Shawn's -4 re-build - Page 3

ShawnR · #21 11-09-2022, 08:01 PM

I made a bit more progress. Still just a matter of learning about what I need to do and ordering some parts for what I want and/or need.

I wanted lights and have now ordered all that I need from flyboyaccessories and ductworks to make that happen.

I have learned that I probably want a fully castering tail wheel and in my case, putting it into the hangar without one will be very difficult as it is now. I have also ordered those parts from flyboy.

I took some photos of a crack in the bubble. I was looking for a new one but a member here has steered me towards repair so I will be following up on that too.

I knew before I purchased the plane that the firewall was wrinkled. The seller pointed me to a thread on here to which I drew the conclusion that as much as it could be a large issue, it was most likely a small one. I was made aware of the heavier duty weldment plans made available by Van's. What I did find frustrating was that I could find no information or comments on Van's website about this newer version of weldment, only comments here. However an email to them yielded a quick reply explaining it. That reply is quoted below. There was a debate here as to whether the firewall was a structural part or not. I realize that some may agree or disagree with the information. For me, I just want to insure it is not an already weakened structure before I venture into less than awesome landings on a grass strip. I need to measure which version of weldment I have but I am suspecting the lighter version, ie earlier. I took some close up photos of the weldments, lower left and right. One thing I noted was that there appears to be a slight buckling in the lower left longeron (I think that is the angle piece in the photo. You can see the black oil spot whereas on the right, the skin is tight to the longeron. This may have been there since manufacture but I doubt it. So I could be in for a bigger repair than I had hoped. At this point, it is still research so that I have lots of reasons to lose sleep..... and order parts so that in the dead of winter, I have parts in stock.

The home renovation and getting an old hangar a little better prepared for winter is keeping me busy right now. I should be able to really get into the -4 in a few weeks. But, I am appreciating the input I am receiving this far, and learning a lot.

The other item I have been putting some time on is laying out the panel. Very preliminary ideas right now. I am using CAD to get a realistic idea of what fits and works where. As mentioned earlier, I have pretty much settled into 2 AV-30's, EDM 350, analog ASI and altimeter and gmeter. That should form most of the left half of the panel. On the right side, I am considering a dock station for an ipad mini for foreflight or a Garmin Aero660. I was hoping not to have a display mounted temporarily or strapped to my leg but the 4 is small. So now, considering planning on only one of them. Any thoughts on picking one of them or would most here find a way to get both in? Both will not go into the panel with the other instruments so it is kind of a one or the other for me right now. I have not used foreflight for flight yet, only in a Nav course I took. But it is talked about so much, it looks like a powerful tool to have. The AV30 uses an input from a GPS so that is why I am considering a 660. It may redundant with an ipad..?

I am thinking the Icom 210 and Sandia transponder may go into a tunnel mount. The intercom and ELT remote panel will fit in the panel. Probably a few things I have not thought of yet.

Any thoughts on those panel preliminary plans?

The response from Van's re firewall wrinkle in a -4 and the heavier weldments. With this email came the drawings for the newer weldments.

Shawn

I have never seen a published document regarding these weldments, maybe there was an article in the RV-Ator 40 years ago but this one never made it to service bulletin status.

The Key difference and easiest way to check is the thickness of the square plate that the bolt head rests on. Current production parts are .125 where earlier parts will be thinner. Simplest way to measure this would be with the depth gauge on a caliper as depicted below.

As for the firewall, all RV-4’s have wrinkles and most even have cracks at the lower corners. Key thing to remember is the thin stainless steel firewall is just that, a fire wall and is not a structural component.

ShawnR · #22 11-09-2022, 09:01 PM

The photos in my computer are right side up....not sure how to fix them.

MS1095 · #23 11-09-2022, 11:27 PM

Quote:

Originally Posted by ShawnR

I made a bit more progress. Still just a matter of learning about what I need to do and ordering some parts for what I want and/or need.

I wanted lights and have now ordered all that I need from flyboyaccessories and ductworks to make that happen.

I have learned that I probably want a fully castering tail wheel and in my case, putting it into the hangar without one will be very difficult as it is now. I have also ordered those parts from flyboy.

I took some photos of a crack in the bubble. I was looking for a new one but a member here has steered me towards repair so I will be following up on that too.

I knew before I purchased the plane that the firewall was wrinkled. The seller pointed me to a thread on here to which I drew the conclusion that as much as it could be a large issue, it was most likely a small one. I was made aware of the heavier duty weldment plans made available by Van's. What I did find frustrating was that I could find no information or comments on Van's website about this newer version of weldment, only comments here. However an email to them yielded a quick reply explaining it. That reply is quoted below. There was a debate here as to whether the firewall was a structural part or not. I realize that some may agree or disagree with the information. For me, I just want to insure it is not an already weakened structure before I venture into less than awesome landings on a grass strip. I need to measure which version of weldment I have but I am suspecting the lighter version, ie earlier. I took some close up photos of the weldments, lower left and right. One thing I noted was that there appears to be a slight buckling in the lower left longeron (I think that is the angle piece in the photo. You can see the black oil spot whereas on the right, the skin is tight to the longeron. This may have been there since manufacture but I doubt it. So I could be in for a bigger repair than I had hoped. At this point, it is still research so that I have lots of reasons to lose sleep..... and order parts so that in the dead of winter, I have parts in stock.

