Galaxy Mustang P51D 1/6 Semi -Scale

[Jon H]

I had a similar experience with them and have given up hope so i would suggest looking elsewhere.

If memory serves me 85 degree units are the right ones to go for and should account for the dihedral.

While i have never used them myself i have seen them up close and was impressed with the Premier UK retracts. Prices arent cheap but they did look really good so its likely to be well worth it.

I suggest you call/email them and explain what you have and let them advise what you need. I would budget for around £250 for a decent set of gear and oleos

**LINK**

[Paul Coxon]

Thanks Jon,

A result !

Phoned them this afternoon and spoke to Paul of Kingfisher Aviation who I think own Premier UK Retracts.

I got through immediately and had a great conversation with him, he clearly knows his business and was able to advise me fully. It's always refreshing to speak to someone who clearly wants to help.

Paul's going to fully research the Galaxy Mustang and check whether it needs a 85 or 83 degree retract, the oleo length etc and all the other requirements, since there are no details in the plans or instructions for the kit that I could give him, apart from the wheel diameter and the fact that the wings are foam.

He promised to get me a quote within a couple of days.

Rough quote for gear, oleos and all the pneumatic stuff all up was a lot more than £250, ouch ! But as you say it's likely to be worth it, at least the service is so far.

Cheers

Paul

[Jon H]

I can measure my oleos if you like? i still have them left over from my old model as they will come in handy one day!

[Paul Coxon]

Thanks Jon, it certainly won't hurt if you can locate them, but is the length of the oleo going to be the same across all types of retract ?
Cheers
Paul

[Jon H]

it will be the same within 10mm or so

[Paul Coxon]

During January I've progressed the fuselage to the point where the instructions tell me to start the wing. I've progressed the wing a bit but are now faced with choices (see photos below) I can either glue in position at the front inboard section of the wing 2 pairs of split blocks or 2 single blocks (shown sitting on the wing) the split pairs have a more forward profile where they meet the fuselage. Which ones do I use ? Also should I continue before my pneumatic retracts arrive in a couple of weeks time ? Getting stuck now so any advice would be gratefully received. Cheers Paul

Edited By Paul Coxon on 05/02/2017 15:17:46

[Paul Coxon]

I've uploaded 2 photos of the wing but can't find the camera icon to insert the photos into the post, help !
Paul

[Denis Watkins]

There you go Paul

[Paul Coxon]

Thanks Denis,
You're a star !
Cheers
Paul

[Jon H]

I'm not sure I understand the question and the photos are kinda small so its hard to see the problem

[Ken Lighten]

I think they may be supplied so you have a choice for which model Mustang you are building, I think there was differences in planform at the inboard leading edge

Ken

[Paul Coxon]

Hi Jon and Ken,
Thanks for you're replies.
Good point Ken, I hadn't thought that they might be catering for 2 wing plans. That makes me think it's the 2 pairs I need which will give a curved line forward from the leading edge to the fuselage.
Jon, Sorry, original uploaded photos and fine but you can't seem to do anything with the inserted ones. Have a look in the album ones which aren't blurred and can be re-sized. If you look at the 2nd photo you can see 2 pairs of blocks laid in front of the wing and 2 solid blocks sitting on top of the wing. Question is which ones do I use ? I think Ken's on to something but before epoxying I want to be sure.
Separate question relates to retracts.
Do I fit the blocks referred to above and continue to build the wing or do I fit the retracts into the blocks before fitting the blocks to the wing ?
Cheers
Paul

[Paul Coxon]

1st photo shows the underside of the wing with just the 2 pairs of blocks. Each pair placed together and laid in front of where they need fixing.

[Denis Watkins]

Trying again Paul

[Paul Coxon]

Wow, that's more like it Denis, hopefully Jon and others will be able to understand the question now
Cheers
Paul

[Jon H]

yea I am with you now. the blocky ones are just the bits left over from cutting out the leading edge. you need to use the pointy ones irrespective of which flavour of mustang you intend to make.

I would probably get the foam bits of the wing done and then add the retracts after as you may need to put spars into that section of foam.

