Steps to scratch build a VW

Discussion in 'Hangar Flying' started by Little Scrapper, Aug 13, 2019.

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  1. Aug 15, 2019 #61

    Little Scrapper

    Little Scrapper

    Little Scrapper

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    What's wrong with doing exactly what the Sonerai guys do but on a V- Witt?
     
  2. Aug 15, 2019 #62

    Mcmark

    Mcmark

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    Aerodynamics. The further you move the prop away into clean air the more efficient. Most of the F1 guys run a 12" extension on the O-200's.
     
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  3. Aug 15, 2019 #63

    Little Scrapper

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    Right but how much improvement would you see? Jeff's Sonerai 1 is a mover. I believe he has a prop extension of some sort
     
  4. Aug 15, 2019 #64

    Mcmark

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    With the VW, the exhaust port on the pulley side hub is IN the cooling inlet. Add the extension, it buys you room to have the exhaust be a non-issue. Personally I wouldn't put an extension on the pulley end of a VW crank, especially for a sport flying airplane. The GPAS unit isn't close to what Witt did, but a darn sight better than using the pulley end. It also allows you to use their starter arrangement. There were some good pics on Bruce Kings BK Flyer construction site with him building his cowl arrangement out of aluminum. I liked his work.
    I'm with Tom, talk to Hjelle about Witts extension. Almost guaranteed bullet proof and simple.
     
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  5. Aug 15, 2019 #65

    Little Scrapper

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    Ok, what about a Wittm
    I keep thinking in my head that I could have a shop turn a extension out of a solid block of aluminum. Wouldn't that be the ideal solution as far as accuracy & efficiency goes?
     
  6. Aug 15, 2019 #66

    Raceair

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    i believe Joe Gibson in Wisconsin built a V-witt and used a Monnett engine, running prop on the pulley end. It was nicely done.
     
  7. Aug 15, 2019 #67

    dmar836

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    Perhaps. Wittman’s prototype had a rolled and welded extension cone(looks like maybe 3/16” or 1/4” steel). Once he made plans available the cones were cast by a third party. I would guess the shaft is not the same as the prototype either and built per his plans. The popular pic of Steve in front of the partially built V-Witt shows the prop hub on the front and IIRC it looks a lot like a C-65 hub.
    Whoever told me he battled with harmonics (Jim Vliet?) made me realize it would be really difficult to get that cone concentric to the crank centerline. Even after machining the cone it likely is a bit different each time it is reinstalled just like a dynamically balanced prop.
    Sorry. Not trying to make this about my issues!
    Dave
     
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  8. Aug 15, 2019 #68

    TFF

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    You can make either way work. Difference is CG. No extension means you may need a longer motor mount or stetch in the firewall to account for the weight missing out front. You will have to figure it out. may not be as much 1600 compared to bigger engine. You have to make some numbers work. Looks will be different at the front somewhat, but probably be more Cheeky which i like.
     
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  9. Aug 15, 2019 #69

    Little Scrapper

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    Honestly, I have no idea what to think about all this. I just have zero experience with anything Volkswagen so I'm just trying to learn as I go.
     
  10. Aug 15, 2019 #70

    Hot Wings

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    Thanks for the link! Somehow I've managed to never see this page!?
     
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  11. Aug 15, 2019 #71

    dmar836

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    From my research, on a V-Witt, it’s the price of the steel that’s a problem. It’s difficult to find 4140 in diameters big enough without spending almost $1000. Then there’s the cone fabrication. The flying wires were likely Stearman or some other WWII surplus but I ordered them to fit the wings and they were $1800. Wittman was known for simplicity but not by today’s standards. A single seat Sonerai is tough to beat for modern sensibility.
    Ed will know which white V-Witt had the whale nose and why. Certainly didn’t have the aerodynamic nose Whitman was going for. Pretty sure it was the engine option. I always forget to ask Ed If Steve ever commented on that one. I think I saw them on film at the same race.
    JMO,
    Dave
     
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  12. Aug 15, 2019 #72

    dmar836

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    I just get a blog entry Crank Basics II. Is there an entry about motor mounts?
    Dave
     
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  13. Aug 15, 2019 #73

    Raceair

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    Dave, that V-Witt was assembled at the Quad city races, but it did not qualify or fly. I heard it was from Minnesota, but I don't have his name. It certainly looked bulbous compared to Steve's
     
  14. Aug 15, 2019 #74

    Little Scrapper

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    I
    I leave for vacation on Saturday. After I get back I'd love to chat one on one.
     
