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I now own a -4!

00Dan

Well Known Member
I went through with it yesterday - I am now the proud owner of a 1988 -4. Short legs, original wheel pants, and a Great American prop. A real blast from the past compared to the newer kits.

As always I have tons of new owner questions. I had started another thread regarding landing light installs and got some great answers.

I believe the prop is a Great American 70 x 74”. On a 150 hp -320 it’s making 2050 static, 2200 on takeoff/climb, and spins up to just over 2700 at 8000’ FT. It seems pretty cruise biased. Anyone have experience with this prop? I haven’t done full cruise performance testing yet (the previous owner usually flew with it pulled back so he didn’t have good numbers on upper end performance).

Is a modern prop worth the squeeze? I know pressure recovery wheel pants are good value and those are on the list.

Is the swivel tailwheel from Van’s any good, or should I consider one of the aftermarket forks? Pushing the non-castering wheel into my hangar is always fun.

I have to weigh it for myself but the W&B I have shows 943# empty at 60.64”. I ran some sample calculations and I’m definitely at the rear CG limit with a couple of my buddies and no bags. What would be the best way to put some weight on the nose?

I’ll post more questions as I think of them.
 
Congratulations on the RV-4!

I'll defer to more knowledgeable folks for your answers. Just wanted to welcome you.

Dave
 
You need a 10lbs landoll weight ring on the flywheel or a 19lbs sabre crush plate. You can also use a 9lb dive weight clamped to the alternator bracket if your cowling will clear it.
 
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Good choice you made!

Dan,
Welcome to the wonderful world of the RV-4. I wont elaborate on how its the best RV.., but I am biased. I built mine, and work on alot of others.This website will fill you with more intel than you can digest, so sit back and read,read,read. I am not familiar with your particular prop, but I do believe most everyone will own more than one prop during their ownership. Yours sounds to be in pretty good RPM range to be honest. A new higher end prop will likely do better, but I advise spending some time flying it, meet others and compare notes before pulling the trigger. As far as the AFT CG concern, it is the nature of a light fronted, wood prop basic -4. My situation is the same, but I learn to manage a few things. Big PAX, carry max fuel and stay above half tanks, loading the baggage with 2 up needs to be light cargo. Learn to fly with a back seater in steps..lighter at first, then move up. Be prepared for extremely light pitch control that can bite you on the landing flare or abrupt pull-ups.Moving the battery to the firewall will help slightly, but not much. I have the OEM tailwheel you do, and refuse to replace it because it works so good. 11 years of pulling in my hangar, picking the tail up by the spring and walking it around..not for everyone! I am the only one who moves mine, and I know not to push it backwards. There a zillion other good options out their for full swivel. Feel free to contact me via PM for specific stuff or learn what I have learned about the -4 over the last 25 years..there is plenty of experience on this site. Have fun!
 
Good comments so far. I’ll look into the weighted crush plate and flywheel. My first several hours in type were actually dual instruction with a big guy in the back - I didn’t solo until yesterday, so I have an idea of what the stick forces are with aft CG.

I plan to fly the plane for while before spending money on big ticket items.

Here’s another question. I could conceivably be in position to use this plane for travel (just me) in a year or so. What would be the most cost effective way to get an IFR panel?
 
Congratulations Daniel! They say RV4 is the best in the Vans family enjoy and stay VFR :)
 
Welcome to the fleet Dan! You did pick the best RV, but I'm also biased, but I'm also right...

How old is the W&B? 60" sounds like the old W&B form. Personally, I would do things to lighten the tail before adding weight to the nose. Does it have a big beacon on it's back? A heavy Whelen power supply in the fuse? Flyboy Accessories sells a light weight tailwheel and you could even upgrade to full castoring while you're at it if you'd like. Moving the battery to in front of the firewall is a good idea too. Mine is up on the right side, mounted to the engine mount inside the right cheek. If you already have an airplane that light, and unless you really intend to carry pax a lot, I would try not to add any weight like a landol ring or dive weights unless you have to.

The prop sound very much like a cruise prop. My Warnke is 68x74 and has similar climb and cruise numbers with 160hp. Personally, unless you plan on flying through a bunch of rain, I wouldn't change the prop until you need to (more horsepower if you choose).

