TOP FLITE GIANT P-51D MUSTANG
by Tony Nijhuis
Want to get into the giant warbird scene?
Then check out Top Flite's P-51...
Once in a while a kit comes on to the market and says I'm new Top Flite 1/5 scale P-51D Mustang was soon up for review, I jumped at the opportunity. Prior to the kit launch in this country I was lucky enough to see the show model for Ripmax being constructed by a fellow modeler and good friend, Brian Perkins of Hastings. I decided then, I must have the model. Prayers answered, a few weeks later a large parcel arrived and al systems were go.
The Art of Packaging
On opening the box, a well presented kit of component parts meets your eyes. So well packed in fact that I had trouble getting it all back in - all the more reason to get started. All the components are either die or laser cut to a very high standard. Various lengths of sheet and strip stock are grouped together ready for the sequence building. The cowl, dummy air intake, wing guns and exhaust stacks are all molded from ABS plastic, and the canopy from crystal clear Acrylic. Again all moldings were of a very high standard. Also supplied is a hardware pack of screws, pushrods, clevises etc. and a beautiful set of vinyl decals. In order to get this box of bits into the air a 60 page instruction encyclopedia and a four sheet CAD drawn plan are provided.
Before you start, take time out to familiarize yourself with the kit components, instructions and plan. Where necessary, put identification marks and sizes etc. on the stock items as this helps speed up the building process. I am not going to give a blow by blow account of how the model goes together, the instruction booklet does this superbly, with construction photos to back up the written bit. When it all becomes a little too tricky a 'Hot Tip' appears to help you out.
At this point it's worth thinking about the additional accessories/hardware you will need to finish the model. Unlike your 40 size sport model, the local model shop is unlikely to stock all you are going to need, so listed below are those items which may need pre-ordering.
- 5" Aluminum spinner
- 5" Light weight wheels
- 16 - 24oz fuel tank
- 180 size adjustable quiet engine mount
- Robart 1/5 scale retracts mains and tail wheel set
- J'Tec in cowl silencer to suit your choice of engine
Take a Deep Breath
Rome wasn't built in a day and neither is this. There is a lot of building so don't be in a rush to get it finished or it will become a chore. For once in my life I decided to stick rigidly to the instructions to avoid falling foul of my own mistakes.
First to get underway were the stabilizer, fin and rudder which was a rib and balsa skin covered construction. All went together very well although slightly on the heavy side which did concern me.
The wings were next. In terms of airframe building, a good 50% of the time will be spent making the wings so if you enjoy wing building this is the kit for you.
If by now you have decided to use the suggested Robart undercarriage mechanism then carry on. If, on the other hand, you are determined to use another make then some serious redesign of the wing ribs W4 & W5 will have to be done.
The major problem with using another type of retract would be matching the position of the leg pivot point which is only an inch or so behind the leading edge. The depth of the wing at this point is only about 3/4-inch -not enough to conceal or support a standard type retract- so you have been warned. The Robart units have been custom manufactured for this kit and Robart work closely with Great Planes on all their scale models. As these two companies had got together to produce retracts especially for the model you might as well enjoy at the hard work that's been done for you and fit Robart units. I also used the oleo struts too as these are designed to replicate the scale lines of the Mustang's legs and look great.
A word of caution about them though - they are not damped and therefore will cause the model to bounce on anything other than a perfect landing. I would strongly recommend the oleo legs are packed with damping grease available from Unitracts International if you want to avoid damage of the U/C mounts and mechanisms.
Construction of the wings is greatly aided by small balsa tabs attached to each wing rib. These allow the semi-symmetrical wing rib to have two points of contact with the building board when constructing the wing over the plan. This subsequently means both wing panels are built straight and true. These tabs are later removed prior to skinning the wing - a very nice touch.
