900 Series P-51 Build

[zed211]

This is my first build and first time on this forum so let me introduce myself a little. My name is Zach, and I am 17 years old, I have a passion for aviation, and I have built some plastic models for a few years now. I went and bought this kit about a week and a half ago, making steady progress on it since I am out of school for the holidays. I just recently completed it and would like to share with everyone my work. I think it turned out pretty well for my first build... could have done better with tissue on the wings. I also decided not to do the landing gear because it was going to be a flying model, and I didn't do the cockpit up either. I have glide tested it and I weighted the nose pretty well, it has a nice glide angle, I have also wound the motor a little bit to see how it would fly, but I haven't given it a proper maiden flight yet. This was a low budget build, I used a piece of card board for a work board haha. one question though, I am using the kit rubber band but it doesnt seem like it is the best one to use, what size rubber should be used? Anyways here are some pics of the whole process.

[Mitch]

VERY NICE JOB! I think you picked a nice model for your first model. The wing, or anywhere there are compound curves are always a challenge to get on smoothly.

For rubber I would check with your LHS (local hobby shop) some will carry rubber. If they do not have it I would suggest ordering direct from SIG MFG. CO.,
SIG SPORT RUBBER 1/8 X 25 FT, is the smallest they have. I think that would be appropriate for that small plane. You will cut to length what you want. You can go as much as 1.5 times hook to peg length and 4 strands.

Good Luck, and once again, YOU DID A GRREAT JOB! Mitch

[Wildpig]

Hi Zach !
Welcome to the forum. That's a nice model you have, really. Appears to be built straight and true. The covering looks decent to me. Did you seal it with anything? Covering is as much an art as is a science.

As for rubber motors, you are correct in thinking the kit supplied rubber is .... insufficient.

Look on your plans: At the very top, middle is the suggested rubber motor size for that model. What you would do with a motor that size is double it over, so that it appears to be 4 strands. Also, you would stretch wind it for maximum flight performance. This kind of motor will need about 600 turns, I'm guessing. Meaning , you would need a winder.

However, a more simpler set up is: 1 strand of 3/16" width rubber approximately 18" long. Tie the ends together and then you could wind this motor with your finger.
Since this is your first foray into balsa models and "a low budget build", I think that will be a good starting point. No special tools or apparatus.
Lubricate the motor. Armor-all for automobiles or Dow 33.

I don't want to get long winded on an introduction but, I have to tell you something about flying these models that is critical.
I'll post it separately.

[Phugoid]

Hi from England Zach!

You have done a fine job there, well done. A really super effort for a first attempt.

Let us all know how she flies.....

Andrew

[Wildpig]

O.k. Zach, don't get offended if you already know this stuff, I''m going to assume you don't. I didn't know it when I built my first model.
Here is the techno- science to flying these models that may not be explained in the kit instructions.

It's called Trimming.
You did right with a few test glides.
*Get the model balanced properly according to the plans.
Next, you will probably need to add a trim tab on the elevator. Check out Mitch's thread with his 400 series P-51 and other WWII models. Search the forum for: trim tab
You want the model to have a shallow glide, slow glide. No pitching up and down and no rolling to the left or right, either. This may require a trim tab on the rudder or on a wing.
*Keep making test glides, preferably over tall grass, until it has a nice steady glide.
You said you have a passion for aviation.... ... so let me throw out a little bit of aerodynamics for you.

Once you have a glide set up, lets just say that it glides at 4 mph. When you wind that rubber motor and let the model go, it will want to fly at 4 mph. But,the rubber motor tries to propel the model at say...20 mph. The only way it will stay at 4 mph is in a climb. With a balsa model that is usually a very steep climb and sometimes will even do a loop. The 4 mph is known as it's trim speed. An airplane will always try to fly at it's trim speed. This principle is true for any conventional airplane, regardless of size.

The bad part is that this steep climb leads to a stall and usually the model plummets straight into the ground and then you have a very discouraged balsa modeler.
To counter this effect, just add a downthrust shim under the thrust button. Search the forum for: thrust shim.
You kind of have to guess with the amount of downthrust but, a 1/16" strip of balsa will probably be plenty. Might have to shave it a little thinner.
Questions.... comments???

[zed211]

Thanks for the great advice guys, I really appreciate it. I'm hoping to give it a maiden flight tomorrow, before that however I will add a trim tab to the elevator and rudder like Wildpig suggested. I did notice with my small test with a little power that it did tend to pitch up and down a little. I hope to get it flying nicely tomorrow. I'll keep you guys posted. To answer your question Wildpig I haven't sealed yet. What are the benefits/drawbacks to sealing it? I have read some tutorials on it. I have shrunk the tissue though.

[Wildpig]

The drawback is added weight. The main advantage is that it helps keep the tissue taut. Humidity causes tissue to sag.
I would say it's mostly an appearance thing. About half of my models do not have sealed tissue.
From the pictures it looks like you sealed it with Krylon Matte Clear or maybe Future Floor Wax... both are good to use.

[Marshdweller]

I built the same kit as my second model and yours is far better than mine. My tissue all turned out saggy or wrinkly or blotchy or some combination of all three. I've also left mine 'undecorated' and intend to see how it flies as soon as the UK's weather is more conducive to flying.

On the subject of flying, thanks Wildpig for your explanation of trimming. I've read the majority of that in other posts on the forum and elsewhere but never before as coherently explained all in one go. It now makes a lot more sense. Little snippets like that are extremely informative to newbies - and more often than not are buried in various threads as brief tangents from the main theme.

[Scott]

Your Mustang looks great,Zack.

[solumn_eagle]

Awesome job, Zack Can't wait to see more of your future builds. Keep up the good work!!

[paul]

Hey Zack, cant believe that was first build. Very nice
Will be asking you for advice in future

[john8750]

Looks great Zach.
You are in for a lot of fun.
Welcome.

[zed211]

Sorry I haven't replied guys. I've been busy with school work. The weather didn't really clear up till the beginning of this week when school started up again. I'm hoping to get an actual flight soon. I'm off to a symposium at my naval air station today however. Hopefully tomorrow I can get a real flight in.

[twospruces]

Now that I am building a 900 series typhoon, I must say I am most impressed with the 900 series so far. The thinking that went into the design is really great.

* the fuselage is very strong. I think quite a bit better than a 500 series fuselage. And, it is lighter
* the wings are very lightly built, yet there are some real improvements. For example, the landing gear being primarily wire, and with a dual wing former used to brace the wire, it should be really durable.
* Overall lightness, yet still enough detail opportunities to result in a really nice plane.

I think of all the kits I have made, the 900s are maybe the best.

[zed211]

I have some unfortunate news and good news as well. Lets start with the good news. I gave my p-51 its maiden flight today. Full power launch. I'm not sure how many turn but it was a lot. It flew great. It had a nice left turn to it. Had some pretty good flight times as well around 20 to 30 seconds. However on the last launch no more then a few seconds after launch the plane caught a huge headwind gust causing it to climb rapidly then stall and nose dive to the ground. The impact broke formers AA and A. It's not to bad though. I can just recut them and replace them along with some new stringers. All in all though it flies great with the stock motor and is pretty stable. If only it had caught the gust a little later because I feel it would have been able to recover then. To sum it all up. First guillows experience was great. What kit would you guys suggest next in the 900 series? I'm thinking about the chipmunk.