As far as the AFT CG... Run the numbers, you might find you're still within limits with more than you think in the backseat. THAT BEING SAID, Bill is 100% right when he talks about stepping it up. 3.5 years and 500+ hours in my -4 now, my opinion is that it's a different animal with a heavy tail. Still extremely flyable, but different. For example, I'd guess that flying solo, it takes maybe 20lbs of pull on the stick to get to 3.5-4 G's. With a 180lb'er in the back seat? Maybe 5-10 lbs of pull. I've never put a strain gauge or scale on the stick and tried, I'm just guessing. Just something to be aware of before you fly with 2up.

Welcome to the club Dan. PM sent too.
 
Good comments so far. I’ll look into the weighted crush plate and flywheel. My first several hours in type were actually dual instruction with a big guy in the back - I didn’t solo until yesterday, so I have an idea of what the stick forces are with aft CG.

I plan to fly the plane for while before spending money on big ticket items.

Here’s another question. I could conceivably be in position to use this plane for travel (just me) in a year or so. What would be the most cost effective way to get an IFR panel?

My 1990 RV4 was a 160hp O320 with a Prince CF prop and SkyTech LW starter. 940lb MT. With full fuel I could have 185lb for 3hrs or 200lb for 1hr behind me, before the CG went out the back of the envelop.

I modified my TW to full swivel. Vans supplied a dwg showing how to modify the bent TW spring. Used a Vans swivel TW bracket someone on the field had. Worked great and was an easy change since my spring came out easily. I added footwells for the back, an extra heat muff for our cold winters, extra vents for our warm summers, canopy partial open catch for taxi air and a few other little things.

Had a great 4yrs and 450hrs in the 4 and still miss the centreline seating and wonderful characteristics. Working on another one now.:)

Enjoy!
 
Daniel,
Congrats on owning the best flying RV ever built! Your airplane is light, but as another poster has said, check when it was initially weighed. Mine was weighed early and the empty weight didn’t include engine oil at that time (around 7 lbs/gal, or about 14 lbs if you fill the crankcase of your Lycoming). You should probably re-weigh your airplane. Put in whatever amount of oil you would normally carry (6-7 QTS). I was concerned with CG on my RV4 when I replaced my metal Sensenich prop (42 lbs) with a carbon Sensenich prop (about 22 lbs installed). My empty weight didn’t change very much because the original W&B calculation didn’t include engine oil, and mine did. My CG did move aft .50”, however. It didn’t make much difference. Most RV4’s have an aft CG that needs to be monitored if you carry a passenger. If you have luggage with 2 up, you are likely near your aft CG limit, and maybe gross weight limit, and you should check where that CG will be at the end of the flight after burning off fuel, which moves the CG aft.

As far as your tailwheel is concerned, if pushing the airplane into the hangar with a non-swiveling tailwheel is your concern, as it was with me, consider this:

https://www.aircraftspruce.com/catalog/pspages/deluxe_towbars.php

This works right out of the box, and it collapses for travel if you want. I put a slightly shorter spring on mine from Menards (about $2) to give a little more squeeze, but it probably wasn’t necessary. I have gotten good at maneuvering the non-swiveling tailwheel while pushing it backwards while pushing on the HS when I don’t have the tow bar with me. It’s not hard to do. The non-swiveling tailwheel assembly is lighter. If you want to change it to full swivel, consider this:

https://www.skydesigns.aero/titanium-tailspring

It weighs 1 lb less than the standard Vans full swivel tail spring, and if you mount the lightweight tailwheel from JD Air (and others) you’ll save another pound. That’s big deal at a point 10+ feet aft of CG:

https://www.jdair.com/tailwheel-tire/

If you do this with your tail spring, send skydesigns your existing bent tail spring, and the new full swivel fork from wherever you get it, and have them precisely drill it for you. Then all you have to do is assemble it when you get it back.

This solution solves your full swivel condition you are concerned about, and helps to alleviate some of your tail heavy concerns.
 
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welcome to the frat. as others have said, the best thing is not to add weight. a light rv-4 is the best performance out there.

as others have said, work your way up to the aft CG. my 4 has a 360 and a C/S prop so it is very nose heavy, Im use to flying it that way, when I put a bubba in the back seat, the handling is way different, and can be a eye opener if your not ready for it. solo, i run neutral trim for takeoff, with a heavy backseater, it takes about half nose down trim for takeoff and gets really touchy.

as for the wheel pants, yes the monster pants are cleaner, but I think the old style look better.

as for landing lights, I have the FLYLEDS strobe/nav lights and love them, my airplane is on his web page as I was one of the first to put the 415 tip lights in. take a look at his page and check out his landing lights. great products, and great service.

bob burns
RV-4 N82RB
 
Regarding CG, I plan to weigh it soon (I have to pull my tanks to reseal the sending plates, so they’ll be empty anyway). My current W&B does not have a date but is the old form that places the datum 50” forward of the leading edge. Engine oil was not included in the empty weight and is accounted for separately.

