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Old Jan 04, 2013, 06:34 AM
So I'M meant to be in control?
Colonel Blink's Avatar
Ilkley, West Yorkshire, UK
Joined Nov 2008
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Build Log
Dart Kitten - Britplan Build Off January 2013 to June 2013

It has taken me some time to decide what to build for this Build Off - in a way, the ‘brief’ was a little too wide, yet (for me) too restrictive! Too wide in that there are so many interesting models that fall into it, that making a decision is difficult - witness tailless, autogyro, contest, scale, electric, rubber, FF, RC..... Yet for me, as I have only just returned to the fold and have one successful model (and a restoration/conversion awaiting maiden) under my belt there are so many uneligible models that could have been a ‘natural’ next build (like the Smeed Ballerina, for which I have had the plans for years awaiting electrical technology to match the required weight & cost!).

So I had made shortlists, changed shortlists, made new shortlists and ruminated and cogitated. Others had started producing balsa offcuts by the boxload and still I had not made a decision! Then I discovered that the search facility on Outerzone enabled one to see the results listed with the plan thumbnail. A ‘final’ shortlist was produced, and the plans downloaded. I realised I had to make a decision, and the Dart Kitten looked to fit the bill.

The Dart Kitten is a ‘typical’ 1930s light aircraft, and I have always been a fan of this ‘Golden Age of Aviation’... it must have been a great time to have lived (assuming of course that one were of ‘independent means’). It would appear to have a few de Havilland influences in the general aesthetics – and that can never be a bad thing in my book. I was surprised to learn that for an aircraft which seems to have been copiously modelled, only four were ever produced. Of those four, only one survives today. That is G-AEXT – which explains why most models replicate that example. I was even more surprised to find that XT is hangared at Breighton airfield nr Selby, which is an airfield that I have visited by air on many occasions. According to G-INFO (http://www.caa.co.uk/application.asp...ype=65&appid=1), XT is registered to a chap who lives less than 10 miles away from Blink Towers....not that I think I'll be troubling him. This is hardly likely to be a superdetailed concourse scale job - more like 'a close approximation as long as you don't get closer than a hundred yards' standard.

There are several plans for the Kitten knocking about, but the one that is eligible for this Build Off is the 32" John Lamble version published in the January 1953 Aeromodeller. The Outerzone plan has been partially cleaned from the one algy2 posted (thanks Algy!) and in some ‘Algy’s plan’ is easier to peruse. Also included is the accompanying article, which is headed by a picture of the designer wearing a rather dashing hat worn at a rakish angle. I’m liking this more and more... However, as I have not got much faith in my own ability to print out the plan at the correct size, and also because the plan is only partially cleaned, I have ordered a full size copy from Derick Scott at http://www.model-plans.co.uk/
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Old Jan 04, 2013, 06:51 AM
So I'M meant to be in control?
Colonel Blink's Avatar
Ilkley, West Yorkshire, UK
Joined Nov 2008
3,464 Posts
Initial sight of the reduced plan above makes me think that it looks to me to be a light construction for a diesel-powered FF scale model with a minimal amount of wood. Obviously, my version (electric and RET) will have a laminated outline built-up fin & rudder...

Hence at 32" wingspan, my gut feel is that the weight is liable to be around the same as the Ajax. That came in at 160g including a 35MHz rx & 14g of lead. The Kitten will be 2.4GHz (lighter Rx) and will need no lead (oh gawd, what have I challenged myself with?) so would I be right in expecting the same sort of AUW? I'm a bit new to this guessing bit....

If it does come in at 160/170g, then I'm actually wondering whether another of those luvverly little D1811s on a 360mAh 2S would fit the bill. What do the honourable gentlemen think?

Conversely, I may choose to scale it up by a quarter to give a 40" wingspan - in which case I'm back at square one
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Old Jan 04, 2013, 07:26 AM
I like real wooden aeroplanes!
Sundancer's Avatar
South-west France
Joined Sep 2007
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An 1811 would certainly fly it at 170 grams Colonel; however, being a "power" model conversion as opposed to a rubber job, a little more poke might not come amiss. I think maybe scaling up to 40 inches would probably make things a bit less critical, in that case a motor rated at 80-100 watts would be a good fit, running from, say a 800 2S. In either case the lightweight structure would be fine for EP I reckon.
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Old Jan 04, 2013, 12:25 PM
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mixer421's Avatar
United Kingdom, England, Kent
Joined Aug 2007
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I'll be watching this with great interest and I think the 40" version would be even more delightful.
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Old Jan 04, 2013, 02:00 PM
So I'M meant to be in control?
Colonel Blink's Avatar
Ilkley, West Yorkshire, UK
Joined Nov 2008
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Quote:
Originally Posted by Sundancer View Post
I think maybe scaling up to 40 inches would probably make things a bit less critical...
Quote:
Originally Posted by mixer421 View Post
...I think the 40" version would be even more delightful.
At this moment in time, I'm pretty much up for a 40" version, but using the same wood sizes and basic construction as the plan. Exceptions (at the moment) will be the laminated fin outline, a tailplane retained by a nylon bolt, and a shear web between the top & bottom wing spars.

