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Old Nov 13, 2002, 07:06 PM
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Guillow's P-40 Conversion

Okay, I have wanted a good scale P-40 for a long time and just having finished my tiny, I had to pick up a guillow's to give it a shot.

I had a couple questions though. First, I did some searching on P-40's here and mostly saw alot of other plans mentioned but nothing about the Guillow's. Is it a bad kit to convert?

The P-40 is my all time favorite plane, but I have had the darndest time finding a "good" one as everyone tells me they fly like junk, just like the real plane did.

Anyways, I now have the P-40 and the bigger P-38 sitting in my basement (heh, should keep me busy this winter). I am looking for any suggestions for either from people that have experience or information about them. I will be using HS55 servos (I got a steal on a lot of em), and probably M250's all around (I remember seeing a post somewhere about a motor similar to the 250 but cheaper if anyone remembers let me know.

One last question, what was up with the olive drab P-40's in Pearl Habor (the movie)...was that the Navy color scheme for em or somethin, I have only ever seen camo ones. If anyone knows a source for a 3 view of a P-40 with a similar scheme please let me know.

Herc
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Old Nov 13, 2002, 09:39 PM
Designing on the edge
Bengtson's Avatar
United States, OR, Portland
Joined Mar 2001
1,518 Posts
Herc,

I have that kit and plan to do a conversion on it. If I remember correctly, Gerald is also doing this one as well.

Here is my take on this kit:
1) Not much room in the fuse to work with with the wing in middle position. I plan to replace all formers and ribs with laser cut light balsa versions with proper size notches and much less wood in the formers. It will open up the fuse and still be strong. I am doing this for the 30" Guillows Hellcat. Use the keels from the kit. Tail feathers are part built up / part solid balsa.
2) Make the wing and bottom of the fuse of that section
removable. Attach the wing to birch dowels in the fuse using rubber bands.
3) HS-55 servos are a good choice and I would place them in the cockpit position. Simple music wire pushrod to the elevator. Fixed Rudder.
4) Replace all stringers with bass. I do this in nearly all my conversions. It is much stronger ( and nearly as light) and if hand launching is required, the fuse can take the stress. This one may not have good ground handling with it's narrow gear spacing.
5) Replace the vinyl landing gear dihedral brace with 1/16th plywood. The landing gear will then be strong enought to take the stress. My Guillows Zero conversion needed this.
6) Cover with Clearfilm. Light and strong. Paint with Krylon. Sure color isn't perfect but it is light and looks great.
7) I mount the motor on the vinyl firewall using a rolled 1/32" ply tube attached to the firewall with a 5/8" hole for the wires. mount the cowl to this assembly.
8) Attach the firewall/motor/cowl assembly to the fuse on music wire studs in the fuse for locating points and use small magnets to hold it in place.
9) My choice of motors would be the plain old 280 with a Horst style gearbox (4:1) and 9x7, 2 or 3 blade prop. A battey choice would be 8x370 Nimh. My Zero flies fantasticly with this combo.
10) Skip the rudder control and put in Ailerons with torque rods to a single servo in the center of the wing. There is lots of room for it. Keep throws to ~1/4" or you will have a real twichy, hard to control plane. BTW, choose the scale dihedral with this option.
11) If you have tall grass to land in, consider no landing gear but if you need to have them then skip the gear covers. They act like rudders and really screw up handling.
12) The battery location on a horizontal balsa plate will probably be near the wing so plan for a nearly permanent battery placement.


The total weight of this kit should be ~10 OZ.

I think that this kit with these mods will be a nice flyer. I have seen an 18" version flying and it looked really neat. Lots of aerobatic moves.

Kurt
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Old Nov 13, 2002, 11:06 PM
Rocky Mountain High and Higher
PROACE's Avatar
Joined Jan 2002
877 Posts
The airfoil used in the kit is very bad for good flight. I found this out the hard way after I was told. I used and scaled the airfoil from my Herr J3 and it was the difference between night and day, actually flew very well and even seemed to have good glid characteristics. Anyway, hope this can save some heart ache.
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Old Nov 14, 2002, 12:07 AM
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Great Post Kurt

I am looking to keep it very scale and only a rare flier (my one hanger queen).

Most of the things you mentioned kurt were on my list of mods:

I was just planning on carefully cutting 1/2"-1/4" (depending on which former) uniformly and carefully away from the inside of it with a hobby knife. I should think this would work, albeit more time consuming (Last year of grad school and budget is tight though).

Just gotta keep the stock airfoil...hopefully it is close to what the original plane has. Being my first "scale" plane, I hope to experience what those pilots had to experience in flight characteristics. I know it may sound strange, but I've heard stranger.

I am setting it up as aileron and elevator only, but had planned on trying to examine/setup the new parkfler mech retracts, but I need to research it first. I am pretty sure I would have to put in gear bay perpendicular to what the P-40 scale is after looking at the baby retracts in the store.

