Specifications Models : (all Woodconstruction)
Boeing B-17 FLYING FORTRESS
|Northrop P-61 BLACK WIDOW|
Douglas A-26B INVADER
1/8th (only the 1/10th plan is available !)
4,00m = 158”
3,45m = 136”
|3,10m = 122”|
3,60m = 142”
2,85m = 112”
2,64m = 104”
|2,28m = 90”|
2,55m = 100”
Mix NACA 4415-ClarkY on Root/ 2415 Tip
NACA 4415 Root / 2415 Tip
|Ownmix NACA 2414-2314/ 0014 tip|
Ownmix NACA 2414-2314/ 0014 tip
4x Laser 70 (11,5cm³) four-stroke
4x Osmax 46SF (7,5cm³) two-stroke
|2x Laser 240-V twin (40cm³) four-stroke|
2x Laser 240-V twin (40cm³) four-stroke
M.A. 13x6 (9000 RPM)
M.A. 12x6 (10000 RPM)
|Engel Carbon 18x11 (8000 RPM)|
Engel Carbon 18x11 (8000 RPM)
Own Construction; Electric
none (Flying Boat)
|Own Construction; Electric|
Own Construction; Electric
2x Graupner GR-24 Hott, 12 channels
2x Graupner PCM double Superhet,
|2x Graupner GR-24 Hott , 12 channels|
+ 2x Engel PMS Plus Powerbox
2x Graupner GR-24 Hott, 12 channels
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,
1/8th B-17 Flying Fortress. Sp. 4m. Weight 19,3 kg.
4x 11,5cc Laser 70 four-stroke
Short Sunderland. Sp. 3,45m. Weight 18,5 kg.
4x 7,5cc Osmax two-stroke
P-61 Black Widow. Sp. 3,10m. Weight 18,5 kg.
2x 40cc Laser 240V-twin four-stroke
A-26B Invader. sp. 3,60m. Weight 21,5 kg
2x 40cc Laser 240V-twin four stroke
In relation to the transport and the manageable, the tailsection had to be detachable, and therefore providings were attached for the Fuselage-Tailsection joining and glued into some formers.
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,
Fuselage-Tail Splitting B-17
Tail-Boom Splitting P-61 Black Widow
Fuselage-Tail Splitting A-26B Invader
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),
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.
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!).
Linkage-Splitting Short Sunderland.
Linkage-Splitting B-17 just like the Sunderland.
(servo’s all in the front of the nose!)
P-61 Elevator & Rudderservos (upsidedown)
in the front of the Tailplane.
P-61 Elevator & Rudderservos (upsidedown)
in the front of the Tailplane.
Linkages of elevators & rudder in A-26B Invader.
STABILIZER- and WING JOINERS:
-On the Sunderland the stabilizer has been glued, in one piece, into the Tailplane.
Stabilizer Sunderland, in one piece
(elevators and rudder are removeable)
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,
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!!
Left Stabilizer-part B-17
Stabilizer P-61 with carbon join tubes
Stabilizer P-61 with the elevator control tubes (so also B-17)
Elevator- and rudder linkage on the P-61.
A-26B Invader Stabilizer Joiners.
A-26B Invader Elevator linkages.
-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.
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).
Winghalve B-17 (innner & outer part)
Winghalve P-61 (inner & outer part)
Winghalve A-26B (inner & outer part)
-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.
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!
Splitted Winghalve B-17
Dural and Carbon Wing & Stabizer Joiners
Outer Winghalve P-61
P-61 Inner Winghalve with Nacelle + Outer Winghalve.
A-26B Inner left Winghalve with partly the Nacelle.
A-26B Inner right Winghalve with Nacelle.
Wing-Joiner Short Sunderland
Cockpithood extending over the Wing
Splitflaps B-17 (still to construct against the wing!)
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,
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,
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.
Fowler Flaps Short Sunderland (upperside)
Fowler Flaps Short Sunderland (underside)
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 !).
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),
Flaps P-61 (on inner- and outerwing)
+ spoileron & tiny tipailleron
Spoilleron + tiny tipailleron P-61
| A-26B Invader Flaps:|
The A-26B Flaps had Double-slotted Fowler Flaps, but for the model it was to complicated to make it scale!
So I made normal Fowler Flaps (but the linkage is different as it is in the Short Sunderland model). These Fowler Flaps are going backwards max. 50mm en max. 50° downwards.
