The Rabe Bearcat

As a boy I had always loved the look of military style aeroplanes. When I had the chance to go to the 1978 world champs in Woodvale near Liverpool, off I went, back-pack in hand, to watch the best aerobatic flyers in the world competing for the right to be world champion - no mean feat, as the top 20 were separated by mere few hundred points and the final two by only 3 points in a total of 6000 points.

Sitting watching in the rain one flyer really stuck out among the crowd. His name, Al Rabe, an American flying a semi scale P51D Mustang that looked so superb in the air, I was taken. So here’s how we get to the bearcat, one of his designs. Up till now no one (I think) has kitted the mustang or the bearcat.

A brief history of Al Rabe: A pioneer of what is now called the “Rabe rudder” - a means to increase line tension in certain manoeuvres, also the adjustable lead-out guide and many other items. In 1978 the Aero Modeller published “Evolution of a Thoroughbred”; a great piece showing how he got to be so good.

Kyle of Tanks Hanger is a firm who makes laser cut kits and any parts you want …at a price of course. They make the Bearcat laser cut kit - cost with postage about £150. You may think this is a lot, but when you see the general quality of the kit you would still pay double and be happy. There is a hardware pack needed for this model. Tom Morris does this on line.

When you lay out the kit and study it you think, “Help!” It comes with a plan that has lots of dimensions on and that’s all - you need to get his videos to help you with construction. These need to be watched before any construction is started unless you are a VERY experienced builder. I won’t say it’s impossible but lack of some info makes it very hard to build. You start by making 2 jigs that the fuzz and wing are built on - this enables a truly straight model. The wing is built on the rod method. NOTE - the rods you should use are 3/8 inch aluminium light tube as the lightness will allow the rods to move if the wing twists. It has dihedral, as you build you will see what I mean.

Before you can start building the wing you have make up the centre section that carries the bellcrank mounting. Now this is fun, 2 pairs of hands are needed to get it all aligned. The video tells you to build it, then put the bellcrank in and glue the main pivot pin afterwards, but I wasn’t sure that was the best way to do it. You decide, as you build the wings it will be apparent how easy it is.

Drawing out the fuzz jig takes some skill. You must use the dimensions on the plan to get the spacing on the jig right, otherwise the sheeting that you get with the kit won’t fit. This is very important. Also, the two jigs lock into each other for final assembly – more about this later. As you carry on with construction, making the tailplane and the tail fin, you will realize how much thought has gone into this design and the whole concept.

The tail plane is easy to build because the trailing edge is the main construction that gives it all the strength, very basic and very strong when covered with 1/16 sheet. The tail fin has a template on the plan that you trace, then cut it out in 1/16 balsa - top half vertical grain, bottom half horizontal grain.

A triangular insert is put into the base of the fin to give it a contour to fit the rear sheeting of the top decking, as you can see by the picture. Nowhere on the plan or the videos is there anything about the Rabe rudder set up, but there is info on the Internet, if you search for it.

Now comes the fuzz. After gluing all the formers onto their ply counterparts, I found that the ply formers and the balsa formers are very slightly different size, but only millimetres. A bit of attention with a sanding block, used sparingly, will make all the difference. When you see that a 72 four stroke engine or bigger is mounted on only 3/8 by ½ bearers only 6 inches long you think, “Not enough,” but believe me it’s plenty, it’s all to do with surface area and such stuff.

Drill the bearers to suit the engine you’re using, allowing 2 degrees offset as the ply plate is already cut for this. The nose construction comes first. The first three formers are mated with the ply engine mounting plate and bearers put into the jig and glued. (In the picture the wing is coming on nicely in the background.) NOTE: building on two jigs, if your bench is big enough, helps speed up construction, as you can glue on one and let it dry while working on the other.

The rest of the formers are put in place and glued. All the longerons are also glued at this time. I found the quality of the moulded sheets that come with the kit needs to be addressed but I still used them as it too hard to make new. Only a little cutting, and gluing new bits in here and there seemed to cure the problem. You can start putting on the sheet sides making sure that the wing aligning longeron is only half covered, as this is a factor later on in the final construction.

So you have all the wing constructed and covered with balsa sheet still with the rods in. Now its like that Clint Eastwood film: “Do you feel lucky?”… enough to pull the rods out and see if the wing is straight or not, because it has to be in the jig to be aligned to the fuzz, and once it’s stuck to the fuzz it’s almost impossible to “unwarp”. So, very carefully pull and twist the rods so they very slowly come out of the wing. Yes, you will break a few ribs, but don’t worry because you are only breaking them around the rod mountings. Hey presto! a perfect wing - or not. If not, see how far out it is and support it and damp it gently and untwist it. Sorry, no pictures of this as my wing was perfect!!! Clean the rods and put them back in, and put it on the jig

Now comes the best part of the whole model - you will now see how easy it is to build a very straight model. Carefully pry out the fuzz from its jig. If it has stuck into the jig use some uncure zap. Next take the wing and jig all in one (this is where you need a BIG model bench) and glue it to the fuzz jig as shown on the plan. The picture shows the wing omitted so you can see how you get the two together . NOTE: there are two lines, one on the fuzz jig and one on the wing jig. Check and double check that these are 100% accurate, otherwise the wing won’t be square to the fuzz and that means no end of problems. Put the wing on the jig and start cutting out the fuzz so that when the fuzz is put back in its jig all formers are located in their pockets and the wing/fuzz fit perfect. The main longeron running the full length of the model should align with the centre line on the wing.

The next step will tell you how accurate you are in construction so far - making the push rod off the plan and seeing if it fits. Ensure that all the pushrod connections are strong as this is a one piece model.

