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Old Jun 08, 2012, 11:09 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
KK Ajax - BritKit Build Off 2012

Well, I have finally been inspired, persuaded and coerced by the likes of brokenenglish, Sundancer, RFJ & kkphantom to throw my hat into the Britkit Build Off ring with a build of the Keilkraft Ajax. Ohmygawd, what have I let missen in for??

This is to be my first balsa build in at least 15 years, and the last one was in a series of only 2 builds…. Hence I will expect any readers to work at least as hard as me with help, advice, anecdotes and insults. Work will be slow, due to pressures of work, home, and family. Although I have tacit agreement from Lady Blink to disappear into the loft, experience has shown that absences from the bosom of the family need to be timed correctly and the frequency needs to be kept under strict control to ensure domestic harmony. So progress and reports may be sporadic, and for that I apologise.

Sooo……Why an Ajax? Well, firstly it was the first flying model I had – I’ve been trying to work out what age I was when I got the kit for Christmas and Father built it with my ‘assistance’. I believe that I would have been anywhere between 8 – 11 years old; making it 1969 – 1972. After construction, Father relinquished any responsibility for it, and it begun a very hard life. It lasted several summers of abuse, and ended up severely tatty and badly repaired, but continued to fly enough to encourage my youthful interest in gravity defying flight. The second reason for an Ajax is that I still have the 40 year old plan in my possession, and what’s more it is still usable. And thirdly, I have a lot in common with the Ajax; we are both simple, neither of us are ravishing beauties, we are both a little corpulent, and we both perform as best we can but fall short of anything remotely competitive.

My aged plan is the one for which locktite401 stitched my A4 scans together to make the .pdf attached and which also appears on
http://www.outerzone.co.uk/plan_details.asp?ID=1368
It is the Albert Hatfull version from the 50s(?); which could loosely be referred to as the Ajax MkII; the MkI being the Louis B Heath original which I believed appeared in 1939. The plan has pretty much all the printwood parts shown with the exception of the wing ribs; however I will simply use the dotted outline shown on the side elevation unless it looks significantly different from the section used for the Achilles (the plan of which does show a ‘typical wing rib’).

It will be electric and 35MHz RC. Motorwise, I have a 20g D2211-1700 [1570kV] outrunner which will turn a 8 x 3.8 SF prop @ 6A on a 2S lipo, though this may be overkill – but I like the prop size. I intend to use HXT500 [5g] servos mounted in the tail, unless anyone can suggest a significantly lighter servo at a price reasonable to an (adoptive) Yorkshireman. The other piece of sacrilege will be the use of some sort of film covering; for although dope fumes may be considered by some to be a heady perfume, I feel that pervading Blink Towers with said aroma would not be seen as such by Lady Blink and young Pippa Blinkette.

I'm not too sure as to when the actual building will start; I still have a few things to sort out – like a building board. On my impossibly small table in a corner of a cramped loft, I have a piece of marble washstand which should be fairly flat; I am making enquiries for a thick piece of cork to affix to it to build on – because then I can push pins in by hand (rather than a tack hammer when using a wooden board) then building can occur after young Ms Blinkette’s bedtime. Luckily I have contacts in a rather large gasket factory in South Africa….. I will also need to see what wood I have in various model boxes, none of which have seen the light of day in a decade and a half........
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Old Jun 08, 2012, 11:23 AM
RFJ
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Northern Ireland
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I spy a Middle Phase - lovely model but you must resist that temptation for now

Ray
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Old Jun 08, 2012, 12:09 PM
So I'M meant to be in control?
Colonel Blink's Avatar
Ilkley, West Yorkshire, UK
Joined Nov 2008
3,615 Posts
The Middle Phase was the other model in the series of two with the Gentle Lady - it's in the eaves behind the door to the right......
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Old Jun 08, 2012, 01:01 PM
I like real wooden aeroplanes!
Sundancer's Avatar
South-west France
Joined Sep 2007
4,773 Posts
All sounds good to me Colonel, your proposed power system will probably fly it at about quarter throttle and as it is a relatively heavy motor two 5g servos in the back end shouldn't be a problem, being a rubber model it has quite a long nose and would tend to be nose heavy anyway. If you should fancy some lighter servos, I have used the 3.7 gram GS3707's from BRC Hobbies - http://www.brchobbies.co.uk/?page=sh...catName=Servos at £3.50 a time with perfect satisfaction, in fact there are two going in my Britkit Sportster build - even as a native Yorkshireman I find that price acceptable!