An 8 kg servo (again slowed down to 5 sec.) controls a long 4mm pianowire via a controlhorn in the middle, on this axle,
there are 2 more controlhorns and these are controlling 2 pushrods (through long guiding tubes),
inked on the upperside of the Flap-leading edges. On the same controlhorns there are M3 rods, but a little bit closer to the axle and linked on the underside of the Flap-leading edges.
On one outerside of the flaps there is a third rod (also through along guiding tube), but not controlled, just for extra guiding!
Because these M3 rods are controlled closer to the axle, they make a shorter way than the upper pushrods, and so the Flaps are turned over, more and more, during pushing.
Very simple, but adjusting the whole, took a lot of time, because the flaps are not rectangular but tapered! So the push-movement is on both outersides different!
Fowler Flaps A-26B Invader.
Flap-linkage A-26B (innerFlap)
Flap-linkages A-26B (upperside)
Flap-linkages A-26B (underside)
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),
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.
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
Balloon method Polyester parts
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).
A-26 Mouldings & Plugs for Cowlings, Cockpit, etc.
GRP Cowling A-26 with radial Dummy
Radial Dummy Engines;
After hardening, there are three possibilities:
2) Alternatively; use the negative mould to form the dummies with GRP.
Selfmade Moulding for the Enginedummies
Vacuum formed Radial dummy engine.
Sometimes you can buy them, also for some purchased plans, but certainly not for your own designs!
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,
Tail Turret Short Sunderland
Nose Turret Short Sunderland
Nosedome Plug B-17
Cheek Gunshields Plugs B-17
Nose Dome & Chin-Turret B-17
Cheek Gunshield left side B-17 Removable Cockpit Hood B-17 with Top-Turret
Sperry-Ball Turret B-17
Turrets & Nosedome of the A-26B Invader Removable Cockpit Hood A-26B Invader
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
the stainless steel tubes from both sides, which are going across through the hull.
Removable & extensable Beaching Gear Short Sunderland
B-17, P-61 & A-26B:
They have a retractable undercarriage, an own construction and works via an electric motor, gears, micro switches and an M6 screwjack.
The micro switches are pressed down by adjustable rods, which in their turn are pressed by the spindle back- and forward moving part.
Own constructed electric Retract B-17, with 6½” wheel
Own constructed electric Retract B-17, down.
At the P-61, the nose strut (with 4½” wheel) is retracted backwards, which is also closing the welldoors.
During retracting the gear, all doors, 5 seconds delayed, get closed by two 180° Servos.
Own constructed electric Retract P-61
The own constructed Retracts with plastic cogwheels as a gear
The plastic cogwheels as a gear, on the inside of the head wall (B-17), was exchanged later on the P-61 by a gearbox directly to 6V. speed 400 motor,
At the P-61, the plastic gear has been exchanged now for a gearbox
P-61; the 180º Servo for the mainwheel well doors
Main Strut P-61 with 7” wheel
Nose Strut P-61 with 4½” wheel
At the A-26, the nose strut (with 5½” wheel) is retracted backwards, which is also closing the welldoors. In the lowered position, the welldoors are kept open by self bended springs
During retracting the gear, all main-geardoors, 5 seconds delayed, get closed by 180° Servos.
A-26B Electric Retracts. Own Construction
A-26B Retract of the right-innerwing with the wheelbay doors
Self bended springs for the wheelbay doors
A-26B Invader. Rightside Mainwheel
A-26B Invader. Nose-guns & Nosewheel
ENGINE LINKAGES & ENGINE MIXERS.
The engines at my multi-engine models have no side thrust and little or zero down thrust (nacelles are being built on at 0 degrees).
-At the B-17 (1/8th) that are 4x four-stroke Lasers 70 (11.5 cc) with MA 13x6 props (9000 RPM), these have a very small overall height.
on the servo (in the center) and control cables (sullivan) to the 2 throttle horns.
And the B-17 is, due to its enormous tail fin in the start, with the wind is in an angle or cross, will rapidly break out to the wind direction.
Controlling the throttles happens here on both sides with control cables of sullivan, linkaged to a servo.
Mixing Rudder / Engines, B17 - Sunderland – P-61 & A-26B:
For this we need 4 mixers, of which mixer 2-3-4 are on the same switch! (at my transmitter a switch on the throttle stick).
Never forget to switch off Mixer 2-3-4 after taking off! (otherwise the engines will react unintentional, when operating the rudder).