Lins

The detail work from what I can see in that pic is fantasic

GoNavy

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I'll take any compliment I can get...especially one from a citizen of the country which nutures DeHavilland of Canada, birthplace of the Twin Otter.

Lins

Not to mention I've ridden in a few!

F86_SABRE

Hi GoNavy... I am perplexed as how tight the gap is between the landing gear fairing and the landing gear strut. Will it not dent/damage the landing gear fairing when the plane lands? Looks really nice and authentic like that!

Reuben

GoNavy

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Reuben: I believe/hope the clearance is sufficient. Others have flown their twin otters and I have not heard of it being an issue.

I hope I can avoid any hard landings. I modified the installation somewhat in case I bent the gear. Portions of the landing gear fairing are removable, to allow for removal of the landing gear, something that you cannot do strictly following the plans. This modification would reduce damage to the fairing in the event of a bad landing, at least making the repair less extensive. I can provide a photo if it would be of interest.

F86_SABRE

Hi, yes it would be interesting to see how you made the landing gear setup. I have not taken the plunge with this plane yet as I already have a number of projects in the pipeline but it is one plane that I shall persue in the near future.

Thanks

Reuben

GoNavy

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Check out posts 147 and 182 above.

I'll try and post additional pics tomorrow.

F86_SABRE

Saw 182. Those two screws sure have to carry the landing load. Would it have made much difference if the aluminium was longer (say another two inches or so) with two other screws further to the centre? BTW are the aluminum main struts availabe as well from the kit/plan seller?

Reuben

Slope Pilot

Thats neat, My Dad fly's and works on real Twin Otters.

GoNavy

My Feedback: (15)

The two screws in the pic at post 182 attach the wing strut to the fuselage. The aluminum attachments extend into the fuselage about 6 inches each, and are bolted to 3/8" plywood.

When I bought the kit, the aluminum backer had to be purchased separately. I made a pattern and had the piece cut and bent at a local machine shop. The plans had a suggested source, but I was unable to obtain the part from there.

Attached are two new pics of the gear fairing and strut to show the removable pieces of the gear fairing and strut.

In the underside pic, from the top to the bottom: the large round hole is for access to the center landing gear bolt. It is on the fuselage centerline. (There are five bolts holding the gear in place; The pattern is one in the center, and two farther out on each side).
Down from that is the first removable fairing piece. It has a hole for the bolt which attaches it to a plywood piece which "sandwiches" the gear to the fuselage.
Below that is the second fairing piece (which is attached by short "legs" to the end of the non-removable fairing (not visible), and a bolt visible from the top.)
Below that are the two pieces that make up the strut. The middle piece fits into grooves in the main strut piece. (It will fit better when I realign the gear.) The steel wire portion of the gear extends through the center strut cover.

In the pic of the top view of the fairing and strut, the (not so smiley faced) cutout accepts the end of the wing strut. In the center of the fairing is the top of the second removable fairing piece mentioned above. Again, the visible bolt (and two bolts not visible) attach that piece to the fixed portion of the fairing.
Below that you see the main strut piece. The upper bolt attaches that piece to the aluminum part of the gear. The lower bolt holds the strut centerpiece seen in the underside picture above. By removing the four pieces from each side, you have access to the other four bolts which hold the landing gear in place, and you can remove the landing gear for repairs.

Is all this worth the trouble? Good question. With this approach, it is not necessary to cut the two main fuselage longerons which run fore and aft over the space for the gear. Presumably that means the fuselage is stronger than if those were cut out. Secondly, in the even of a hard landing which bends the gear out of whack, the gear can be removed without cutting off a glued on strut and without cutting into the fairing. Perhaps... repairs to the fairing and/or strut will be reduced or made easier.

Hope this answers your questions.

GoNavy

P.S.: My thanks to the People of Malta for assisting in the rescue and repair of the USS Liberty in 1967.

F86_SABRE

Thanks for the explanation. Photos show quite a good setup for strut movement. As far as the USS Liberty goes I never knew of this incident. Was still young when this happened. There is some footage of the drydocking of the ship: http://www.criticalpast.com/video/65..._carry-coffins
I remember going on to the USS SARATOGA and USS AMERICA when they used to call at our ports and where opened to visitors. Amazing time.
Anyway...back to the Twin Otter....nice build...may have a go at this plane as well.

Reuben

F86_SABRE

Whole footage of USS Liberty: http://www.criticalpast.com/products...alta/1960/1967

RBIRON

Did you every get ahold of John i am trying at the moment he sent me a e-mail answering one of my ?s but can't get a reply for a shipping price does he even sell to Canadains if not i would like to know at least that much???????

RBIRON

You just gave me a idea for retracts on this otter.

Lins

Yes, he does ship to Canada, and it was fairly reasonable. It was a couple years ago, so I don't remember the price. You just missed out on a kit for sale a couple weeks ago on a Canadian RC site.

