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Old Apr 30, 2006, 01:25 AM
a.k.a Maltone
Australia, NSW, Goulburn
Joined Jan 2005
6,850 Posts
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Dornier DO-23 scratch build

I had never intended to build this aircraft but noticed the plan on RCM plans website while looking for Gordon Whitehead's 46" Hawker Demon.

A twin of some sort was always on my wish list, and the Dornier immediately looked interesting (I'm easily distracted ). It was a bit bigger than the average model I'd built, was simple-ish, and designed for two 400 can motors - ideal for those cheap bell outrunners I like so much. So the plan was ordered.

It is interesting to note, that both Peter's Baboon and the Hanriot were mostly started and completed before the plans from RCM arrived

The DO-23 was a so-called civilian aircraft designed in the 30s when Germany was prohibited from developing bombers. It was a more successful derivative of the DO-11 and the DO-13 result was renamed DO-23 (rather than unlucky 13). This plane was a forerunner to the famous DO-17.

The model was designed by Laddie Mikulasko and spans 60" with a suggested max weight of around 4 lbs. With twin 7.2v 400s on 10 cells, this seems ambitious but as a slow flyer with no aerobatic requirements this may be OK.

Two 850 kv BL outrunners and 18A escs were purchased off EBAY, with the intention of running APC 9X6 props off 3S lipo. When the motors arrived, they were 750 KV in 850 packaging. As I cannot fit larger props without moving the motors outboard a little, I am hoping there will be enough grunt.

Pat
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Old Apr 30, 2006, 01:33 AM
Victim of gravity
Upcountry, South Africa
Joined Jul 2002
373 Posts
Maltone

Looks very interesting-good luck, we'll be watching closely! Suppose you can increase the pitch of the props, or go for some of Graupner's 3 bladers?

How 'bout some more pics of the plan?

Marius
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Old Apr 30, 2006, 01:41 AM
a.k.a Maltone
Australia, NSW, Goulburn
Joined Jan 2005
6,850 Posts
This isn't a blow by blow description so here a few photos. The wing is mainly flat bottomed, esp at the tips but with its root profile, gives the impression of considerable washout. It certainly gives a curvaceous wing shape!

Wing parts are all balsa with 4 hard balsa spars. The wing halves are joined by a 1/4" hard balsa dihedral keeper with a thin ply lamination. The centre section is faired to match the fuselage shape.

When I studied the full-size aircraft data, I realised that the model's ailerons and flaps had been simplified from the original Junkers-style as found on JU52, Stuka etc. As I could find no data on the effect of these on a model, I opted for the normal ailerons shown on the plan then discovered an early version of the -23 that was so equipped. This version also had radial engines which suited my bulky outrunner motors and so I was happy to be a little closer to scale

The finish of the chosen machine was all silver (probably some silver paint on the ply covering, plus aluminium sheet around engines etc.). I'll use aluminium finish Litetex all over with just the red band with the black swastika on white disk. There were no other national markings I can see.

Pat
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Last edited by Pat Lynch; Apr 30, 2006 at 03:43 AM.
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Old Apr 30, 2006, 01:54 AM
a.k.a Maltone
Australia, NSW, Goulburn
Joined Jan 2005
6,850 Posts
Marius - here are a couple of pictures of the plans - not very good - they are large and difficult to photograph.

Yes I will check out options for the props. The motors I have give max output with 11 X 4.7 acc. to the data sheet. The original A/C had 4 bladed props - I'll keep my eyes open!

Pat
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Old Apr 30, 2006, 03:56 AM
a.k.a Maltone
Australia, NSW, Goulburn
Joined Jan 2005
6,850 Posts
The fuselage is of simple construction - 1/8 balsa sides with 1/32 ply doublers, with 3/16" hard balsa longerons. These are attached to the top and bottom of the balsa sides.

Formers are 1/8 Liteply and 1/8 balsa. Yellow aliphatic glue was used on all framing, while sheeting was secured with medium CA.

