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Twin Otter - Electric Twin from Anton Eisele Plan

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Wasaforumite07/10/2017 19:42:05
115 forum posts
33 photos

I am currently building from this plan that I bought from AirAgeStore.com in the USA. The plan arrived quite quickly, about 10 days and post cost was $14. There was no Duty or VAT. The plan is on 2 large sheets and is nicely printed and I rate it at good value at $19.95.

It wasn't easy to find a suitable plan. The ones I found on the web are too big or too lightly constructed for my purposes. This one is semi scale which doesn't bother me as I want the plane for everyday flying. At 65 inch span it is about the same size as a traditional trainer.There is a huge range of liveries available to disguise its appearance!

Hangar 9 did an artf slightly bigger than this a few years ago and currently there is another quite costly artf availble from Europe. I believe they are all good fliers - the Twin Otter makes a good prototype to turn into a flying model. The good ole Twinstar is a great flying plane and I believe the Hobbyking twins go well too. But it is nice to have a balsa model that's been build the trad way.

There is a youtube video of the plane I am building at **LINK**

I have spent some time time studying the plan and there are only a couple of minor errors found so far. The AirAge web site has links to some building instructions. Originally the plan was for geared 480 brushed motors and Nicads. Standard sized servos were used with long rods to the tail and bell cranks to the ailerons.

I am not going to change the plane extensively apart from up dating the servos and motors/batteries.The large fin looks rather fragile so a few strips of carbon will be used. I think adding flaps will only increase weight and complication without any real benefit. The plane evidently takes off in a few metres and has plenty of drag to slow it down.

I hope this will be of interest. Given the advantages of electric for twins it is rather surprising that they are still quite a rarity. Some photos of the build will follow in later posts.

Denis Watkins07/10/2017 20:08:18
2124 forum posts
108 photos

Very interested in all aspects of this build, a good size twin, manageable by most of us, and not so far out of reach

Of club flyers. This build holds loads of problem solving and set ups for all to enjoy.

Biggles' Elder Brother - Moderator07/10/2017 20:12:52
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Moderator
14784 forum posts
1310 photos

Very interesting - I sahll be following.

I have the Hangar 9 Twin Otter ARTF and I can cinfirm that it is indeed a very good fyyer. It is electric powered and runs off two 4s 5000 mAh Lipos very well.The high aspect ratio wing, with large high deployment flaps, make slow speed flying a dream and making final aproaches into a slight breeze is great fun - and totally safe down to ridiculously low airspeeds.

One small issue with the model - and I have heard others say this about the Otter - it can come out a bit tail heavy. Mine has about 6 oz of lead shot epoxied into the nose cone to give a good solid CoG position - maybe just one to think about whilst you are building?

I have adapted the working side door on mine so it can be opened with a servo and drop 4 "paracutists" - great fun and always pleases spectators - through a I did have a dog run off with one of my "little men" on one occassion!

BEB

Percy Verance07/10/2017 20:16:38
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5716 forum posts
108 photos

I had a hankering for something like this a while back, and not being aware of any other plans other than the Ivan's Plans one, that's what I looked at.

I might take a look AT the AirAgeStore one now.........

Edited By Percy Verance on 07/10/2017 20:17:20

Wasaforumite08/10/2017 13:06:52
115 forum posts
33 photos

Regarding the Hangar 9 version, I think it's quite a bit bigger than this one - it weighs about 10/11lbs whereas I'm hoping for 5/6lbs for this. H9 TO has its batteries behind the engines which saves wiring length and a little weight but against this there is the possibility of battery voltage imbalance and the fixed position prevents the batteries being used to balance of the plane. Not a criticism, the designs are just different. H9 version is a lovely plane, a triumph of production, lets hope I can get somewhere near it!

Apart from a Twinstar, I have built a Eurotwin and a Short Scion. In all of these having a single battery worked out fine. I didn't experience any motor problems having fairly long power supply wires to the ESCs mounted behind the motors. Perhaps with bigger motors it can be a problem.

I looked at the Ivan's TO as well. It was too big for me and looked rather fragile. Unless laser cut parts are available it looked a challenging build and I would be too frightened to fly it having spent that amount of time and effort.

Parachutists eh! Sounds great. I think I will use mine for carrying a camera.

Edited By Wasaforumite on 08/10/2017 13:07:45

Wasaforumite08/10/2017 22:31:25
115 forum posts
33 photos

20171008_211403.jpg20171007_174137.jpgHere's some pictures of the early stages of the build.

The fuselage is in two main sections. The main section at the front has parallel sides. I cut a sheet of 1/4 balsa accross the grain the exact width between the frames and then slice it for the sticks in between the sides. I set it up using 4 set squares.

The rear section is just a straight taper built out of two frames and again 1/4 square sticks in between. I ruled a line on a fresh sheet of plasterboard and marked the centre of the front cross beam and pinned the tail triangle down to line. It seems to work. Underneath both sections there will be notched formers to take stringers.

There is an article on the web giving the designers notes on the build found here:

**LINK**

I will try not to duplicate this too much and only give some comments that add to that article. The plane dates back to about 2004 and since then digital photographs have vastly improved on the old grainy images. Hopefully my pictures will make it easier to visualise how the plane is built.