Would the roll bar structurally support hanging some lighter bags on it? Say a backpack or soft side duffel, if needed to keep it out of the back.

On a semi related note, how much pro seal should I buy to do just the sending plates on both tanks?
 
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The roll bar can handle it, but why? It will be in the way of the canopy crossmember and rear stick, so you must not be planning a rear seater? If flying solo you can load it like a truck and not worry. Input a body bag duffel in back seat with harness on. As far as Proseal, get a couple tubes..PM me if you need help.
 
The roll bar can handle it, but why? It will be in the way of the canopy crossmember and rear stick, so you must not be planning a rear seater? If flying solo you can load it like a truck and not worry. Input a body bag duffel in back seat with harness on. As far as Proseal, get a couple tubes..PM me if you need help.

I was just thinking in terms of where to put bags with a passenger if the arm on the baggage compartment proves excessive.


Another question I’ve thought of and I couldn’t find in a search: does anyone here have measurements for making a fuel dipstick?
 
I conducted some flight tests today at gross weight and aft CG.

I determined Vx to be approximately 90 MPH indicated, and Vy to be approximately 102 MPH indicated. Vy resulted in not quite a 1200 ft/min climb.
At 8000' a three-way GPS run at 2700 RPM resulted in 158 knots TAS. At 2400 RPM I got 141 knots TAS.

Do these results sound about right for a wood cruise prop and the old wheel pants?

I also conducted stability testing and had one result that seemed odd. In a sideslip test (max rudder deflection and appropriate aileron to track straight) when I released the stick the wing rose quickly in a moderately damped mode. However, it coupled with a longitudinal response that approximated a short-period response. This perturbation resulted in a negative G (about 0.3 on my G meter, it didn't go fully negative) that momentarily interrupted fuel flow to the engine. Does this sound normal? (I don't have comparable experience to say if not even -1g is sufficient to interrupt fuel in a non-inverted flow installation).
 
Lunch

Dan, come to lunch with us from Falcon Field. Every Tuesday 11:30 at Mellow Mushroom in Peachtree City. Lots of RV discussion. We have about 60 RVs now at Falcon.
Mark
 
Dan,
I have fuel dipstick measurements that I’ve tweaked 3 times, and it is pretty accurate. Every tank might be a little different, but this would be a starting point. I used a 1/4” wide piece of hardwood trim from Home Depot with markings every gallon starting with 4 gallons. I also have one of those plastic fuel dipstick tubes from Sporty’s that I’ve remove all markings from and then made my own. I take the measurement at the back edge of the fuel cap opening, with the dipstick held straight up vertical. Doing it the same way every time is important because of the slope on the tank bottom skin. PM me with your email address and I’ll send you those measurements and a picture of my sticks.
 
Welcome to the -4

Welcome to the fleet Dan! You did pick the best RV, but I'm also biased, but I'm also right...

How old is the W&B? 60" sounds like the old W&B form. Personally, I would do things to lighten the tail before adding weight to the nose. Does it have a big beacon on it's back? A heavy Whelen power supply in the fuse? Flyboy Accessories sells a light weight tailwheel and you could even upgrade to full castoring while you're at it if you'd like. Moving the battery to in front of the firewall is a good idea too. Mine is up on the right side, mounted to the engine mount inside the right cheek. If you already have an airplane that light, and unless you really intend to carry pax a lot, I would try not to add any weight like a landol ring or dive weights unless you have to.

The prop sound very much like a cruise prop. My Warnke is 68x74 and has similar climb and cruise numbers with 160hp. Personally, unless you plan on flying through a bunch of rain, I wouldn't change the prop until you need to (more horsepower if you choose).

