P-66

Cvairwerks · **Posted:** Wed Jun 03, 2009 6:14 pm

I'm not sure that you guys are truely cognizant of all the work required by what you are proposing. So far the only major components you haven't talked about changing yet is the hstab, elevator, vfin and rudder, brakes and seat, and that's because you haven't figured out that most of them will need mods too. This isn't a project where you can redesign and retrofit this, then move on to the next mod.
All the design work has to be done and proofed out first, or you will be continually backtracking and redesigning and fabbing componets. As a quick example, you can't finish the QEC til you do the hydraulics, but that has to go with the new gear system. That can't be completed til the spar mods are done, but that is now part of converting to a dry wing. That entails designing new spars and upgrading the wing skins to handle the new design loads because you are eliminating a significant portion of the center section's internal structure. At the same time, since you are changing the spars and skins, you now have to do the same to match the outer panels that you are cutting down and now need reskinning to match the center section. And so it goes for every part of the a/c.

If you have some of the fundamentals of aircraft design and performance and are more of a mechanic than a parts changer, I'd bet that you would be pushing 4000 into the project before you reached doing final assembly. Once you get it together and start testing, you will find things that need redesign or some serious modifications.

Doing a huge mod like this takes significant time and effort, even for those that do it all the time. Heck, just look at the average time required to assemble any of the RV fast build kits. Those kits are of a mature and has very detailed instructions and assemble sequence along with most parts having been designed to use matched hole assembly techniques. I don't think I've seen anyone complete a basic RV fuselage and QEC in less than 1200 manhours. Personally, because of all the design issues, I wouldn't even consider taking on modding a BT to lbe a standoff scale P-66.

RMB · **Posted:** Wed Jun 03, 2009 6:49 pm

That was well put "CV"

snj5 · **Posted:** Wed Jun 03, 2009 6:59 pm

Cvairwerks wrote:

This isn't a project where you can redesign and retrofit this, then move on to the next mod.
All the design work has to be done and proofed out first, or you will be continually backtracking and redesigning and fabbing componets..

I think most are very cognizant of the amount of effort required. As I said before, the conversion really needs a no-kiddin' AE to walk through it. Certainly very few of us would be willing to saddle up if they didn't.

I do think that the project is as do-able as some others that are currently flying, but by no means a weekend bolt together. It will take a talented AE to bring the components together, and talented fabrication in several aspects.

But for fun on WIX, nothing beats a little 'comparative anatomy' to discuss design for enjoyment.

Cvairwerks · **Posted:** Wed Jun 03, 2009 7:48 pm

Sure it's a doable project, but one has to decide where to devote their time. Engineer a major mod to an exsisting airframe so that it looks like another and take years and years to build and test, or, just start working off of a set of already proofed engineered plans and get it built and in the air.

I know that for me, I do enjoy building and overcoming obstacles, but it's a heck of a lot more fun being at the point of dragging the bird out of the hangar and getting airborne.

It may seem like I'm being the devil's advocate here, but I would rather be vocal about it now, and run the risk of torquing off someone, before they commit a significant amount of time and money to a project that might be too much for them in the long run and never get completed.

snj5 · **Posted:** Wed Jun 03, 2009 9:22 pm

A Devil's advocate? On Wix?

We do agree that this is a huge project - much, much more than a P-64 replica, that's for sure.

I think it would be about a 5 - 10 year project. All of the immediate gratification guys are building 7/8 Nieuports (sorry, couldn't resist). As you imply, it's all about where you want to invest your resources.

There are no P-66 extant, nor are there realistically likely ever to be, although I hold out hope. For someone with large time and resources, it could be a really interesting and very pretty project.

Dan Jones · **Posted:** Wed Jun 03, 2009 9:28 pm

CV's got a pretty good handle on what all would be involved. I think you'd have to go at it with the mentality that it would be a total scratchbuilt project (doable but big, or big but doable - your choice) with the bonus of having a few BT parts here and there that could be incorporated. For starters I wouldn't modify a 65 year old original fuselage truss, I'd TIG weld a new one out of 4130 chrome-moly.

snj5 · **Posted:** Wed Jun 03, 2009 9:35 pm

Dan Jones wrote:

For starters I wouldn't modify a 65 year old original fuselage truss, I'd TIG weld a new one out of 4130 chrome-moly.

I also think that is wise, and the original drawings are available from the Smithsonian (I have a set).

