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RV-4 #4175 Fastback Conversion

Jjackh10 said:
This is good to know, my canopy should be here in the next few weeks (I ended up going to airplane plastics). I'm actually in Dumas, Tx for work (due South lol) and it turned off cold here too. Amazon diesel heaters are great, but 2 of them can't warm the drafty T-hanger I rented haha.

If I make a trip back home in the near future I'd love to stop by. Your other projects are just as interesting to me.
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I'd be really interested to see if there's much difference between the profiles of the Airplane Plastics and AeroCanopy. Mine was remade after the first try because the profile came out kinda weird. I like it now, but I will say it is quite steep up front and very little clearance to the rollbar, Maybe 3/8 of an inch. That easily could have been my fault though when I got excited early on and started trimming a bit way before I was ready. Definitely use a spacer like AX-O did and don't start cutting anything until you're ready to do the canopy. Luckily, I'm not tall and have no issue with head clearance. Oh and make sure you get a good cut off wheel designed for plastics. I just got one off amazon and it worked really well for the main cuts. Then a handheld belt sander for the fine trimming and an oscillating tool with 220 grit sanding pad for the final smoothing. A 440 grit would have been even better I think.
 
climbak said:
I'd be really interested to see if there's much difference between the profiles of the Airplane Plastics and AeroCanopy. Mine was remade after the first try because the profile came out kinda weird. I like it now, but I will say it is quite steep up front and very little clearance to the rollbar, Maybe 3/8 of an inch. That easily could have been my fault though when I got excited early on and started trimming a bit way before I was ready. Definitely use a spacer like AX-O did and don't start cutting anything until you're ready to do the canopy. Luckily, I'm not tall and have no issue with head clearance. Oh and make sure you get a good cut off wheel designed for plastics. I just got one off amazon and it worked really well for the main cuts. Then a handheld belt sander for the fine trimming and an oscillating tool with 220 grit sanding pad for the final smoothing. A 440 grit would have been even better I think.
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Thanks for the tips. I have a belt sander (well knife sharpener, but it will work) and an oscillating tool. I'll get on Amazon and find those wheels.

I will share plenty of photos and whatever measurements you'd like for comparison. I'm just going to make a new frame instead of trying to modify the old one. I'm not tall either but I intend to trim as little as possible from the sides and take the side line lower like AX-O did. Hopefully that and the added width and space forward will make the cockpit feel a little more roomy. Or it might end up looking like a jetsons car haha.
 
Jjackh10 said:
Thanks for the tips. I have a belt sander (well knife sharpener, but it will work) and an oscillating tool. I'll get on Amazon and find those wheels.

I will share plenty of photos and whatever measurements you'd like for comparison. I'm just going to make a new frame instead of trying to modify the old one. I'm not tall either but I intend to trim as little as possible from the sides and take the side line lower like AX-O did. Hopefully that and the added width and space forward will make the cockpit feel a little more roomy. Or it might end up looking like a jetsons car haha.
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Not a bad idea on the frame. I had originally wanted to just do a full integral frame from fiberglass, but was passing by Van's to pick up another project nearby so decided to get the frame. I'll say, that was a gigantic pain in the ***. A ton of bending, welding, more bending and more bending and it's still not perfect. The front square bar is the biggest problem. I should have just split it like Axo did. I'm also a really bad aluminum welder so that didn't help either. If you can get the front bar fitting well, I think the rest of the frame will be relatively easy. And certainly far cheaper than getting the one from Van's and chopping it up. Next time I'll just build from scratch. I'll stick to aluminum though. I'm just like it more than fiberglass. Though maybe I'll change my mind after making the few fairings I need.
 