As far as the AFT CG... Run the numbers, you might find you're still within limits with more than you think in the backseat. THAT BEING SAID, Bill is 100% right when he talks about stepping it up. 3.5 years and 500+ hours in my -4 now, my opinion is that it's a different animal with a heavy tail. Still extremely flyable, but different. For example, I'd guess that flying solo, it takes maybe 20lbs of pull on the stick to get to 3.5-4 G's. With a 180lb'er in the back seat? Maybe 5-10 lbs of pull. I've never put a strain gauge or scale on the stick and tried, I'm just guessing. Just something to be aware of before you fly with 2up.

Welcome to the club Dan. PM sent too.

Welcome to a great machine.

I humbly agree. 943# is a good weight.
Not sure where your battery is located. If it is in the rear, the simplest fix is to switch to an EarthX battery and save tail weight.
If you have a standard Vans tailwheel (if there is such a thing-dual fork), another good improvement is the lightweight tailwheel.
Better to remove tail weight than add nose weight.

Daddyman
 
Tail heavy landings

Welcome to the fleet Dan! You did pick the best RV, but I'm also biased, but I'm also right...

How old is the W&B? 60" sounds like the old W&B form. Personally, I would do things to lighten the tail before adding weight to the nose. Does it have a big beacon on it's back? A heavy Whelen power supply in the fuse? Flyboy Accessories sells a light weight tailwheel and you could even upgrade to full castoring while you're at it if you'd like. Moving the battery to in front of the firewall is a good idea too. Mine is up on the right side, mounted to the engine mount inside the right cheek. If you already have an airplane that light, and unless you really intend to carry pax a lot, I would try not to add any weight like a landol ring or dive weights unless you have to.

The prop sound very much like a cruise prop. My Warnke is 68x74 and has similar climb and cruise numbers with 160hp. Personally, unless you plan on flying through a bunch of rain, I wouldn't change the prop until you need to (more horsepower if you choose).

As far as the AFT CG... Run the numbers, you might find you're still within limits with more than you think in the backseat. THAT BEING SAID, Bill is 100% right when he talks about stepping it up. 3.5 years and 500+ hours in my -4 now, my opinion is that it's a different animal with a heavy tail. Still extremely flyable, but different. For example, I'd guess that flying solo, it takes maybe 20lbs of pull on the stick to get to 3.5-4 G's. With a 180lb'er in the back seat? Maybe 5-10 lbs of pull. I've never put a strain gauge or scale on the stick and tried, I'm just guessing. Just something to be aware of before you fly with 2up.

Welcome to the club Dan. PM sent too.


With 600+ hrs in mine, I still find it hard to wheel land with an adult over 170# in the back. My brid just wants to squat and 3-point. Hard to stop it.
Daddyman
 
With 600+ hrs in mine, I still find it hard to wheel land with an adult over 170# in the back. My brid just wants to squat and 3-point. Hard to stop it.
Daddyman

I did both a three point and a wheel landing yesterday with 185# in the back. The wheel landing definitely required more positive forward stick, it wanted to sit down the whole way. The three point was a non issue; it may have even been slightly easier to get the nose at the correct attitude.
 
on the roll bar?

Regarding CG, I plan to weigh it soon (I have to pull my tanks to reseal the sending plates, so they’ll be empty anyway). My current W&B does not have a date but is the old form that places the datum 50” forward of the leading edge. Engine oil was not included in the empty weight and is accounted for separately.

Would the roll bar structurally support hanging some lighter bags on it? Say a backpack or soft side duffel, if needed to keep it out of the back.

On a semi related note, how much pro seal should I buy to do just the sending plates on both tanks?

Dan, If it swings at all, it could cause damage to your canopy or head. remember whatever is in it could "weigh" x4 under G-load.

Suggestion: if you want something handy, wear it in your flight suit or if you have a glove box stash it there.

Happy Landings,
Daddyman
 
dipstick

I was just thinking in terms of where to put bags with a passenger if the arm on the baggage compartment proves excessive.


Another question I’ve thought of and I couldn’t find in a search: does anyone here have measurements for making a fuel dipstick?

Dan,
I calibrated a dipstick from a spruce 3/4" square piece about 15" long.
I never use it.

I can take some pics, yet it is a crude device.
I have used similar sticks in Pipers & Cessnas, but you cannot easily visualize the fuel, whereas in the -4 it is pretty simple. Remember to calibrate your stick with the tail down.
Daddyman
 
Modern Prop advantages?

