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  1. #1

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    8 foot scratch build Otter

    I have been slow to start this build thread and hope the photos will help viewers to see and understand how I designed this build. It is a composition of plywood, balsa, and pink foam. The basic design came from dimensions taken from an enlarged 6 foot Otter plan. I wanted to involve the pink foam as much as possible!

    I started first figuring the size of the fuse top, bottom and twin sides with a 1/2" square balsa edge glued to the edges where they would meet each other on a 90 degree corner. This allow me to put a 1/2" triangular strip inside and on the outside of each corner. I was left with a perfect balsa corner to radius. The corner was strong and smooth. Please note: all the fuse surfaces will be glassed. I did this by marking all around the plan with a red narrow point marker 1/2 inch in from the edge of the sides and top shown on the plan. I laid the red outlined plan over the foam sheet and used a black narrow pointed pen to poke holes through the plan at the ends of straight lines, and every inch or so around any curves. When I had completely encompassed the part lifted the print and then connected the dots. Hard metal 18 and 36 inch rulers help considerably.

    Secondly, I designed a thin 3/32" plywood box to support the 1/4 inch plywood firewall and 2 bulkheads and hardwood stringers needed to give the fuselage it's strength. It was approx. one third the length of the fuse. I drilled lightening holes in various places in the sides of the box but left ample bonding surface to bond with the pink sides. I Titebonded the sides to the box by stacking the box between the foam sides laying on their sides then placing a large flat board on top and anything I could find that was heavy and left in place overnight. The next day the sides were pulled together and the top rear section was clamped in place. It started to look good. The firewall was glued onto the fuse after all construction of the fuselage was completed.
    Click image for larger version. 

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    Last edited by Roger Gray; 02-08-2014 at 02:56 PM. Reason: move photos, clarification of instructions

  2. #2

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    More Otter photos

    After the basic fuselage was put together, I built the tail feathers. The vertical fin and rudder was outlined on the plan, however the horizontal stabilizer was not, I had to figure the shape and size of this part which turned out to be 34.25 inches wide with a 96 inch wingspan. I wanted each part to build as light as possible, yet very strong. I decided to go with a 1/2 thick balsa built up construction open framed to be covered
    with Sig Koverall and dope. The vertical fin got a sheeting for strength. It will be sealed and painted only. The other parts were doped and
    sealed then primed now ready for color.
    Click image for larger version. 

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    Last edited by Roger Gray; 02-08-2014 at 02:38 PM. Reason: structure

  3. #3

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    Cowling

    My engine is an excellent used BME 44 and I had a time trying to figure out the cylinder orientation, with the cylinder slightly offset left at say the 4:30 position allowed the carb inside. The exhaust would not configure in that position. So, back to the 6:00 position and the exhaust would go straight down and out looking good! However, the carb was sticking about 3/8 to 1/2 inch outside without the choke open. Decisions decisions. I had to make a choice. The true otter had a scoop under the cowl bottom side, so. I have a carb scoop on the side at about the 8:30 position.
    .Click image for larger version. 

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  4. #4

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    Otter

    The build has gone on but slowly and I've made a few photos to show the progress.The fuse was finally glassed, the floats engineered and cut with a hot wire and and glassed, and everything primed and now the painting process that I absolutely love to do which includes a little panel line work and weathering. This process brings the whole plane to life!
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

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  5. #5

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    Very nice work Roger. What weight cloth did you use over the foam?
    Tony Hallo

  6. #6

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    I used 2 plys of 3/4 oz. trying to keep the weight down.

  7. #7

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    More photos of progressClick image for larger version. 

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  8. #8
    Thunder Chicken's Avatar
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    Sioux Lookout, ON , CANADA
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    Very nice Otter sir! A unique aircraft to model, not many kits or plans out there! Unionville Hobbies in Canada have a 96" span "fun scale" Otter kit/plans, and a smaller one too I believe.
    I assume you have flaps on it. The full scale Otter has a 'fore flap' which lowers the ailerons with the flaps. I can't remember exactly how it's rigged up. (I fly a twin otter for a living and get all these dhc planes systems mixed up in my head )
    The unionville kit has a fore flap which lowers the flap and aileron separately from the flaps. With it fully down, and full flaps down, you almost have to add power to make the field! Pointing the nose down is a huge must! And down she comes, albeit slowly, just like the real deal.

    Please keep us posted on the completion and how she flies!!

    One thing to keep in mind.......in Canada, if a float pilot forgets his water rudders down on takeoff, the penalty is a case of beer =)

    I converted mine into a "Texas Turbine" Otter. Powered with an electric set-up, pulling about 1700 watts on 9s. I wish it was on floats.
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

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  9. #9

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    Painted the wings and put them on this week, what a difference! I'll disassemble everything and shoot the clear soon and then install the electronics. I'm a fishing guide and I'm very busy these days. Click image for larger version. 

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  10. #10

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    Another picture to get a view of the size of this plane.Click image for larger version. 

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