Skyraider test

This is an incomplete page, it is an ongoing project. At present it shows what can be done with construction articals.

From January 2006 to end November 2007, Phil Clark from Fighter Aces has been busy building and reporting progress on the above project within the RCMF forum as a series of post's, what follows is a short extract from that forum and is a veritable feast of technical expertise and information on "how to do it" for large models. Any text by me will be in this colour, all other text is Phil's. So over to Phil!

Just a short update......I'm having a meeting with Keith Mitchell (my over 20kg inspector for this project) this coming Wednesday to discuss the project, and go through any design and material changes required by the plan enlargement. Once this has been 'OK'd, I'll be ordering up the 1st batch of wood to make a start on cutting a kit of parts. 1st part to hit the board will be the tail plane, all 72" of it........followed by the forward fuselage.

Confirmed over Xmas, a full retract package is being custom made for the project by Darrell at Sierra Precision in the US. This will take the form of 2 massive twist & turn main units, with scale over centre drag links. A scale tail wheel mechanism using scale actuation, as well as a set of aluminium wheel hubs with scale hub pattern to fit to 10" tyres I'll be sending him......all of this lot is due for delivery to me around April.

So.......until I have something worth showing.........TTFN. (for the younger generation this means Ta Ta For Now)

The meeting with Keith went very well...........we discussed all areas of the airframe, and any modifications and changes to wood selections required, as well as hinging, servos, linkages etc etc............The main topics were obviously how to securely & safely mount a 22HP 20lb 400cc engine to the front , as well as spar design and the methods required to joining the outer wing panels, the stab 1/2's and the 2 fuselage sections. Most methods will be almost identical (just bigger) to what I've used on the B26, so I'm pretty familiar with how it's all going to go together already

All of my suggestions were agreed by Keith, so he's cleared me to make a start as soon as, and he wanting to have a look once the stab is complete, and the forward fuselage is partially sheeted................the aim is Haigh hall in late February.

So..............I've placed a BIG wood order via Ali to SLEC, as well as 1/2 a rain forests worth of Cyparis from Stuart at Solutions.

Back with news of wood cutting in a few weeks...........

Bit of good news..............

The MASSIVE canopy was one area of the project that was worrying me. Didn't really fancy making a plug for a 1 off.......................

A chap by the name of Mike Emilio in Canada offers plans for a 1/3 scale, 148" span P-51D. Looking at it's canopy, it's a VERY similar in side profile to a Skyraider, so a mail to him soon had a few photos and some overall dimensions to see if it would be possible to cut down the 'bubble' rear section for use on the Raider. His canopy is around 4" too long and about 1" too high for the raider, but nothing a pair of scissors won't sort..............so looks like I have a canopy source. The front section is a lot more straight forward as it's all flat plate on a raider, so a brass/wood frame can be made up, and flat sheet acetate used for the glazing.

The canopies shown are 31" long, and around 9" high.......

The 10" wheels have also been ordered today, From RS, they are basically steel hubbed, pneumatic trolley wheels. The hubs are naff, but the rubber tyres have quite a nice diamond tread pattern, so couples with Sierra's nice aluminium hubs, they will look the mutts...............

The operational versatility of the Skyraider was simply amazing...........

This is what you call a set of wheels

They are actually 260mm dia trolley wheels. The tyres are a pretty meaty pneumatic rubber job with a heavy tread. I will be removing most of the tread, and making the tyre a little more 'round' & smooth in profile rather than flat as it currently is. The method is to put the wheel/tyre in the freezer, then once nice and hard, to spin it up on a wood lathe held on a mandrel, and using a Black & Decker power file with a course sanding belt, sand the hardened rubber away until the desired profile it left........simple !

Once that's done, they'll be off to Sierra Precision to be fitted with a nice set of scale machined aluminium wheel hubs. We're on the move....................1st cuts have been made today. (1:5 scale 190 fuselage in there just to give scale to F1 & 2)

Anyone who knows the Ziroli Skyraider will see I've made major alterations already. The internal ply fuselage sides used to end on the back of F1, and an engine box was butt glued onto the front of F1 (good practice ??......NOT !!)..............not any more. The internal sides have been moved slightly close together, and now pass right through F1, tying the firewall in with the LE & TE of the wing, as well as the former at the break point of the fuselage..........these internal sides (the piece the formers are resting on, all 71" of it) are also from 1/4 birch ply, and have an 1/8 ply top and bottom to create the box, going back as far as F3.

