|F/A 18 HORNET
by Adrian Wall
Speaking of building, the Airborne designers behind this fantastic model adaptation of one of the greatest fighting modern aircraft of our time, have done an outstanding job of drawing a rather complex looking model. But really folks, don't let the looks of this design scare you off. It's quite easy once you study the plans for a while and just take your time reading through these building steps. The following steps are not a blow by blow description of how to build this great model, but just a guide to keep the sequence of events flowing smoothly.
If you're just reading this article for the fun of it then read on. You might learn something, or you may even take the next step and order yourself a copy of these plans and proceed with the construction. If that's what you have already done, then leave the knife on the bench for the moment and take a careful look at what your about to embark upon.
This aircraft is a sixty size model, (10cc), a rather 'fast' looking airplane and you would be quite correct as the Hornet is very fast with a high performance .60 size engine up front. Don't be put off by this brief description. This model will fly quite slow all day long. (Just don't expect to impress anybody unless it's a glider comp. you're in, then you'll beat them.)
The F/A-18 Hornet model will require some slightly different building techniques than what you are probably used to, such as having some of the radio gear placed at the aft end of the model for balance purposes. This presents no real dramas and when completed most of the linkages are hidden, adding to the looks of this sleek aircraft. There are quite a few servos on board this bird but don't be too concerned as they are fairly cheap these days. Besides, once you have flown this plane you will never want to remove them for anything else!
Well I'm going to do something different here, and that is tell you about the flying of this fantastic looking model. That way you won't have to scan through the whole article for the really interesting bits. So let's see how the Hornet flys.
The Test Flight
Having completed the model to look like the Blue Angels of the United States Airforce aerobatics team, and I might say that it did look quite stunning, I must admit to being just a little bit scarred/worried/nervous and what ever else you might like to call it about flying this model considering the day chosen for the test flight was less than ideal, (been raining and windy). But on with the show they say.
The review model was around 5 plus kgs and was being powered by a rear exhaust OS .61 engine on a pipe. Now that was going to make the next few minutes very fast and interesting and I was quite right. With the model sitting at the take-off end of the runway I gave the throttle the big push and the model was off and running like a scared rabbit, (without the zigzagging).
After running for what seemed like only a few feet the aircraft took off and climbed away like a homesick angel.
No need to reach for the flaps. I didn't use any although they were there if required. Don't forget the C of G was only an approximation at this stage, with flaps out it might have behaved a bit odd!
So here we are with the model going like a cut cat. I tried a few basic manoeuvres just to see how the balance was working out. Pretty good so far.
Better do some slow and low passes for the camera man just to make the boss happy!
Now this plane looks just like the real thing. Turning onto final approach with the clouds in the background and the exhaust streaming out you would think the RAAF, (well in this case the USAF), was about to land at our model field!
The camera work over with, it's time to do some more aero's & loops. No worries, and rolls as crisp as you would like them. Even inverted flying was no trouble at all. Be a bit careful with knife edge type manoeuvres, those dual rudders have quite a dramatic effect on the aircrafts trim while placed in sideways flight. I'm sure the real aircraft can't do them .
Time to try out those rather large looking flaps. Oh S..t! I think I put too much out at once. The model went up like a Space Shuttle! That shows just how effective they are.
I think I will try that again, this time with a little less travel. About 15 degs seems about right, any more than that and you will need quite a bit of down elevator trim just to keep it flying level. A computer set with mixing would be a great help here. You can tell by the way I'm talking here that I didn't have my whiz bang computer set on this model, at a later stage I did and I can tell you that a computer set makes this model behave entirely differently.
With the small flap setting, the models speed was quite a bit slower now, and with careful judgment one could fly this model around almost like a trainer. The washout built into the wing is quite handy with these slow speeds. Just don't push your luck beyond your personal flying skills.
The handling with respect to the ailerons is very good, even with the flap hanging out quite a lot. The Hornet can and will bite you if you try to fly it too slow. Extra lift generated by the flaps will have a more aggressive stall, mainly due to the higher angle of attack, and slower forward speed.