climbak said:
Not a bad idea on the frame. I had originally wanted to just do a full integral frame from fiberglass, but was passing by Van's to pick up another project nearby so decided to get the frame. I'll say, that was a gigantic pain in the ***. A ton of bending, welding, more bending and more bending and it's still not perfect. The front square bar is the biggest problem. I should have just split it like Axo did. I'm also a really bad aluminum welder so that didn't help either. If you can get the front bar fitting well, I think the rest of the frame will be relatively easy. And certainly far cheaper than getting the one from Van's and chopping it up. Next time I'll just build from scratch. I'll stick to aluminum though. I'm just like it more than fiberglass. Though maybe I'll change my mind after making the few fairings I need.
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I've got guys that can weld anything from the crack of dawn to a broken heart haha. But aluminum is just a pain to work with in this instance. So I'm mimicking how Steen does the Skybolt. Some 1/2".o35 wall 4130 square for the 2 bases. and 1/2" .035 round tube for the frame. I did some gorilla math and I think it will be 3/4 of a pound heavier. But should save me hours of bending nonsense lol.

I even considered making it tilt up and back like the skybolt (or F-16). But I'm not sure I want to get that creative.
 
Jjackh10 said:
I've got guys that can weld anything from the crack of dawn to a broken heart haha. But aluminum is just a pain to work with in this instance. So I'm mimicking how Steen does the Skybolt. Some 1/2".o35 wall 4130 square for the 2 bases. and 1/2" .035 round tube for the frame. I did some gorilla math and I think it will be 3/4 of a pound heavier. But should save me hours of bending nonsense lol.
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And will weld nice all day long. Can't wait to see it. If you haven't already bought the steel, Wicks has a whole bunch of wildly cheap 4130 square and round tubing right now, though I don't know if they have the sizes you need.
 
AX-O said:
Great to see this progressing. Also, nice to see some of the things I would do different on Dilemma.
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I’m following those that have gone before. Making adjustments to suit my needs and skills (or lack there of). I sincerely appreciate your attention to detail, in the build, and in sharing it for others benefit.

Whenever I have something meaningful to contribute I will. So far this is what I have;

Match drilling in the tailcone requires elves.
Studying pics doesn’t mean you can shortcut.
The right tool for cutting a panel is CNC, oh well.

At the end of the day just do something on it every day and it will fly again.
 
Jjackh10 said:
I’m following those that have gone before. Making adjustments to suit my needs and skills (or lack there of). I sincerely appreciate your attention to detail, in the build, and in sharing it for others benefit.

Whenever I have something meaningful to contribute I will. So far this is what I have;

Match drilling in the tailcone requires elves.
Studying pics doesn’t mean you can shortcut.
The right tool for cutting a panel is CNC, oh well.

At the end of the day just do something on it every day and it will fly again.
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Thanks for the kind words. Also, those are good lessons learned.
 
Jjackh10 said:
I’m following those that have gone before. Making adjustments to suit my needs and skills (or lack there of). I sincerely appreciate your attention to detail, in the build, and in sharing it for others benefit.

Whenever I have something meaningful to contribute I will. So far this is what I have;

Match drilling in the tailcone requires elves.
Studying pics doesn’t mean you can shortcut.
The right tool for cutting a panel is CNC, oh well.

At the end of the day just do something on it every day and it will fly again.
Click to expand...
Just to add on to the point about cutting the panel CNC (though for round holes an instrument punch and a good ruler are definitely good enough), if you have the actual avionics, measure the size cutout you'll need directly. Do not trust the numbers given by them. I did and a couple of the square holes I blindly trusted, multiple measured and they were wrong. The radio was close enough that with very careful mounting I was able to hide the oversize, but for another, I had to make a new little cover plate to make it work without recutting the panel.
 
climbak said:
Just to add on to the point about cutting the panel CNC (though for round holes an instrument punch and a good ruler are definitely good enough), if you have the actual avionics, measure the size cutout you'll need directly. Do not trust the numbers given by them. I did and a couple of the square holes I blindly trusted, multiple measured and they were wrong. The radio was close enough that with very careful mounting I was able to hide the oversize, but for another, I had to make a new little cover plate to make it work without recutting the panel.
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Yes, I trashed my first panel blank not having the items in front of me to verify. A drill and a Jig-saw eventually got me by.32.jpg
 
Jjackh10 said:
Looking good! I'm a bit behind you but plugging away. I noticed you and Axo were able to have the canopy reach further forward over the boot cowl. I live a little ways due North of you and obviously want to fly more than a month or 2 a year lol. So I'm wondering about putting a few holes in the cowl there for a defrost of sorts? Do you think it would work/ be needed?

