? I could not find a lot of direction in the plans so it sounds like each to his own devices on this aspect. Attached is what I have. There are 3 aluminum channels inside that hold the shell off of the pipe. They are worn and the whole assembly rattles around so I was going to address that when the question of whether it is appropriate came up. I see that Van's sells a small cross tube but it does not look like it would be overly effective. However, I do not know. Any input for me?
Thanks

 

[PaulvS]

With winter brings me back to working on the -4. Today's project is the carb heat muff. I have found a few threads with images o the topic, but not a lot of images.. A friend saw mine and felt it was way too big. I was wondering what most have in their 4? I could not find a lot of direction in the plans so it sounds like each to his own devices on this aspect. Attached is what I have. There are 3 aluminum channels inside that hold the shell off of the pipe. They are worn and the whole assembly rattles around so I was going to address that when the question of whether it is appropriate came up. I see that Van's sells a small cross tube but it does not look like it would be overly effective. However, I do not know. Any input for me?
Thanks

Some people believe in the short stove pipe heat muff but I honestly don't understand how it can have much effect because only a small half round section of exhaust pipe makes contact with the air to heat and there is also a slot cut in the pipe, which lets in colder air. I purchased this stove pipe kit and did not use it because of these concerns. Instead, I fabricated a longer heat muff similar size to your pic.
The heat muff that Van's supply in the current finishing kits for O-320 is MUCH bigger than the stove pipe, so there must be a reason for that.

 

[Dan 57]

Nice to see you're back on it Shawn
My aircraft, different bird, different engine (O-360), standard FAB, stove type muff. Experience, flown now close to 2K hours, in conditions you guys will probably never fly in with moderate airframe icing etc. several times, but yet to have any symptoms of carb icing. Yes, this is MY experience on MY aircraft only.
RPM drop during run-up at 2K RPM gives only 10-20, so I think of it more as an alternate air than carb heat feature. On the definitive pros, light, cheap, easy to install

 

[ShawnR]

Hey Dan
Thanks. I was looking at those, but I read previous comments about the little affect they have. Today, I decided it would just be easier to repair the old one and throw it back on. Over effective is better than not as effective I suppose. And the muff was already built. I just had to replace one standoff.

Not that I plan on flying in conditions that warrant it, but none (most) of us do not plan on it.

It is reinstalled and, now, on to the next task...

 

[fixnflyguy]

I made my own with similar theory. It wraps around the pipe with openings along the outer side, has a flange on the FWD end that goes to carb FAB via SCAT. The RV tight cowls make pretty warm air on their own, and even with the muffs, there is little RPM drop noticeable when CH is pulled. Many will agree it's not even necessary.

 

[ShawnR]

Thanks Bill. That is way neater than what I had. I will still use my heat muff, but need to rework the adapter that goes to the intake.

 

[Snowflake]

Nice to see you're back on it Shawn
My aircraft, different bird, different engine (O-360), standard FAB, stove type muff. Experience, flown now close to 2K hours, in conditions you guys will probably never fly in with moderate airframe icing etc. several times, but yet to have any symptoms of carb icing. Yes, this is MY experience on MY aircraft only.
RPM drop during run-up at 2K RPM gives only 10-20, so I think of it more as an alternate air than carb heat feature. On the definitive pros, light, cheap, easy to install

View attachment 75760

My -6 came to me with this toy attached too. 10rpm drop during a runup was generous. I replaced it with a Robbinswings muff instead, which wraps around about 8" of the crossover tube and draws air in from the gap between the two crossover tubes. RPM drop is now 50rpm *minimum* on a run-up. Have cleared carb ice multiple times with it. Would not recommend the little stovepipe to anyone, to be honest. Oh, and i'm running an O-320 E2D.

 

[Flyhud]

I wouldn’t worry about the heat muff being “way too big” the more heat the better, I would however consider replacing your old style unfiltered intake setup with a current version of the filtered air box (FAB). It’s a worthwhile upgrade.

 

[ShawnR]

Thanks @Flyhud. Yes, that looks like the way to go. My air intake is in rough shape, ugly and worn. When on the Vans site to see about a replacement, and going through the plans looking for information on this piece, I can find nothing, but I did see the new FAB though. I will probably tackle that mod next winter, or and if I get this plane out of my shop and back to the hangar. But for now, going to try to make a new one or at least fix this one up.

Is my intake an old vans part or is it one that a builder makes up? This one looks homemade, and repaired more than once or just modified, but I seem to recall very similar ones on other planes so wondering about the source.

 

[ShawnR]

I took a closer look at my intake fixture. It is too rough to save so perhaps now is the time to jump into the FAB. Any input from anyone that has installed this kit onto an old RV4?