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Old 01-02-2010, 10:59 AM   #1
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Detailing a DeHavilland Beaver


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This is a thread about detailing a DeHavilland DHC-2 Beaver model for scale competition.

The basic model was built from a kit, so I will not be showing or discussing the normal kit building process, but I will be discussing the deviations from the kit, and other changes for extra detailing.

Some of the detailing will be beyond what is normally done, but this model is intended for scale competition to eventually replace my 1/3 scale Super Cub. I am sure that some readers will find this excessive or even obsessive, and that is ok, as we all have different needs and interests. Personally, I have come to enjoy the research part of this kind of project as much as the challenge of building an accurate scale reproduction. Even so, I am reminded of Dave Platt’s advice – we do not have to build an exact scale replica – it only has to look like one. I have learned recently that the folks who build ship models for museum display often make the small parts larger than scale as they look better. My own example is the hinges on a stabilizer. The stab is thicker than scale. Scale size hinges looked dinky and unrealistic. Hinges larger than scale looked better.


Why a Beaver?
I love Beavers!! My first attempt at a “serious” scale model was a Beaver from the 8’ Unionville kit. Since I was starting scale competition at the Novice level, it served its purpose by getting me into scale competition and gaining experience. As I moved up to more competitive levels, it became apparent that this model would not generate the static points to remain competitive. However, this Beaver model is still part of my fleet, and I still enjoy flying it.
Another aspect is the Beaver is that it was built in my hometown. I have always thought that the DeHavilland Canada facility created some great aircraft.
The more that I researched this project, the more involved and interested in Beavers that I have become. There are great stories out there about Beavers. They always feature largely in any aviation documentary about Bush Planes or Float Planes.


Why a Kit??
When I started out, I had expected to design the whole model from scratch. I did a survey of the kits and ARFs on the market to form some ideas of size and power requirements. In doing that, I found that most available Beaver models are not very accurate. During this search, I happened upon the MR Aerodesign Beaver https://mraerodesign.securicom.ca/ . It was about the right size for me, it has very accurate outline, and it had some other very neat design features. The scale landing gear immediately caught my eye. So … I bought the kit to save myself a lot of design effort, and a lot of fabrication effort in making the cowls and landing gear.
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Old 01-02-2010, 11:04 AM   #2
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Re: Detailing a DeHavilland Beaver -part 2

Finding a Beaver to Model:
The next step was finding a specific Beaver to model. For competition, the model has to be of a specific aircraft, not a generic type.
Although most Beavers look very similar, there are small differences between them due to aftermarket modifications. The Beaver Mk I was originally built with the circular porthole window in the aft cabin. On many Beavers, this has been replaced with one or two windows to provide better visibility for passengers in the rear seat.
Another popular modification is the “Alaska Door” which provides a huge cargo entry behind the normal doors.
A number of Beavers have wing modifications which include leading edge droops and wing fences.
There are even a few Beavers which have had the engine moved forward about 10” to provide better balance with heavy cargo.
And of course there are small fins mounted on the stabilizer or sub-fins on the fuselage fitted to float equipped Beavers.

All this means that you should pick the aircraft to model before you cut wood!

It is very helpful to have an aircraft near your home to visit several times during the build, or at least to visit your selected aircraft and take a few dozen – or hundred – photos of all the details, also keeping in mind that photos that you need for your “Documentation Package”

My selection process involved finding a “pretty” Beaver on wheels, as almost all scale competition takes place from runways. Yes - I know some scale rules allow the use of dollies for water aircraft, but that was a complication that I wished to avoid.

There are a couple of great resources for finding Beavers. The best is the website called Beavertails www.dhc-2.com which has photos of most of the Beavers ever built, plus some technical resources. Sometimes a web search of “DeHavilland Beavers for sale” will turn up some interesting photos.

The Yahoo chat room for Beavers http://groups.yahoo.com/group/DHC-2Beaver/ is a great place to visit. Lots of interesting Beaver stories and also some technical information if you search the archives. Plus an associated photo album section with more Beaver pictures – including some models. A search of this website also will help identify some key places to visit and watch Beavers. For Example: Campbell River, Vancouver and Nanaimo harbours, and Tofino in BC; Kenora, Dryden, Red Lake and Sioux Lookout in Ontario; and Selkirk, Gimli and St. Andrews in Manitoba.

There are several other Beavers in Museums across the county, and a number in museums in the USA, as well as New Zealand and the Netherlands. Beaver #454 at Robins Air Force Base Museum near Macon Georgia was neat one to visit as the aircraft was in a quiet corner, and I could walk right up to her and measure things like corrugations, door handles and rivet sizes.