The home renovation and getting an old hangar a little better prepared for winter is keeping me busy right now. I should be able to really get into the -4 in a few weeks. But, I am appreciating the input I am receiving this far, and learning a lot.

The other item I have been putting some time on is laying out the panel. Very preliminary ideas right now. I am using CAD to get a realistic idea of what fits and works where. As mentioned earlier, I have pretty much settled into 2 AV-30's, EDM 350, analog ASI and altimeter and gmeter. That should form most of the left half of the panel. On the right side, I am considering a dock station for an ipad mini for foreflight or a Garmin Aero660. I was hoping not to have a display mounted temporarily or strapped to my leg but the 4 is small. So now, considering planning on only one of them. Any thoughts on picking one of them or would most here find a way to get both in? Both will not go into the panel with the other instruments so it is kind of a one or the other for me right now. I have not used foreflight for flight yet, only in a Nav course I took. But it is talked about so much, it looks like a powerful tool to have. The AV30 uses an input from a GPS so that is why I am considering a 660. It may redundant with an ipad..?

I am thinking the Icom 210 and Sandia transponder may go into a tunnel mount. The intercom and ELT remote panel will fit in the panel. Probably a few things I have not thought of yet.

Any thoughts on those panel preliminary plans?

The response from Van's re firewall wrinkle in a -4 and the heavier weldments. With this email came the drawings for the newer weldments.

Shawn

I have never seen a published document regarding these weldments, maybe there was an article in the RV-Ator 40 years ago but this one never made it to service bulletin status.

The Key difference and easiest way to check is the thickness of the square plate that the bolt head rests on. Current production parts are .125 where earlier parts will be thinner. Simplest way to measure this would be with the depth gauge on a caliper as depicted below.

As for the firewall, all RV-4’s have wrinkles and most even have cracks at the lower corners. Key thing to remember is the thin stainless steel firewall is just that, a fire wall and is not a structural component.

Those look the newer firewall weldments. they may be the the .090 and not the .125 versions but I don't see any cracks that would worry me.

fixnflyguy · #24 11-10-2022, 04:58 AM

Those are the more desirable "new style". Mine are the same, and you have dodged the bullet on needing to replace them. The old style weldments have separate vertical and horizontal legs that attach to the longeron, sort of fork like. The firewall wrinkles are in 75% of RV-4's if I were to guess. Lots of flexing down there. Not a significant structural issue. Some have installed a large triangular gusset between the longeron and the vertical angle of the firewall, but I cant find a picture of one, I am not sure if it was a VAN's recommendation or not. I have attached an old picture that shows my new style weldments. The uppers are similar.

ShawnR · #25 11-10-2022, 06:28 AM

Thanks guys. That is interesting. I just went through the log book again to see if the new style had been documented as installed and there is no documentation. Seeing as this is a 1985 model, I am surprised that these are the "newer" style which I thought were circa 1995 ish...

With the plane, I got a large binder of the old RVator newsletters so may try to find a reference to weldment changes that the builder may have incorporated into his build. There could not have been many flying at that time though since the kit had only been available for 7 years?

I did note two things. The paint on the bolt on the left one looks like it has been either removed and reinstalled or has shifted. Perhaps not torqued correctly? The right one shows no such paint break.

In the upper left, there is a very minor looking crack. It may be paint only and appears not severe, just something to investigate more when the fuselage is here in my shop.

fixnflyguy · #26 11-10-2022, 06:41 AM

The large bolt is as you probably know, the engine mount attach bolt. Most are done with a drilled bolt, castle nut and cotter pin, which may be was "turned back" to get the cotter pin in, thus slightly loose. I installed mine with 12 point tension lock nuts. You can simply re-torque yours most likely. I'd dye penetrant inspect that suspected crack. At least who ever built yours did a pretty nice job of spacing the fasteners in the weldments..some I've worked on are horrible swiss cheese looking disasters.

ShawnR · #27 11-10-2022, 09:09 AM

Quote:

Originally Posted by fixnflyguy

..... may be was "turned back" to get the cotter pin in, thus slightly loose. .....You can simply re-torque yours most likely....... I'd dye penetrant inspect that suspected crack. At least who ever built yours did a pretty nice job of spacing the fasteners in the weldments..some I've worked on are horrible swiss cheese looking disasters.

Thanks. You bring me positive hope....

Taltruda · #28 11-10-2022, 09:22 AM

Where are these “wrinkles” that you say most -4s have?

00Dan · #29 11-10-2022, 09:26 AM

If you have the opportunity to pull the engine mount off (which if you need to replace the weldments you will), firewall cracks can just be stop drilled and sealed with an appropriate firewall sealant. I used a tube of 3M fire barrier caulk from the aviation aisle at Home Depot. You can opt to replace the lower firewall but it will just end up cracking in the lower corners again; it’s a design flaw that everyone has just come to live with.

fixnflyguy · #30 11-10-2022, 10:51 AM

The wrinkle will appear in the lower half of the firewall/footwell usually just above the lower engine mount bolt and some "oil canning" can occur. There is a load of flexing going on with landings that can cause them in the soft stainless firewall. It has relatively zero structural purpose, and the load is carried through the engine/gear mount and the stiffeners behind the firewall. See attached picture..not mine, but they are abundant.