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Old Nov 10, 2005, 06:26 PM
Carl
Michnet76's Avatar
Riverland, South Australia
Joined Nov 2004
594 Posts
Another GWS P51D Build Thread - wth Flaps, Retracts and Film covering though!

Hello to all foamie fans...

I recently aquired a GWS P51D Mustang kit from a fellow flying buddy in exchange for my UltraFly Extra 300S which see's little airtime. The E300S had the U/Fly brushless motor and gearbox setup which I kept for this P51, that motor combo along with a decent 3S lipo would pull around 20A but when she was pointed vertical and given WOT it would gain speed as it climbed!! The E300S weighed just over 700g AUW too! So should be ample power for a P51. I'm expecting AUW of this project to come to nearly 700g as well, with film covering and 5 servos.

Anyway, the P51 kit I've aquired has already had the fuz joined together and has a few little dings here and there. So not being a big rush to build a bird to fly I figure I might take my time with this one and do her up nice and scale like.

I recently built an Ace Simple Ultimate glow plane which had a ply/balsa slab fuz with EPS foam wings. The foam wings where strapped with fibreglass tape and covered with film. I thought that was a great idea and was fairly simple to do yet added alot of strength to the wing while keeping it relatively flexible and looked great!! I also remember reading an article a while back from a US magazine about where the writer covered a GWS Formosa... so I dug the magazine up and studying up on his techniques will I've started to employ with this P51. The film I'll probably use will be oracover/profilm chrome, granted it is heavier but much stronger. I'll experiment more with some scrap EPS to get temp settings right, but should look nice in a chrome/aluminium finish!

As a part of the aquisition deal I got some GWS retracts - the black ones which I've only just found out reading through some threads here aren't the ideal ones, but hey, I'll work with what I got for now. I'm not intending to land on them all too often as I fly on grass with an access road along side which I used to ROG off of, so I'll probably end up belly landing on the grass most of the time.

So I figured whilst going to the extent of covering this P51 and adding retracts I may as well go the full monty and do the flaps as well.

So without further a-do I'll start on the building...

First job is to start cutting away at the retract wheel wells. I chose to use Drubo treaded rubber wheels for scale looks, means I will have to have deep wheel wells but the wing is thick enough for it, I'll add some reinforcing rods to help make up for all the missing foam afterwards. Tool of choice for the foam gouging is a cheap rippoff dremel cordless thingy. Bit of a rough job but will do the job! I might get energetic later and tidy it up with filler and sandpaper!





Wheels only there to test positioning. That's one side done, now to finish hacking the other side away and dig out the servo stuff...






Next is to get the sanding pads out and start sanding off those renound mould marks and all the dimples that characterise these foamies. I've only done the wing at this stage, the fuse can wait till the wings are finished and ready for covering. Then I filled up the mould injection marks with foam filler...



Next to turn the wing over and fill in those contraversial panel indents!



Then back out with a medium sanding pad and sand all the filler flush with the foam. Can certainly see that it's a much smoother surface already. Next step after I've sorted out how I'm going to handle the aileron/flap linkages I'll water down some filler and coat the whole wing and sand back to a perfectly smooth finish ready for covering.
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Old Nov 10, 2005, 06:46 PM
Carl
Michnet76's Avatar
Riverland, South Australia
Joined Nov 2004
594 Posts
I spend alot of time thinking of how to do the aileron/flap setup. I didn't want to go dual aileron servo's in the wings so I thought I'd go for a pull/pull setup - run a tube through the wing and fit control horns on the ailerons. Then I'll use the original torque rod setup for the flaps... I'll gouge out the aileron servo hole in the centre of the wing so I can fit two servo's in there, one for flaps, other for ailerons. The setup doesn't seem to bing much which is good... no where near as much as the torque rods binded on my GWS F4U with single servo setup!!



That tubing will be glued into the slot BTW.



Once the tube is glued into place, I'll use filler over the top and you wouldn't even know it's there!

