Topic: Galaxy P51

I hope to be starting to refurbish a Galaxy P51 Mustang Stratton gave me some time ago (thanks mate it's a good starting point  ).  I will get a new glass cowl from Galaxy for it as the nose at the moment is poorly shaped balsa and as I would like to put a ZG38 in it I think a glass cowl will go round it easier than trying to fit balsa round it.
I will have to modify the fin it has a fat bottom to it at the moment but my 1st job will be to replace the fixed undercarriage with retracts.  I have 1 Robart 90 degree unit at the moment and will be picking up a 2nd next week but I can at least start to figure out how to install them.  I have only fitted 2 sets in the past both small ones and mechanical and rather than the in line with the spar fitting I would like to have them so they rake back as I believe they do in the mustang when retracted.
As far as I can see I angle them backwards to the desired rake to get the leg back in the wing in the right place then cut the mounting block so it rakes forward which will put the wheels slightly ahead of the wing when retracted and also make the wheels track straight throughout it's retraction is this correct?

I will take a picture to discribe my thoughts if that will help assuming I'm correct in thinking P51 wheels do retract slightly rearward 

Get stuck in Shaun! 

....... And I must do the same 

Alan

In other words................ HELP 

Once I get the retracts in I will look for a better 3 view on the internet so I can remove the strip ailerons and fit the correct size (ish) flaps and ailerons.  I don't intend trying to make a silk purse from a pigs ear but rather use it as a leaning aid for something better in the future.  At the moment it's covered in silver Solartex so I will pull all that off and maybe.............. but I have never done it before.................... glass it and pop a few lines and rivets on it.

From what I remember Shaun, there isn't actually a huge amount of leeway within the wing to get the retracts in any particular position to get any rake sorted.

Again, from what I remember, with lots of advice form Phil Clark they only just fit in starlight and you have to be really careful not to go through the upper wing skin.

I mounted mine onto a large ply plate as opposed to bearers to spread the load as bearers by themselves are no where near enough.

Sadly I think most of the photo's I did from that part of the build went in the great crash, but if you want any help  just holler.

Charlie C

Hi Shaun

Fitting retracts in foam wings ain't easy. In my pattern flying days we epoxied   a light ply box into the foam vertically downwards to take a pair of hard wood or birch ply rails to mount the retract units on .This worked much better than fitting a ply plate parallel to the surface. My drawing skills are poor so I can't do a quick sketch and load it but I could draw it properly and email you a scan . I had one with fixed UC, it flew well on a saito 180 which also fitted the cowl well, I sold the airframe because I didn't fancy doing what you are about to start !!The engine is still hanging about .

Alan

Thanks chaps I am rather anxious about getting these in and having them work reliably and be strong enough for my arrivals 

I mocked up a bit of tree to hold it at what I believe to be about the right angle.  The wheel tracks straight all the way from open to closed as it is and I believe there is enough meat in the wing to get it in but there wont be much left when it's all dug out.  This Gorilla glue stuff that expands............ if that a suitable glue to use I bought a bottle ages ago from Tescos to see what it was like but never used it yet.

A few snaps to give an idea of my intensions below.

They look like pukka Mustang retracts from here . You could let two vertical bits of lightply into the foam parallel to the mounting flanges going back to about 1/2 chord with mounting rails attached which will spread the landing loads over a wide area of foam

Alan

I'm not so sure Alan I just been out there aving a fag looking at it and I cant see a way of getting strength in it.  The inboard side where the cylinder is will have no strenght at all I'm not happy and may leave it for a bit I just cant see a way to make a secure job of it 
I will have to remove all the strenght from the inboard area by the oleo cut out and cylinder cut out so the ply or whatever will be hanging in the breeze.

Anyone else fitted these Robart types in a foam wing before please? 

Thanks Alan for the sketch you sent me but to put what would in affect be a rib in the foam I think I would loose to much strength in the wing, a few good G's on a bank and yank and it may fold up!
But it did make me think more and I may be able to slide the retract in from above and through the slot rather than as I was thinking having to drop down and slide back into the slot in the ply.  Worst case I will have to put a hole right through the wing and a non scale removable patch/hatch on the top surface to cover what might be a 3/4" X 1" hole necessary due to the angle the unit will have to go at to get the cylinder in.  The unit is very deep.

What do you thinki do I have them positioned about right for a non scale toy?  The wheels will have 24 1/2" between oleos when down is that a bit much?




As you can see the rest of the airframe will be neeing a tad of work to 



Almost forgot........ is a retractable tail wheel worth the effort on somehting like this non scale job?

Anyone care to comment?  I have moved the units in toward the centre a tad about 1/2" each and am about to put knife to wing so shout now if you think I'm wrong!