The sheeted upper fuselage is 1/16 soft balsa wetted on the outer surface and lightly misted with CA accelerator on the underside. Then, using medium CA, the sheet was glued vertically on its edge to the upper longeron. When dry, the sheet was carefully curved around the formers, glueing a small section at a time until the centre of the fuselage is reached. The sheet was trimmed about 1/2" oversize. The same is done from the other side and the overlapping sheets are then simultaneously trimmed down the centreline with a steel straightedge and scalpel, leaving the cut edges exactly fitting one another. The join is then glued from the underside with 1/4" X 1/16" strips and CA.

This method allowed the edges to be glued accurately aligned with the fuse sides, and a top finish butt joint which is completely gap free. I hope that was clear

Pat
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Old Apr 30, 2006, 04:17 AM
North East England
Joined Feb 2004
3,181 Posts
Don't know if you found this pic during your research, Pat, but I think it looks very attractive - and a bit menacing with that skull logo. The caption says it's an aircraft of the 'Forestry Defense' squadron !!! (which of course was simply their way of hiding it's true intent as a bomber - tut tut)


Steve
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Old Apr 30, 2006, 04:24 AM
a.k.a Maltone
Australia, NSW, Goulburn
Joined Jan 2005
6,850 Posts
Steve - great view - doesn't look like my idea of a forestry plane! I've seen those big struts underneath before but dont know what they are! Any ideas?
Also, there are handrails or antenna running along the fuse top?
Great scheme except I have this roll of silver Litetex to use (I'm meaner than Peter Rake )

Pat
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Old Apr 30, 2006, 04:25 AM
edi
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Elstertrebnitz, Germany
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Maybe some anticipation of acid rain? (Would also explain the wheel pants.)
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Old Apr 30, 2006, 05:03 AM
North East England
Joined Feb 2004
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Just noticed that your b/w pic is actually one of the 'Forestry' planes (got the skull on the front).

No idea what those things are that are hanging down under the fuselage - they look to have an aerofoil section to them if you blow the pic up a bit. Interestingly, only the 'Forestry' version has them - none of the others do, so perhaps they're water dispensers to fight the supposed forest fire? Which also asks the question; were they real or only there to add credibility!

I think that might be a handrail just ahead of the rear gunners opening, which would have helped the paras as they were clambering out onto the wing. I looked on my DVD's to get a screen print of that shot, but it's not on any of mine so it must have been one I borrowed. I'm sure someone else has seen it though, it's been in a lot of documentaries.

Steve
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Old Apr 30, 2006, 05:08 AM
a.k.a Maltone
Australia, NSW, Goulburn
Joined Jan 2005
6,850 Posts
If you look at both those "forestry" pics, there is a deflector shield ahead of the airfoil things and a rear vision mirror under the nose!! curiouser and curiouser..Pat
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Old Apr 30, 2006, 05:46 AM
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New Zealand, Otago, Harwood
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My guess is that they were dusting the forests with some sort of insecticide, the deflector would ensure that the dust wouldn't blow back along the fuselage in the boundary layer (there is a smaller deflector in front of modern day hoppers) and the mirror is often seen on ag-aircraft here so that the pilot can monitor the flow and confirm when the flow starts and stops.
Nev
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Old Apr 30, 2006, 06:02 AM
Victim of gravity
Upcountry, South Africa
Joined Jul 2002
373 Posts
PAT

Beautiful build so far-very neat! This plane just oozes character! 'Like the Forestry defence colour scheme too.

Keep up the good work

Marius
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Old Apr 30, 2006, 07:24 AM
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United States, VA, Chesterfield
Joined Mar 2001
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An interesting aircraft! Here is a photo from last summer of Don Srull's
DO-23 flying with electric power after many years of gas power. They are beautiful to watch in the air.

Pat Daily
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Old Apr 30, 2006, 11:15 AM
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Moab, Utah, USA
Joined Apr 2003
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Quote:
Originally Posted by Kiwi
My guess is that they were dusting the forests with some sort of insecticide...
Could come in handy for dispensing mustard gas too

Larry
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Old Apr 30, 2006, 11:17 AM
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Quote:
Originally Posted by maltone
I hope that was clear Pat
It might have been more clear had you used Windex instead of the cheap window cleaner

Interesting method for applying sheeting. I may have to try that some day.

Larry
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