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Old Aug 28, 2009, 10:29 AM
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Guillows P 51 Mustang

Hi there, I am starting a P 51 Mustang from Guillows, 28" span.

This would be my 3rd Guillows build, but the first one that I will convert to rc.

If anyone has tips for me, please feel free to write.

I will try to keep the plane around 12 oz. The controls will be elevator and ailerons.

My electric setup will be:

Motor around 1500 rpm
2 small 9g servo (1 aileron, 1 elevator)
11.5 battery
prop... i think either 8 6 or 7 5 any advice ???

I have not bought the electronics yet, so if you have any thoughs feel free to add any combination you have in mind.

I am thinking about sheeting the top of the wing and the body with very thin aluminum foil ... either will be a disaster or something interesting to see. I am not looking to build a plane that will do acrobatics, but rather fly at slow speed.
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Old Aug 28, 2009, 11:22 AM
MPP
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Hi Alex,

Welcome to RCG's, I did this a couple of years ago and came in at 11 Oz.'s. It fly's fast and is not a floater. I sheeted the wings and did not correct the wing incidence or airfoil. I would look at Smoking beavers P-40 and Zero 400 series builds with the wing incidence correction to the wing saddle before pinning it to the work board. I also used a little screamers hi Kv motor with a 7 5 APC prop. takes a bit to get on step but once it does it goes pretty good .

I would think aluminum over balsa sheet could work, however i would stick to a film covering and just paint it.

Good luck post some pictures and ask for help as there are some great and very skilled modelers on here.

Mark

Guillows P-51 conversion

Smokingbeavers P-40 conversion

And of course,

List of Guillows Conversions
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Old Aug 28, 2009, 12:09 PM
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Thanks a lot for the info, I will post some pics soon
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Old Aug 28, 2009, 10:10 PM
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12oz is actually achievable with the P51, built as you are planning. My Guillows 190 is around 14oz AUW with 1/32" sheeting, with the exception of the wing bottom and tail feathers, and is painted over Econokote covered. The P51 has an advantage in that if the tail is built equally light, you will need less or possibly no ballast, as the nose is longer. I have a light framed tail in the 190, but a good 1-1/2oz or so of lead in the nose, due to the short nose. The 3s-900 batt is also larger than necessary, but I am using it for ballast. The P51 could use something more like a ProLite 3s-480, if you are wanting lightweight. Scrap the 9gm servos, and use something like 5.4gm GWS picos, or lighter. Irregardless, mount all gear and batt absolutely as far forward on these planes as possible, especially when sheeting.

I built the P51 as a display model. One thing that can be conveniently done is using the oil cooler vent as the rear wing locator/hold down, on a sheeted model. I did this on mine, and have locator blocks on the top of the rear wing area, to keep it from moving side to side. The wing simply slides into the fuse to install, and the hold down bolt is in the front of the wing.
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Old Sep 01, 2009, 02:56 AM
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small motor

I think the brushless engine I am buing might be to small for the airplane,

it is a 26 grams engine and the size is extremly small like 18 by 25 mm ???

I saw that most of the people are using propeller spiners. any thoughts on how big the engine should be to handle the propeller and the spinner (cone) ?
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Old Sep 01, 2009, 01:50 PM
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These planes do make good conversions, but the trick is to keep everything as light as possible. With Guillows this usually means making copies of the parts onto lighter, better wood and discarding what came with the kit. I don't know what it is with their wood but it does seem to be excesively heavy. As a comparison, I'm most of the way through a West Wings Spitfire with a 25" WS and that will come in at under 200g (about 7oz) fully sheeted, though with depron tailfeathers to save nose weight later. www.rcgroups.com/forums/showthread.php?t=1097519. This is with some scale details too, including a molded resin pilot from Pete's Pilots. (look him up on ebay - very good quality, cheap, light and speedy delivery.)

