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Old Feb 07, 2013, 04:24 PM
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Build Log
Guillows P-40 RC conversion

So I have gone out and started building the Guillows P-40 Kittyhawk and converting it into a RC version and found there is not many threads or hints on how to build this model and the instructions that come with the kit are not very detailed.
This is my first build from scratch so still learning.
I have found Redtacos thread has been very helpful and thank you for putting in the time to upload all your experience in building your model.

So far I have only done the fuselage , rudder and elevator and been holding off building the wings as I am planning on putting in retracts.
I just hope that it wont make the plane too heavy.

Here is a list of the items I will be using in my model

Motor

http://www.hobbyking.com/hobbyking/s...idProduct=8614

Prop

http://www.hobbyking.com/hobbyking/s...idProduct=8092

ESC

http://www.hobbyking.com/hobbyking/s...idProduct=2161

Servos

http://www.hobbyking.com/hobbyking/s...?idProduct=663

Retracts

http://www.hobbyking.com/hobbyking/s...dProduct=17539

Model Pilot

http://www.hobbyking.com/hobbyking/s...dProduct=22789

Battery
http://www.hobbyking.com/hobbyking/s...arehouse_.html

I ordered all this stuff from HK and they are really good at getting the stuff out really quick the only thing is that I got caught out with Tax and UK duties as I paid over $50 for postage then had to pay the shipping company another $40 as it was coming into the EU.

Any comments or suggestions would be welcome as i am just working of my little experience in repairing my ARTF models and scowring the net for hints from other people.
I am hoping that my build log will give other people the same help that i have got from people posting their experience
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Old Feb 07, 2013, 04:34 PM
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So I started with the fuselage building it like the instructions advise to do without any mods
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Old Feb 07, 2013, 04:49 PM
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I did make the rudder and elevator with the pieces that came with the kit and place a solid piece of balsa in the middle and did a pretty good job with it but the thought i wanted them to be a little thicker so I could shape them better and save on sheeting it which would probably have made it the same thickness
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Old Feb 07, 2013, 04:53 PM
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I received all my gear from HK so I started thinking of where the best position for the servos would be, I was thinking of putting them in the cockpit area but that would have left me no room for my pilot or easy access.
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Old Feb 07, 2013, 05:01 PM
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I then used the piano wire that came with the kit and drilled holes in the last former to to give it some support. and started at thinking of how I could add a steerable tail wheel.
I used the method that Redtaco used. I bent a piece of wire and used solder to make the a loop and a stopper. I then used a plastic tube to attach it to the rudder pushrod
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Old Feb 07, 2013, 05:07 PM
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I have now started the sheeting of the fuselage this I found kinda easy so far. I used gorilla glue as i think its kinda lite and will hold the sheeting down.
the only thing is i might struggle with the final sections of sheeting
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Old Feb 08, 2013, 09:24 AM
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Australia, WA, Warwick
Joined Jul 2003
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Looking good there Flyboy.

Have a look on this thread, there people who've gone before you can help.
If you have a question, go on to their thread or PM them - they'd love to help you.
http://www.rcgroups.com/forums/showthread.php?t=827861

I'll also post this thread there so you will get a big audience who will be able to give advice.


- Phil
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Old Feb 08, 2013, 04:02 PM
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Thanks for the comment Smokin.
I do have a question do you think the battery I am using is to big I went for that 1 cause I wanted to get about 15 min flight times. Should I maybe get an 850mh or a 450mha
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Old Feb 08, 2013, 04:52 PM
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Well, you may need it for nose weight. At first glance though, it does look a little oversize. A word of caution - these little guys need to be really light to fly well. I mean really light. Your beautiful steerable tailwheel can't be faulted for workmanship, but those wire pushrods and the plan to use retracts worry me a bit as far as weight goes. Same with the fully sheeted tail surfaces and using Gorilla glue. It's heavy stuff. Thin CA or yellow wood glue used sparingly is much lighter. And Gorilla glue can be nasty stuff to sand. The Guillow's kits can be successfully converted, but all too often the cool picture on the box traps new builders into thinking that a good flying easy building model lies within the box. Unfortunately, that's not always the case. I'm not trying to be discouraging, just offering some hard learned advice!
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Old Feb 08, 2013, 05:31 PM
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Thanks for the advice von. I appreciate the comments I have been trying to keep it light. I have been following Redtacos build and using Smoking beaver weight guide to try and keep it all lite. As for the Gorrilla glue i know what your saying it is nasty stuff and i am thinking of just using wood glue for the rest of my sheeting. Also I have bee sanding it down alot cause i was going to cover it in lite cloth. That is 1 thing I have been deliberating with myself if I should use cloth and resin and sanding it down loads or using tissue and dope but not sure which will give me the best finish. I f I go by the fact that Smokinbeaver used solorfilm which is kinda on the heavy side I am think what I want to use will be the same weight. As for the retract they come in at 27g each or 2oz for both and I think i need to aim for a weight of about 8oz so I am going to be on the limit with the weight.
Also I agree with you on the kit it does give the impression that it can be a good model and the instructions are not the best I have not really looked to much at them and just using the forum as a guide and winging it
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Old Feb 08, 2013, 07:09 PM
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Hey Flyboy,

Nice start. This is one of the Guillows models I haven't converted. Tissue and dope over your sheeting will give the finish you want along with the light weight you'll need. Good luck and keep posting.

