Warbirds Replicas P51 Mustang

[Eric Robson]

Mine is still attached to the box, I forgot about it (old peoples home beckons). It fits on the front of the wing it will help you to shape the leading edge to blend in to the fuselage, 

Had some more flights with mine today the wind was a lot lighter than yesterday the 10mm difference in C of G did not seem to make any noticeable changes to flight pattern it looked great drifting in with the flaps down and gently caressing the ground as it rolled to a halt, a  shaking bundle of nerves. The plane that is not me. 

Edited April 12, 2021 by Eric Robson
added some text.

[Paul Johnson 4]

9 hours ago, Jonathan S said:

Guys another question.  The front of the wing the plate that the dowels goes into, is that attached to the leading edge or attached instead of the leading edge.  I cannot make out from Paul's photos how this part sits. 

 

Thanks 

Jon

Jon,

I will have a look at the cut files for the model, my one was different and the ply section with the location holes was too wide and high so I had to trim it to size, Richard didn't use it at all in the very first variant just a balsa leading edge.

Either option is fine. When I fitted it, after resizing, I had left off the top and bottom skins between R1 and R2 so could see what was going on.

I placed the dowels into that piece of ply, fitted it into the fuz receiving holes first then allowing for the thickness of the very thin pieces of ply used to finish the wing root.

Placed the wing centrally on the fuz and glued the dowel and ply plate into the wing directly onto the leading edge spar. Once the glue has dried remove the wing and finish dressing it etc.

 

[Trevor]

This is the corresponding pic from my build - same approach as on Paul's.

 

Trevor

More pics at: http://www.bartonhewsons.uk/home/modelflying/scale/mustangprojectdi.html

[RICHARD WILLS]

"Tidy "  as Ness would say . 

[Jonathan S]

Thanks guys.  Got the right wing flaps and aileron hinges glued in and the pins in.  Only managed to glue the gloves to the flaps once....  I really hate thin CA.  

Both long leading edges are on.  Getting there like the tortoise.  

[Phil McCavity]

I've also been toying with the idea of a retractable tailwheel and full undercarriage doors so I'm grateful for you documenting this @Trevor. ?

[Paul Johnson 4]

Guys, please be careful with the added extras as the weight will creep up rapidly, as I discovered, in my case the spinner, a work of art, added almost 200gm. + U/C door servos + tail wheel servo + bigger battery...... before long you will have a very heavy model with a high stall speed and will have an approach speed of a rocket. This in turn puts a greater stress on landing gear....

I think you get my point.

 

[Paul Johnson 4]

9 hours ago, Jonathan S said:

Thanks guys.  Got the right wing flaps and aileron hinges glued in and the pins in.  Only managed to glue the gloves to the flaps once....  I really hate thin CA.  

Both long leading edges are on.  Getting there like the tortoise.  

Jon

Your not an official model maker until you have walked around the house looking for the wife's nail varnish remover (acetone) to unstick your fingers from the wing!

And your wife adding her advice about 'if you put that down it would be easier to look....?!

[Trevor]

1 hour ago, Paul Johnson 4 said:

Guys, please be careful with the added extras as the weight will creep up rapidly,

 

Point taken Paul. That's why I felt I had to turn down the offer of the sound system. I'll also be going for a simple film finish so hopefully will be able to claw back a few ounces there. A few years ago I witnessed the total destruction of a beautifully built P51 on its maiden flight due largely to its being overweight. I don't want to see that again - especially if it's going to be my model involved this time!

[Jonathan S]

Paul,

On the weight front I am trying to be frugel with the sticky stuff where possible.  and I did not go for the sound system even though I really really want one.

Can you share what target weight etc we are aming for and any ideas how I can check if I am on track before I finish covering etc.

 

I will try and make this pretty stock i.e. Predetor 540, ali spinner, 4 blade prop and 4s3300 battery.

 

Thx as always

Jon

[Paul Johnson 4]

1 hour ago, Jonathan S said:

Paul,

On the weight front I am trying to be frugel with the sticky stuff where possible.  and I did not go for the sound system even though I really really want one.

Can you share what target weight etc we are aming for and any ideas how I can check if I am on track before I finish covering etc.

 

I will try and make this pretty stock i.e. Predetor 540, ali spinner, 4 blade prop and 4s3300 battery.

 

Thx as always

Jon

Jon,

if you look to be between 6 to 7 lbs all up it will be fine, much more and the pilot will be getting out and pushing.

If you want a sound unit you will need to put the transducer rearwards of the cockpit.

It needs a piece of depron at least 3" sq to be fitted onto a balsa frame and fixed where there is a outlet, something like the rear radiator vent I added.

I would place that piece of depron and balsa frame in place but not fit the sound system until you have flown it and gained some confidence with it before adding extra weight. 

When and if you fit one double check your CofG!!

I don't know what you use to check this but there are some good ones at a reasonable price out there and take the guessing out of it.