There is also a jig now for the tail-plane - same concept to help align all surfaces. (You can see it in the pic) This jig also gives the tail plane incidence of about 1/16 on the l/e. Once the push rod is made and connected to the wing and tail plane stick the tail plane and wing to the fuzz. After it’s all dry take the whole model out of the jig and see how straight it is - if you have done it to plan it should be perfect…

Do as much work as you can in the jig, it gives you a platform to work on and protects the model. I left my tailfin off till the very last moment, as it is so tall and prone to being snapped off!

Fancying a change, I made the sprung mounting u/c. You may think this overkill but at the end of construction when the model is finished you’ll see why it’s not

Back to the final sheeting of the top decking: before that, put a small amount of glass cloth and resin around the inside of the wing join just for a little extra strength, after the top decking was finished the cockpit and canopy was set about.

Roy Cherry, a good friend and a master builder, showed me how to get a canopy to fit tight years ago: stick some sandpaper upside down on top of the model where the canopy is going but a little bit bigger all around. Then cut the canopy to a rough fit, slide it backwards and forwards on the upturned sandpaper until you get a good fit. Finishing the inside of the cockpit is purely personal choice. It’s like ink lines: done nicely it looks great, if you’re not confident leave it empty and just spray it blue.

I now took my model out of the jig, removed the rods and discarded it. Not the model, the jig! I put it on the scales and mine weighed 28 ounces; notice my tail is still not stuck on yet as it is next to be done.

The next task to tackle now you can do it is the wing tips. The outboard tip comes off, unlike a wing tip box, for many reasons, the main one is it’s neater. The inboard carries the adjustable lead-out guide and again is pretty straightforward. The flap and elevators were made as I went along with the model. Nothing really needs to be mentioned except the l/e on all the control surfaces were made so that the hinge pockets were stuck on afterwards hence giving a perfect hinge line. The nose ring is basically an inch balsa stuck on and carved. The tank is straightforward from the plan, also the bottom sheeting and the tail wheel too. The cowl is easily made from the sheeting supplied.

NOTE: Al Rabe covers all surfaces in layers of glass cloth put on with 2 pack epoxy resin. Yes, it gives great strength, but this model has a very short nose and I’m always worried about a tail-heavy model. All I can say is, go carefully, pick all your wood (that’s not supplied) so the lightest is to the back of the aircraft, without compromising the rigidity of the frame.

Well that is the construction finished, almost, yes there are little bits I’ve missed. This is for the more experienced modeller, but saying that until you try and build a model like this, following the instructions to the plan you won’t get experienced.

The whole construction time was only 2 weeks and I have kids, and 2 jobs. Once you get into it with zap there’s no excuse. This has a been a joy to build - you could never cut the formers or the ribs as well as a laser cutter, so pay the money for the quality!

Now comes finishing the model: you decide what make of finish, just remembering that this model has huge surface areas on the fuzz and will soak up weight very easily. I use all BRODAK products, because they are very light and durable. I’ve decided to glass all the wing 1 coat, and the elevator 1 coat, and the fuzz up to the back on the wing only, the cowl (due to the heat of the large 4 stroke is fibre glassed in and out to protect it). The whole model is then given a careful sanding, then 3 coats of 50/50 dope thinners. Allow to dry for 24 hours, sanded again then covered in medium weight white tissue. NOTE: when you cover a model with fibreglass cloth and resin, covering it with tissue afterwards stops the weave of the cloth coming through the finish.

Again, three more coats at least of 50/50 dope thinners mix, allow to dry for 24 hours. NOTE: the longer you leave dope to dry the harder it gets and the easier it is to sand. Yes, you can leave it only 5 to 6 hours and then sand it but you will leave very fine scratches in it that you won’t see now, but will show when the model is buffed…too late then.

When you’re happy with the finish so far, you now have to decide what colour finish you are putting on; the reason I mention this is it’s no good putting on silver primer if the model is going to be white.

I decided to paint mine in USA navy colours, the same as Al Rabe did. The colour is insignia blue - that is a brodak colour. I started by spraying 3 coats of silver on all surfaces, allowed it to dry for 3 days, and then it was sanded 600 wet and dry using it wet with M600 degreaser. NOTE: you must never use water as if it get in to the airframe it will cause the wood to swell and ruin your finish. After sanding, if there were any shiny bits in the paint there will be small indents in the finish and more silver will be needed to fill the gaps etc. The picture above right is the plane after sanding silver to a point where it’s as smooth as you can get, then spray another coat and do it again and again until perfection. Each coat and sanding is about 10 hours work!

After sanding again a uniform dull finish is what you want. Next spray 3 coats of top colour. This must dry for at least a week. Again sand, this time with 1200 paper and M600 degreaser until you have a dull finish. If you sand through the colour, don’t panic, just touch it up and carry on.

Final detail is again up to the builder. I have put on all the navy details. These were supplied from the USA with a crib sheet telling you where they all go. The ink lines are put on with silver gel pens, the sort you get from Ryman, they don’t dry very quickly so the utmost care is needed trying not to smudge them (I did many times) and you think that you have rubbed the smudge away but when you put clear on it shows up - BE CAREFUL!!!

The entire model was given two coats of two-pack lacquer as at the time it seemed to be a harder finish than brodaks, but there is a weight penalty - about 2 ounces, but as I was under my target weight this was done. Now the model has been lacquered the weight has crept up and now is 2 ounces over the target weight. …Maybe should have stuck to clear dope ….we learn by our mistakes, but boy does it look good. The model is waiting for good weather for its first test flights…………

UPDATE: Now we have had some reasonable weather, here is a video of its first flight. The flight was good, but it was very tail-heavy, wrong handle spacing, and the weather deteriorated very quickly, after just one flight.