You carry on fella, as long as you try and spread the take off/landing load in the wing it should be fine, od course there comes a point when nothing would hold up!

As for the retracting tail wheel, it's only 'worth doing' if you think it is, it doesn't matter what anyone else thinks! If it's gonna bug you that you didn't do it  -- then do it, if not then don't!!
If you do, a robart jobby would be fine, the heavier duty plastic one that is. Don't forget that they retract forward on a stang 

Muds 

Anyone care to comment?  I have moved the units in toward the centre a tad about 1/2" each and am about to put knife to wing so shout now if you think I'm wrong!

That's  a lot of wing going to disappear Shaun.   The cantilevered pintel means an even bigger hole, normally it is in the gap between the mounting brackets.  You will need to have a good bit of  spar from outboard of and behind the retracts and maybe a corresponding load bearing leading edge running through I would have thought . You alluded to the problem earlier with your comment regarding yanking and banking.

No doubt there are plenty of other worthies hereabouts with real experience - I'm just looking at it from  "beam (ie the wing) bearing a distributed load perspective"

That's probably not the encouragement you were looking for ........ Sorry!

Alan

Sorry Shaun, but from experience which took into account a few hours of measuring, particularly with depth of wing available against the "ideal" retract position I think you will find it worthwhile moving the retract cylinder and frame away from the leading edge slightly and having a "Straight" retract, as in straight across the wing as its the only way you will get it all into the wing.

Even then, you will end up going in up to the veneer on the wheel well and very close to it in the cylinder well. I lined the bottom of said two wells with 1/64th ply.

That's the reason why the retract was mounted onto a large surface area ply plate to spread the load away from the that area.

Just my 2ps worth.

Mine only ever ad 3 landings and the first two were very hard and bouncy with no ill effects on the retract mountings. (Due to a Cof G issue I should add).

The third landing   

Charlie C

I changed my mind again before cutting as this is a not even close to scale toy:



[ Specified attachment is not available ]

I have put a couple of small bit's of tree in starting to line out what I have cut out using Gorilla glue and so far I like it...... strange stuff 

Sigh........... I wish 

<a href="http://www.youtube.com/watch?v=rAKFLTrQtxk" target="_blank">http://www.youtube.com/watch?v=rAKFLTrQtxk</a>

Whats to stop the whole wing going across a circular saw and putting in a full span, full depth spar, something like 1/4 hard balsa??
 
Couple that to a substantial leading edge and maybe even  tennon a half rib at the outer end to support the retract mount and a full length/depth aileron/flap hinge spar, that ought to put a bit of support and strength back.

I have a FW190 german kit which is also foam wings. The plan just shows a surface plate retract mount which i don't think would be any good at all. I am thinking of running the cores across the circular saw several times, inserting full depth / span spars and then putting it all back together again. I'll be interested to see where you go with yours.
stu k

Hi Stukno, I am a little concerned about the amount of meat I have removed and also how to get the ply mounting plate on the inboard side to be secure because at the moment it's hanging in the breeze but it is in hand.  I think just a couple of spars let in the wing just behind the retracts will be fine tapering off to nothing a few inches past them I'm not sure what material to use probably a bit of 2x2 cut down to 1/4" x 1/4" let in and glued with my new friend Gorilla glue.

I have cobled in 1 retract mouting ply plate and am confident it's strong enough but what a performance it was and not pretty either.   When I get the other unit I will start on the other side    I am not enjoying this refurb at all 

Look on the bright side Shaun. I'm doing a new kitchen for SWIMBO so all my projects are on hold for the winter 

Alan

I hope to be in the same boat some time next year Alan SWMBO is looking to buy a house, something tatty with plenty of land so will need lots of work and the land will need constant upkeep.

My retract install is nowhere scale but I'm getting it together to fly not win any prizes although once I get a think aluminium cover over the mouting screws area and a door attached I think it will look ok.  One day I will do my own build and can do the correct shape wheel wells and inner doors to

Hello NFg,
Interesting approach.  I think the way you ''forced'' installation of the landing gear opens up knew options for us that struggle with this part of a build.  Nice techique.
Albert

Hi Albert........ not sure there is another way of doing it TBH so nothing new here.  The one thing about the Robarts in this configuration is the massive amount of material needing removing which leaves nothing under 1 corner of the ply plate.  I have almost completed one side which is good to go but the other side you can see what I mean in them needing a BIG hole 

Don't worry Shaun,

Its what mine looked like and it all worked.

Charlie C

Hi Shaun

Looks a top job to me ,what did you use to cut the foam ? You got some nice crisp faces especially the wheel well bases, which I can't get.

Alan

Thanks Charlie I think I will still let a spar in the top of the wing.  From what I seen foam wings usually fail by compressing the top surface.

