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Old Oct 31, 2009, 07:21 PM
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Guillows P-40 warhawk build log

Hi

I'm currently building a 16.5" wingspan Guillows P-40 warhawk and thought I'd share some photos of the build process. Hopefully this can be a source of inspiration for someone converting a guillows kit or maybe some other free flight model.

A couple of months ago I made a 16.5" Guillows Hellcat with a 2204 sized brushless outrunner. It flies way really for its size. It also climbs vertically like a missile. One of the reasons I'm building the P-40 is that it has a longer nose than the hellcat. Therefore the CG will probably be just about perfect from start without additional weight in the front. Also I want to build this lighter to get a bit lower wing loading. It's not going to be a slow plane at all though (Edit: dopplered it @ 150 km/h during a slight dive). I'm just hoping for slightly better performance when the battery is drained mid-air....

Enough talking, here's the good stuff a.k.a. pictures:


Update:
Here's how it turned out!


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Old Oct 31, 2009, 07:25 PM
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More shots of the fuselage. I made lots of balsa inlay pieces for the lower part of the fuselage. Hopefully it'll give enough strength for some rough landings/crashes. Also, I'm going to scallop all the formers later.
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Old Oct 31, 2009, 07:32 PM
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I tried to plan the layout before I started to build the fuselage, and it seems like it payed off! Man, that thing can hold a 400 mAh 3s LiPo! Not that I'm going to fly it that heavy, 200 mAh is probably enough for over 5 minutes flight time .
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Old Oct 31, 2009, 07:38 PM
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Some more pics. Got to sleep now. Hopefully I'll be able to work on the P-40 tomorrow . I'll be back!
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Old Nov 01, 2009, 09:43 AM
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I worked a bit on the wing today. Still needs some work - a few stringers, ailerons and maybe a little sheet balsa at the root and leading edge.

I also finished the fin. I added some stringers to make it look a little bit more "authentic". I think it came out pretty nice.
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Old Nov 01, 2009, 10:09 AM
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Looking good!

The Hellcat would be fine on the 5gram brushless motors and a 2x130mAh pack I think.
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Old Nov 01, 2009, 10:39 AM
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Not mine, it's too heavy . But built lighter it's probably ok
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Old Nov 01, 2009, 02:29 PM
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A friend of mine tried that same 16" P-40 years ago with a 12mm GWS motor and 3X3 prop. Used 2 cells Lipo and Hitec "Feather"/ HS-55 for flight pack. Was very heavy and fast, almost impossible to control with R/E/T and crashed in less than 20 second! I have a Guillow FW-190 in the pipe line, 5 gr outrunners and light Rx and servos, but because of its short nose I might have to use a 17 gr GWS for power just to balance it when I build it. Have been more lucky lately with a foamy Me-109(converted from rubber free-flight)of about 15" span and 60 grams. Using 3700 Kv/outrunner from HC on single cell with 4.5" or 5X3" prop. Two Spektrum 1.5 gr servos and MI Rx (tried with Toki originaly but realised it would be too hard on them at that weight). It is hard to turn on rudder without ailerons coupling but OK if I keep the speed up. And glad to see you back Epilot!
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Old Nov 01, 2009, 04:13 PM
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I can imagine how that P-40 flew. I once made a plane with that setup and it really sucked. It tip stalled at almost full throttle and barely flew at all. I should have maybe tried 3 cells but whatever... Brushed is sh-t, brushless is the sh-t .

Update so far: Wing is almost finished. It only needs aileron linkage of some sort and also ailerons. It has two uninterrupted main spars from tip to tip and also a beefy center reinforcement spar. On top of that I added some sheet balsa to the front and middle. Cartwheeling? Crashes? Bwah! no problem. And it still only came out at 13 g! Maybe I've made it 5 g heavier than it could be, but at least it won't break.

So the whole plane will probably weigh about 110-120 g rtf. My hellcat weighs 135 g and flys like a dream (as long as the motor is running).
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Old Nov 01, 2009, 08:23 PM
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Good advice for anyone building a Guillows kit:

Throw away the balsa in the box and replace it with 4 - 6 Lb density contest balsa if you can find it. Then build per plans with this wood. The kit balsa is like concrete, and adds needless weight.

Once the airframe is built to a point that you can get a reasonable estimate of the total airframe weight - less electronics, motor, ESC, battery, etc., then multiply by 1.4.

That number is your limit for motor, ESC, Rx, Batt, servos and pushrods, horns, covering, paint, whatever else.

Now, try to determine from the plans what the wing area is (in square inches). Divide that number by 144 (the number of square inches in a square foot). This is the amount of square footage of the plane's wing.

Take the airframe weight, add the equipment weight and calculate the sum in ounces. Divide by the square feet in the wing.

If the result is less than 3, it should fly fairly well outside. At 2.3 or less, it should fly pretty well in a medium size gym. Over 3.0, be prepared to fly a missile!!

Only then can you estimate how big/small the motor needs to be vis-a-vis the thrust it develops - unless this is your fourth or fifth kit!! For a docile, sport plane, the static thrust need only be around 60- 70 percent of all up weight.
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Old Nov 01, 2009, 11:47 PM
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That's some good advice. I'm too lazy to replace all the balsa though. I'm hoping the motor is powerful enough to make the plane into a missile . I can't build light either. Everytime I try, it still gets overly beefy because I'm thinking "oh, that's a weak point, it needs some strengthening, oh and there's another one. etc etc"
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Old Nov 05, 2009, 01:35 PM
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Wings are now completed apart from a fuselage section on the bottom. I'm going to use 2mm carbon rods for the aileron linkage in order to get it really stiff and precise.

Also I made a motor mount and fitted the tiny brushless motor. It really looks nice! Now I only need to get a 28-30 mm spinner. I'm thinking the 28 mm spinner for the graupner nemesis would be fine, but it's so darn expensive compared to a slightly larger (30 mm) aluminum spinner. 28 is absolutely perfect, 30 is a tad too large though (but probably looks "ok" anyway).
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Old Nov 06, 2009, 03:56 AM
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Now it's completely ready for covering!! woohoo!! I'm going to cover it in olive green SoLite and then we'll see if it needs additional paint or if it's enough with some nice decals.
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Old Nov 06, 2009, 03:35 PM
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Covered with olive green and white SoLite! I'm thinking of also spray painting it to get a more flat finish. I picked up a can of olive green color for the cowl, it should be enough for the whole plane. Then I'll spray paint the white bottom with grey primer. Then it's time to print some self adhesive decals!

What do you guys think, should it have a shark mouth or not?

Now the plane desperately needs a spinner. I've ordered a graupner nemesis 28 mm spinner. It's expensive but since I ordered all the other stuff from hobbyking the price is not that bad in total.

Weight seems like it will end up around 120 grams auw. It's about 15 grams lighter than my Hellcat. However I also noticed that the wing area is slightly smaller. So maybe I've built another missile that drops out of the sky like a rock as soon as the motor cuts out . The wind resistance is much lower though, so this should maintain airspeed better than the hellcat.
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Old Nov 07, 2009, 04:42 AM
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Nice job Truckerboy, some very smooth lines there indeed.
Good luck for the maiden.

What is the motor & prop combo you have there?
I'm about to do a Guillow's DH-80 Puss Moth.
http://www.rcgroups.com/forums/showt...6#post13373529

Finding a motor small enough to go into the nose is a problem.
Needs to swing a 6" or 7" prop but only 13mm max dia.

Also, I have posted your build in to 'The List' of Guillow's conversions in the scale planes forum.

http://www.rcgroups.com/forums/showt...2#post13524992

Cheers - Phil
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