Large Model Association Forum

I’ve taken on a build of a 1/4 scale Hawker Sea Fury which will be my winter project for this year. It’s the Belair laser cut kit from the Jerry Bates plan, and my input to the project will be to build the airframe, glass cloth it and finish it to a primer coat of paint stage. I’ve been given a print out of Phil Clarke’s build thread from RC Scale Builders, along with a CD Rom from Phil, (many thanks), which is full of photos of his build from a couple of years back. These are going to help tremendously, and I’ll be incorporating a lot of his ideas and mods to the design in my build.

First job then is the tail plane and elevators. The tail plane is built up over the plan in two halves, top and bottom, and then stuck together. Everything went together and lined up reasonably well. The mods to the tail plane consist of 1/4” square Cyparis spars being added with 1/16” balsa sheer webbing, and a 1/8” ply tongue that protrudes from the top and bottom, to line up with a spar in the fin and a former in the fuselage (both of which are extra to the plan).

The plan shows the elevators being operated via one servo and joined with a piano wire joiner. This idea was scrapped and the elevators will each have their own servo. The method of hinging was also scrapped, large Robart hinges, lengthened in brass tubing, will be used instead. These will be glued into full depth hard balsa blocks in both the tail plane and elevators. Also extra to the plan are 1/16” ply cores for the elevators which were fretted out at the hinge points. 1/8” ply plates were made up for the servo brackets and fixed in situ.

The top surface was then sheeted with 3/32” balsa and trimmed. Provision was made for the servo hatches and the hard balsa hinge blocks were added and drilled. The hinges were dry fitted at this stage to check alignment and, once satisfied that all was in order, sheeting of the bottom surface was started.

While the glue was setting on the tail plane sheeting, I turned my attention to the fin and rudder. Again, there are no spars shown on the plan for the fin, and the stern post is cut half way up to accept the rudder mass balance. Two spars, made up of 1/4” x 1/8” Spruce, with 1/16” balsa sheer webbing were added. The shorter rear sub spar to stiffen up the stern post, and the longer front spar to tie in with the ply tongue that passes through the tail plane.

Once one side was sheeted with 3/32” balsa, the hard balsa full depth hinge blocks were added and the hinge positions drilled. The other side was then sheeted and the top of the fin, made up from soft balsa, laminated to a 1/16” ply core was added and the whole structure was then sanded to shape.

The rudder is made up the same way as the elevators will be, with a 1/16” ply core, fretted out for the hinge blocks. The laser cut rudder posts are 3/8” balsa, which are laminated together to make a thickness of 3/4” and 1/8” ribs added. I cut one of the posts up the middle, trimmed it and fixed one half to either side of the ply core. This was then faced off with the remaining post and 1/8” balsa ribs were then added to both sides. One side was sheeted with 3/32” balsa and then the hinge blocks were added and drilled. Once satisfied that all was in line, the other side of the rudder was then sheeted.

Once satisfied that all was in line, the other side was then sheeted. The bottom section was then made up from soft balsa and sanded to shape. I decided it would be easier to shape the leading edge before adding the mass balance, which will be added later. All that remained was to make up a trim tab which is “hinged” with 1/32” ply sheet and will remain fixed, to avoid inducing any flutter.

Ahh the memories........lookin good Dave

Phil

Hi David,

Nice to see another Sea Fury taking shape - have you decided on an engine yet - mine was flown for a few years on a Moki 250cc which was fine but I re-engined it last year with one of the new 300cc units, it is slightly smaller in diameter and although a little heavier allowed equivalent lead to be removed from the nose required when the 250 was fitted.

Although this engine has less than an hours running it has allowed a significant prop load to be turned, based on my experience the 300 would be my engine recommendation for this size of Sea Fury.

Keep up the good work and don't hesitate to get in touch.

Trevor Wood LMA 687

Would you please not swear on your thread, S++++ce is considered a swear word in my circles ;-)

Hi Trevor, I will be giving you a ring in due course, thanks for the offer. I'm building the model for someone else who already has a brand new Mocki 250 for it, so I suppose the power plant is settled on.

