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de Havilland DHC-4 Caribou

Old 07-23-2014, 09:02 AM
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ByLoudDesign
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Default de Havilland DHC-4 Caribou

Thought I would throw this out to see how many folks might be interested. Staring the design in 1:10 scale, 114.700" [2.9m]. The model its self will be simple enough, until you have to deal with the hellish aileron and flap system. With 4 sections, all split, where you have to control a inner and out half! Glad the hinging is out side the surface!
Old 09-30-2014, 02:43 AM
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Sounds good to me. The Caribou is definitely a interesting plane and a popular plane in Australia. Nice size also. Keep us updated with progress please.
Old 09-30-2014, 07:02 AM
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Well, The tail up to the Cargo ramp opening is done. Took a while to figure out the system to control the horizontal stabilizer which is a function of flap position, Elevator and rudder and get it in the narrow tail section. The wings are two section separating on the center line of the fuselage, so all the electronics, batteries and the like have a nice home that is easy to get to. The servos for all the tail function are there also connected with the carbon filled plastic push rods and tubes. I have the basic structure for the wings and nacelles done. But even with the great info the Canadian company King Air provided I am still noddling on how to make the flap arrangement work in scale, the individual parts are small enough to cause trouble even are 1:10 scale. Have the scale LG drawing done as far as the struts, but need the input from Century Jet on what the the retract mechanism will look like as standard type will not work because of their placement in both the fuselage and nacelles. I post the 6-views shortly!
Old 09-30-2014, 09:53 AM
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Not very good quality!
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Old 10-20-2014, 11:02 AM
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Was able to discern what some of the Caribou structural drawing were showing, so I have the inner control surfaces pivot point [Hinge line] figured out, but do not yet have the other pivot information for the outer surfaces. Kind of got the controls figured out in my head. as soon as I get the outer surface information I'll see if it works in CAD. Some times the brain is a big disappointment. LOL! Have the wings; with the exception of the flap/aileron nightmare, and the entire tail section done up to the TE of the wing. From there to the back of the cockpit area is a constant section and will go fast. leaving the pug nose, won't do that until Century Jet comes up with the nose LG as it is only a short distance from the nose and most likely will require a special retract. So make no sense to spending time designing and then have to regroup.Century Jet has the scale drawing for the landing gear, plan to provide both sport and scale gear, electric or air, and with or without brakes.
Old 10-20-2014, 01:39 PM
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Default flap detail