I'm getting a bit giddy now - Derick is fighting his way through the Christmas backlog and reckons his printer is steaming so it'll be a few days before the plan arrives. I've got my Balsa Cabin order written out ready, but they don't reopen until Monday. Not sure I'll equal the original 3s 6d build cost; my balsa order totals nearly £40 - but that does include enough wood for a Tomboy and some extra besides.....

I'll have a look around for some possible motors and will ask advice before purchasing
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Old Jan 04, 2013, 03:25 PM
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Canada, ON, Hamilton
Joined Oct 2005
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Colonel Blink, nice choice in the Dart Kitten. It looks really nice in the pictures, certainly no lawn dart here. If your build does come in at 170g, the small 200 RimFire at (10g) might be of interest.
Good luck with your build.
John
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Old Jan 04, 2013, 03:29 PM
Agricultural flyer
mixer421's Avatar
United Kingdom, England, Kent
Joined Aug 2007
508 Posts
I'm probably teaching an elderly ancestor how to remove the yolk and albumen from an egg without fracturing it's enclosure but this you may find useful.
http://www.peakeff.com/beta/Default.aspx
These figures for the Keda 'ThumRun' series of motors are also a useful guide.
http://dl.dropbox.com/u/11633794/Thu...Eff_graphs.htm
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Old Jan 04, 2013, 05:05 PM
So I'M meant to be in control?
Colonel Blink's Avatar
Ilkley, West Yorkshire, UK
Joined Nov 2008
3,464 Posts
Quote:
Originally Posted by Sundancer View Post
I think maybe scaling up to 40 inches would probably make things a bit less critical, in that case a motor rated at 80-100 watts would be a good fit, running from, say a 800 2S.
That throws me a bit of a curve ball.... I am aware that the '100W/lb minimum' has been outdated by experience and more efficient equipment, and these days I read c75W/lb for a lightly loaded scale model (which hopefully this will be!). Even at 40", I would hope for less than 250g AUW, and hopefully closer to 200g. A motor which produces 80W would give 140W/lb @ 250g and 180W/lb @200g.

Would I not be after a motor which would produce in the region of 75 x 0.5 = 37.5W; so perhaps rated for 50W?

I was thinking of something like these:
http://www.brchobbies.co.uk/catalog/...roducts_id=857
http://www.brchobbies.co.uk/catalog/...oducts_id=1148
http://www.hobbyking.com/hobbyking/s...er_1700kv.html

Quote:
Originally Posted by mixer421 View Post
...this you may find useful. http://www.peakeff.com/beta/Default.aspx
That looks a little complex for my meagre brain!
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Last edited by Colonel Blink; Jan 05, 2013 at 01:20 AM.
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Old Jan 04, 2013, 06:01 PM
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Australia, WA, Perth
Joined Nov 2010
617 Posts
Aaaargh! so many numbers! I know, DC Dart diesel, no numbers,no problem! good model choice Colonel, I'm sure you'll do a great job. Gary
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Old Jan 05, 2013, 01:52 AM
So I'M meant to be in control?
Colonel Blink's Avatar
Ilkley, West Yorkshire, UK
Joined Nov 2008
3,464 Posts
Quote:
Originally Posted by kkphantom View Post
Aaaargh! so many numbers!
I know!! Here's some more....

I found this this morning:
http://www.modelaccessories.co.uk/em...fications.html

I am thinking that if my logic is right and we [notice the 'we'] need a motor capable of (say) 50W max, then the previously mentioned E Max GT2203 is an economic and light option @ 16g

http://www.brchobbies.co.uk/catalog/...roducts_id=857

But if it is more in the region of an 80W capability that is required, then the E Max GT2205/33 @ 23g would fit the bill and is actually cheaper than the 2203:

http://www.brchobbies.co.uk/catalog/...roducts_id=858

Views, please....???

