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Old Feb 08, 2013, 02:06 PM
Balsa Flies Better!
Stamford, CT
Joined Oct 2000
6,758 Posts
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An indoor Comet P-40

A bunch of years ago, my fine flying nemesis, Rich Zapf, gave me this plan for a Comet P-40. I built one from the kit probably a couple of dozen years ago, but I did keep the prop/spinner/noseblock.

Needing something to fly in a smaller venue than my P-51 (and be easier to transport), I began building this airplane a couple of weeks ago. It's funny how some things start feeling familiar- like when the fuse formers don't fit...(D'Oh!) I of course remember this after cutting them out...

I decided to try framing this airplane up a bit lighter than my normal construction, so I went to 1/20th square for most of the fuse construction. (there are a couple of stringers up front that are 1/16"- I was feeling lazy and noseweight is generally helpful. Rather than cut out ribs, I opted to try a cracked rib construction. I think I used a pretty firm piece of 1/16" for the main spar though- on the stock airplane, the wing was a real weak spot, a single 1/16" spar is just not enough on this size airplane no matter how strong it is. For the tips, I got daring and used 1/32" sheet- we'll see if this works in practice. I often have trouble laminating stuff, and the other problem with laminated parts is if they break- they're very hard to fix without a splint or a notable kink. So I just went with sheet for the outlines, although the tailfeathers are sanded very thin- less than 1/32" I think.

I decided to do an 'F" version because it has a lengthened aft fuselage- the Comet plan is a bit indeterminate as to which model it is, but its supposed to be something like a "B". The "F" also has a different radiator arrangement since it's got a Merlin stuffed in the airframe rather than an Allison which also eliminates the top hood scoop for the carburetor. Other tweaks- the rear of the belly pan on the plan is wrong- it doesn't taper to a point- its an oval opening- think for supercharger gases. Added a bit of area to the horizontal stab- just built it to the outside of the outlines.

When I started on this airplane, I thought the wingspan was 18", but it turns out that good flying buddy Richard had pulled a fast one on me- the airplane was enlarged about 10%- maybe a bit more. I didn't notice this till the airplane was largely framed out- shows you how observant I am! Couldn't figure out why it seemed to be so much bigger than the old Comet Mustang I have lying around. This also meant that some of the Guillow parts I ordered such as a canopy and spinner aren't going to work. It's one thing to go from a 16" airplane to an 18" airplane and hope that nobody will notice- it's something else to go to a 20" airplane. Oh well, I have a Guillow's P-40 that I want to build for RC anyway- some spare plastic might not go amiss. Ordered a canopy from Easy Built instead- they have a 20" P-40B kit- should be pretty close and probably a lot lighter than the Guillow's version.

Now I'm waiting for Jeffrey Ethell's book on the P-40 to arrive. I want to do a North Africa color scheme- brown on top, blue on the bottom, but I'd like to avoid as much lettering as possible. It's really annoying the people only took pictures of the airplanes with striking (and hard to reproduce schemes) and not just an average ordinary airplane....I have got to try this inkjet printing tissue one of these days, but making the pattern is frightening- I don't want to spend so long on a computer. Dunno if I'll be able to finish the airplane in the next two weeks- i.e. before the next contest, hence I'm keeping my Mustang around for a bit longer- and may have to work on my EB Hurricane too.

Sam
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Old Feb 08, 2013, 10:39 PM
For us He died, in me He lives
Jimmy JFlyer's Avatar
United States, MI, Saint Clair Shores
Joined Dec 2008
5,121 Posts
Will be watching with interest. Just now catching the FF bug after a hiatus from scratch building foamies.
Love WWII birds, especially the P40.

