The TECHNICAL SOLUTIONS for my Large Scale Models.  Jan Hermkens. 
 

 
My drawings  are available (P-61, B-17 & Short Sunderland plans updated in 2010).             
  (see Downloads or Contact-Plans-Links)                         

  But from the B-17 only the smaller version 1/10th of 1983 (spw 3,16m).

  For my 1/8th version I have cut out the necessary parts from my own 1/10th plan and copied them 125%, and have adapted the constructions a little bit for a fuselage-splitting, and extra wing-splittings.
 

 FUSELAGE-TAILSECTION CONNECTION.

 In relation to the transport and the handiness, the tailsection had to be detachable, and therefore providings were attached for the Fuselage-Tailsection joining and glued into some formers.
 At the joining so a Dualformer (Sandwich:2x 1mm ply with inbetween them 6mm balsa with plywood rings, the outer ply rings not glued on yet, later after planking !!), is bolted together
 with four socket bolts and blind nuts M4, (2mm balsa strips between them, this for the later on two outersides glued 1mm ply rings.
These as completing the sandwich Dualformers, and as protection against damaging the balsa sheeting, and for a perfect seamfitting of the fuselage parts).

 The fuselage-joiner itself can be very light: flat springwire 6x1mm  in flat brass tubes 7x2mm. The flat brass tubes are provisional in one piece and on both sides,
 glued in 2 formers (front- and tailpiece must be sheeted apart), and later, after planking and the bolts have been removed, sawn through between the the dual formers (perfect fitting).
 Now the the outer 1mm ply rings can be glued to the Dualformers, to finish these as a Sandwich.
 

     Fuselage-Tail Splitting  Short Sunderland

 
Fuselage-Tail Splitting B-17. 1/18th .(See also Below; A-26)

 Steering Rods & Linkages:

 In the B-17 & Short Sunderland, all the Fuselage-servos are in the front of the nose (to avoid a lot of extra lead) and all linkages to the rudders are a closed-loop system (plastified control line wire),
 these linkages had to be disconnectable on the spot of the fuselage splitting.

 On a 3mm ply strip, in the front of the tailpiece, there are 3 cranks (3mm axle), which all are connected with kwiklinks and a closed-loop system to the inner control horns of rudder and elevator.
 On these 3 cranks there are also, all on the outside, threaded ball links (M2).

 The connection forwards take place with alu. ball links and and moved on security clips, naturaly also with a closed-loop system to the servo’s.

 The kwiklinks on the servo’s have to be disconnected every time!

 In the P-61 & A-26,  the servos for rudder and elevators are as far as possible forwards in the tailsection (In the P-61 for both booms!).
 

 STABILIZER- and WING JOINERS:

 Stabilizer joining:

 Short Sunderland;

 -On the Sunderland the stabilizer  has been glued, in one piece, into the Tailplane.
  The elevators are direct linked, internal via 2 apart built in cranked pianowires (3mm bended pianowire, bearinged in plastic tubes) with control horns.
  The elevators they have glued in tight fitted plastic tubes, and are slided over these cranked pianowires, not glued, so they are always removeable. So also the rudder.
 

 B-17 Flying Fortress, P-61 Black Widow & A-26B Invader;

  -On the B-17  & A-26B, the stabilizer is in 2 halves, removeable and joined to the fuselage with carbon tubes Ø 11mm

 (1/10th B-17 carbon tube Ø 9mm; in updated drawing in 2010!).

 -On the P-61 the Stabilizer is removeable between both booms and joined to the booms with carbon tubes Ø 9mm.

 The elevator linkage control is provided, by both, in the moment that the Stabilizers have been slided against the fuselage or  boom.

 Solution for these 3 models:

 Square brass tubes sliding in each other (5mm in 6mm). The 5mm tubes in the elevators are provided with 1mm brass strips for more gluesurface against 2 ribs.

 The brass tubes in the fuselage are splitted in a left and and right part (separated linkage for also here each an own servo),on the outer ends on the tubes are soldered small pieces round brass tube,
 and bearinged in paxolin strips. Each halve has so his own control horn for a separated linkage.

 The P-61 however, has only one stabilizer with a single elevator, but is yet linkaged to 2 servo’s, in each boom 1 elevator-servo. (8kg servo’s, but currentless to move with one finger!!
 In case one fails, it should not be a problem for the other servo, pulling this around too).
 