BTW I sincerely appreciate your posts and pics. Many times already I've left the hanger scratching my head. Then found the answer here.

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Whats the length around the front end of that fast back? Will a 4x8 sheet be enough to build it?
 
Also, are you guys using .025 for that skin or sizing up to .032"? I have a 4x12 sheet of .032 I bought to make some bigger fuel tanks but I'd rather use 8' of it for this purpose if that's appropriate.
 
t0rin0 said:
Also, are you guys using .025 for that skin or sizing up to .032"? I have a 4x12 sheet of .032 I bought to make some bigger fuel tanks but I'd rather use 8' of it for this purpose if that's appropriate.
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That would be about a 28% increase in weight. Unless you need the additional weight aft, I would stick with .025.
 
t0rin0 said:
Does he sell something that Spruce doesnt? I only see .025 and .032 available. The original skin that came with the -4 kit (not installed yet) is .025
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I'm not sure what his supplier is. I've only seen .028 a few times and it's pretty difficult to get I think. I pulled the Harmon plans out and it calls for .025 2024-T3 so I very well could have my measurement wrong or had a strange batch, can't remember if it was stamped. I remember thinking the .028 was odd. I believe .032 would be fine and the weight isn't enough to be real concerned about, but it would increase the stiffness a decent amount. It's likely worth at least thinking about if that would cause issues for being too strong or harmonic problems. My gut says no, but I'm not a mechanical engineer. I know of a couple replica warbirds being built based roughly on RV style construction that are larger and much beefier than the 4, and they're still using .025 skins in the rear cone. One of them is being built by a former Boeing engineer. I have a feeling you'll use up that .032 anyway. I've probably used a bit over half a 4x8 sheet just in random pieces I've made.

Here are the rough cut dimensions of the skin from the plans:
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climbak said:
I'm not sure what his supplier is. I've only seen .028 a few times and it's pretty difficult to get I think. I pulled the Harmon plans out and it calls for .025 2024-T3 so I very well could have my measurement wrong or had a strange batch, can't remember if it was stamped. I remember thinking the .028 was odd. I believe .032 would be fine and the weight isn't enough to be real concerned about, but it would increase the stiffness a decent amount. It's likely worth at least thinking about if that would cause issues for being too strong or harmonic problems. My gut says no, but I'm not a mechanical engineer. I know of a couple replica warbirds being built based roughly on RV style construction that are larger and much beefier than the 4, and they're still using .025 skins in the rear cone. One of them is being built by a former Boeing engineer. I have a feeling you'll use up that .032 anyway. I've probably used a bit over half a 4x8 sheet just in random pieces I've made.

Here are the rough cut dimensions of the skin from the plans:
View attachment 103857
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Awesome, thanks so much.
 
t0rin0 said:
Awesome, thanks so much.
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I ordered the "kit" from Harmon as well. Mine wasn't marked, I just assumed .025, I'll try to measure today. As climbak and Mel mentioned a thicker skin will be heavier and stiffer. The size is already adding weight vs original. And I personally wouldn't want any stiffer. It's already a pain in the a$$ to get it fitted, drilled, and installed.
 
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Jjackh10 said:
I ordered the "kit" from Harmon as well. Mine wasn't marked, I just assumed .025, I'll try to measure today. As climbak and Mel mentioned a thicker skin will be heavier and stiffer. The size is already adding weight vs original. And I personally wouldn't want any stiffer. It's already a pain in the a$$ to get it fitted, drilled, and installed.
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The drawing posted above says .025, so I'll just use that. I have a cracked skin on my c172 that I could use that big sheet of .032 on.
 