Both will work with a 10A ESC and will swing 8" props. If I enlarge the model to 40" to give a scale of 1:9.5, an 8" prop equates to 6ft 4in - so shouldn't look too far out of scale (the similarly-sized Tiger Moth had a 6ft prop).
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Last edited by Colonel Blink; Jan 05, 2013 at 08:48 PM. Reason: Changing gobbldegook to English!
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Old Jan 05, 2013, 02:51 AM
I like real wooden aeroplanes!
Sundancer's Avatar
South-west France
Joined Sep 2007
4,424 Posts
Go for the bigger motor Colonel. Although 100 watts/pound doesn't apply at all to models like your Ajax and my Witch, they will fly happily on30/40 watts per pound, with a model like the Dart Kitten I would want some power in reserve. So the bigger motor has two advantages - it is closer in weight to the diesel the model was designed for so will help with CG problems and it is cheaper! And, as you have the throttle lever under your thumb, a bit too much power is no problem, whilst a bit too little at full throttle definitely would be! And, if uncomfortable with the power at full throttle when test flown, no problem, just go down a prop size.

The nearest comparison in my fleet is the Bantam at around 12 ounces this has an 80-100 watt motor propped for 70 watts and is just right.

I am definitely not an advocate of the "stuff in a huge motor and lots of cells" approach for models like this, I think much of this is a throwback to the fact that a lot of IC fliers are now flying electric and have brought some of their building - or buying? - habits - ie heavy - with them, however, I think your smaller motor proposal is just a bit too marginal. Read the "Electrickery" piece in the latest RCM&E, big models, but the logic is sound.
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Old Jan 07, 2013, 12:33 AM
So I'M meant to be in control?
Colonel Blink's Avatar
Ilkley, West Yorkshire, UK
Joined Nov 2008
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Motor ordered this very morning - I flirtatated with ordering both motors, on the grounds that the smaller one would be a fine replacement for the dubious bell motor that is currently on the KK Gypsy.

However, one does have to keep expenditure as far below the radar as possible, and what with the wood order that should go in later today I'll be asking the chauffeur for the price of a cup of Earl Grey before the month is out.....
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Old Jan 07, 2013, 06:48 AM
So I'M meant to be in control?
Colonel Blink's Avatar
Ilkley, West Yorkshire, UK
Joined Nov 2008
3,464 Posts
Having now maidened the Gypsy and found the 40" w/s and 225g AUW more to my liking with regards to it's 'sit and and prescence' in gently moving air compared to the 30"/170g Ajax, I will go ahead on the premise that this will be scaled up 25% from the FF original...and why not, I'm sure that the Blink chapeau is at least 25% larger than Mr Lamble's....

Good old Dereck Scott has pulled out the stops, and I now have the full size plan. I'll wait until after work, and hit the photocopyer scene [man] to get an idea of size etc. First job will be to draw up a built-up fin and a tailplane with elevators. The full-size original had large control surfaces, which I will replicate - but I may need to tame them down with either throw or EPA rateonential or whatever it is..... I'm also struggling with how to make the u/c plug-in - I like Lamble's method of spreading the load such that backward landing forces are less likely to twist and break the 1/8" balsa lower wing spar. Like Poirot, I must exercise 'ze leetle grey cells' further.

After some hiccups with emails not getting through, I managed to place my £46 balsa order with Balsa Cabin this morning - with that amount of stock, I'll have to build another model after this one. With this being their first day back after the holidays, they are fighting a backlog but reckon that the order should be despatched this week - which I reckon is pretty good.
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Old Jan 07, 2013, 07:03 AM
I like real wooden aeroplanes!
Sundancer's Avatar
South-west France
Joined Sep 2007
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[QUOTE=Colonel Blink;23737845]I'm also struggling with how to make the u/c plug-in - I like Lamble's method of spreading the load such that backward landing forces are less likely to twist and break the 1/8" balsa lower wing spar. Like Poirot, I must exercise 'ze leetle grey cells' further. /QUOTE]

Undercarriage will need some thinking about Colonel. One of my short list models to follow the Rubberdub is Hoh Fang Chiun's Bebe Jodel, very similar in a lot of ways to your build, and after some brain racking I am still short of a really good way to do the undercart, so if you come up with one I shall shamelessly steal it if the Jodel wins the lottery.

[QUOTE] After some hiccups with emails not getting through, I managed to place my £46 balsa order with Balsa Cabin this morning - with that amount of stock, I'll have to build another model after this one. /QUOTE]

You can NEVER have too much balsa Colonel! I'm sure we will be able to think of another build off to follow this one in July - I already have a couple of ideas!
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Old Jan 07, 2013, 08:49 AM
So I'M meant to be in control?
Colonel Blink's Avatar
Ilkley, West Yorkshire, UK
Joined Nov 2008
3,464 Posts
I'm on the scrounge......

If anyone has the October 1950 Aeromodeller, could they do us a favour and scan in the three view of the Dart Kitten? All the copies on the interweb don't seem to stand blowing up to A4 (ish) size.

Many thanks!
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