I'm using a 350mAh 2s lipo and a 15g bl that provides 240g of thrust, could get the weight down with a smaller motor but it's one that's been looking for a home for a while. Besides, better than 1:1 power is always fun and I'd rather add nose weight in the form of power than as lead ballast.

Also, the 3.7 - 4.2g servos would be fine for this scale and would save some more weight. I've found it's often lighter to use a servo in each wing than torque rods, and it's certainly easier to install the ailerons that way. You also then have the option - if your tx can mix it - to use flapperons to slow you down for landing. Not tried that before but it'll be a feature of my spit.

If you plan to sheet it you should sand the sheeting down as this will not only save weight but will also make the wood form more easily. It's a bad idea to sand the sheeting after it's been fitted as what tends to happen is it pushes down between the ribs, stringers and formers so it ends up going through over the framing and being raised in between. An easy way to get it down to the thickness you want is to epoxy two lengths of piano wire to a board, about 4 1/4" apart and parallel, using the thickness you want the wood to be (I like mine to be about 0.3 -0.4mm thick), use a little spray mount to hold the balsa in place, and then sand with a block until you're on the wire. It's also easier to butt join the sheeting before using it if you need pieces wider than 4", ie, for the wing skins. For this you slightly overlap the sheets by a few mm and then cut through them both with a straight edge to get a perfect join, tape the two pieces together all the way along, turn them over and use the tape as a hinge to open the seam up by folding the wood like closing a book, run a bead of glue along and then open the pieces up again. Tape the other side, leave to set and then sand off any excess glue.

My personal favourite method for sheeting as to use regular multipupose UHU, get the piece of sheeting ready and cut to shape, tape it to the structure on one edge, hinge the piece back, apply a fairly generous bead of glue to all the framing it will come into contact with and then hinge the piece onto the glue, wait about 5 seconds and peel the piece off. You'll see a lot of the glue has formed strings, swipe these away with a finger or balsa scrap and press the piece back into place. This makes a very light and strong bond that you can work immediately.

Hope this has helped, don't forget to post pics of your progress, and remember there's always someone to help you with any problems or questions here.
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Old Sep 03, 2009, 02:30 PM
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first pics of the P 51

Ok, I post some pics today

wing is done, so is the body of the plane. total so far about 100 grams, that is ... 4 oz I think.

Fuselage has the top and bottom sheeted with balsa, the wings only the front and the lateral sides.

I also bought the engine, esc, battery and 2 small servos. Probably will work in the weekend.

I also weighted the aluminum foil, is about 40g that's 1.8 oz. any thougs on that ? I might need some advice on making electric setup later on since I looked at the wires and there is a bit of a mess in my head right now. Tried to hooh up the engine. Hope I did not burnt it.
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Old Sep 03, 2009, 02:40 PM
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I am thinking about weels, do I need weels ? should I just forget about them ???
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Old Sep 03, 2009, 03:00 PM
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Alex looks great. I would rethink the aluminum foil. I would make sure you do a range test if you use an internal antenna. Seems I have read about foil blocking or interfering with the Rx. Again Docalum makes for good tough light weight covering that paints well.

Also the Mustang has a longer nose than some of the other 400 series. You should not have to add weight to the front as mine had the battery aft of the CG.

There are also some good light weight spinners available. I like to have 90 watts per pound and a motor that can handle that should be able handle a spinner. You could also make a backplate and use the Guillows plastic spinner.

Again looks great keep up the good work.

Wheels I think is your option, just get some light weight foam ones if you do. ROG is fun and can make for a less exciting maiden. landing that 's another story.