John's top aft skins were .025 2024 T-3. As far as upgrading to .032, it gets exponentially harder to "wrap" the skin around the bulkheads, especially the last one. Even with .025 it takes some "extra" strapping ideas to get a good fit with no "pucker" ...

Here's a couple of pics - note the date ~ 29 years ago ...

HFS
HR 2 - S/N 002
 

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I apologize if I'm hijacking your thread a bit. I'm pondering the rear seat fit issue and wondering about doing something like this. Is there a consideration I'm not seeing and maybe this is a bad idea?
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Jjackh10 said:
I apologize if I'm hijacking your thread a bit. I'm pondering the rear seat fit issue and wondering about doing something like this. Is there a consideration I'm not seeing and maybe this is a bad idea?
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All I did was to remove the upper fiberglass part, cut the seat back down by enough to make it clear and then riveted the upper back on. I can still sit back there comfortably but taller people and soft back cushions it might push into their backs.
 
climbak said:
My 4 is down for a bit for a several little projects, like elevator reskinning due to some cracking, adding a light to the tail, possibly electric trim, fiberglass repair due to some less than perfect fits over the years, etc. While it's down, I decided to make it way worse for time and money and do the fastback conversion plus a new paint job. It's not a full build, but it'll make it more my own until I can start building a new kit. I'll be using the Harmon Rocket bulkheads and top skin, and a Rocket canopy. I'll be using Axel's (user AX-O) really good writeup on his fastback build as a reference and stealing a lot of ideas from Dave Paule's RV-3 build log, especially his full fiberglass canopy frame since he lives a few towns over from me and is a wealth of knowledge. I'll try to update whenever I make any real progress or come across something interesting. Might throw in a few WW1 biplane replica photos since I'm bumming some hangar space from the Vintage Aero Flying Museum that I do a lot of work at to avoid having to buy a lot of extra tools and such.

Here's the current winning paint scheme for my own motivation since I was bored waiting for tools and parts to show up before I could really get to work and have just been photoshopping in the meantime:

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Wonderful classic paint scheme for a classic looking RV. Nice incorporation of the blue on the nose around the canopy, and extending the blue on the tail onto the fuselage.
 
koupster said:
Wonderful classic paint scheme for a classic looking RV. Nice incorporation of the blue on the nose around the canopy, and extending the blue on the tail onto the fuselage.
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Well it was classic, I've decided to go much simpler now because I just want to get flying and it'll be much easier to do.
 
Been hard at work on the canopy skirts. I'm just about done. 2024-T3 is a gigantic pain to shape though. The same piece that takes me about an hour to work in the english wheel from .032 aluminum of unknown soft alloy, takes about 8-10 hours in .025 2024. Just need to finalize some trimming, a tiny bit of adjusting fit and drill a few additional rivet holes and it'll be time to glue and rivet the whole thing together. Should be done this week I think. Then it's just the elevators, some fiberglass and all the fiddily stuff and it'll be time to paint.

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After about 2.5 months, the canopy is finally finished, minus just some clean up that I'll do later on. They weren't kidding when they said the canopy was the hardest part. I bet I have about 250 hours in it.

Skins are all metal, no fiberglass. Everything is Sika'd and then riveted as usual. For the hold open, I still need to add a simple string, but I welded a tab onto the rollbar and used a "surplus" 737 baggage door strut I got from a friend. Still need to do a doubler and cut a couple spacers to replace the test washers, but that'll be quick. All in all it went well, only ended up with a couple small scratches on the plexi near the skins. I'll polish and fill those later before the first flight back. Still need to add the safety latch too, but I bonded some spacers in yesterday so needed to wait for those to cure before I start messing with it. Missing a couple sizes of pop rivets too so I'll get those in next week when they come in.

