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Old May 09, 2012, 03:40 PM
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Build Log
Berkeley DHC-2 Beaver

Being Canadian, I have a soft spot for bush planes like the DHC Beaver and Noorduyn Norseman. I recently came across a laser cut reproduction of the 1/12 scale DHC-2 Beaver kit (Berkeley Models circa 1955) from Dan Walton at Laser Technologies. Although not a complete kit, it does contain the 'bones' of the model including the wing ribs, fuselage formers, fuselage sides a couple of other bits.

This thread will document the build including the modifications needed to convert it to RC and electric power. I will also be making significant changes to the fuselage in an effort to lighten the plane. With any luck I hope to stay under 16oz AUW. Crossing my fingers...

So let's get started...

The plans can be found in the 'Vintage Plans' thread here on RCG: http://www.rcgroups.com/forums/showp...postcount=1778

Update 12.08.19

Photos of the finished plane and specs can be found here: http://www.rcgroups.com/forums/showthread.php?t=1649565&page=5#post22490275
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Old May 09, 2012, 05:01 PM
Big gov never Works
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Skunk Water, Rhode Island
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That brings back memories!

Fuzz
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Old May 09, 2012, 06:28 PM
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First up is the wings. The kit does not include spars so I had to cut my own from 1/8" sheet balsa. This is where the first modification starts...

The top of the plans shows a front view with the dihedral for both scale/CL (~2 deg) and FF/RC (~6 deg). However the wing spar shown in the parts plan is the 6 deg version. Since this is going to be a 4ch plane, I redrew the spar and reduced the dihedral to 2 deg/side. The attached PDF file shows the re-drawn spars. I will continue to add drawings and photos as I go so stay tuned.

There are some more peculiarities with the wing ribs. I'll get to that shortly.
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Old May 09, 2012, 10:00 PM
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Wing construction in progress. Note the last 5 ribs are shorter. They have already been cut for the ailerons. I was almost ready to glue the centre section ribs as well, but I'm going to hold off on this until I finish the wing mount on the fuselage. My intention is to rework the wing so it can be bolted on as opposed to using rubber bands. More on that later. For now, I'm going to stop at the first rib.

Interestingly, the wing ribs have an undercambered profile to them. This isn't exactly scale as the full sized plane used a NACA 64A416 which appears to have very little undercamber. The build instructions on the plans mention this:

Quote:
You will note that the ribs at the dihedral break have a deeper camber than the others to match the scale airfoil at the cabin. Slight undercamber outboard of the center section increases wing efficiency for better performance.
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Old May 09, 2012, 10:29 PM
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The Beav' has a short nose and long rear fuselage. Recommend you lighten everything aft of the wing trailing edge to make getting the cg right easier to do without having to carry a lot of nose ballast. On my Berkeley Stinson Reliant I had to mount the 3S lipo pack protruding through the firewall next to the Esskay 400XT outrunner , used pull-pull rudder and elevator linkage, mounted servos and receiver more foreward than usual and still had to add some nose ballast. Models like this are critical with respect to cg , for the maiden it's better to attempt first flight somewhat nose heavy.
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Old May 10, 2012, 06:19 AM
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Quote:
Originally Posted by E-Challenged View Post
The Beav' has a short nose and long rear fuselage. Recommend you lighten everything aft of the wing trailing edge to make getting the cg right easier to do without having to carry a lot of nose ballast.
I scratchbuilt a Beaver from foam a few years ago and I became painfully aware of it's very short nose moment. Those lessons aren't lost on me!

Back to the wing....

The trailing edge appears to be fabricated from a piece of 3/4"W x 5/16" stock which is not included in the kit. This leaves a small nub for the wing ribs that make up the ailerons. Rather than work with such oddly shaped pieces. I plan to make up new aft wing ribs and swap the TE for a smaller piece of 3/32"x1/4" balsa. This will also drop a considerable amount of weight from the wing assembly.
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Old May 10, 2012, 09:06 AM
I think I can glue that..
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following! you can make all the mistakes so I dont have to when I build mine
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Old May 10, 2012, 10:54 AM
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More free advice: I inlayed balsa around the nose and cabin area, added functional doors, instrument panel with spoked control wheels, front seats and a carved balsa pilot figure because I worship Stinson Reliants. Covering was Doculam with white and red/orange latex house paint. Battery was 3S 1300 lipo. Model came out heavy, had to fly and land faster than scale, stall prone. Moral of story, keep it light, err on the side of flyability.
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Old May 10, 2012, 01:55 PM
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Quote:
Originally Posted by E-Challenged View Post
Moral of story, keep it light, err on the side of flyability.
I wholeheartedly agree.

Back to the build....

I was looking at the wing construction. The upper surface forward of the main spar is sheeted with 1/16" balsa. Although it looks beautiful, the sheeting adds another ~10g in weight. I am going to revert to a 'turbulator style' upper surface using 1/16" sq balsa equally spaced at 3 locations. I have a few of Pat Tritle's designs that use this construction method and it works quite well.