Anyways, the only question I had is about Clearfilm, I was reading up about doping (never done it before). I have never even heard of Clearfilm...can I get it at LHS or Hardware store? If you have a link I would be forever grateful.

Are you saying all up weight including battery at 10oz? If so that's lighter than I was guessing. Shoot, the M250 might just be able to hover it if I through a 10x4.7 on it. LOL a P-40 hovering, what a site that would be.

Lastly, speaking of 280's have you checked out the M250...I have had several 280 kits. I just built the tiny, check out the post in micro flight. Weighed in at almost 9oz and the M250 will hover it on a 10x4.7 with a 8cell 500mah NIMH and only weighs 2oz...its amazing (I gotta try a 300 just for fun tomorrow) and still go vertical (not unlimited) on an 8x6 with more flight time.

Thanks again,
Herc
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Old Nov 14, 2002, 10:18 AM
Designing on the edge
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United States, OR, Portland
Joined Mar 2001
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Herc,

The method you mentioned would work fine to trim the formers. Another way would be to use a Dremel tool with a rotary stone and grind the inside down. Some folks also sand the whole former down to make it thinner and therefore lighter.

I bought those lightweight gear retracts from GWS and wonder if they will work for this type of app. Tom Hunt also tried to mount them in a Dumas Hurricane. He indicated that they were not successful and removed them. Tom is of course a real expert in this area. Search for the thread where he talks about his experience with them.

Clearfilm is a thin hard mylar based documant laminating film with an adhesive base. It is sort of milky clear and becomes completely clear when heated. It shrinks nicely though it does not shrink as much as the other heat shrinkable coverings. I get around this by using a very hot heat gun and take it up to just before the melting point. Then I can get the odd wrinkle out. It takes paint fairly well. You can get it at http://www.modelresearchlabs.com/

Yes, the weight is with a 8 cell 370 nimh battery. I could be off by an ounce though.

The airfoil queation is curious though. I looked at it and I would like to know what is bad about it. I checked my Guillows Zero kit and it has the same airfoil. My Zero files great. BTW, check out my web site for photos and details of these conversions including my Zero. (Use the WWW button below)

I have been interested in the M250. It looks nice. My choice is based on simplicity and what I have a lot of lying around.

Kurt
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Old Nov 14, 2002, 10:46 AM
Balsa Flies Better!
Stamford, CT
Joined Oct 2000
6,704 Posts
Rethink a little...

Herc

I have the Sterling P-40 done to the same scale, i.e. 27" wingspan. Since the size and weight are comparable, I'll bet what I found will apply to your bird as well.

1) I'm flying with rudder and elevator. I find the airplane relatively fast, with lousy slow flight characteristics- wants to stall/spin- it's a bit overloaded at around 8-9 oz. I'm leery of ailerons- they decrease lift and add weight- my bird is a sleddus nicaddus already. I also just have a one piece airplane, covered in tissue and dope to save weight.

2) Your prop combos from something like a Tiny won't work- this airplane needs a lot of pitch speed.

3) I'm using a Speed 280 geared 3:1 (Titanic airlines hunk of junk- I think the MP Jet stuff is far superior. This is spinning a 7 x 6 white Gunther prop- gets it the pitch speed it needs.

4) I went to an 8 cell 110 mAH nicad pack- the 8 cell 300 NiMH packs didn't cut it- only got a powered glide.

5) If I were doing it over again- I keep hearing that the M100 motor on qualcoms works. If so, then Li-polys should work as well- I'm trying this setup in a 10 oz airplane. (2 cell 1020 li-poly pack) This will provide more power than what I used, with excellent duration (my airplane only flies for a few minutes) and should be lighter to boot. If this combo does indeed work, then you may consider adding more detail. Note that weight is your enemy, and you should consider HS-50s (or equivalents) instead of 55s. Alternatively, a direct drive Astro 010 or some of the new lightweight brushless motors direct drive are an option, but I suspect heavier than the M100, which should have plenty of power.

6) Your comments about wanting to fly with a scale airfoil are noted. Let me point out that air does not share your fantasy, and air molecules and flow do not scale. I don't know of a single free flighter (guys who build lots of airplanes in this size) that try to stick with scale airfoils if they want the airplane to fly well.

Good luck with yours,

Sam
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Old Nov 14, 2002, 11:43 AM
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My approach will be much like Kurt's ideas except for a few minor points. I'll use hard straight grain balsa for stringers rather than bass and probably increase the dimensions from 1/16 square to 1/16x3/32. Some will get 1/16x1/8.

I always sand the backsides of the diecut sheets to help the parts remove easier and to shave a little weight. Fuselage formers get trimmed to minimum on the inside openings.

Covering will be a mix of clear Ultracote-Lite, and 1/32 sheet balsa sanded thinner after application. All will get airbrush painted with Polyscale or Testors acrylics.

I'll shoot for 8 oz weight to enable use of a GWS DXA motor or similar. Otherwise the 280/Horst combo may be next in line. I also have an Orion Elite Stock motor that might make a good substitute for the 280.