I think your characterization is accurate as well - big but do-able. It's not quite like we are making ME-262s, but closer to that than the typical P-64 conversion.

A2C · **Posted:** Wed Jun 03, 2009 9:54 pm

Quote:

Sure it's a doable project, but one has to decide where to devote their time. Engineer a major mod to an exsisting airframe so that it looks like another and take years and years to build and test, or, just start working off of a set of already proofed engineered plans and get it built and in the air.

In Canada? Not here. You are using the word engineer quite loosely.

Quote:

We do agree that this is a huge project - much, much more than a P-64 replica, that's for sure.

I don't. Both are modifications of other planes.

A2C · **Posted:** Wed Jun 03, 2009 10:24 pm

Quote:

Personally, because of all the design issues, I wouldn't even consider taking on modding a BT to lbe a standoff scale P-66.

I think it could be made totally accurate within 99%, and I don't know that the spar would have to be modified. If the wing is shortened, there would be less of a moment arm on the spar as well.

Stoney · **Posted:** Wed Jun 03, 2009 11:48 pm

CV we talk about flying and dreaming here, it gets the brain going. I know it would take bigger bucks then I have, but I still like to fly and dream.

A2C · **Posted:** Thu Jun 04, 2009 12:14 am

Stoney:

It's all conjecture anyway, what does an opinion matter if you think differently?

A2C · **Posted:** Thu Jun 04, 2009 12:41 am

SNJ5 shows the tubular fuse to be a little longer on the BT. I'd probably use it as is, and shorten the engine mount to shorten the nose so it's identical.

Cvairwerks · **Posted:** Thu Jun 04, 2009 5:28 am

A3C: Take a close look at how the center section for a BT is built. The front spar and the leading edge form a structural box. The front spar and the rear spar are also a box. Both spars taper from a/c centerline all the way to the tip. By cutting out the 7 ribs in the leading edge, you would significantly alter the forward box and make a major change in the load paths. Couple that with moving the gear fitting to a more outboard point in the spar again changes the loading. What that results in, is allowing a greater twisting moment on the front spar during any time the a/c is in movement with the wheels on the ground. A single hard landing in that configuration has the potential to rake the gear back sufficiently and twist the front spar and fail the wing. So to correct the now structural deficiency in the spar, you have to develope a mod or replacement for it.

Now, combine that with the fact that to convert from a wet wing to a dry wing, requires removing all the internal ribs from the wet bays, designing and installing new end ribs and adding finger spars on the upper skins, then a stress panel on the bottom to close out the structure Now you have to develope the tanks to go in the wing and all the stuff that goes with that. At this point, you have had to completely redesign the biggest and most complicated part of the a/c and had to manufacture it.

The point I'm trying to make, and it seems to kinda blow past, is that when you start looking at doing this much inter related change to an exsisting a/c, it is probably going to be easier to start from scratch, especially when the plans for the desired final outcome are available. Or to think of it in another way, I could convert one of my pickups to a 'Vette, and it would be a neat project, but why expend the time when I can get all the stuff on the open market to assemble one and be driving it in a few months rather than a couple of years....

Food for thought.....

JDK · **Posted:** Thu Jun 04, 2009 5:47 am

A3C? Is that a promotion?

As a bar chat, it's kinda fun, and we all know great projects that started with a beermat sketch. However I do think A2C's channelling our infamous Defender builder...

Cvairwerks - can you validate my pop riveted high-back on a BT concept? I reckon that's good to go. I'm also going to paint 'wells' on the wing underside and ring-clamp some 'doors' to the fixed gear. A new Chiseese scheme, and I'm good to go. You may laugh, but I'd be flying first...

(Assuming I had a BT, could fly, and wanted to do any of that...)

Cvairwerks · **Posted:** Thu Jun 04, 2009 5:51 am

Stoney: Nothing wrong with dreaming and brainstorming, but one has to temper that with engineering reality. In this case, it's easier to build a replica right off the factory drawings, and probably cheaper too.

The exception would be that if you would be satisfied building a replica with a fixed gear. In that case, converting a BT would be a easier route. A new steel tubing section and some careful forward panel changes and you could be pretty close as a standoff replica. Stick with the stock wing and not worry about clipping it. Unless you jumped up to a 1340, there wouldn't be any significant changes for the aft fuselage either.

At that point, unless someone was really familiar with the -66, it would fool 90% of people that saw it.

Maybe a little change in your thought direction????

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