The skinning consists of gluing five pieces of 3 inch wide balsa sheet edge to edge to make one large panel (this process is done 4 times - 2 top, 2 bottom). I had to add another 1-inch wide strip at the root leading edge because the suggested method did not quite cover the open structure. The wood selection for the sheeting was thought a little hard and heavy but it proved to be a blessing as it was far more resilient to the knocks and dents dished out during construction.
The ailerons & flaps which again were of built up construction were last to be completed- now you're coasting.....
The construction technique employs a simple box type construction method with a rolled sheeted forward top deck and a block sheeted rear top deck. Before getting too stuck in you will have to decided whether to use the Robart retracting tail wheel or a fixed castor type. Again the fuselage has been designed around the Robart system so deviations will require some pre-planning. A decision concerning type/size of elevator servo will also have to be made around this time too. About halfway through the fuselage construction, have your choice of engine and mount ready for fitting. This is done to make light work of the engine installation before the balsa top cowl is fitted.
The engine range as stated in the instruction booklet is for a 30 cc to 45 cc glow, 30 cc to 60 cc petrol (although the box lid details state 35 cc glow as being the minimum). After a long consultation with colleagues and our editor, I finally decided on the new SC 180AR (30 cc) glow engine and a j Tee in-cowl silencer.
As the position of the engine is inverted there should be no problem cowling the engine in. The half cowl idea (fixed top, removable bottom) works very well and allows good access to the engine without having to removing the prop or spinner.
Construction progressed quickly, the kit box soon emptied and the fuselage was almost complete. Detailing of the cockpit area was now on the agenda- apparently a vac formed cockpit interior can be purchased for instant realism. I prefer at this point to fit the canopy prior to covering to protect the cockpit detail (the only time I deviated from the instructions).
At this point it is worth checking the balance point so weight can be added easily. I was pleasantly surprised to see the balance was spot on. (The finished model required no ballast to achieve balance). My earlier fears about the heavy tailplane? -I should be more trusting with an experienced manufacturer like Great Planes.
For the review model a total of eight standard servos and one 1/4 scale servo (for the elevator) were used. 1 elected to fit a 20oz fuel tank that would give about 10-15 min flying time. Up to a 40oz Dubro tank will comfortably fit if you are using a larger engine. With everything installed (prior to covering) the model tipped the scales at 18 1bs. I was going to be hard pushed to achieve the 19 1bs. suggested target weight. I don't think there was anything that could have been done to reduce the weight other than replacement of the sheet stock. Having said that, a model of this size can easily absorb another few pounds and fly without any ill effects.
Fitting of the retract leg covers did prove a bit fiddly and not much in the way of guidance was given here. Do not be tempted to leave the fitting out as the final job to do before hauling it away to the flying field. The bigger the model the more dents and scratches are going to happen when wheeling it around the workshop.
With a true to scale kit it is worth taking the time and effort to produce a scale finish. By this I mean panel lines, rivets, access hatch and weathering. Now before you decided it's all too much trouble and reach for the Solarfilm, just remember, to get this far you have already spent in excess of two hundred & fifty hours, so what's another few more hours.
Firstly the airframe was given a good rub down and then any dust is removed with a 'Tack Cloth'. I covered the model silver Profilm. Make sure to iron it on to the wood (do not use a heat gun). If you are using Profilm, the surface will need to be keyed to accept paint. So using fine grade wet 'n dry and plenty of water take the surface shine off the film. At this point glue on the vac formed exhaust stacks and wing guns. Now give whole airframe a single coat of neat dope. T@s will firstly help to avoid slackening and secondly act as a good base to paint on to.
Now for the scale bits..... The back page of the instructions show a plan and side view of the aircraft highlighting the panel lines in detail. Using this as a guide, pencil the panel lines onto the airframe, then with a rounded piece of 14 swg piano wire and a ruler, indent over the top of the pencil lines being careful not to go through the covering. This will now give you your panel edge. To create small panel & access hatches etc., use some 2 inch wide aluminum tape and cut out shapes to represent the panels and hatch and stick them on. To create the effect of small rivets a tool was made by taking a piece of 1/4 inch sq. balsa (about 6 inch long) and at regular 1/4 inch intervals, placing pins through the wood so they protrude about 3/16 inch. By pressing this tool on to the airframe surface (along each side of the indented panel line) and penetrating the skin, a 6 inch line of pinholes to simulate rivets, is produced. Areas where the Dzus fasteners were used on the full size aircraft were simulated by pushing a piece of 4 mm dia. brass tube over the end of a 1S watt soldering iron and using the heated end to lightly melt a ring into the covering surface. This process also works well on the plastic cowl too.