Well after flying more I discovered two things. The first is that I suspect my carburetor is running under-jetted and quite lean. I found some old threads here on how to approach that and will see how it helps temperatures and performance.

The second is that I am apparently under propped. At 8500’ the other day full throttle I was turning 2900 RPM. Obviously there is some performance headroom there, but how much? Anyone have some numbers to share for an old wood prop who went with a modern composite (my searches didn’t turn up much quantitative info)?
 
The second is that I am apparently under propped. At 8500’ the other day full throttle I was turning 2900 RPM. Obviously there is some performance headroom there, but how much? Anyone have some numbers to share for an old wood prop who went with a modern composite (my searches didn’t turn up much quantitative info)?

Sounds like you need to call Craig Catto. https://www.cattoprops.com/
 
Mike is right. Catto is worth the scratch, based on your numbers. Bit of a waiting list, so sign up early. 2-blade makes removing the cowl easier for maintenance when you work single-handed.

If your Vx/Vy tests were stop-watch climbs, run Nigel's level acceleration technique and see if you get similar numbers. IAS is what it is, you can use Kevin Horton's technique for computing static source pressure error and build yourself a good CAS curve. Excellent gouge on his website. Add a good AOA system :)

Interesting about the unload during your slip tests. My O-320-D2J with an MS carb and standard pick-ups runs smoothly to +.25G, but how well any engine does is dependent on fuel system and carb rigging. They all vary. With plans type fuel vents, I get venting during post-stall maneuvering. I included discussion in the training manual on venting and un-porting post stall in the training manual.

All of my performance charts are in the POH I have posted on the POH tab. Still have old-fashioned wheel pants and two-piece aluminum fairings on short gear. I run a 68" diameter Catto Gen 2, retrofitted with nickel leading edges. FWIW, as soon as we finish up flight test for the AOA project first phone call is to Craig for a prop update.

Drop me a PM or email and I'll share some analysis spreadsheets if you need 'em. Happy to help.

Welcome to the RV-4 frat!

Vac
FlyONSPEED.org

Your profile says you're an engineering student--we can use a good aero analyst that knows MatLab. There's a thesis in our project just waiting to be typed, case you need one ;) Add a Dynon pitot/AOA probe, and I'll send you hardware for that good AOA system.
 
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Dan,
I was also turning 2900+ with my original metal Sensenich, so I switched to the carbon fiber ground adjustable Sensenich. Their pitch pin system and Nord-lock washers make adjustment a quick, simple exercise. Once I got it dialed in, I’ve just left it there. It only weighs about 22 pounds (mine is 71” with long gear legs), but that is probably heavier than your current wood prop. You can buy that prop from the Vans Aircraft web store. I bought mine directly from Sensenich in Florida for the same price.
 
If it's a 3 blade Catto for a 160hp RV-4 you're after I have one for sale. I'll even fly it up to you in Georgia (on the front of my RV-4) and fly my Sensi GA back. It was a great prop, just had a really good deal on the Sensi that I couldn't say no to and the adjustable feature fit my mission (XC+airshow formation flying).

PM me for details.

Fitz
 
Engine mount cracks

Unfortunately I found some cracks while I had the cowl off to plan some fuel line routings. They appear to be horizontal hairline cracks on the crossmember beneath the two bottom attach points on the firewall. I sanded off the paint on one and confirmed it’s existence. My plan was to see if I could find someone to weld them in place, which my searches here indicate others have successfully done.

From my searches most people encountered issues with cracks either at the gussets on the opposite side of the attach points or at the gear leg attachments, not at the horizontal lower crossmember. Any other considerations I should have in approaching this repair?
 

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Dan,
Looks like a crack(or two) right at the weld. I’m no expert, but it seems like you could hook up an engine hoist to take the load stress off those joints, grind out the crack, clean it up and re-weld it in place, like you said, provided you have access to that area. Good catch!
 
Watch the back side of the cage...

If you can confirm that the cracks don’t go through to the back side, I like the plan of welding in place. When I found cracks there, we used UV penetrant dye and found the cracks were bigger and extended to the back side of the cage and was forced to pull everything and send it away to be repaired/welded/powder coated again. Good catch and good luck!
 
New 4 Owner

Dan,

Congrats on your purchase. A lot of good advice I see from others.
Highly Recommend W&B and take the time to know your unique aircraft - getting through a full condition inspection besides pre-buy may continue to be enlightening.