There's quite a large forward moment ahead of the C of G, that being a .60 size engine complete with all the trimmings, and this will have the model behaving a little different than your average sports model. Besides, the real aircraft performs aerobatics rather gracefully.
I'm trying to give you modellers out there that don't have a complex computer radio set a good idea how you can expect this model to fly. The rest of the flying story will only reflect flying with a simple radio set, (or maybe a simple pilot like me).
Now with the model retrimmed to suit the flaps hanging out I tried some basic manoeuvres. Yes that's right, loops and rolls. That's called a 'dirty' roll and all were done quite successfully, just don't expect it to be as neat as a 'clean' roll! Any power changes will see you changing the elevator trim while you have the flap still extended.
This model goes where you point it and really grooves, not unlike a pattern ship type model, and flys rock solid.
Let's try a landing with the flap out, actually the first landing come to think of it! Now with the power reduced to about quarter throttle and a slow rate of descent the model was lined up with the runway. This setting was held until a landing was assured. Once over the fence, so to speak, the power was reduced to idle and a landing was made very much like the real thing, a high nose attitude, (I like a model - or is that a woman - with attitude). This was achieved with the use of lots of elevator. Dual rates would be an advantage here.
Now that I had completed the first flight I was rather relieved as was the boss. The steerable nose wheel worked really well along with a front oleo leg that was made up by a very good friend of mine. Just goes to prove it's not what you know but who you know! The taxiing in was a good way to finish off a very successful flight. That little performance sure shut up the sceptics! I'm really pleased with this model and I can only say that you will all just have to build one so you to can experience the thrill of flying an FA-18 Hornet. A few more flights were done and it just got better. A real pleasure to fly.
By the way, the test model only required a few clicks of up trim after takeoff. I'm sure this was mainly due to the fact that the C of G was an educated guess and could now be moved forward a little at a time as the 16oz of fuel burnt off the model required less trim change. If you build it according to the plan the C of G is just about right.
A few tips for those of you that have building and flying experience. I found that the model has a generous amount of wing area and would lend itself well to having a reduced wing size, (not too much, say around ten percent). This would improve its handling at the expense of a slightly higher wing loading. I would retain the use of the flaps if you intend to reduce the wing size as mentioned. It would also make the model look more scale like. The reduced wing plan would be easier to achieve with the foam wing version. If this is your first attempt at this sort of model leave the wing area alone, you can't get into too much trouble then. If you own a decent computer set, which I'm sure a lot of you do, then you could mix in the ailerons with the flaps when landing and taking off. This will give you some dramatic effects, just like the full size counterpart. I have done this on later flights and can only say that the model behaves something fantastic, rotating in a very short distance and carrier type landings, minus the tail hook of course!
Well there you have it. The flying was great, and if you all had been there then I'm sure the Airborne Plans Service would be run off their feet with orders. Don't take my word for it, go and build one. I guess that the building will slow you all down a little bit but don't let that phase you. Just read this story every now and then. That will sure whet your appetite. I just can't tell you how fantastic this model looks in the air!
Some of you are thinking I wish this model was one of those ARF's. Well forget it. Nobody makes a model like this one but yourself. So sharpen those knives and start building!
The Wing Construction
The wing is built up by either one of two methods, one being the conventional built up type, (ribs and spars etc.), and the other being made from hot wire cut foam cores. I must admit that building a wing is not my favourite part of this hobby, but if you choose to build the wing the way I did for the review then it is actually quite good fun. Besides, foam wings are very strong and can take a lot of damage and still fly great if you get hit by a S.A.M., (Surface to Air Missile), or a Sudden Affliction with Motherearth.
If you have chosen to build the wing using foam cores then the next few paragraphs are for you, and if you are building the rib/spar method skip this section and proceed on to 'Alternative Wing Construction'.