That's as far as I've got so far... will work on it further over this weekend and post progress as I go.
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Old Nov 13, 2005, 04:35 PM
Carl
Michnet76's Avatar
Riverland, South Australia
Joined Nov 2004
594 Posts
Well, got a bit done this weekend...

Next job on the list, finalise the aileron linkage setup - so out with the epoxy to to commit the modifications. Also glued in the bamboo reinforcing rod.



Then once the epoxy was cured enough it's time to trim the edges and smuther in filler...



On the top side I also had to increase the central servo hole size so I can fit two servo's - 1 for ailrons and the rearward one for the flaps.

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Old Nov 13, 2005, 05:02 PM
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Vancouver, British Columbia
Joined Mar 2004
1,165 Posts
Why did you change the alerion system to useing pushrods and tubes? The stock, single servo system works perfectly well.
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Old Nov 13, 2005, 05:04 PM
Carl
Michnet76's Avatar
Riverland, South Australia
Joined Nov 2004
594 Posts
Once I was happy all the major dings, imperfections and other holes where filled in it's time for the final filler step. I thinned down some foam filler with water till it was a nice creamy consistency and then brushed it on over the whole wing, making sure to work it into the foam so it'll fill in all those little holes between the foam beads. This coating doesn't have to be all the neat or thinned out too much as it sands off pretty easily. Also had to get a skewer point and go around the aileron moulding edges to keep it clear from filler.





Couple hours of waiting for that to dry hard and it's time to hit it with the fine sandpaper to get a nice smooth finish ready for film covering.

Next step with the wings is to cut out the control surfaces and put some fibreglass strapping tape lengthways over the wing top and bottom and reinforce the centre part, might even run some glass tape over the leading edge of the wing, I'll have to see how much this tape weights first!
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Old Nov 13, 2005, 05:12 PM
Carl
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Riverland, South Australia
Joined Nov 2004
594 Posts
Quote:
Originally Posted by David Winter
Why did you change the alerion system to useing pushrods and tubes? The stock, single servo system works perfectly well.
Hi David.

I've done the aileron system this way cause I want to have flaps as well, therefore the torque rod system will get in the way of the flap hinge area. I initially thought of running two torque rod systems but I rekon that'll weaken the rear of the wing too much, so gone with this way of doing in.
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Old Nov 13, 2005, 05:22 PM
Carl
Michnet76's Avatar
Riverland, South Australia
Joined Nov 2004
594 Posts
Whilst waiting for the brushed on fill on the wing to dry I started sanding away at the fuz which was already joined together when I got the kit.




After sanding I proceeded with filling in the panel lines...



I'm still undecided on how I'm going to setup the tail wheel. Whether to go with the stock tail wheel under the tail rudder or to try and go more scale and have it further down the fuz near the belly bulge... although the full scale p51 has the tail wheel retract, but I rekon it'll still look better with it forward there. I could probably set it up similar to how the GWS F4U has it setup with the tubing through fuse but then have control setup similar to a nose wheel setup on a trike. Will think it through more... any ideas are appreciated!!
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Old Nov 13, 2005, 05:53 PM
Registered User
Crossville, TN
Joined Dec 2004
2,907 Posts
The GWS P-51 is a very well behaved plane with a BP 21 at 14.5oz....
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Old Nov 14, 2005, 03:14 PM
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Aiken, South Carolina, United States
Joined Apr 2004
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looks great!
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Old Nov 14, 2005, 04:02 PM
Carl
Michnet76's Avatar
Riverland, South Australia
Joined Nov 2004
594 Posts
Thanks TooSlow... I've got a busy week this week so probably won't get alot done. Would like to get the ailerons and flaps cut out of the wing though and get it all ready for covering. I 'thought' I had ordered chrome oracover (aka profilm) and the package rocked up yesterday with a roll of silver monokote along with some other films to fix up a glowie. Needless to say I wasn't happy - I made the order over the phone and was sure the guy said it was profilm chrome! Monokote isn't going to be suitable so I'll stash that away for another project one day... I havn't been happy with the service from that hobby shop so I've ordered online some silver oracover from another hobby shop who have been a bit more reliable in sending what I actually order. Problem is it's coming from interstate therefore probably won't be here before this next weekend which is when I was hoping to start covering. Such is life!