RBIRON

Good but i can't seem to get a reply from him other then stated the kit i am looking at is $395 plus $60 for the plans [1/8 scale] it would be good to hear from him before i seal the deal so i pay the right amount of shipping.To bad about the other deal but i am sure there will be more there are more and more short kits coming available which will bring down the prices.
There is a guy in Prince George that has one for sale but again can't get a reply from him either he did note he was biss in his post and hasn't been on line for 3 months.
Hear is his web link if anyone needs it.

GoNavy

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All together, ready to go. That's my brother who has promised to hangar this giant in his house!

For you who are still building, a word about balance fore and aft.

The plans have the C/G 3.295 inches back of the leading edge, that is, 25.4% of chord. To achieve that I would need to add 23.8 ozs to the nose. (I already have three batteries in the nose: a 2600mah NMH 6v, a 1650mah 4.8 volt NMH, and a single 9V alkaline for landing lights and beacon. The heaviest of those, the 6V. is mounted on a tray which slides forward to locate the battery just behind the nose block)

John has advised me that his Twin Otter needed just less than a pound (16oz) to balance per plans. If memory serves, he was running two OS 200 4 strokes Those weigh about 33oz each without muffler (heavier if they are the pumped version). The Saito 125s we installed are just under 22 oz each. Doing the math and comparing the two different engine weights (about 9.75 inches in front of the C/G) x 22 oz = 214.5; Thus I would need to add, in the nose (about 34.5 inches in front of the C/G, 214.5 /34.5 = 6.2 oz because of lighter engines. Assuming John needed 16oz to balance, I would need 16 + 6.2 = 22.2oz total in the nose. That is pretty close to our measured 23.8oz.

John added that in flight testing he gradually moved the C/G rearward, and that at 34% (4.42 inches back of LE) it became "very sensitive to rudder inputs, but all else remained quite stable".

I found that with the C/G at 30% the additional nose weight needed would be 14oz.

If I add no weight to the nose, our TO balances at 33%.

Haven't figured out how to weigh it just yet.

Oh, one more thing. The beacon circuit has an electronic gizmo that dims and brightens the beacon light about 1 cycle every 1.5 seconds. This created a big time interference with the 72 mhz receiver. All servos glitched with the beacon on. The problem was solved when I wrapped the beacon wires around a toroid ferrite. Worked like a charm.

Lins

Nice job! Can't wait to find out the total weight.

Harjes

My Feedback: (1)

Go NavyI found the C/G to be very close to where the factory recommends Just aft of main wing tube. You definitely don't want to fly the Otter tail heavy.The Best Hank Harjes.

GoNavy

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Roger that, Hank. I'll have to add a few ounces up front (in addition to the 4.8v 1650 Nmh pack, 6.0v 2100 Nmh pack and the 9.0 AA alkaline pack).

That is a great shot of an attractive plane. Is that your first one, the one we saw a couple of years back?

We still have 12 inches of snow on the ground. I haven't even been able to run up the engines yet.

alex5

GoNavy,here is an image to illustrate the main landing gear shroud(like that of it's predecessor,the Beaver).It is a fat chord profile going to a larger identical profile,then to a more rounded,higher ratio profile that would terminate about equal to the radius of the fuse,except the fuse cuts that profile.Remember that it is nothing more than a shell to cover the suspension,and should be mounted with rubber grommets,or spacers.I have photos,if you need them...just pm me.Alex

alex5

Check out MRaerodesign.com for the landing gear component of the Beaver(it is an idea way to make the universal brackets for floats or wheels).Think of two U channels on the front by the door,each side and two under the wing,each side.Both are drilled for 4/40,or 1/8 bolts to retain float mounts,or wheel brackets,and are unobtrusive,as they are capped with covers or landing gear shrouds.The biggest part of it is to replicate the Beaver's landing gear...but is so universal.On my beaver,I made two lower fuse formers in aluminum, separated them with 3/16 ply to allow my landing gear to pivot and shock absorb.The system works great.ALex

alex5

Here is a close up of the lower main gear shroud showing how it is made to slide over the upper main gear shroud when a load is applied.In other words,the upper shroud does not move at all,and is attached with the mounting points of the landing gear,and strut.The lower landing gear pivots or flexes below that connection.

GoNavy

My Feedback: (15)

Alex5:

Good photos of the gear detail.

When I began this project, I had sketched some ideas for a more scale like landing gear design, steel hinged just inside the fuselage with bungee cords for springs, but I decided to stick with the plans.

Per the plans the gear struts, with steel rods backed by 1/4 inch thick aluminum stock, are wider than scale where they extend outside the portion of the fairing which is attached to the fuselage. I can live with that small deviation from scale.

However, the outer fairing is attached only to the gear brackets and can move up and down as in the full size.

Per my earlier posts, I made portions of the fairing affixed to the fuselage, removable, so making repairs to bent landing gear brackets or struts would not require cutting into the fuselage.

GoNavy

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Is that a deicing boot on the leading edge of the lower gear fairing?