Steve
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Old Feb 08, 2013, 07:11 PM
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OK, just had a read through your proposed gear list and details of your build.
As von Jaersky has said, the tail will dictate what happens at the front of the model and the flight envelope available to you is dependent on the weight you use their to get the CG right.

So, a technical assessment of your gear? I'll give it a go.


Motor Kv appears on the low side but prop is a 7x4x 3blade I can see the de-rating calculation has been applied.
I see it is rated at 6 amps max and is suited for indoor models which is appropriate.
If one works on a 100Watt per pound calculation ( the electric scale modellers rule-of-thumb) you would get from this motor at launch (8 volts x 6 amps) 48 watts. Your models All Up Flying Weight (AUFW) needs to be 8 oz. You could probably get away with 10oz but more will significantly diminish flyability.

Prop MAS 3Bwill need some rpm, to me I think the low pitch and the low rpm that you will get, combined with the weight of your model would give it a narrow flight envelope at a low speed. MAS props are not raved about in the hobby and I have used 6x3x3B which needed a lot more rpm to get the same results as (technically equivalent) 2 blade props.
I have not yet risked one on a balsa model as I can't get comfortable about them.
So you can get it balanced correctly, assuming the stock items is balanced, you will need a 3 blade spinner = weight

ESC Looks fine, set it in airflow in the radiator section of the plane as this type has no heat-sink in it.

servos Good choice - these are my servo of choice for reliability

retracts - Interesting and worth looking at but come with a big weight penalty. Again if you can fly a model this size well you will be OK. they add weight, weight = speed to maintain flight. Landing will need to be quick and slick. It will likely nose over on grass due to the amount of weight up front.
Also - check the pivot point of the leg, the mechanism of the retract servo may actually require the pivot point to go near or behind the CG line = fail

pilot Not scale but nice looking. Will add weight aft of the CG = not good

battery Weight would be useful but 2S might be too under powered. I'll come back to this later.

Airframe OK - a critical mod needed before you go any further.
You need to drop the LE of the wing at the saddle joint to the airframe by 3mm and lift the TE by 2mm. Basically the flat bottom section of the main wing needs to be parallel to the horizontal stabilizer. If not the plane will zoom and loop and behave badly. It was designed for free flight - to glide back to earth after rapidly gaining height under power. You are providing power so it will behave as it was designed and trying to find that level flight 'sweet spot' will be quite hard.

Wings - make sure you sand into the LE, a nice long curve for the entry point. Flat bottomed airfoils have limited applications in RC scale.
making a rounded edge will give better flight envelope. Not super critical but just an tip which costs nothing to do.

Covering - I'd go tissue/dope as opposed to glass. I'm not a big user of glass as i don't see it's advantages in models this size. I use film covering as it is quick and if done right adds a lot of strength tot he frame.
But each to his own.

Summary
In all honesty, I'd look at dropping the MAS 3B prop, go to a smaller diameter lighter weight prop (say a GWS 7035) and get a 3S battery of the same weigtht as the one you have.

What you have will probably fly but you need to sacrifice what appears to be a lot of weight in your plan.

My $0.10c worth anyway. Enjoy the fun of building it and flying.
- Phil
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Old Feb 09, 2013, 06:07 PM
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Thanks for all the advice Phil
I was really struggling to find the rite motor and still very confused with electric flight as all of my models have always been IC. I was originally going to put a cox Black widow into this model but steered away from that idea cause of a fuel issue its becoming harder to find 1/2a fuel with a good castor oil mix.
As for the prop its the same 1 from Redtacos build and that is why I went for it, I did just in case purchase some other props which are theses:
http://www.hobbyking.com/hobbyking/s...dProduct=25457
do you think they are any better.
The other thing is that Redtaco used a 1300KV motor so I went slightly higher to compensate for the retracts I was putting in.
I took your advice and adjusted the airframe as you said I did think when I was reading your build guide why were you doing that and you didn't really give a reason so thought it was really to do with the fact you were sheeting the wings.
The tails section is not covered I made them from a solid piece of 3mm balsa sheet and sanded them down and the the ones that came with the model came in at 8 grams at my modded ones come in at 10g with the piano wire.
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Old Feb 09, 2013, 06:18 PM
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So an update on the build.
I took Smokinbeavers advice and did the adjustment to the airframe which took a bit of brainstorming to not have to cut the frame up and make a mess of the mistake that I had done.
I have started sheeting the other side of the fuselage and now using tacky PVA glue.
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