I've decided to go silver instead of the shiny chrome/aluminium because after seeing some pics of a mustang in chrome I thought it looked too reflective and by the time it's in the air and flying around it would be quite easy to loose orientation given that it'll be relfecting the sky and ground and will be nicely camoflaged againts any background!
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Old Nov 15, 2005, 08:45 AM
Got Speed?
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Aiken, South Carolina, United States
Joined Apr 2004
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looking forward to the aileron,flap setup and very interested in the covering. How much weight do you think the covering will add?
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Old Nov 15, 2005, 09:31 AM
Excellence is Expected
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Aurora, Colorado
Joined Nov 2005
3,736 Posts
I am not familar with this particular covering, but my guess, and it's only a guess is to 2.0 + oz.
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Old Nov 15, 2005, 09:34 AM
Excellence is Expected
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Aurora, Colorado
Joined Nov 2005
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Quote:
Originally Posted by Michnet76
I've decided to go silver instead of the shiny chrome/aluminium because after seeing some pics of a mustang in chrome I thought it looked too reflective and by the time it's in the air and flying around it would be quite easy to loose orientation given that it'll be relfecting the sky and ground and will be nicely camoflaged againts any background!

Yes, I have a chrome Scat Cat that is hard to see. Yellow, surprisingly, is also hard to see sometimes.
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Old Nov 15, 2005, 04:32 PM
Carl
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Riverland, South Australia
Joined Nov 2004
594 Posts
Well looks like I can't get ahold of silver profilm/oracover from this other shop I tried to order from - out of stock!! argh! So last night I ordered from yet another retailer based over if Perth, WA some silver solarfilm! But now I'm definatly not holding out to it's arrive before this weekend! But I suppose that'll give me more time to do a better job on what needs to be done prior to covering.

Solarfilm is lighter again than profilm (I think) and requires even less heat to apply... Solarfillm was my initial choice of use but no one seemed to have it in stock, but this other place I ordered from last night will hopefully have some, well their website said they did have stock, but goodness knows how often they update those kinds of details.

I've been reading on other threads here that covering with a lightweight film such as econokote or solarfilm is roughly the same weight as painting a bare foam model... but this P51 was already painted, plus I've added a significant amount of filler (lightweight foam type), but I have sanded a majority of the old paint off, so I'm guessing maybe 50-100g of additional weight. I'm also adding 2 extra servos (5g & 8g servos) plus retract setup... so I'm hoping she'll turn out to around 650g and no more than 700g, I think over 700g and the wing loading will start getting too high. I could imagine at 700g she'll be flying like a pylon bird!! But flaps should go a long way in helping to slow her down for landing.

I am also considering hacking up the foam a bit more to create 'lightening holes' specially on the rear fuse and tail feathers... which ought to limit any need to add dead weight to the nose to obtain CG considering the fact that the film ought to add some strength along with strapping the wings and along the fuz with fibreglass tape. Tail feathers could receive the same treatment. My old F4U (the bird I learnt to fly on) had numerours crashes, mainly cause I was starting to get cocky and do some stupid stuff and all the damage was from the trailing edge of the wing and up to the motor... snapped the fuse in half a few times, the wings in half etc... the rear of the fuz and tailfeathers were hardly touched.

Any thoughts?
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Old Nov 16, 2005, 07:41 AM
Got Speed?
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Aiken, South Carolina, United States
Joined Apr 2004
247 Posts
put some fiber glass tape on the inside of the fuse. one piece down the lenght on each side will help.
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