The notches to take stringers & longerons will be made once I have picked up the Cyparis on Wednesday morning......................so until next week when I should have a full kit of parts for the fuselage.

I had a very pleasant few hours getting covered in wood dust..............much better for you than glass dust

The Raider in as you say a 'blown up' Ziroli, outline only really, I'm adding major structural alterations in again, similar style to the B26 just to cater for the size and load increases. Span has gone from 100" to 180", giving a scale of 30%. The wing in a 3 piece affair, 85.5" centre section with 47.25" outer panels. Length is 136", 91" front and 45" rear. Stab span is 72", split in 2.

Estimated AUW is around the 100lb mark, 47.5 sq/ft wing area giving a VERY light wind loading on only 2.1lb sq/ft

Construction is 100% wood, no glass, not even the cowl. Birch ply, lite ply, a rain forests worth of Cyparis and balsa is as complicated as it gets......there is just a lot of it

Retracts are custom made from Sierra Precision, and the engine is the new 400cc 5 cylinder 4 stroke radial from Moki/Mackay/RCS (call it what you want) 400cc, 22HP, 20LB weight, swings a 39 x 25 carbon prop at just under 4,000 rpm....................oh, and did I mention the NOISE

Radio will be SM's Rx Buddy coupled to a pair of JR PCM Rx's, 2 x 15/20kg digital servos per surface (14 servos in total just on control surface) & heavy duty switches and wiring. Batteries................don't know yet............Ali may choose to go Lipo to get a huge amount of capacity, but with weight not being an issue really, BIG NiCad's or NiMh won't be a problem either.

Batteries................don't know yet............Ali may choose to go Lipo to get a huge amount of capacity, but with weight not being an issue really, BIG NiCad's or NiMh won't be a problem either.

Good progress.................the 'kit' of parts for the forward & rear fuselage sections are almost complete.

The 2 internal side plates are both 1/4" Birch ply, just under 6ft long. The firewall and 2 wing hold down plates are all 3/4" Birch ply.

The former set is a mixture of 1/4" Birch ply, 1/8" Birch, and 1/4" Lite ply. The 'centres' of most have yet to be removed. All of the notches to take the longerons etc..... will be cut when the formers are in place to make sure all longerons & stringers remain straight. Working from enlarged plans, you can never be too sure how accurate the drawn on positions are, so rather than cut them, then have to move them, it's best to cut them correctly when the stringer is ready to be installed.

I've also now got all the Cyparis required for the build, so the 1st 'assembly' job is the construction of the horizontal crutch that the fuselage is build around.

To make the notches, 1st I mark the position of the stringer/longeron, then using my Screwfix pull saw, I make two cuts to the correct depth, one either edge of the stringer/longeron, then using a Permagrit spar slotting tool, I sand out the material from between the 2 cuts.............easy. I have 2 spar slotting tools, an 1/8" and a 1/4", added together I have a 3/8", anything bigger, I make a custom tool from the stringer/longeron Cyparis in question, with 80 grit paper double sided taped to it.

The method used it to notch say F1 and F8, push the Cyparis into place, and let the wood find it's own 'straight', then mark it's position of F2 through 7.

Complete forward fuselage inner structure dry assembled.............

The Cyparis horizontal keel will be built next over the plan, then this lot will be jigged around it to ensure everything remains totally straight.

.....the fuselage has been clear coated today, wing underside yesterday, so wing top surface tomorrow and fuselage underside on Thus.........................that'll have it fully cured by the start of next week to finish the RC & engine fit and get the cockpit installed , silencer built and all final checks done.................the raider is simply filling useful time whilst I can't touch the 190.

Front fuselage horizontal crutch partially complete to allow the two 1/4" ply inner frames to be joined.....................the 'square' of ply is the 3/4" firewall supporting the 2 sides whilst the 2 hr epoxy cures.