  15. Aug 16, 2019 #75

    Mcmark

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    Mike take a look around in the files section of the Tailwind forum. I remember a group of the guys own some of the V-Witt stuff and will lend it out for others to use as patterns for their projects. Worth a look and a post to get some intel.
    I’ve always wanted to purchase the plans for the extension but have never pulled the trigger.
    I too have the V-Witt plans and it’s on my list of want to build items. Maybe someday. I’ll follow along with you and learn.
     
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  16. Aug 16, 2019 #76

    Little Scrapper

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    Locking up the shop now after a work session. Fuselage sides are coming together nicely.

    Something in my mind is telling me to just follow Wittman and do it his way but that could just be fear talking. I don't know. Gonna read them VW books and just keep soaking it all in.

    One step at a time.
     
  17. Aug 16, 2019 #77

    TFF

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    This is not just a VW problem it’s it’s a race plane being used as a sport plane problem. In a lot of ways it’s easier but you have to fix racing solutions with regular solutions. The extension is a race part. VW or some other engine it was there only for better aerodynamics. Not meant to be simple, meant to win races. It was an edge. Building hot rods is one thing, but building a race car is completely different even if the skills are the same. Taming this plane in building options is going to take a mind set. The problems for building a Cassutt or a Midget Mustang or a Sonerai are making race planes into regular planes. Like making a Sprint Car into a street car. I tend to like race cars driven on the street if you can do it. This thing is going to be sharp. The Tailwind group I think will loan out the casting mold patterns and maybe there was a couple already cast. Have not looked there much lately.
     
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  18. Aug 16, 2019 #78

    Turd Ferguson

    Turd Ferguson

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    I think W. Randall Bray is the custodian of the V-Witt parts. That's who I would contact.[/QUOTE]
     
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  19. Aug 16, 2019 #79

    Little Scrapper

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    Am I correct in saying that regardless of the direction and method of engine orientation the engine itself is built the same?

    I dontt want to jump the gun too much here. I want to keep building the airplane and read and study the VW.

    So far the general consensus here is the 1600 is the most reliable and authentic version correct?

    Another question. I haven't read the books yet because I'm waiting on vacation to do that which starts Saturday. What type of engine stand and people using for building these engines?
     
  20. Aug 16, 2019 #80

    Vigilant1

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    1600cc is almost certainly what was on the original, if that's where you are going with "authentic." IMO, there's nothing mechanically more reliable about a 1600 than an 1835. The 1600 was on there due to the racing category rules, and, free of that constraint I doubt Wittman himself would use that displacement in this airplane. If you are going to be asking it to give you more than 55hp for takeoff and 50 HP continuous, then you'll get more reliability with an 1835 than with a 1600. These engines live long, happy lives if they aren't run near the ragged edge.
    Steve wanted to win races, and I'm sure he used a lot of tricks to get a lot of power from that engine, as all racers are known to do. Maybe high compression, maybe no air filter, maybe anti detonation fluid, maybe 4500 rpm, maybe ran it at a 475F CHT on race day, etc. Unless you do what he did, your 1600 engine won't perform as his did. As far as performance, an 1835cc built to normal, reliable daily-flyer trim might actually be more authentic than a 1600 engine that is also built to go hundreds of hours between rebuilds. Heck, a "regular", non-racing 1600 might give disappointing performance. I'd look into that before deciding to go with a 1600.
    If you want/need 60 HP for cruise, a 1600 running 9:1 CR and 4000 RPM will be less reliable than an 1835 at 7.5:1 and 3400 rpm.
     
    Last edited: Aug 16, 2019

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