Bob Banka at Scale Model Research. http://www.bobsairdoc.com/ has Foto Paaks of Beavers available for those who cannot get up-close and personal with one. MR Aerodesign also has a CD full of Beaver photos.

The Beaver that I have chosen to model is C-FFHB, the very first Beaver, and also the one in the Canadian Aviation Museum in Ottawa. I am planning on the Norcanair livery.
I visited the museum to look at and photograph the aircraft, and to make a prearranged visit to their archives. They have some photos of this craft through its history, as well as all the log books and maintenance records and other information. I found enough information to document C-FFHB on wheels in the Norcanair colours, and have enough supplementary information to document the details.
While at the museum, I discovered that they have modified the aircraft. They changed the call letters to CF-FHB to match the markings when the aircraft was built. They also changed the cowl to the original one with the small lower scoop. So what is on display is an aircraft that accurately represents neither the original as-built aircraft, nor the aircraft as flown by Norcanair!
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Old 01-02-2010, 11:10 AM   #3
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Re: Detailing a DeHavilland Beaver -part 3

Documentation:
In addition to the websites, museums, and visits to full scale aircraft, there are a number of good references on Beavers.
In My Library are:
• The Beaver Bushplane at home in Ontario by Henry and Linda Feisen: ISBN 0-9686597-0-5.
• The Immortal Beaver by Sean Rossiter: ISBN1-55054-519-1.
• DeHavilland in Canada by Fred W. Hotson: ISBN0-921022-10-7.
These books do not necessarily provide a lot of scale detail, but they do provide some interesting background on the aircraft.

Of more value for finding scale details, dimensions, and information are:
• Beaver DHC-2 Flight Manual
• Beaver Repair Manual
• DHC-2 Beaver Illustrated Spare Parts Catalogue
• The FAA Type Certificate - AIRCRAFT SPECIFICATION NO. A-806

The Illustrated Spare Parts Manual has cutaways and exploded views, plus all the layout dimensions of the fuselage bulkheads and wing ribs for accurate rivet placement. There are also many many sketches of all the parts and aircraft system, letting you dig up all kinds of details.
The Repair Manual has details of all the sheet metal panels and metal thicknesses for setting the panel lines accurately
These references are available on the web - for a fee.

Three-View Drawings:
Accurate three –view drawings of the Beaver are hard to find, particularly ones with panel line and other details. Bob Banka has one at Scale Model Research. http://www.bobsairdoc.com/ I believe that the original source was Aeromodeller magazine in October 1949.

I have ended up making my own three-view drawings using CAD software.
A sample of the wing drawing is attached. Panel lines are blue, Rivet lines are red. Sorry – but this work is not yet finished or available for sharing at this time.

For the “ultimate” Beaver model – have a look at http://www.mhm-scale-aircraft.com/me...p?search=DHC-2
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Old 01-02-2010, 11:12 AM   #4
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Re: Detailing a DeHavilland Beaver - part 4

Engine Selection:
The next step for me was developing a power system. My main objective was to have everything enclosed in the cowl. A secondary objective was to have a four-stroke. The sound of a four-stroke in a scale model is hard to beat. Note that a full scale 9 cylinder radial running at the rated 2300 RPM has 5175 firings a minute. A model four-stroke running at about 10,350 RPM has the same.
My research and scaling determined that I wanted to have about 3 HP (as rated by the engine manufacturers) to achieve realistic scale performance with an expected weight in the 25 to 30 pound range.

I quickly determined that most model radials would not fit in the cowl, except for the Technopower 9C which was probably too short on power, and definitely much too expensive.

Some gas engines in the range of 25 to 40 cc would work, but all had the spark plug wire hanging out of the cowl.

Single cylinder four-strokes in the range of 1.8 to 2.5 might work, but probably with a bit of the head exposed. Their fuel consumption is also high, requiring a large tank.

Of the multi-cylinder four-strokes the Laser V-240 would probably work. It does have a good reputation, but there is not much experience with this engine in our area, or parts availability.

Two-strokes in the range 1.08 to 1.6 would also work, and most of them fit in the cowl.

I ended up with an OS AX 120, which is a nice compact engine, which fits nicely in the cowl, and leaves room for a dummy radial. Bison Custom Muffler made me a special version of their standard muffler for the AX 120 which puts the model exhaust at the correct scale position and size.

Since I made that decision a couple of years ago, the progress in electrics has been phenomenal. I have reconsidered the use of an electric motor, perhaps with an audio system to get that nice radial sound, but my construction has proceeded to the stage where I am committed to the glow engine. Maybe next time!