 Wing Joining:

 -On the 1/8th B-17 the wing consists of 2 halves , which are slided to the fuselage with wingjoiners. The wing joiner on the front is a loose thinwall Dural tube Ø30mm and the rear a Ø18mm one.
  (Each winghalve on  the 1/8th B-17  is also divisible in 2 parts ).
  (For the 1/10th B-17 drawing I have updated it in 2010 with a loose thinwall dural tube Ø 25mm and carbon tube Ø 11mm).

 -On the P-61 & A-26B,  the wing is also in 2 halves, the wing joining is the same as on the B-17, but now with dural tubes Ø35 and Ø20mm.
  ( Each winghalve on the  P-61 & A-26B is also divisible in 2 parts .)

  These tubes are thus loose and in a single piece and slided into fiberglass guide tubes (glued in to the fuselage and innerwing halves).

  The wings, also provided with guide tubes, are slided over the stretched out tubes and secured with long “Parkers”, through abachi blocks (glued on the guide tubes) into the tubes,
   which are provided  internally with short and small  ash-wood or hickory blocks  (on her sides and so making the tubes even stronger against nodding).

 -Each winghalve on the 1/8th B-17 , P-61 & A-26B is also divisible in 2 parts  and also these are connected with wingjoiners, but now glued in, and not loose in one piece.

 The outer wingparts;

 On the B-17: in front a Ø18mm dural tube and the rear one a Ø11mm carbon tube.

 On the P-61 & A-26B: in front a Ø25mm dural tube and at the rear Ø11mm carbon tube.

 The innerwing parts have on the outside, glued in, polyester guide tubes.

 On the spot of the deviding there is of course a dual wingrib (for each part, one) and during the open construction, the joining has to been attached, this for an accurate fitting!
 The security is done, as with the fuselage-wingjoiners, with “parkers through abbachi blocks into the tubes, internally also provided with ash-wood or hickory blocks.
 The stabilizer joining with the fuselage consists of glued in carbon tubes Ø11mm, forward and rear, which are slided into polyester guide tubes glued in the fuselage.
 Here also the security is done with  “parkers”.
 

A-26B Inner right Winghalve with Nacelle.

Wing-Joiner Short Sunderland
(Plan updated in 2010, so now, loose thinwall dural  tube Ø 30mm and carbon tube Ø 12mm)

 Short Sunderland Fowler Flaps:

 This are Flaps moving simultaneous backwards and downwards, giving a lot of more lift in slow flying or allowing even a more slower landing.

 At the Sunderland model that had to be max. 9 cm backwards and 40° downwards!

 But how to make this complicated system practicable for a model?

 The end result looks very simple and finally it is so! But before that it was a long way to go. A lot of experiments, hours! For certain, because the Flaps have a trapezium shape,
 so the travelway is on each outerside different, and adjusting of them did require a lot of time.

 The Flap itself was constructed again, with clearfoil between it, against the hollow underside of the rear wingedge. Also here, each Flap is linkaged to an 8kg servo, and for the same reason as at the B-17,
 slowed down to 5 sec.

 From the servo there goes a rod (M3 with ballinks) to both sides of each flap to large cranks. From these cranks there are leaving 2 rods, both connected on the same side of the crank.
 One (the outer one; M2 rod with kwiklinks) for the there and back movement. To this rod there (beared in hardwood blocks provided with a piece of plastic tube) the Flap is connected, hinge jointed,.
 The second rod (the inner one; M3 rod with ballink and kwiklink) goes from the crank straight to the control horn of the Flap (the Up and Down movement).

        Drawing; linkage Fowler Flaps Sunderland

 P-61 Flaps and Spoillerons:

 The P-61 had conventional slotted Flaps (Not the ZAP Flap as described in some articles  or books! These were only on the prototype XP-61 !).
 They can be lowered max. 60º, and are as well at the inner- as at the outerwing section, so total 4.
 The special flaphinges are recessed into flap- and wing undersurface. Again there is a gap between wing undersurface and flaps, when these are lowered, giving more lift and less drag!
 They are linkaged with M2,5 rods and kwiklinks and controlled by 8kg servo’s, and again slowed down to 5 sec.

 The spoilerons are laminated, in a halfround and tapered moulding, of 3 sheets 0,4 ply, and between them carboncloth + epoxy.

 They are hinged (almost at the rear, on the upperinside of the the outerwing), on a long 3mm pianowire in a plastic tube, so it can turn out of the wing (therefore in the ribs are sawed segment shaped slots),
 and is eccentrically controlled direct from a servo, turning up simultaneous with the small tip aileron on the same side. On the other wing the tip aileron is going down of course,
 but the spoileron remains, almost unmoved, inside the wing (on account of the eccentric control linkage).  