The 'old' hands use their fingers..... there are some fat fingers out there!

Mind you Richards Fingers are like knitting needles....

[Phil McCavity]

I don't need to worry about battery weight, I'm going IC. ?

[Paul Johnson 4]

1 hour ago, Phil McCavity said:

I don't need to worry about battery weight, I'm going IC. ?

Traitor ?

[Tim Kearsley]

I have to admit to yet another daft mistake!  Reading the posts about the front ply plate for the wing dowels, I realised that I have omitted it completely!  I ran the balsa leading edge all the way round, shaped it and drilled out for the dowels etc.  They feel very solid, but I'm thinking now ought I to cut away the balsa from around the dowels to make room to retro-fit the ply plate?  I'm beginning to think that I'm not cut out for this building lark.....

 

Other than that, progress is fairly good.  Next job I think is to either extend the battery box or build a new one, as I have the ali spinner from Richard, will be using 4S, 4000mAh batteries and have a slightly heavier motor than the FMS Predator, so I will definitely be into CG problems otherwise.

[Paul Johnson 4]

Don't panic Richard left the plate out of the first prototype and it's fine. The box extension is easy to do, again Don't worry. You'll be fine ? 

[RICHARD WILLS]

Tim , 

       Just put a little epoxy and glass cloth round the pegs where they protrude from the wing skin . 

[Eric Robson]

24 minutes ago, RICHARD WILLS said:

Tim , 

       Just put a little epoxy and glass cloth round the pegs where they protrude from the wing skin . 

I did not do that on mine and have had no problems so far. If it does work loose I will retro fit the plate as the dowels are shorter than the W.B. Spitfire. After many flights I have not dropped a wing the stall has been straight so no cartwheels to loosen the dowels. 

[Eric Robson]

Looking through the worries on c of g I think with the predator motor and a 4s 4000 you will have no problem with the balance as mine is built with the box as plan and the motor is heavier than the Predator. I do not have sound so nothing extra on the front. At this time I am flying with a 2 blade prop and no spinner I am going to mod. the ali spinner to take a 2 blade prop when I get round to it and fit a 12" prop to increase flight times. I am making use of the good weather so not much done other than flying at the moment.

[Tim Kearsley]

Thanks for the replies chaps.  I probably would have followed Richard's suggestion but I have not a scrap of glass cloth in the house!  So, after a very enjoyable morning's flying at the club, I came home enthused and set to and retro-fitted the ply plate to the front of the wing.  Once the epoxy is thoroughly hardened I will tidy it all up.  From your comments Eric I probably needn't have bothered, but I feel a bit more at ease knowing it's a bit "beefed up"

Regarding the battery box, I'm using a slightly heavier NTM Propdrive motor, so I suspect I might have CG problems if I don’t extend it.  What I might do though is wait until the model has the tail feathers in place and do a trial balance with battery, cowl, prop, spinner etc in place and see how it goes before I finally glue the box in position.  I don't want to mess about with the box if not necessary.

[Eric Robson]

Hi Tim, I have an NTM Propdrive  I had intended to use but it has a fault. It weighs 100 gram more than the Racestar I am using, so you should be ok with it. My P51 handles much better on the ground than an FMS one that a club member has. He struggles to get away on the grass without nosing over, I don't have a problem with mine so it must balance well or mine may have the wheels further forward, we as yet have not had them together to compare.

Cheers Eric.

[Trevor]

Tim, Faced with similar uncertainties about the cg, I’ve opted to make the battery box removable. It’s not difficult and I can post pictures of how I’ve done it if it would help.

 

Trevor

[David Holland 2]

Do not believe a word young Tim tells you. I was flying with him at our club field this morning and he was flying his first attempt at building, a DB Mascot, and he has made a fabulous job of it. Puts some of us old lags to shame, and it flew beautifully too.

 

David

[Tim Kearsley]

That's very kind of you David.  The Mascot did turn out fairly well and I was pleased with it as a first build.  I learned quite a bit too!  As for how it flies, well it's a beauty and a testament to Boddo's design skills.

[Tim Kearsley]

15 hours ago, Trevor said:

Tim, Faced with similar uncertainties about the cg, I’ve opted to make the battery box removable. It’s not difficult and I can post pictures of how I’ve done it if it would help.

 

Trevor

Trevor, that would be most useful, thank you.

[Trevor]

Okay. This is my first try at posting inline photos on this forum, so here goes. First, an additional 3mm ply flange or collar glued to the battery box, reinforced with triangular balsa stock:

 

Four screws through this flange into the front former secure the box

 

Then, just for peace of mind, a small countersunk screw through the rear of the box floor into a hardwood block glued to F2:

The rear extension of the box will be fitted later when the battery position is known. I’ve not yet decided whether this extension is best built into the fuselage rather than added onto the box. 
 

Hope this helps,

 

Trevor