Controls will be elevator and aileron. Ailerons will have about 2:1 up differential and hinges shrouded a scale-like manner to reduce drag and loss of lift.

Servos will be CS10BB, RX GWS Pico, Azarr antenna (or homemade equivalent), speed control CC pixie-light, battery 8 cell 370mAH 2/3AAA NiMH.

I'll forgo the landing gear to simplify life. Airfoil will be left stock but incidence may get reduced (or add a little washout). Wing may be made removable but retained by screw and dowel rather than rubber bands. Battery and radio access TBD.
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Old Nov 14, 2002, 11:05 PM
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United States, CA, Garden Grove
Joined Oct 2000
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EPS 100C 2.8:1

I'm getting much better thrust and duration out of the GWS EPS 100C 2.8:1 and GWS 9X7 than I got from the Titanic Airlines geared 280 3:1 with Gunther 7X6 I'm using the same 8-cell 300mah NiMh pack. The EPS 100 C has breathed new life into my old "tip-stally" Ziroli 36" w/s Aeronca Champ. I would bet that the same setup could work well in the smaller Guillows warbirds. I'd leave off the landing gear to save weight if flying and landing on grass. Ailerons and elevator work well for rolls and inverted flight but ailerons can become ineffective during dead stick landings. If using rudder and elevator I'd increase dihedral and use tip washout.

Would like to hear more on performance comparison with ailerons vs rudder for small low wingers.
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Old Nov 15, 2002, 08:57 AM
Balsa Flies Better!
Stamford, CT
Joined Oct 2000
6,704 Posts
Got a better idea for a motor

I just tried what I think is a killer combo on an airplane formerly powered by a TD 020- the M100 with a 2 cell, 1020 mAH Li-poly pack. This setup has more power than a Speed 280- especially on an 8 cell 300 NiMH pack, is lighter, and has far better duration to boot. If you've already got the Speed 280, then try a 3cell pack of a slightly smaller set of cells.

Gary- I really built my geardrive into the P-40- I wish I could yank it out, but it's probably more hassle than it's worth. I'm not surprised that the GWS works better than the Titanic. However, if you really want a performance boost for your Aeronca- try the combo listed above- great replacement for an 020 powered airplane. Why, oh why didn't I pick up that Stearman C3B from Flyline?

Sam
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Old Nov 16, 2002, 09:51 PM
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Joined Oct 2000
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Flyline Bucker Jungmann

One of my future projects along with the General Aristocrat and some others. Maybe your suggested power setup would make the Jungmann cook.
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Old Nov 16, 2002, 10:47 PM
ARFs make me BARF
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United States, MI, Roseville
Joined Dec 2000
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Wow, you guys...seems like more work to "Convert" this kit than to design one from scratch!

P40 were not bad flying aircraft in full size.They were early fighters,with relatively short tail moment arms.They are a bitmore pitch sesitive than say a JUG or 51, but not too bad.
I have spoke to several guys that flew them duting the war,and all said it wasn't a bad ship.The later N model with the longer tail WAS a better handling bird though.Keep that in mind.
My 42" P40E flys very well.At a loading in the 21 ounce range, it still takes off easily from a hand launch.Elevator throw is minimal for this ship, somewhere in the neighborhood of 1/4".
SCREW a scale airfoil.Nobody will care or know the difference.
You could always scale this one down to 23" to 27" span and have a sweet flyer...
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Old Nov 17, 2002, 10:52 AM
Now in TN!
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Chapel Hill, TN USA
Joined Apr 2001
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Mark,
Do you have a list of your available plans posted somewhere? If not, could you PM me a list? Thanks. J.Morgan
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Old Nov 17, 2002, 12:37 PM
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The Guillow's P-40 airfoil is nowhere close to scale. It is a simple flat bottom airfoil. Should provide reasonable lift for its area. Just be sure to round the leading edge adequately.
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Old Nov 17, 2002, 01:00 PM
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would love those plans myself

Keep me in mind too if you're going to send out those plans...that plane looks great, what's it covered in. That is almost the exact scheme I want to do to my future P-40.


Herc
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Old Nov 17, 2002, 04:51 PM
The blade numbers go up to 11
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Sydney, Australia
Joined Aug 2002
4,380 Posts
Guys, I built a Guillows P40 but kept it free flight, rubber powered, weighed only a few ounces RTF. The airfoil is a beast! The stall is as sharp as I've seen, and even 1/4" washout doesn't prevent tipstall - I spent hours trying to get the thing to climb in a gentle circle but get it too slow and it stalls and spirals right in. The other problem I found, which may not be a problem for RC, was that the finr/rudder area is too small due to the deep cowl. I enlarged both tail sirfaces around 10% and it made quite a difference. BTW - I did eventually get it trimmed and flying for around 30 seconds (doesn't sound long - but stand there and watch your plane fly without any control input for 30 secs and you'll see just how long it is!) in a nice climbing circle with a nice albeit fast glide
regards, Stu.
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