This brings in neatly on to retract mounts and I recommend you go all out to make them as strong as you can. my suggestion is to cut out the mount area so you have a hole right through the wing. you can then fit spars fore/aft and then box it in. Your mounting plate then sits in the middle. As the gear sits really close to the leading edge on the p51 I suggest you glue a 1/8 ply leading edge to the triangular part of the wing and where it meets the straight section continue it into the wing by making a cut into the straight section. not only will this beef up the gear but also help hold the wing together.

I have added a photo below showing the retract boxes I did recently on my hurricane. Hopefully you get the idea

[Paul Coxon]

Brilliant Jon,

Just the definitive advice I was looking for !

I've ordered the Premium UK retracts,
I scaled the oleos off the plan at 170mm and increased them by 5mm to 175mm on the basis that you can always shorten them and you had said previously 10mm either way was fine

I'll get on with glueing in the blocks now, then move onto the tail whilst I await the arrival of the retracts. In the meantime I'll try and find some 1/8 ply, either 3 or 4mm when I'm in Bordeaux later this week. There's an RC shop there, currently unvisited by me.

Cheers

Paul

Edited By Paul Coxon on 06/02/2017 08:03:09

[Jon H]

Sounds good Paul.

I did a quick sketch up to show what im on about with the spars. The yellow is the balsa leading edge and the orange is where i think you should put the ply spars. You may need to move the u/c back a smidge to get it in but you can compensate with a steeper rake forward to prevent noseover.

Hope it helps

[Paul Coxon]

That helps a lot Jon, thank you. Particularly seeing the spar position in the wing and the fact that the raked part of the leading edge is ply AND balsa. Will this move the leading edge forward an 1/8 or do I cut 1/8 off the balsa to compensate ?
Cheers

Paul

[Jon H]

The ply added to the leading edge is my recommended modification and is not part of the kit so dont expect to see it on the plans. As its only 1/8 inch, you could easily just stick it behind the balsa leading edge and not worry about it.

Also that rear spar can be longer if you like. Without a plan in front of me its hard to visualise where everything will go. The objective here is to spread the load from the u/c as widely as you can, and with that leading edge piece you are putting some of that load into the fuselage directly and not into the wing.

Even with all of this you will still need to land well to prevent damage. The key is not so much the rate of decent but the angle at which you hit the ground. You want to have the model level at the absolute minimum but nose up is ideal as then the impact goes up the leg and is absorbed by the spring. If you are beyond a certain angle (nose down) the entire load is a rearward one and nothing will stop that pulling the unit out of the wing. Just watch a few warbird videos on your tube and you will see clearly.

[Paul Coxon]

Thanks again Jon, all clearly understood.

Pairs are now shaped, glued together and will be glued to the main wing this morning.

Retracts will be despatched from Premier UK retracts later this week, so hopefully will arrive in France some time next week.

So progress on wing will stop until they arrive and until I source the ply.

Bring on the tail !

Cheers

Paul

[Paul Coxon]

Firstly I've just discovered why I was unable to present photos in the reply box before !

Normally I use my smartphone to access the forum and I doesn't give you any icons to select.

This morning I'm using my laptop and all the icons including the camera are there !

Solution is a) Make the forum phone friendly or b) use a computer if you plan to present a photo.

Regards to all

Paul

[Paul Coxon]

Now on to the serious stuff, my Galaxy Mustang wing !

Well the 2 pairs of blocks have been epoxied into the wing and I've put the wing aside until the retracts arrive, I'm guessing at the end of next week.

In the mean time my thoughts have moved on to servos and leads within the wing and pneumatic tubes as well !

The penny has just dropped that I have foam wings, a first for me and that there is absolutely no guidance within the plans or instructions as to what I must do.

To add to this, I had the kit supplied with the wing and parts cut for flaps, flaps are an option but there are no instructions and the guy who did the cutting probably rightly assumed I knew what I was doing, so frightened of making a horrible mistake I've come back to the forum for advice.