Originally Posted by ByLoudDesign View Post
Was able to discern what some of the Caribou structural drawing were showing, so I have the inner control surfaces pivot point [Hinge line] figured out, but do not yet have the other pivot information for the outer surfaces. Kind of got the controls figured out in my head. as soon as I get the outer surface information I'll see if it works in CAD. Some times the brain is a big disappointment. LOL! Have the wings; with the exception of the flap/aileron nightmare, and the entire tail section done up to the TE of the wing. From there to the back of the cockpit area is a constant section and will go fast. leaving the pug nose, won't do that until Century Jet comes up with the nose LG as it is only a short distance from the nose and most likely will require a special retract. So make no sense to spending time designing and then have to regroup.Century Jet has the scale drawing for the landing gear, plan to provide both sport and scale gear, electric or air, and with or without brakes.
they are fowler flaps,whch in essence puts the hinge arc center point below and behind the leading edge of the flap.All of the dehavilland planes use the same system,so look at twin otter,and Beaver pics for better documentation.Even the Buffalo (dhc-5) has more recent images
Old 10-20-2014, 01:57 PM
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here is a view of the split,slotted fowler flaps.The small arms are actually the controlling arms,and the rest is providing the hinge point
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Old 10-20-2014, 02:04 PM
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The nose gear is probably the simplest of all the retracts...servo-less metal retract,needs 2 x 2 inches (hobby king),90* swing,mounted just below center axis,probably 5" leg oleo.I have modelled a Buffalo,8 foot,it requires a 4" leg.Ultimately make yourself a 6" x 2.5 x 2.5 inch box,and you should be good to go
Old 10-20-2014, 02:08 PM
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Suggestion...model the inboard wing as one complete unit,approx 1/2 of your total wing.and make the rather peculiar wing spar one continuous piece,to absorb the landing impacts from the engine nacelles
Old 10-20-2014, 09:58 PM
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alex5 ~ Thanks for your suggestions. But sense I design models in true scale the split flaps and flap/ailerons is a task that will have to be tackled. I have a ton of detail photos and more on there way, as well as actual structural drawing from a Canadian company that has been helping me with getting the info I need, I also have an Australian friend that flew one and can get more photos if they are needed! .
Old 11-10-2014, 08:21 AM
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doug bartley,in owen sound ontario,has modeled several of the dehavilland aircraft split flaps,ie twin otter,beaver.Maybe get ahold of him and he could point out where the hinge points could be.
Old 11-10-2014, 08:28 AM
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doug bartley,in owen sound ontario,has modeled several of the dehavilland aircraft split flaps,ie twin otter,beaver.Maybe get ahold of him and he could point out where the hinge points could be. Ray Mcdougall has built the next plane in that series(the Buffalo) and it has the same flaps.Have a look at how he did it.www.raysmodels.ca www.raysmodels.ca
Old 11-10-2014, 10:30 AM
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Alex5 ~ Again this is a true scale project, the model McDougall did seems to have flap that are under the wing. It is a nice model, The Buffalo is a very different animal the a Caribou.
Old 11-12-2014, 12:04 PM
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Here is a build that seems to have overcome the design issues regarding flaps,and gear.
http://khmertube.khmerelite.ws/index...l#.VGO8RmeLHrQ
Old 11-12-2014, 01:00 PM
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Thanks! I have looked at this before, interesting. I have the pivot points for the first stage from the full size plane plans I have but no information about the second stage. on the real A/C the stages work independent of one another. I am just going to have to CAD up the fists stage and the work at finding the pivot for the second..
Old 11-12-2014, 02:15 PM
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the second stage is pivoted(pulled ) by a connecting rod,as the furthest flap is deployed,it pulls on the iedge of the second stage.Although the connecting rod is seemingly tiny,it controls the orbital motion,while the main hinge pivot point controls the lateral movement.Ifyou look closely at the photo I sent before,you can see the connector closest to the flap surface.
Old 11-12-2014, 02:27 PM
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The operation is best described by this web page.
http://www.flightglobal.com/FlightPD...20-%203033.PDF
Old 11-12-2014, 02:35 PM
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Alex
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Old 11-12-2014, 04:53 PM
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From the pilot's review,there was nothing inferred about there being any unique controls,in the Caribou,and the cockpit photos substantiate that.This means that the flaps and ailerons were linked by fixed couplings,and adjusted via common controls,Nothing individual,right versus left,or from front to back.The only thing modifiable was the trim,(by knobs).I did a little photo editing ,to get the inboard flaps setup.the out board ailerons have a link to prevent over- curving the outboard flap,when acting as a flaperon.Alex
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Old 12-11-2014, 11:06 AM
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From the drawings supplied by King Air and some actually taken from the A/C I have the position in plan and profile of the pivot point of the inner flap hinge, the Beginning .of the flap pocket [LE of the wing] and the LE of the inner flap section. Then it did not take to long to play around with the shapes and outer pivot point. Realizing that the the nose of the flap section have to be the radii drawn from the pivot points to keep the space between them constant. The control of the flaps for the nacelle into the fuselage is shown, 40 of travel for the inner section and 20 for the outer. There will be a hinge pylon on the two ends, these are simple as this section is a constant foil shape. Have the second section, outboard of the nacelle done. Pretty much just scaling the same pattern scaled down and fiddling with the shape of things.To make the pylons look scale I will most likely have to provide covers.
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Old 02-22-2015, 03:11 PM
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Still working on it. Making plug parts for the nose section, including the windscreen. Continuing the work on the flap/aileron system. It is a little tedious has you have to set up each hinge and control point and the transfer the measurements the the wing drawings [plan & elevation] and make sure they form a straight line the each other and their neighbors. Most of the time the are close, but still require a little tweaking!
Old 04-24-2015, 01:37 PM
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maybe ,use some long drill rod,and align the pivot points on each hinge.Alex
Old 04-24-2015, 03:41 PM
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I was planing on using that idea with #4 push rod to insure the hinging is aligned before tightening the hardware down on both the wing and flap/aileron when it time to install them. The hold up is having the hours to get the drawings done. I have a paying project for a 1:4 scale King Air 350i. So I work 5 days on that, and the Caribou a spec project as much as possible on Saturday and Sunday! Have a distributor in Australia that is going to do the composites, Century Jet is doing the LG. So I got most of the ducks in the row, also have talked with the supplier that might want to do the flaps and ailerons and their attached hardware in glass and foam. Even as big as the model is the out board aileron is pretty small in section which makes hardware attachment hard. The outboard aileron is only 2.688"C x .468"T [root] x 17.3125"L x 2.125"C x .375"T [tip]. Thinking of using a CF sq. rod thru its length that will pass through all the hinges and ribs, which I think will not allow it to twist end to end. With each part of the flap/ailerons attached at the root middle and tip, there should be no problem with the flexing end to end! I want to get it done as I have several possible builder, Israel, Australia and a couple of them here in the good old USA!!
Old 04-24-2015, 07:28 PM
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the fowler hinges arent that big,so the real issue would be getting enough material around the pivot points.When you scale it down,it might mean a 1/16" between holes.By the way,Solidworks is great for animating the working hinges.You draw them up, then operate them to see if they function as predicted
Old 04-24-2015, 09:42 PM
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They are not Fowler flaps!

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