After deliberating long and hard I decided to stick with their suggested color scheme with a slight variance to the nose (being yellow instead of the checkerboard finish) and a yellow rudder.
Car paint was used for the silver areas and cellulose thinned Humbrol enamel (50/50 mix) was sprayed on to finish the colour scheme.
The decals were then applied and now for the weathering. Using fine wet 'n dry with water, lightly rub the Humbrol painted areas only (The silver paintwork scratches badly) especially around the pinhole hole rivets, the fasteners and the edges of the aluminum tape panels. You should start to see the silver of the profilm/solartex and the tape showing through giving the impression of worn paintwork. Also rub down the surface of the decals to match the worn and tired paintwork. Once happy, mix up a thin mix of matt black and spray the dirt streaks around the exhaust stacks and along the fuselage and around the wing guns.
To protect the paint job, a spray coat of Flair Spectrum Satin Fuel proofer was used.
By now you have probably spent close on three hundred hours. Ready to fly, the model tipped the scales at 21 lbs.
Beating up the Strip
With the fine weather at the beginning of August and the Hastings & District Scale weekend in full flow, the Mustang was ready a week after the final coat of paint was put on. After ground checking the aircraft thoroughly the new engine was fired up and a short period of breaking in commenced. There was a slight nagging doubt about the power to weight ratio having heard a few days earlier that Nigel I'Anson of Ripmax had flow the show model powered by an OSBGX 35 cc and considered its performance to be marginal. But with deadline date approaching, the SC 180 was going to have to do. Once happy with the engine reliability and set to run very rich to avoid over-heating the enclosed engine, she was t@ed out to the runway. With camera support from Brian and George, the throttle was progressively opened and the cameras started to click. With minor rudder input needed to correct a small amount of swing and she was tracking straight. After some 60 feet a nudge of up elevator was held in and a shallow climb out was started. The engine was nowhere near its peak rpm and at this point the flying was marginal. With one circuit completed sufficient height was achieved to check trims - four clicks of up and three of right aileron and she flew hands off. Another few circuits and the engine leaning slightly, she was put into a shallow dive for a low pass. With speed gaining, the sense of momentum is quite amazing, enough to carry through into a very fast and steep climb out.
Not happy with the engine needle valve setting I lined her up for finals - U/C down, throttling back and the engine cut. To save possible damaged I retracted the U/C and she came in for a perfect belly landing with no damage. A great feeling with hopefully some excellent flying shots in the bag.
So fueled up and ready to go again the engine was leaned out further, (still running a couple of hundred rpm off peak). The additional thrust was promising as she powered her way down the runway. This time the climb away was perfect. Height was achieved quickly and she was put through her paces. Loops are no problem as long as you have sufficient air speed before entering. Rolls were slow and very scale like. All control surface throws were set to high rates and were found to be acceptable. Lining her up on finals again she descended beautifully. I decided not to deploy flaps having up to this point not checked the trim changes. With a long low approach the model slowed down comfortably to a perfect landing... Excellent.
The quality of manufacture and flying manners of this model have lived up to my expectations and in some areas surpassed them. I would not hesitate to recommend this model as an ideal leap in to giant scale.
In producing the 1/5 scale version of their very successful 1/7 scale Mustang they have moved in the right direction following the trend that club models are becoming larger and now accepted as the norm rather than the unusual. There is no doubt about it, big aircraft do fly better.
Reprinted with permission.
November/December 1998 R/C Scale International Magazine