I worked together with an A&P on quite a few mods for mine - some needed and others just a wish.

Best Regards and good luck on repairs.
 
The old style mount is 4130 steel, correct? I have someone coming to look at it tomorrow and he wanted to verify the material.
 
Yes it’s 4130, make shure he uses aircraft grade welding rod. There is a difference, between aircraft grade and anything else. Aircraft grade has a copper outer coating, outhers I have seen look like nickel but arnt aircraft grade.
 
I completely concur! Great work from Russ and peace of mind that it was fixed right.


It’s an option I’m considering if I can confirm it’s a crack. The welder I had look at it thought it may just be undercut and wanted to do a dye penetrant test first before we pull anything.
 
Fuel tank removal

I disconnected my tanks to pull them for a sending plate reseal yesterday (and for wing wiring access). After getting all the screws out and disconnecting the front attach bolt, I could not get them to come free. I got a plastic putty spreader and ran it under the screw dimples to no avail.

Am I missing something on pulling these? Either I’m being too gentle or I missed a fastener.
 
...Am I missing something on pulling these? Either I’m being too gentle or I missed a fastener.
There are tank attach brackets bolted to the spar - that might have been overlooked.

Correction: It seems that the Z brackets are not standard on older models like the -4 and the -6.
 
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There are tank attach brackets bolted to the spar - that might have been overlooked.


I think that may be it. I pulled one of the inspection panels behind the tank and saw the two nuts, but I wasn’t sure if they were for the tank. My builders manual only talks about the screws and forward attach.
 
originally no tank-spar attachment brackets... but who knows :confused:

Maybe you can try to have a look at the space between the spar and the rear tank baffle using a flashlight/mirror...
I remember that removal of one tank required a hefty pull to overcome the clamping action of the dimpled skins on the spar and wing LE...
 
Just pulled my -7 right fuel tank to fix a leak. The -7 has 7 ‘Z’ brackets that bolt to the spar. My buddy with a -4 had to pull his tanks and he didn’t have any ‘Z’ brackets. We did use aluminum shims under all of the dimples on the top. The tank came right off.
 
My plane’s vintage indicates it definitely wouldn’t have had Z brackets originally. The last time the tanks were out I suppose conceivably they could have been retrofitted but the logbook entries only mention resealing the sending plates, so I find that unlikely.

Guess I’ll find more shims for the dimples and give it a little more muscle.
 
No Z-brackets on standard build RV4’s. They weren’t on my 2001 RV6 either. I think they started on the RV7/8.
 
It's just #8 perimeter screws and the bolt thru the forward mount that hold the tanks on. I use plastic "for sale" signs (cut in half) from the aviation aisle at the local Ace hardware slipped under the dimples to free the tanks. The dimples do an amazing job of holding the tank in place, so you'll need to slip the plastic into most of them simultaneously to "pop" the tank off. It can be difficult to slip the plastic in place, especially under the rib dimples as you move forward to the leading edge. Give me a call at eight five zero nine seven four 4472 if you have any questions, happy to share the corporate knowledge.

Also, if you aren't aware, you can buy a set of plans from Van's on a thumb drive that are handy for maintenance. The plans include hardware callouts, which is also very helpful. Alternatively, you can buy a set of "preview" plans and builders instructions in a binder if you prefer a hard copy.

Cheers,

Vac

P.S. If the tank is off, perfect time to add an AOA line and pitot tube with an AOA sensor :) Offer to send you hardware for an AOA system stands if you are interested.
 
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Leak testing

Does anyone have a link on how to leak test the fuel tanks? I’m about ready to do so and I’m not entirely sure how. I’ve seen references to a balloon test on this site but they didn’t have any instructions. From what I can tell, apparently the newer RV manuals describe this method but of course, my ancient -4 manual does not.
 
Make sure the filler cap is well sealed.

Put a (toy or party) balloon on one of the tank fittings (for example the outlet). Blow (with your mouth) in the vent fitting (patience and good lungs required) and blow up the balloon that way. Cap up the vent fitting. Note that there is a delay for the air to reach the balloon. so using an air compressor (even at low settings) is not recommended. I guess you could use a manual air mattress pump or similar.

Balloon should stay inflated for a day or more. However, the size will vary with temperature.

Finn
 
Balloon? Testing my tanks beginning of the 90s, Vans recommend using an altimeter... you might check the period RVator...
 
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