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Old Feb 14, 2013, 10:31 PM
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Canada, AB, Fort Saskatchewan
Joined Oct 2011
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Love the build!!
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Old Feb 15, 2013, 09:54 AM
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Dorme's Avatar
United States, NJ, Manchester Township
Joined Dec 2000
1,058 Posts
Nice build, Sam. I understand the hesitancy to use inkjet printing, but it is really very simple. The hardest part is coming up with a design. Many of the details such as numbers and images can be scanned and then cut out and placed on a mock up of say, a wing. Then scan the whole thing and print it on tissue.
For tail surfaces, I preshrink and iron the tissue just before attaching it to paper with temp spray (3M Spray Mount). You don't have to get all the wrinkles of the tissue to have a successful print, just make sure the leading edge into the printer is flat.
What I do is cut the tissue approx a 1/4" less than the paper it is bonded to. Quick mist on the paper and then lay the tissue onto the paper lightly for one long edge. Run a finger down the center both ways, smooth to the corners from the center and finally lightly smooth the rest. You might find that using a bathroom tissue will help smooth down the tissue into place, as I frequently do.
Not everyone has a program such as AutoCad or Corel Draw to create the nice sharp details but careful cutting from scans, as I mentioned and pasting for a final scan will work and look good. There is no reason one can't create even panel lines with this method (draw them in ink). I have a friend who imports the paper planes from Fiddler's Green, blows them up and prints out on tissue and they look really good.
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Old Feb 15, 2013, 01:41 PM
Balsa Flies Better!
Stamford, CT
Joined Oct 2000
6,758 Posts
Thanks all...

Dorme- I think you hit the nail on the head- coming up with the design. I think it took me 2 hours to come up with the Herman Munster head on my Volksplane- about 5 minutes to find the artwork and the remainder getting it to print the correct size! And it still wasn't what I wanted- I tried to flip one of the images and finally gave up in disgust. I hate doing that stuff- it kills me- I'd much rather build.

I have been making some headway on the build- might have it done by next weekend assuming the canopy arrives. (I have the Guillow's canopies- if desperate, might use one instead.)

I also made a terrible fumble and got too aggressive about shrinking the tissue. I had a horrible bend in the underside of the center rib- and lots of wrinkles to boot! I probably put the tissue with the grain oriented the wrong way- I can never keep it straight. So I had to add some beef to the center section of the wing. I tried gluing the wing into the saddle to see if that would pull it straight- but there was way too much tension. So I cut out the center tissue and will have to live with the additional panel lines on the underside. However, on the plus side, the airplane has some pretty big fillets and I may be able to incorporate them although I may be dreaming here. I've also got some bowing of the wings which I may be able to steam out. It'll bug me aesthetically, but probably won't hurt the airplane in the air.

I think I was also dreaming about the weight- I'm up to 18 grams sans canopy although most of the tissue is on. Got the fillets to go too though and some additional doo dads. The exhaust stacks from Guillows only have 5 stacks- don't ask me why since the shots I've seen of both the Allison and the Merlin show 6 stacks- one per cylinder. I'll have to dummy one up in balsa.

Not sure I want to repair the spinner- it's got war wounds from the first Comet P-40 I built a couple of decades ago- adds character- doesn't it?

Sam
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Old Feb 15, 2013, 03:56 PM
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Dorme's Avatar
United States, NJ, Manchester Township
Joined Dec 2000
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First, Sam, you can flip an image with Microsoft's Paint that comes with all PC's that use Microsoft for an OS. I've done alot of things with Paint when I didn't have Adobe Photoshop. And by the way, you can buy an old version of Adobe PS on line for $15 and it will do just about everything you need in the modeling areas.
Second, for your P-40, I would preshrink some tissue, iron it and then apply it to that questionable area you're having problems with. The best way to apply preshrunk tissue is to iron it, apply the glue stick (if you're using one) and apply the wing to the tissue on a flat surface. That way it is evenly distributed and you won't have huge wrinkles. Once you turn it over, resist the attempt to do any pulling and simply press down the outer edges and you're done. You will be surprised at how easy it is to get a good looking finished effect this way. Try it on all your surfaces from now on-even the top of the wing-just roll the wing on the tissue and then press the edges without pulling - done! You know my planes. This is how I do it.
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Old Feb 15, 2013, 04:16 PM
Balsa Flies Better!
Stamford, CT
Joined Oct 2000
6,758 Posts
Hi Dorme

Thanks for the suggestions. One thing- I'm on a Mac. I think the problem may be in my printer software because I have a very hard time getting it to print what's on the screen. My problem is that since I spend so much time writing on a computer during the day- I'm damned if I want to keep working on the blasted thing when I want to relax and build airplanes. (Call me a luddite...)