Okay then, let's see if you can cut some foam core wings. The templates required for this wing plan form are at the bottom of the plan, make up the root rib template and the tip template as per the shape shown. Be extra careful here as the more accurate you make the templates the better the overall wing shape. I like to make the templates out of aluminium, mainly because they last forever. Once you've achieved a good pair of templates, (one each that is), you will then need to mark out on the blank foam wing panel where they need to go. (For experienced builders have a quick read at the end of this section first.) Just remember that there is a good amount of washout to be built in at the cutting stage. The wing cores when cut will also incorporate the ailerons and the flaps. You could make this model without flaps, but it sure does add not only to the looks but the performance. The controls, (flaps & ailerons), are cut out after you have skinned the foam blanks, as well as the centre section of the wing aft of the trailing edge. Please take note that the wing panels are to be cut with the bottom of the wing as flat, in other words the bottom of the root template and the bottom of the tip template are to be in line with each other, allowing for the washout, got that? The plan shows the relationship of each template.
Now that you have two cut wing cores you can either cut out the servo holes, two in each wing panel as per plan, or cover the cores with 1.5mm balsa and then cut out the servo holes latter. I used some store bought servo hatches, they really finished off the servo installation. You will need to make some access holes for the servo leads by either plunging a hot rod, (sounds good), into the foam from the root ends and finishing up at the servo holes, or cutting through the wing skins from the underside. Your choice. I made a small narrow cut in the wing and committed a few servo extension leads to never see the light of day again! Servo choice with respect to the flaps will need to be made at this point, single or dual units that is. The plan shows all. Now cover the wing panels with 1.5mm balsa if you haven't already done so. Don't forget to use the foam wing panel 'jackets' for support when working on them.
Having completed the wing panels up to this stage you will need to mark out the positions of the control surfaces on the wing skins. Don't forget to include the 13mm extra that needs to be cut away for the wing trailing edge and the control surface front face. (That being two 6.5mm sections.)
A tip here with the cutting out of the control surfaces: Cut half way through one side only then turn over the wing panel. Mark that side out the same then cut right through. If you have done the job right you should end up with two pieces of foam covered in balsa about 13mm wide.
Next glue on the trailing edge pieces onto the wing made from 6.5mm balsa. The control surfaces can also be faced with balsa as indicated on the plan. The leading edge pieces can also be glued on once you have removed the forward piece of the wing as shown finishing off the ailerons with trailing edge stock. The wing tips might as well be glued at this stage while you're hot.
It's time to join the two wing halves together. First sand the root ends of the wing panels to a slight angle. This is done so the wing halves will butt up together when placed flat on the building board. A trick here is to place one wing panel at a time flat on the bench with the root end just at the edge of your building board. Now, using a sanding block, sand the end with the aid of the edge of your bench. Keep the sanding block vertical with the bench, (the bench acts as a guide). Once dried you can cut out the front centre section known on the plan as B1, and replace with a solid block of balsa. This will make the forward wing mounting a lot stronger.
Drill the three wing mounting holes at this stage, (two at the rear and one at the front), then place a piece of tube or plastic down the holes and cut flush with the wing surface. All the hole sizes will need to be big enough to accept the nylon wing bolts plus anti-crush tubes you intend to use. Make sure there is no exposed foam showing around the holes, (fill with epoxy glue if there is). This is because if you use polyester resin with the fibreglass cloth you are about to fit to the wing centre section it will weaken the structure around the mounting holes. In other words, it will eat the foam! Do some sanding to the wing leading and trailing edges at this stage to make a good overall aerofoil shape, then fibreglass a 100mm bandage around the centre section.
Next make up the missile mounting rails from balsa. I chose to mount some hardwood blocks into the wing ends to accept some screws which will hold the rails in place. You will be surprised how easy these can get broken off.
Hinging the control surfaces is done in the usual manner paying particular attention to having only the smallest gap needed for smooth operation. Take note that the flaps are hinged from near the bottom of the wing trailing edge. Just refer to the plans here. The control horns mounting positions will need to have a small ply plate inserted into the foam for the mounting screws.
The review model used a single servo for flap operation, it worked okay but would have been better with the twin servo version shown on the plan, less control rods to set up!
Alternative Wing Construction
'Ribs 'N Things'
You will find that if the foam wing type of construction is not your idea of fun then just make sure you have done this type of building before, because to get the model to fly the same way that I described, you would need to make sure there are no warps in the wing and that it's built rather solidly. This is required mainly for the very effective flaps that make this model so outstanding. On with the building.
