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TexasWade's Mountain Models Mustang (with retracts) build along thread

#1
I just got my kit last night and so far I've only had a chance to look through it. So far I'm very impressed! It came very well and neatly packed and is much more complete than I think any other kit I've ever had. It came with the wheels, gear wires, pushrod wires, very nice rolled plan, 33 page instruction booklet and several very nicely vacuum formed parts including canopy WITH COCKPIT, seat and pilot, radiator scoop, cowling and dummy engine. All wooden parts seems to be very nicely laser cut from top grade balsa. Really the only thing I could think of that I could possibly want would be a spinner. I'll have to take care of that later on. If anyone knows of a suitable spinner available for this plane please LET ME KNOW ;)

With all the detailed info, and the fact that even the straight stringers have been laser cut, I feel that this kit was very much designed with the beginning builder in mind. As such, I intend to follow the instruction booklet as closely as possible. Hopefully doing so will demonstrate to anyone interested in building this model at a later date that following the provided instructions will make for a simple and accurate build.

Step 1) read the manual! I'm going to resist the urge to pop all the parts out of the sheets and will instead take the time to read the instruction booklet. I'll probably even read it twice to make sure I don't miss anything or do anything out of sequence.

And today's pics showing what I see so far. All first rate looking stuff.




 

Joker 53150

Mmmmmmm, balsa.
Mentor
#2
Looking forward to your build, and I've got the builder's list updated with this thread. It'll be interesting to see the differences between your P-51 and Ranger351's, as his is getting a lot of changes from stock.
 

ranger351

Warbird Crazy!
#3
Looking forward to seeing you progress! If you have any questions just message me or write on my thread. Like Joker53150 said mines getting highly modified. I just hope it flies in the end.
 

ranger351

Warbird Crazy!
#4
Do you have the ability to weigh the fuselage when you get it built. It would be interesting to see what the difference is. Mine weight 2.25 ounces as it sits in the picture.
20161125_163920-3024x2268.jpg
 
#5
Looking good! Yep, I have a decent scale and I'll be sure to report weights as much as you like. I'll let you know when my fuse is at the same stage as yours =)
 
#6
Custom graphics ordered from Callie's! She's going to be sporting the Angel's Playmate colors. Looking through all the P-51 possibilities, I happened along the Angel's Playmate, which I thought looked great, but I was also blown away by the pilot's story. Seems he was shot down over Czechoslovakia and returned to his home base in a stolen FW 190! Here's a link in case you'd like to check out a very cool and amazing short story. http://www.rb-29.net/html/50FtrPltStory/FtrPltStory/50.01.00.htm


My major holdup so far has been getting all my details worked out before starting the build. At first I was going to use some retracts that I had squirreled away, but then after reading the instruction booklet, I decided I'd save a minor headache and just buy the ones that the plane was designed to fit. Well those are backordered and I didn't find another source immediately so I'm going back to the original plan of using what I have on hand. I actually have two that would probably do and both have some good and bad points.

The black Great Planes gear looks like the actual mechanism is a better fit in the mounting box, and it has nice up and down locks, but it operates a bit stiff and the flanges are pretty wide fore and aft. The grey Robart's 1/2A gear locks down but not up, is a little lighter and more compact vertically, but the mechanism is longer inboard to outboard. Still fits between the ribs though so I could use them. Also the mechanism operates a little smoother and the mounting flange is much smaller measured fore and aft. Pictures below show the relative fit compared to the plans. I'm kind of leaning more towards the black ones because of the up and down locks and spring coil in the gear wire, but I'm a bit worried that the flange width really is too much. Decisions decisions....




 
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Joker 53150

Mmmmmmm, balsa.
Mentor
#7
I've used mechanical retracts like that a few times, and got them from Hobby King, so you know the quality was "questionable". They took some work with a small file to clean things up, but eventually I got them to operate smoothly and lock in the full up & down positions. After playing around with the servo speed through the transmitter (Taranis goodness) I found I could make them move at a good medium speed and still lock properly. Moving too slow would let them bind, and moving at full speed from the servo made them snap too hard at the lock positions. On a lightweight plane like these I think the mechanical retracts are a good choice as they don't add a lot of weight. Getting them to both work together from one servo is often the biggest hassle as it requires some fiddling around.
 

ranger351

Warbird Crazy!
#8
The flange on the black one looks way to big! I'm thinking the gray ones might be the best bet. Let me know if i can help! Like some measurements or more pictures.

Here's some pictures of the mods I've done to fit the air retracts.

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Top of wing.

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Bottom of wing.

20161215_142924-3024x2268.jpg
Bottom of wing with skin on.

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Retracts and components fitted.
 

Turbojoe

Well-known member
#9
I really have to stop looking at the MM Mustang posts. I am NOT a warbird fan but I know from friends that this is a great kit worth owning. Next time I see a good deal on one I'll just have to cave in and snag it. Not having built the Mustang but looking at the retracts you posted I'm guessing the black retracts are GP10's? I used them in the prototype Mountain Models Firestorm. I broke one when I misjudged clearance to a berm on final approach but in normal landings they hold up well to a plane more than twice the weight of the Mustang. If you have room to use them take them apart and spend a minute or two with 600 grit paper on the trunions and you can make them operate smoother than a babies butt. As long as you get the cables run without restrictive bends you'll get positive locks and never hear any servo buzz. I really like those GP10's. I'm thinking about building another SwitchBack wing with retracts using the GP10's this time.