I should be OK on the P-40 from here on in- because with the wing glued into the saddle- it's not going anywhere so I should be able to water shrink without too much trouble. In this case, I'll stick with what I know on this airplane. However, on my next simple build- I'm going to try your ironing trick. Having seen your planes- (his stuff is gorgeous by the way) I'm willing to try a new technique.

Thanks,

Sam
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Old Feb 17, 2013, 09:06 AM
Balsa Flies Better!
Stamford, CT
Joined Oct 2000
6,758 Posts
It's getting there....I did manage to use a single piece of tissue on the underside which tightened up OK. I'll probably wind up with some wrinkles from having to steam in washout.

As I've gotten older, I've started to add more details to my airplanes. Years ago, I'd have thought that the airplane at the state it was in a couple of days ago was nearly done. Now I'm getting used to that being about two thirds of the way there- and keeping a fair amount of time blocked out to add details- things like windows, exhaust stacks, control surface outlines, etc.

Sam
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Old Feb 17, 2013, 09:16 AM
Balsa Flies Better!
Stamford, CT
Joined Oct 2000
6,758 Posts
Unfortunately, I really screwed up during the building and I managed to crack the starboard wing spar about half way out. I tried the CA divebomb trick through a hole in the tissue- and that made a mess. Then I hit the wing again (D'Oh!!!) and really snapped it- so out came the Ambroid- should be fine now- but I tend to really get aggravated at myself for doing so much damage before the airplane has even flown.... I may get aggravated and put in a new panel- I probably will...it'll look better than the blotch. The only hope is if a decal will cover it up, but I don't think it's quite in the right spot.

Here's how the bird sits this morning- a bit shy of 20 grams- still no canopy and exhaust stacks which will probably add a couple of grams at least.

I tried a new trick on the aft windows. I should have made a paper pattern and put it on before covering the fuse- but the plans didn't have one and by the time I remembered I needed to do something (FAC rules say that windows must be represented by clear material- no inked outlines) the fuse was covered. So I cut out a window pattern out of the tissue already attached to the fuse and came up with some really lightweight covering plastic used on some indoor duration ships I built many years ago. A little RC 56 and I think it came out OK- and is very light.

Sam
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Old Mar 19, 2013, 07:33 PM
Balsa Flies Better!
Stamford, CT
Joined Oct 2000
6,758 Posts
Took the bird out this past weekend and got her flying. Very easy to trim- a bit of up- a little tip weight because the turn opened up and a shim to get rid of some downthrust! Floored me that I actually built in too much downthrust into an airplane- go figure. 1/8" rubber wasn't quite enough- had to go to 5/32". Last flight was 45 seconds, so I think it'll be competitive in a smaller venue. I may try the other prop/noseblock I've got. I recycled two noseblocks for this airplane- the one I was flying it with using a 6" Tern Aero prop somewhat lightened, but I've got a slightly bigger Peck prop with a modified blade shape. Dunno if the airplane will crack a minute though...

Sam
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Old Mar 19, 2013, 08:25 PM
For us He died, in me He lives
Jimmy JFlyer's Avatar
United States, MI, Saint Clair Shores
Joined Dec 2008
5,121 Posts
Good to hear he's airborn. Any chance of a vis? Would love to see it in action.
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Old Mar 19, 2013, 09:01 PM
Balsa Flies Better!
Stamford, CT
Joined Oct 2000
6,758 Posts
I'm a bit of a luddite- don't have a vid camera. Generally people don't shoot vids when we're flying indoors but you never know...

Sam
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Old Mar 19, 2013, 09:18 PM
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carbondale il
Joined Jan 2007
2,568 Posts
Sam, how many winds are you able to get with the rubber you are using?

Kev
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Old Mar 19, 2013, 09:31 PM
Balsa Flies Better!
Stamford, CT
Joined Oct 2000
6,758 Posts
Hi Kev

I'd guess between 2200-2400 turns- think it's about 220-240 cranks on a 10:1 winder. Figure about 2x nose to peg for a loop.

Sam
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Old Mar 20, 2013, 07:39 AM
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carbondale il
Joined Jan 2007
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That's a lot of winds.

Kev
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