To complicate life a bit, I have chosen to install an instrument panel and pilot seating in the front of the cockpit. This means that I cannot mount the fuel tank just behind the engine as we normally do. The tank will be mounted in the center of the cabin just behind the centre of balance. I will pressurize the fuel tank using crankcase pressure, then use an Iron Bay Fuel Regulator to manage the fuel to the engine. I have bench tested this system, and it seems to work ok. Actually, on the test stand, the AX 120 seemed to draw fuel well with the remote tank even with normal exhaust pressure and a simulated steep angle of climb.
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Old 01-02-2010, 11:19 AM   #5
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Re: Detailing a DeHavilland Beaver - part 5

Engine Installation:
Here are some photos of the engine installation:
You will note that I have relocated the throttle servo to the firewall. I did this to make the throttle linkage simpler, accessible and maintainable.

The dummy engine is a 1/6 scale Wasp from Williams Brothers. Still some detailing to add to it.
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Old 01-02-2010, 11:22 AM   #6
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Re: Detailing a DeHavilland Beaver - Part 6

Wing Hinges
One of the few things that I did not care for in the MR Aerodesign Beaver were the hinges for the flaps and ailerons. The hinge point is in the right scale position relative to the wing, but the parts do not look very scale like.
I made my own hinge parts from 0.040” and 0.060” aluminum. They are bolted to the ribs in the wing, aileron and flap. The hinge pin is a 2-56 bolt, set in a nylon bushing to avoid metal-to-metal contact.

One picture shows the wing portion being installed, and the jigs that I used to ensure proper spacing and positioning.
Another picture shows the portion for the control surfaces and the jig that I used to put the kink in them.

For a drawing - see Part 20
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Old 01-02-2010, 11:24 AM   #7
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Re: Detailing a DeHavilland Beaver - part 7

Wing Hinges 2

These two pictures show the finished hinges on a prototype piece of wing.
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Old 01-02-2010, 01:10 PM   #8
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Re: Detailing a DeHavilland Beaver

just going over your scale sound and can't figure how you got to 5000 impulses per sec I get 2300x9 cyl devided by 2 ( fires every second stroke)=10,350 pulses per min

a 5 cyl rc 4cycle motor @ 5000 rpm =12,500 pulses per min

a twin 4 cycle at 10,000= 10,000 pulses per min

keep up the great work I will be following colsely ,another beaver guy here.putting the 5 cyl in mine but now relize pulses may be a bit fast ,I guess I will have to stay off the throttle to sound wright .man you do learn something every day.Roger

PS: I am doing a set of wings now and think I will borrow your hinge Idea nice .is it the same for aileron & flap.
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Old 01-02-2010, 04:10 PM   #9
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Re: Detailing a DeHavilland Beaver

Hello Cageon Flyer: AMAZING attention to detail here!! I will look very much forward to your progress with this build.
You are not taking the next step, you appear to be going several levels above normal. You might consider an anamated pilot or finding a very small dwarf!!
Joking aside, I would never have the patience to achieve these levels of perfection, I am keen on the expertise it takes, and enjoy learning the techniques and fabrication methods.
I sort of copied Mr Aerodesigns landing gear front and back on my 8 ft Unionville Turbo Beaver, big improvment over "wire" LG. Made no attempt to change aileron/flaps configuration, I will think about it now! Your pictures have given me the general layout and shapes, now they make sense.

Where is Bobcageon from Owen Sound? Our little field is 450 ft X 150', our club would love to have you here for our annual fly-in held in early June.
Will advise dates as soon as there official.
Builds like this one are the prime reason for being involved in a site like RC Canada, the planes, their builders, the hints, tips and genuine dedication to the sport is the best!!
No matter what level each person choses to build to, these build sites give us all the desire to achieve higher levels, make better airplanes.
Thank you for proceeding with this build,all will be impressed!!
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Old 01-02-2010, 06:32 PM   #10
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Red face Re: Detailing a DeHavilland Beaver

You are right Ramjet - I mistakenly divied by 4 instead of two!!!

Quote:
Originally Posted by RAMJET View Post
just going over your scale sound and can't figure how you got to 5000 impulses per sec I get 2300x9 cyl devided by 2 ( fires every second stroke)=10,350 pulses per min

a 5 cyl rc 4cycle motor @ 5000 rpm =12,500 pulses per min

a twin 4 cycle at 10,000= 10,000 pulses per min

keep up the great work I will be following colsely ,another beaver guy here.putting the 5 cyl in mine but now relize pulses may be a bit fast ,I guess I will have to stay off the throttle to sound wright .man you do learn something every day.Roger

PS: I am doing a set of wings now and think I will borrow your hinge Idea nice .is it the same for aileron & flap.
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