I will have to "wing" it here a little bit, but should be no problems. Let's see how we go. First start by making the usual kit of parts that will be necessary to build up a quick basic wing structure; ribs, spars, leading and trailing edges. Take note that the ribs are cut complete with the aileron/flaps, and with the tabs needed to keep the wing straight. These will be cut off later.
Start with placing some glue proof paper, (see through cling wrap is good), over the plan and then lay down the lower main spars. All sizes are quoted on the plan so I won't mention every size unless it needs to be emphasised. Next glue in place all the ribs, W5 through to W9, making sure they are nice and straight, bolt upright that is. The whole wing can built as one unit here. That makes for easy building flat on the board. Slide the wing brace B2, (sounds like an episode of bananas in pajamas, you know B1&B2), into ribs W4 right through to W4 on the other side, then slide B3 into place also, this time from B3 to B3. Now take this assembly and glue to the lower spars so they can join their mates. Make sure that all the rib tabs are sitting firmly down onto the building board.
Now that you are at this stage fit the aileron/flap 3mm sq. spars in place bottom and top, and glue in place the top main spar while your at it.
A few gussets and extra balsa block can also be fitted at this stage. Just check the plans for their locations, such as balsa block wedges as noted on the plan. Also don't forget the balsa block shown placed on top of B1 between the two W1 ribs, and at the rear of the wing mounting hole positions. Do this to the bottom also. These will need to be shaped to conform to the rib shape.
Fit out the servo mounting rails as shown or dream up your own, what ever you're used to. You could use the store bought ones that I used in the foam wing version as mentioned previously, just make the required adjustments at this stage. If you intend to use the bellcrank method, actually the least preferred method in my mind, now would be a good time to fit the pushrods as required along with the bellcranks. (Hope you remembered to cut the pushrod holes in the ribs first).
Cut suitable balsa to size for the leading edge, make sure you cut the balsa a little wider than the front of the ribs, this is so the wing sheeting can butt up against the leading edge.
At this stage I would consider covering the top of the wing with 1.5mm balsa sheeting including the ailerons and flaps as one unit. This way you can be assured the wing and control surfaces will be of a uniform shape. The only drawback with this method is when you remove the wing assembly you will need to cut away the ribs at the joint between the wing and controls. If you have done this then it's time to fit the balsa trailing edge and the leading edge of the flaps and ailerons. A bit of careful sanding of these pieces will see a good fit to the wing sheeting. Once you have completed this step, mark a line where you will need to cut through the wing in order to separate flap and aileron control surfaces.
Well, having done all this so far you can now remove the wing from the building board and turn it over, it's time to operate on the underside. First make sure you have suitable packing under the wing to support it, otherwise you could build in a rather nasty warp. Begin by cutting off the tabs that are at the back of the ribs, then make sure that the wing trailing edge and the leading edge of the control surfaces are nice and flush with the bottom of the ribs.
Okay then, cover the entire bottom of the wing with 1.5mm balsa, the same as you did with the top surface. With that step over again mark out where you will need to cut for the control surfaces, (the same as the top again), also mark out the positions for the aileron & flap servo hatches, (if that's the way you have gone), otherwise the aileron bellcrank hatches, you should make up hatches even for the bellcranks, just in case they come loose at some stage down the track. Now cut through the wing at the marks you made being careful not to cut all the way through on one side, half way on each side of the wing will produce a much better result.
Make up all the hatches while you are at it and secure to the wing with small screws. These should ideally be screwed into hardwood blocks of some sort. The flap torque rods can be made at this stage if you elected to use a single flap servo. Actually this was the method used in the review model and worked okay but the extra servo would have been a little bit better. It's a personal choice really.
Well apart from some sanding and control surface hinging that's about the back of the wing construction broken, (bad choice of words really). Just remember that the flaps are hinged close to the bottom edge, and like I said earlier, they are very effective in flight.
This construction article will be continued next issue.
F/A-18 Fornet plans are available from:
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