Stuart, sorry to use foul language. When I made up my wood list I had my misers hat on, I wanted to use Cyparis for all the spars / stringers, but it appeared that it only comes in 3 or 6 foot lengths. For some spars 4 foot meant the least waste, so I opted for Spruce (oops, I swore again). If you sell Cyparis by the foot I'll keep that in mind for the next project.

Hopefully the garage will have warmed up by now so I'll get in there and crack on with the elevators. Jonesey.

Now it was back to the tail plane and elevators. As mentioned, the elevators are made up the same as the rudder, with 1/16” ply cores and 1/8” ribs. Again, one side was sheeted, and then hinge blocks and hard points for the control horns were added before the other sides were sheeted. While the glue was going off I was able to add the tips to the tail plane. As with the fin, the tips are a lamination of soft balsa on a 1/16” ply core. I’ve been able to finish the right hand elevator today which has been sanded to shape and dry fitted to the tail plane. The elevator shroud was then continued to the tip by rebating the soft balsa and in-filling with a strip of 1/32” ply. All that remained then was to make up a trim tab.

Apart from a final light sanding, the tail feathers are now ready for glassing.

It was now time to turn my attention to the wing, which is made up of a centre section housing the undercarriage and two outer panels, which are retained by two joiner tubes each side. Starting with the centre section, it is built pretty much as per the plan, apart from all balsa spars being replaced with hardwood, extra spars will be added to give more support to the 1/8” balsa sheeting, and the undercarriage mounts will be beefed up.

The main and rear spars are 1/8” ply, with half inch upper and lower spars. The lower spars are glued to the sheer web before being pinned onto the plan. The ribs are then lowered on from the top.

The retract mounts shown on the plan are hardwood rails, spanning just two 1/8” ply ribs. This idea was scrapped and half inch ply plates were made up which will spread the load over three rib bays. The front plate is glued to the ribs and the rear face of the main spar sheer web. A full depth 1/8” ply doubler was added to the outer rib in the retract mount bay. After a final check that the undercarriage plates were in line with each other, all was glued in place.

A ply laminate was then added to the rear plate which ties it to the front face of the rear spar sheer web.

I had now reached the stage where the undercarriage would be fitted but, until I get the wheels, I am not in a position to determine the exact fixing points, so I decided to make a start on the outer wing panels. These were built up as per the plan, apart from all balsa spars being replaced with Spruce.

As previously mentioned, the outer wing panels fix to the centre section on two aluminium tubes each side. I’ve no doubt that people have their own method of fitting joiner tubes, I’ve found the following method works for me.

On laser cut kits, where the holes for the tubes are a tight fit, one or two, sometimes all, have to be enlarged to get the panels to line up with the correct amount of dihedral. To compensate for this, and to add a larger gluing area, I like to fit ply “doughnuts” either side of each rib. Starting with the left outer panel, the phenolic sleeves and “doughnuts” were dry fitted. The outer panel was chocked up in position, with a 1/16” gap at the root and the sleeves were then tack glued in situ. The sleeves were cut using a hacksaw blade and then cleaned up at the rib faces. The joiner tubes were then inserted and the outer panel was fitted to check for alignment. Once satisfied that all was in order, the sleeves and “doughnuts” were glued permanently in position. The following photos show the dry fit, further photos of the final fit, "doughnuts" and extra strengthening will follow in due course.

Extra sheer webbing was added to the spars and the sleeves will be bonded to them in due course to give even more gluing area. The right outer panel will have to wait for the time being as I am waiting for a missing joiner tube to arrive.

With the wing construction being put on hold, I’ve decided to turn my attention to the fuselage.

The fuselage is built in two halves, top and bottom. Starting with the top, the only variance to the plan is that all stingers will be 1/4” square Cyparis instead of Balsa, and an extra former will be added to cater for the retractable tail wheel. This former will also tie in with the tongue that will protrude through the bottom of the tail plane. I’ll make it up once I receive the tail wheel mechanism.

The upper formers are positioned over a horizontal crutch, made up from two 1/4” ply stiffeners and 1/4” square longerons. Instead of building it over the plan, a centre line was drawn on the bench and the position of the formers marked off. Initial dry fittings threw up a few inaccuracies, which is not uncommon when building from plans.