Bottom right you can just see the rear end of the rear fuselage horizontal crutch which is also complete and former installation is well underway . Holding a large motor in place needs a strong mount

3/4" ply firewall, 1/4 ply box sides, 1/8 ply top and bottom. 1" hardwood triangle in all internal corners, firewall bonded using 'Extramite' (new came for 'Cascamite') and screwed for added security. As you can see, the 1/4 ply box sided are full length from firewall to fuselage joint, so the loads are transferred right through the forward fuselage over a distance of about 6ft..............don't think we'll have a 'strength' issue. Obviously using the correct glues is important?

Pretty standard stuff...................Pink & Green ZAP (everything else is C**P), slow cure (2 hr +) Epoxy, Hysol for any wood/metal joints (steel to steel) wing & fuselage plates) and for anything REALLY special (Firewall, gear plates etc etc...), 'Extramite'.................it's the new name for 'Cascamite' which is a powder & water mixed adhesive used in full-size 'homebuilt' aircraft, high quality furniture etc etc......it's pretty good stuff and stick like you know what to a blanket.

Initial frame up going well.............

Basic front & rear fuselage complete, wing hold down plates in, firewall in, 3 out of the 4 sided engine box in..........

Yes, the firewall (3/4" ply) is screwed in via the 1/4 ply side frames. This isn't really 'structural' more of an aid to 'clamp' the joint when bonding (Extramite) There is some 1" triangular hard wood on the inside of the joint to further increase gluing area.

The 'corners' are of 1/8 lite ply, with a 1" triangle balsa edge to allow a large radius to be added once the fuselage is sheeted. Note also the 'wide' Cyparis longerons where the steel to steel plates will soon be attached. (you're only looking at the bottom 1/2 of the fuselage from C/L down)

Basic rear fuselage structure, minus it's corners. The 'solid' former will eventually be the tail gear mount............this won't be 'cut' until I have the gear.

Full length shot.............just under 120" end to end. F1 and F2 still to be fitted.

Forward fuselage off the board and all cleaned up. The engine box 'top' is also now on. Rear fuselage has all it's 'lower corner' sections on and will be sheeted tomorrow....................

The top 1/2 formers are just clamped on at present.......................I'll get a few 'for scale' shots done tomorrow.

Latest progress..................

Wing hold down plates....3/4" ply. Note how they are interlocked with the inner frames, as well as the outer wing seat's

F 1,2,3 plus engine box top plate.

Underside nose sheeting..............1/8 balsa.

Steel to steel rear fuselage joining plates. (each plate is 3/4" wide, 6" long, and 1/16" thick, retaining bolt is an M5 cap head into an M5 nut, silver soldered to the back of the inner plate) There are 4 sets of plates, 1 either side, plus 1 top and 1 bottom.

Rear lower fuselage sheeted in 2mm lite ply (the horizontal crutch was then removed as once sheeted, the structure was totally rigid, so the crutch served no specific purpose other than adding unnecessary weight in the tail)

Underside complete, awaiting top 1/2 formers to be added.

The fuselage was at Haigh Hall on Sunday, and was looked at by Keith Mitchell & Mike Jackson................apart from comments linking it to an 'canoe' rather than an aeroplane................all is well, so I'll be getting it sheeted up this week before moving onto the tail surfaces.

Top half formers then added, followed by the top keel and the 1/4 sq Cyparis stringers.

The stringers were positioned 4" apart to suit the width of the 1/8" balsa sheeting, meaning minimal trimming of sheets etc.

With 1 side complete, the 2nd 2mm lite ply lower skin was added, clamped & weighed down over night to dry.

The upper forward fuselage required to careful sheeting.............here, the cockpit coaming.

.............and the cut outs for the engine exhaust pipes..........

Starting to look a bit more Skyraider like though

Does the balsa skin sag between the formers or do you do something special?

with 4" spacing between stringers, and around 10/12" between formers, the use of medium 1/8 balsa works fine (I trialled it with a piece of 3/32" 1st, and it was too thin)..................add 0.6oz glass onto this, and it'll be perfect. Anyway, a model of this size isn't really going to be held inverted in a trestle for any length of time to put the wings on, it'll be much easier to assemble stood on it's nose etc............so a little 'give' in some areas of sheeting isn't an issue.

To see the full series of Phil's posts, go to (note: The white text and photos are copyright Phil Clark 2006 - 7)

http://www.rcmf.co.uk/4um/index.php/board,112.0.html

This page was last updated on 23/11/2007

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