In the wing I'm planning to install 2 servos for flaps, 2 servos for ailerons and various tubes for retracts, wires to operate them and a pressure vessel somewhere.

Question is:

Do I surface mount all of these wires ? I guess not since it would look horrible.

Do I build a duct on the underside of the wing ?

Do I cut slots through the wing covering ? I'm guessing this would weaken the wing !

Do I push rods through the wing and thread the servo leads through ?

Do I cut slots in the foam along the leading or trailing edges before gluing the edges on and create ducts back to the servos ?

I went flying yesterday, first time this year, which went very well, but when I mentioned my dilemma to a Dutch friend at the field, who speaks good English, he took a deep breath and showed his concern that I had already joined the wing panels together !

He did add however, that this was one of the reasons he didn't like foam, which made me think he's probably biased against finding a good solution.

I'm pleased to say I haven't added wing tips, or leading or trailing edges yet, so all is not lost. Neither have I added additional ply spars and leading edges yet, as recommended by Jon at Laser, waiting as I am for my retracts !

I'm hoping there will be a number of you, not necessarily Galaxy Mustang builders, who seem to be few and far between, who have confronted this problem with other foam wing models.

What is the best tried and tested solution please, given also that I assume it may be necessary to repair or remove leads and tubes at some time in the future !

Cheers

Paul

[Paul Jefferies]

For what it's worth, I built a Galaxy Mustang many years ago and it lasted precisely one flight...... I builds into a very nice model and seemed to fly very nicely until it suffered Elevator flutter on it's first flight and that was the end of that! I immediately throttled back but elevator control had been lost and it just continued in a shallow dive into the ground. I had used a bigger, more powerful servo for the elevators but in the subsequent inquiry I discovered that the flutter had caused the servo arm to break. I don't know if other people have had a flutter problem with this model but as an "anti-flutter" measure I suggest that you leave the trailing edge of the elevators at least 1/8" thick, possibly thicker, use a good stiff pushrod and make absolutely sure there is no play in the system. Also, I discovered that there was a bubble in the servo arm moulding which had caused it to break at that point so now I only used disc outputs on controls that could come under high load. OK, I had an unfortunate combination of circumstances but...... for-warned is for-armed.

[Jon H]

Hi Paul

Cable runs/servos in foam wings are dead easy and i do them very late in the day. After leading/trailing edges etc are long since forgotten. You need your control surfaces finished and temporarily attached with hinges as well so you know where the servo needs to go. 

So with that in mind, you mark out where your servo boxes will go with a pencil onto the wing surface. make sure you draw on the right side of the wing and that the servo boxes are big enough for your chosen servo. i recommend you make the measurements even numbers as its easier down the road.

Now you have the box size sorted, add 1/2 all the way around to make a bigger square than the actual box. The inner square is the actual hole you cut in the foam for the servo. The outer box is going to be a plate glued into the wing with a hole in the middle for our box. i would then cut out the bigger square from 1/8 ply and remove the hole in the middle leaving you a 'picture frame' in ply. Then take 1/8x1/4 balsa and glue strips around all the edges. This lets you set the plate into the wing and the balsa can then be sanded to match the curve of the under side. You will notice also that there is 1/4 inch of the ply showing and this is the area the little door (the next thing to make) will sit on.

Use 1/8 ply or good quality light ply for the door as the servo mounting blocks will glue to it.

Once you have all the bits lay the 'picture frame' on the wing and with a sharp knife cut through the veneer all the way round it. Make the cuts as tight as you can. Gently peel the veneer off the wing and slowly remove just enough foam for the frame to sit in the wing flush to the surface. Mix up some epoxy, glue it in and bosh. All done. You can then open up the hole in the middle of the frame, attach the servo to the door. fit the door, sand it to shape and then drill the holes for the screws.

To run the cables, take 1/2 inch balsa sheet and put it side on to the wing. Draw a line each side, cut out the channel, install cables, cut a strip off the 1/2 sheet and glue it in the gap.

I did the same with my hurricane as you can see below

 

 

Edited By Jon Harper - Laser Engines on 10/02/2017 09:20:36