 Balloon method.

 Glue to the mould a Block or a attach a pin and jam this in a vice, and so, that the mould is free well! The mould has been covered with clearfoil (less  fouldings as possible), which is secured with  sellotape.

 Over it comes a 80 grams, or heavier, open wave mat. The whole is coated with polyester or epoxy fast-acting (10 min). Over this is loosely (less wrinkles as possible) a clearfoil again.
 The start of hardening, (keep an eye on a residue in the pot very well), it begins after about 10 minutes. In the meantime, inflate a very large party balloon (For sale in a festive article shop,
 uninflated up to 50cm diameter available. Advice Size: Balloon diameter not inflated; 2.0 to 2,5x mould diameter, the larger ones to inflate with a bicycle pump or compressor).

 This inflated balloon is kept ready just before the hardening process, together with a potential balsa inner ring (for forming a leading edge in certain types of cowlings) pushed against the front of the mould.
 Continue pressing, and let escape some air at the same time, until the balloon is at the back of the mould. Keep tension on the balloon and keep the trunk of the balloon tightly squeezed,
 and keep the balloon pressed over the mould with your arms. This is why not immediately the balloon is going to be pressed against the mould, because then you stand there, after at least 15  minutes, with an aching back!
 After the start of hardening, the balloon and the outer clearfoil can be removed and then let it harden properly. Then the exterior can be sanded wet with waterproof sandpaper, cut off the folded back,  
 slide the product of the mould and remove the inner clearfoil.

 Of course, this balloon method is also suitable for other types of polyester parts!
 

 
Cowlings P-61 &  A-26B

 These are not the same diameter over its entire length, so the methode for the Sunderland & B-17could not be used (aluminium stove- or flue pipe with a GRP nose cowl-ring).
 Therefore a positive wooden mould have to be made first ​​(with 3mm plywood bottom former + some cross-sections and between them balsa blocks, than planing and sanding it in shape).
 Then the cowlings (largest diameter Ø210mm) were made ​​entirely of GRP with my balloon method above.
 

    P-61 Mouldings & Plugs for Cowlings, Cockpit, etc.
                               

GRP Cowling P-61 with radial Dummy  

 Radial Dummy Engines;
 These can be made yourself ​​of plastic (hollow), or polyurethane foam (solid).
 First make a positive mould with balsa parts, to glue on a plywood base, make a negative print of this in a tray form resin or plaster.
 

 After hardening, there are three possibilities:
 1) Treat the mould with a release stuff,  fill it with polyurethane foam and remove the product after hardening.

 2) Alternatively; use the negative mould to form the dummies with GRP.
 3) Using the positive mold and 1mm ABS or transparent PVC to vacuum form it.

 The outer push rods can be made ​​from small pieces of 2mm plastic rod!        

 Turrets:

 Sometimes you can buy them, also for some purchased plans, but certainly not for your own designs!
 To make them our own, one must first produce a positive mould or plug (3mm plywood bottom former + some ply cross-sections and between them balsa filling, than planing,
 sanding it in shape, and for a vacuum method finishing it  with 25 grams mat and G4 polyurethane).
 For the vacuum method one can contact hobby stores, some of them have the equipment to do this.
 I myself apply the 20 years ago myself developed Kitchen oven method.

 Kitchen oven methode:

 Bond to the plug, a block as a spool handle. Then make an increased framework of 6 to 10mm plywood, make an opening, 1mm around larger than the basic shape of the plug,
 place over this a cockpits appropriate 0.5 to 1 mm thick plastic plate (clear PVC or Buyrate), tighted around, and place it in the kitchen oven (± 200° C).
 Keep an eye on everything and good as the plastic begins to sag, take out the whole quickly from the oven and push the plug through it, until just below the edge of the baseplate.
 Immediately cool off with a damp cloth, so that the material shrinks tightly over the plug. One can take the product from the plug with sharp scissors and cut it to size.

 UNDER-CARRIAGE

 Short Sunderland:

 The Sunderland was a flying boat and not an amphibian aircraft, so it really does not have an under-carriage for take-offs and landings on land!
 The original could only be provided with a so-called  beaching gear for maintenance on land.
  I copied this scale to be able to start on land, but spring Oleo's, also the tail wheelthing is scale, from this the original was towed out of the water.
 The beaching gear can easily be extended to a wider track, by pulling out both sides, otherwise it is too narrow for land take-offs.  For water-flying it is removable, by pulling it out of the stainless steel tubes
  from both sides, which are going across through the hull.