I am leaving the frames to dry thoroughly before fettling the joining surfaces so that when glued I get a straight fuselage.(Hopefully!) I don't use cyano because the Modellers White Glue gives more time to adjust components and sands better.

I seem to remember Peter Rake has used this system of two module fuselages in his WW1 biplanes. The result is a rather boxy fuselage but there is no stress during construction and it is comparatively easy to get it straight.

20171006_131529.jpg20171008_120745.jpg

Biggles' Elder Brother - Moderator08/10/2017 22:57:22
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Moderator
14784 forum posts
1310 photos

Nice neat work, good start!

BEB

Wasaforumite09/10/2017 21:29:45
115 forum posts
33 photos

The front and rear components of the fuselage are now joined. Tomorrow I'll start on the stringers.

Pictures from my phone often post here upside down.

twotter fuz frame.jpg

Wasaforumite09/10/2017 21:36:47
115 forum posts
33 photos

Sooner or later I am going to have start on the wings. There are in set ailerons and I am showing the catch-all cross section here. The wing is easy enough, looks like Clark Y but I have some fear about building the ailerons. I really prefer to build them as part of the wing and cut the out but it doesn't look like that is possible here. The idea of getting an accurate chamfer on the 1/4 sheet aileron leading edge of the aileron looks very challenging as well as building using fiddly little triangles. I going to have to think of a another way.

I will be using separate aileron servos and no bellcranks.Servos are one of the few things that are cheaper than in 2004!twotter wing sect.jpg

Wasaforumite20/10/2017 22:27:35
115 forum posts
33 photos

I've started on the wings now. I have decided to build the wings entirely as normal and then cut the ailerons out. Similarly the engine 'gap' will be cut out later. The ribs have holes in them for the wiring. I never seem to be able to make a good trailing edge by camfering the top sheet and sticking it down along the edge to the bottom sheet. Instead i have planed the edge of the wing and glued on a 3/16 by 3/16 strip. This is then planed and sanded to an edge about 3/32 thick.This is a similar idea to when trailing edges are put on foam cored wings.

There are two relatively inexpensive tools I use all the time. One is a plastic ruler with notches to gauge balsa sheet thicknesses. The second is a Great Planes sanding bar about 2ft long. Both seen in the picture below.

The fuselage has had some stringers added and part of the nose. So far it is entirely as per plan. I'm not quite happy with nose in the original design, it looks too 'beaky'. This is probably because the designer wanted to make construction simple avoiding compond curves. I'm not about to make it more complicated. I just think by shortening it a couple of cms it will look better even though it will be less to scale.

20171020_212035.jpg

Edited By Wasaforumite on 20/10/2017 22:30:21

Edited By Wasaforumite on 20/10/2017 22:30:54

Wasaforumite07/12/2017 22:42:51
115 forum posts
33 photos

This is the stage where progress seems to slow. Work becomes more to do with details that creating structures.

I am trying to keep to the original plan as far as possible because it was the basis for a commercial kit many years ago so it was basically well sorted and also modifications usually mean more weight. However the photo below shows a depature from the plan which had a standard servo in the middle of the plane operating the front wheel and the rudder via long control rods.

I have used a sprung noseleg, I believe it is a Dubro part but i've had it so long I could be wrong. Also a small metal geared servo is used for steering with control wire bent in a elongated 's' shape (not visible in pictures). This should have some shock absorbing properties as a result. The servo is just under the cockpit of the plane.20171114_121603_resized.jpg20171129_214902_resized.jpg

Wasaforumite07/12/2017 22:49:00
115 forum posts
33 photos

This time there is a photo of the tail mocked up. Others who have made this plane have said that although the tail seems to work OK it is rather prone to damage when the plane is handled. The main problem is weakness of the fin. I have doubled up some of the frame and used 1/64 veneer each side of it under where the stabiliser or tailplane is fitted. It is much stronger as a result. I am going to use two Savox 225mgs to operate the rudder and elevator, deleting the two heavy standard servos in the middle of the plane under the trailing edge of the wing.20171203_201451_resized.jpg

Wasaforumite07/12/2017 23:02:07
115 forum posts
33 photos

My final posting today just shows the splitting of the ailerons from one of the wings. This is not a job I have been looking forward to as it is difficult to measure where the cuts go. The new trailing edge can be see (oversized before planing and sanding).

I have had some graphics arrive from Callie in the USA. I will be dressing the plane as a WinAir Twin Otter, mostly white, with stripes, blue tail and wing centre panels and red rudder. I decided against the yellow Canadian military strip as it has been done before. Similarly, I avoided the US para team. The former was available as a VMAR ARTF, the latter a Hangar 9 ARTF. For those impatient to haqve a new Twin Otter, I saw on Ebay that a German ARTF manufacturer is doing a Swiss survey liveried version (very nice it is too). It's rather expensive and with the power trains it will cost about £400 to get into the air plus battery and radio. Mine will cost about half that even after buying Oracover.

20171207_210833_resized.jpg

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