M
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Old Sep 03, 2009, 05:37 PM
Beware the Axis of Weasel.
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A way to use the vac moulded spinners that come with these kits is to mark a circle slightly larger than needed onto light-ply or hard balsa, drill out a hole the same diameter as the prop shaft, and then use a nut and bolt this size to turn the disc using a dril and a sanding block. Check often til you get a perfect fit, and then just glue in place once you have the disc and prop fitted. To balance it you can add a blob of PVA glue inside the spinner first, and then run the motor up briefly to spread the glue around the inside. This'll give you a nice, vibration free setup.
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Old Sep 03, 2009, 07:11 PM
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Everett Wa.
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Guys,
I have to ask why so many of you all go through the problem of doing all that inlay work for multiple bay fills? I would think it easier, faster and stronger to remove the former pieces between the stringers and use inlay strips (plank) not little blocks. Looking at some of the builds I'd be tempted to even remove the stringer in some areas and just sheet the area in question.

Just asking as I see this a lot. I'm wondering if I'm missing something.

All the best,
Konrad

P.S.
I think I see why now. The plans show this block fill as a reinforcement for "Glow powered conversions". Can't say as I see a lot of strength with the blocks. It seems to just add some hard points to help with handling as one tried to start that damn Cox engine.
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Last edited by Konrad; Sep 03, 2009 at 11:28 PM.
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Old Sep 04, 2009, 01:27 AM
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Just some talking points to Wild Weasel, not that WW is wrong.

I agree that the dual servo is often lighter than the single with all the torque tubes and bell cranks. And that they are often more precise. I have to add a caution here that the sub 6 gram servos are current hogs even at idle. If you are going to use 3 axis control be aware of your BEC limits. Three or more servos might drive the BEC into shut down.

Never never use outboard ailerons as flaps (flaperons)! This gives in effect wash in. This allow the wing tip to stall before the wing root. This causes a tip stall snap just as you are trying to slow down. Please don't do it.

Now using the outboard ailerons as spoiler (spoilerons) is very advantageous. This adds more effective wash out, adds the drag when we want to slow down, and corrects for adverse yaw of most aileron inputs. See some of the mixing used in sailplanes. Better radios have reverse aileron differential for this mixing. This is nice but not needed. Check your owners TX manual for this.

For sheeting I like the iron on method. This is paint the structure were you want the sheeting to adhere with Titebond glue (I thin it about 15% with water) let dry. Then fit the sheeting as best you can. Once satisfied with the shape of the sheeting. Heat up the iron to the cotton setting. place the sheeting in position then run the iron over the areas were you previously had applied the Titebond. The heat going through the thin sheeting will activate the dried Titebound. Bonding the sheeting to the structure you previously applied the glue to. For me this makes a very clean sheeting to sheeting joint that allows for very little glue on the surface which can cause the glue line to show when sanded. Using sharp sandpaper and hard backing most sanding issue can be minimized.

All the best,
Konrad
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Last edited by Konrad; Sep 04, 2009 at 01:40 AM. Reason: Shift key not working well
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Old Sep 04, 2009, 01:31 AM
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Hi Konrad, my answer as you guest it is very simple, I just read on the plans instruction. I also have a small version of this plane I sheeted above the strings with 1/32 balsa stips. Plane looks nice but it is a bit "puffy". I tried to get a more scale look on this one.

Alex
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Old Sep 04, 2009, 02:06 AM
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Everett Wa.
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Alex,
Have you tried the inlayed gusset and scalloped former method shown in this thread.

http://www.rcgroups.com/forums/showt...=960089&page=2

Well it won't produce a Top Gun model finish. At these scales I think it produces a pleasant look and allows for a light very flyable aircraft.

Maybe some better angles.

http://www.rcgroups.com/forums/showp...2&postcount=43


All the best,
Konrad
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Old Sep 04, 2009, 03:41 AM
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Plymouth, Devon
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Thanks for clarifying that, I got mixed up between flapperons and spoilerons... Interesting idea using an iron to apply sheeting, I'll have to see if I can find some titebond over here and give it a go. I've never personally had any problems with the current draw from up to four sub-micro servos affecting an ESC, but that is something I shall certainly bear in mind. Live and learn!
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