Joe
 
#13
I decided to go with the Great Planes gear. Opened one of the units up and worked on the little slider piece inside until it didn't drag when the linkage is pulled out to the stop. Then I reassembled it only to find that the gear has a few degrees of slop and the up and down positions. Well that's pretty unacceptable so that one is ruined, lol. On the opposite side gear I just drilled out the hole where the linkage feeds through. That let the linkage not bind up near the end of it's travel, and the gear is still nice and tight at both up and down positions. So I'd recommend drilling the hole out to about .089" or 2.26mm if you want to free up the gears without making it sloppy.

Since that one is sloppy now, I'll go with the Robart gears instead. The setup is going to be a bit more fiddly since the Robart gears don't allow for any over travel, but I think it will work out ok. The lack of an up lock doesn't seem to be much of a problem since I played around with the gear for a few minutes with one of my wheels stuck on the gear wire. The Robart's are a bit lighter too. My GP gears weighed in at 16.2g each and the Robart's at 11.4g so about a 9.6 gram total savings. And the mounting flange fits on the wing better so I don't feel too bad about using the grey ones.

My motor, esc and servos all came from the FT Spitfire which was a bit larger and heavier, and it was an easy hand launch so I expect the Mustang will be as well. Actually I'm hoping I can get it to take off from the grass but I might have to try it right after the field gets mowed! I can hand launch but would rather ROG if I can.

How many feet of artificial turf do you suppose you would need for a temporary runway for this plane? lol
 
#14
Sheeting the fuselage top got me frustrated to the point of being ready to just wad the whole thing up in a ball :( I got my pieces joined per the plan and wetted them a little bit, then put them on with rubberbands as I was supposed to but the things wouldn't make the compound curve so they stayed open at one end or the other. I did my best with it but cracked the forward sheet in the attempt. Got the crack repaired really nicely with super glue and took both sheets off to make another run at forming them. Second time I soaked them good and got them back on with the rubberbands and it was starting to look a lot better. After everything was nice and dry I took the sheets off again preparing to do the final trim and fit. With the sheets off I could see that several of my top fuselage formers had buckled a bit, which no doubt is what helped the ends close up nice on the last wet fit. So I straightened out the formers and hardened them with some superglue which seemed to work ok. Then after all that straightened out I tried to fit the sheets again but it seems like they shrunk from the water??? Well whatever happened, they don't cover all the way from side to side and I split the aft sheet while trying to pull it down to the stringers on both sides. THAT was when I had to put it away for a while.

I think I have an alternate plan though. I'm thinking I'll cut some 1/16 balsa I have into strips and plank the top of the fuse with narrow strips instead of trying to do it with a one piece sheet. I planked a boat hull with strips like that once and it was pretty easy. Just put one on each side and one in the middle first, then lay more in between, sanding the ends of each strip to a bit of a taper so so the compound curves all work. Also planking with 1/16 balsa instead of the supplied 1/32 sheet will allow for some final contour sanding after the planking is complete. I think I'll like the results better as I could see a bit of that "starved horse" look in my sheeting and I don't really like that look.
 
#15
I think the strips will do the job nicely and I totally agree on having a little meat left on the bone for sanding. The 1/32 sheeting is too thin in my opinion to give a nice finish without filling low spots.
 

Joker 53150

Mmmmmmm, balsa.
Mentor
#16
That should work fine. Remember that the narrower the plank, the smoother the curve. When I plank it's normally a complete grab-bag mixture of anything from 1/8" or less widths to full-width sheet, depending on the curve I'm planking over. Once you plank it, rough-sand it and then cover it all with balsa filler or lightweight spackle (the lightweight stuff, not the heavy stuff) and finish sand. I normally thin my filler with a LITTLE bit of water.

Just a growing pain that's not uncommon with balsa. Find a problem, fix a problem, move on, repeat!
 
#17
Yeah, I'll try that. I already have the lightweight filler that I used on the last plane I built. But since that one is a .25 glow powered classic pattern plane, it wasn't nearly as dainty. That one came out really nicely smooth and straight, but it's built with 3/16" sides and a 3/8" top block! There was actually enough wood on that one that I mostly carved it to shape before getting out the sanding block, lol.

But I really appreciate the construction of the MM Mustang. It feels very stiff for it's weight so far but building it requires a much lighter touch!
 

ranger351

Warbird Crazy!
#18
Yes the top sheets are frustrating! I had a similar experience. After removing the rubber bands I had to fix a damaged former and yes the sheet seemed to shrink. But here's what I did. I started gluing the sheet on one side curving and gluing it over the formers to the opposite side.This left about 3/8"gap on the opposites side to be filled. So then i took the left over balsa that the sheeting is cut from and cut strips about 1/4" wide and glued them to the sheeting horizontally between the formers. This gave me a backing to glue another piece of scrap that I cut and fit to finish off the sheeting. Then I took light weight balsa filler and filled in the seam. I did get a bit of a starved horse look on mine but was able to remove most of it with balsa filler and primer as I plan to paint my whole plane and not cover it with solite.
 
#19
OKAY! I broke a few of the diagonal braces with all the handling and tape stretching while getting the planking lined up, but I was able to overcome the urges to throw it all on the floor and stomp it flat, lol...


Here are a couple pics showing my successful planking process, and one of the completed and fully repaired fuse along with the discarded top sheets.







I still have some final sanding to do on the planking but the roughed in shape looks great so far. And I'm very impressed at the weight at this stage at only 1.5 oz or 42.5 grams. Seems very light to me!


On to the wing next and looking forward to a bit smoother construction process without all the sheeted compound contours. :black_eyed:
 
#20
Graphics arrived today! Thanks to ranger351 for the inspiration to do a bit more than the basic silver with black and white stripes that I probably would have done otherwise. The graphics look great, can't wait to see them on the plane =)