Alan I used a jig saw for the wheel wells then dug out the excess and finished the surface with a piece of 80 grit glued to a block of wood.  The rest was knifed out then finished with the same block.

If you fit a spar in the top surface, do you intend joining it to the retract plates? It'd be a strong job if you did. You could put a full depth spar in there. Thin ply spar with balsa doublers top and bottom to give area at the wing skins, with a local stiffener around the retract plates. These balsa spars should run outboard of the ply. The ply would be better with a long birdsmouth cut on the outboard ends too.

HTH

Ian.

Oh poo 

Might be a bit late to start trying to attach to the ply mounts which are 6" X 3" 1/8" ply doubled up with a further 1/" bit of ply 3" x 4 1/2" then another 2 pieces 3/4" X 3" which run along where the mounting screws go.  I wish I had designed in at the start what you are suggesting as it makes more sense 

I'm hoping I can get away with a single spar on the top wing just behind the ply plates maybe from ply or tree which will go 3/4 the way to the tip and be a taper from about 2" down to 1/4" at the tip.  I think it would be ok without anything but I do tend from time to time to yank things around in the sky a bit so a spar would help.  I am comfortable the retracts will stay in as they are I have lined most of the cut out with light ply all glued up with Gorilla.

I will take another look at it this eve or tomorrow and see if I can do it the right way but I'm off out today and wont be home till late.

Both retracts are in mostly lined out and I'm about to line out the wheel well with 1/32" ply, the disc in the bottom will have to have a slot to take the oleo other than that it looks okish and I have given everything a good yank and nothing moved, creaked etc however I have 4 boxes to let into the wing yet for aileron and flap servos 
I think that ply (1/8" ?) full or almost full depth will have to be let in and close to the rear of the retract ply mount.

The ply is in just a few more bits to tart up such as a light ali cover over where the retract mounts and I can move onto something else there is a lot to do to this Mustang to make it flyable let alone look ok.

Holy crepe I jus been looking on the Galaxy website for a glass cowl and noticed the retracts there is one set at £173.57 with no picture so no idea what they look like or the 2nd hand ones I got off Ebay http://www.galaxymodels.co.uk/detail.asp?id=25798&rootid=#lift  £357.43    Looks like my twenty quid was well spent!
I think I will order the glass cowl it will save me a lot of messing around and is £19.87 delivered.

Scaling things up from a 3 view I found on the net it appears the flap is set further into the wing than the aileron.



I'm thinking rather than do that I will put them both in the same amount in line with each other then when I cut the wing I can put in a single full length medium/hard balsa spar for them to hinge to.



Or are they actually in line on the full size and it's just the fairings that make them appear offset not that it matters I think the 2nd option is the right one for a knock about non scale Mustang.  BTW they seem HUGE!!!

Some nice details here: http://www.ipmsstockholm.org/magazine/2005/12/stuff_eng_detail_p51d_02.htm

Martin

Shaun,

When I did mine, I left the ailerons on the same rear spar/hinge line but at the correct scale width, then inset the flaps to look right. About 3 or 4 (maybe 5mm IIRC)

It was dead easy to do and would look soooooooo much better that ailerons and flaps in one continuous line.

Just my 2.99p's worth.

Charlie C

From the 3 view I have the offset should be around 20mm on this size, I will hack the trailing edge off allowing for that amount and block the ailerons out a bit to give a stagger.  There is no point in trying to make a silk purse out of this perhaps if I were starting with a new kit it would be different but I'm happy just to get it looking ok and flying.................... 1st thing to go will be the 1/4 size pilot who fills the office!

After my experience with glass and how it affected my hands and everything I wont be glass clothing this I'm thinking perhaps if it's lucky it will get diatex and Ronseal satin varnished before painting that should not upset my skin or chest as much.
I used Diatex and Cellulose clear coat on a Rafalroo which is as hard as nails a very ding proof finish on closed structure so  Ronseal will do a similar job I will do a test or 2.

Thanks Martin for that link it has depressed me seeing all that detail I wont be adding    Great pictures though which I can possible use for a larger P51 I may refurb and detail next year.

Have you tried the resin and cloth form Fighteraces 

It blurry brilliant.

Charlie C

No and it would be a huge outlay for something I potentially could not use and once on the airframe not able to rub down.

No and it would be a huge outlay for something I potentially could not use and once on the airframe not able to rub down.

I am the same, Shaun, with allergies to petrol and glass..... I use rubber gloves (very thin) and run down wet most of the time and not have any problems since

I have used nylon and dope on sheeted parts  with good results . If glass causes you problems don't use it .The only real  advantage of glass and epoxy is its glow fuel resistant, and you are using petrol . I haven't tried PU varnish does it stick like dope ?

Alan