Only major parts left now are the elevators which I'll start today, some fiberglass work and then paint, final assembly and the condition inspection.

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climbak said:
After about 2.5 months, the canopy is finally finished, minus just some clean up that I'll do later on. They weren't kidding when they said the canopy was the hardest part. I bet I have about 250 hours in it.

Skins are all metal, no fiberglass. Everything is Sika'd and then riveted as usual. For the hold open, I still need to add a simple string, but I welded a tab onto the rollbar and used a "surplus" 737 baggage door strut I got from a friend. Still need to do a doubler and cut a couple spacers to replace the test washers, but that'll be quick. All in all it went well, only ended up with a couple small scratches on the plexi near the skins. I'll polish and fill those later before the first flight back. Still need to add the safety latch too, but I bonded some spacers in yesterday so needed to wait for those to cure before I start messing with it. Missing a couple sizes of pop rivets too so I'll get those in next week when they come in.

Only major parts left now are the elevators which I'll start today, some fiberglass work and then paint, final assembly and the condition inspection.

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I’m excited for you brother!
 
climbak said:
I'd be really interested to see if there's much difference between the profiles of the Airplane Plastics and AeroCanopy. Mine was remade after the first try because the profile came out kinda weird. I like it now, but I will say it is quite steep up front and very little clearance to the rollbar, Maybe 3/8 of an inch. That easily could have been my fault though when I got excited early on and started trimming a bit way before I was ready. Definitely use a spacer like AX-O did and don't start cutting anything until you're ready to do the canopy. Luckily, I'm not tall and have no issue with head clearance. Oh and make sure you get a good cut off wheel designed for plastics. I just got one off amazon and it worked really well for the main cuts. Then a handheld belt sander for the fine trimming and an oscillating tool with 220 grit sanding pad for the final smoothing. A 440 grit would have been even better I think.
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My canopy showed up yesterday. I set it on for a quick look last night. I like the lines but he pre- trimmed a bit more than I would have preferred. This is with 1-1/4" foam block on the rollbar. I'd have liked it to reach further forward, and lower on the sides to make the cockpit feel a bit bigger. On the other hand it's less trimming I have to do lol.
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Jjackh10 said:
My canopy showed up yesterday. I set it on for a quick look last night. I like the lines but he pre- trimmed a bit more than I would have preferred. This is with 1-1/4" foam block on the rollbar. I'd have liked it to reach further forward, and lower on the sides to make the cockpit feel a bit bigger. On the other hand it's less trimming I have to do lol.
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Oh interesting, very different profile from mine. I like it though. I had initially started trimming mine with a block of 2x4 on the rollbar, but I over trimmed and trying to ge tthe shape to match the frame as best I could, now have about 3/8" clearance. I would definitely get your frame fully situated before any additional cutting. And get your front to fit before any trimming too. I didn't do that and had a roughly 2" gap up front I had to take up with fairing.

Looking at the sides of yours too, I think you're slightly below where mine ended up and I think I'm still lower than the stock 4 by a little bit so You've got some room to play. Excited to see what you come up with!
 
climbak said:
Oh interesting, very different profile from mine. I like it though. I had initially started trimming mine with a block of 2x4 on the rollbar, but I over trimmed and trying to ge tthe shape to match the frame as best I could, now have about 3/8" clearance. I would definitely get your frame fully situated before any additional cutting. And get your front to fit before any trimming too. I didn't do that and had a roughly 2" gap up front I had to take up with fairing.

Looking at the sides of yours too, I think you're slightly below where mine ended up and I think I'm still lower than the stock 4 by a little bit so You've got some room to play. Excited to see what you come up with!
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Good info. I'd like to maintain an inch and a quarter at the roll bar as I want to mount my GPS up there. I forgot I could use the fairing to make up a little gap. I'm gonna use the upcoming cold weather as an excuse to finish the panel inside the house. then I can set it in and start building the frame.
 
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