Another change is the deletion of the rear spar. Since I am adding ailerons (and possibly flaps), the spar will be replaced by a former further back at the hinge line. The slots for the rear spar will serve a purpose though... to pass the servo wiring through!

Speaking of servos... I need some small 3-6g servos. Still undecided on that one.

Note, there is currently no webbing between the upper and lower spar after the 3 or 4th rib. My initial impression of the wing in it's current build state tells me the webbing is needed. So off I go and cut some 1/32" balsa shear webs.

The rear former along the hinge line is 1/4" by 1/16" stock. Next up is the trailing edge, aft ribs and ailerons.

Oh, in case your wondering... The wing in it's current state is 21g or 3/4oz. I'm shooting for about 70g or 2.5 oz without servos.
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Old May 12, 2012, 06:52 PM
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Right side wing construction is nearly complete. A few details to note:

- The last 5/8" of each wing rib was removed, and a rear former was added.
- New ribs were cut for the ailerons and flaps. The trailing edge is 1/4" x1/16" balsa. The leading edge of the ailerons and flaps is also 1/4" x 1/16" balsa set at 30 deg from perpendicular.
- Slotted flaps were added. More details on this later.
- 1/32" shear webs were added between the spars to stiffen the wing.

I still have a few details to wrap up including servo mounts, turbulators on the upper surface LE, and the wing tip. I'm thinking of carving rounded foam wingtips which will be covered with Microlite covering.

Finally, I decided to change the center section of the wing. The section forward of the main spar will be incorporated into the fuselage instead. The wing will plug into the fuselage via 2 dowel pins in the spar and be held in place with a nylon bolt. More details on this once I start construction of the fuselage.
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Old May 14, 2012, 09:24 AM
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I've started the LH wing construction. Note the following:

- Flaps have a 'reverse' hinge from the ailerons. These will be slotted flaps using Sonic Tronics Pheonix hinge for attachment (#SOT130 and SOT131). A 1/8" x 1/16" filler strip on the upper wing surface will seal the gap when in it's full up position.
- 1/16" turbulator strips have been added. Also note the filler pieces glued to the top of the main spar. These will make the ribs continuous from the spar rearwards.
- The W3 ribs are thicker in chord than the outboard W4 ribs. I really didn't care for the looks as the full scale model doesn't have this feature. I re-shaped the second and third W3 rib to match W4. The first inboard W3 ribs remains stock to mate with the fuselage.
- The first inboard W3 rib has to mate with the fuselage sides. Be sure they are installed perpendicular to the center portion of the main spar, which is NOT the same as the outboard ribs.
- The first W3 rib forward of the main spar had to cut from scratch to fit the turbulators. This will also form the separation line of the wing and fuse.

A few tips regarding construction:
- When sectioning the ribs for the ailerons, stack all the ribs together and use pieces of 1/8 x 1/4 balsa in the spar notches for alignment then carefully cut all the ribs at once using a razor saw.
- Completely form rounded the leading edge piece (using a small hand plane or sandpaper) before gluing. It's much harder to do this afterwards once it's glued to the wing.
- Shear webs are 11/16" W x 5/8" H. These are NOT shown on the original plans but are required for wing strength.. I oriented mine with the wood grain lengthwise, but I have used vertical orientation on other builds. I suppose the latter is better, but I found the former simpler to cut. The webs are then glued to the forward face of the upper and lower spars.

Keep in mind this is a very LIGHT plane. As lightly as this wing is constructed, it's still far stronger than what is needed for scale flight and then some! I had an accident where I inadvertently leaned against the TE of the wing. I put a 3" bend on the LH side with no damage. Yikes!

Even though the wing isn't completed yet, I'm only at 1.38oz. I fully expect to be around 2oz before servos.
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Old May 15, 2012, 09:53 AM
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I came across a great deal on some NIB Hitec HS-45HB servos for $10 ea. Just couldn't pass it up. At only 0.38" thick (9.8mm), they are the thinnest servos Hitec makes. I should have no issue fitting them in the wing. They fit my Herr Mini-Sport just fine and I'm really happy with their performance:
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Old May 15, 2012, 05:00 PM
Rodrigo Navarro
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Mexico, NL, Monterrey
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Following. Nice build thread. I saw some techniques you are using that can help me with my nearly first build. Thanks.
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Old May 17, 2012, 06:22 AM
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I framed up the other wing half, same as the first.

- For the flaps and ailerons, I glued the LE & TE pieces and the two end ribs first. This helps set the alignment for the rest of the ribs.
- There is a 1/16" gap between the flaps, ailerons and end ribs. I purposely keep this a bit on the wide side. This compensates for the covering thickness and expansion of the balsa due to humidity.

I'll finish up the wing tips before moving to the fuselage. The center section won't be completed until the fuse is done. The servo mounts will also have to wait until the servos arrive in a couple of days.
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Old May 20, 2012, 09:30 AM
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Fuselage construction in progress.
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