The loft corner looks OK to me; I've built in worse places (eg a Boddington Ghost Rider 38 on the back of a hotel bedroom mirror when I was working in Manchester and a Rubbadub on a piece of blue insulation foam in a god forsaken B&B in Germany)

Added your link to the first post of the build off thread

As we say in the Haute Vienne - Allez et bon courage!
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Old Jun 09, 2012, 08:16 AM
*jj
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United Kingdom, Birmingham
Joined Jul 2008
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I used the dotted outline for the wing ribs to make my Ajax a couple of years ago. This is a rubber FF version and flies well; it is my favourite model at the moment! (It is on its third fuselage at the moment but the wings & tail are original).
I also made another with a gearbox/propeller unit from a plastic toy, which didn't go so well - in fact in its last flight, it flew round in a circle and collided with my winding stooge!
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Old Jun 09, 2012, 08:36 AM
So I'M meant to be in control?
Colonel Blink's Avatar
Ilkley, West Yorkshire, UK
Joined Nov 2008
3,615 Posts
Quote:
Originally Posted by Sundancer View Post
All sounds good to me Colonel, your proposed power system will probably fly it at about quarter throttle
...just the conclusion I was coming to! And I think weight may well end up a bit of an issue, so I'll get me one of them that D1811s everyone's raving about. What sort of current do they pull on 2S? Would a light 6A ESC handle it?
http://www.brchobbies.co.uk/?page=sh...dditem&item=53


Quote:
Originally Posted by Sundancer View Post
If you should fancy some lighter servos, I have used the 3.7 gram GS3707's from BRC Hobbies - http://www.brchobbies.co.uk/?page=sh...catName=Servos at £3.50 a time with perfect satisfaction, in fact there are two going in my Britkit Sportster build - even as a native Yorkshireman I find that price acceptable!
If you mean this one
http://www.brchobbies.co.uk/?page=sh...ditem&item=611
its interesting that the 'headline' weight is 3.7g yet the 'gross weight' is 5g. I can only presume this is including wire and plug (I have seen this done before!). Does anyone have one that they can actually weigh on a gramme scale, because I have a sneaking suspicion that they may actually be the same thing (or near as dammit) as an HXT500
http://www.hobbyking.com/hobbyking/s...?idproduct=663

That just leaves a prop and a Lipo to think about - should I be looking for a slowfly prop? And what capacity of Lipo - 300/350mAh? I've seen a 2S 360mAh that only weighs 22g.....

I had a dig around and found my old balsa stripper (an 'aluminium channel and plastic slider' type) and had a practice. It is as I thought, and as I remembered. Either I don't have the knack or there is something I'm doing wrong, but the wood strips thereby produced are not square, nor are they constant thickness.........
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Old Jun 09, 2012, 08:39 AM
So I'M meant to be in control?
Colonel Blink's Avatar
Ilkley, West Yorkshire, UK
Joined Nov 2008
3,615 Posts
Quote:
Originally Posted by *jj View Post
I used the dotted outline for the wing ribs to make my Ajax a couple of years ago. This is a rubber FF version and flies well; it is my favourite model at the moment! (It is on its third fuselage at the moment but the wings & tail are original).
I also made another with a gearbox/propeller unit from a plastic toy, which didn't go so well - in fact in its last flight, it flew round in a circle and collided with my winding stooge!
Any photos? I'm happy for anyone to post photos of their Ajaxes here for inspiration!!!!
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Old Jun 09, 2012, 11:38 AM
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United Kingdom, England, Lancs
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Quote:
Originally Posted by Colonel Blink View Post
.
If you mean this one
http://www.brchobbies.co.uk/?page=sh...ditem&item=611
its interesting that the 'headline' weight is 3.7g yet the 'gross weight' is 5g. I can only presume this is including wire and plug (I have seen this done before!). Does anyone have one that they can actually weigh on a gramme scale, because I have a sneaking suspicion that they may actually be the same thing (or near as dammit) as an HXT500
Manufacturers/retailers are usually "optimistic" about weights aren't they? These servos are advertised as 4.3 grammes. Mine weighed in at 4.9 and 5.0 in their bare state. Add an output arm with it's screw and two mounting screws and they come up to around 5.2 - 5.3 grammes. No doubt it's no big deal for the kinds of models were building (Senator in my case) but it does show we can take published weights as a "guide" rather than dead reliable. The 1811 motor is stated to weigh 10 grammes. Mine weighs 12.7 with the prop driver and what use is the thing without?! Overlander do a 350 2s lipo they claim is only 16 grammes. But what about the connectors etc? I shall probably get one of these before long and will be interested to find out.
Really looking forward to your Ajax build as it's similar to the Senator so a comparison of methods etc. will add interest to the build-off.
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Last edited by Raf_Bob; Jun 09, 2012 at 11:41 AM. Reason: Tidying up.
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Old Jun 09, 2012, 12:05 PM
I like real wooden aeroplanes!
Sundancer's Avatar
South-west France
Joined Sep 2007
4,773 Posts
Hi Colonel

The 1811 motor would be a very good choice for the Ajax; current depends on the prop you want to use, I use a 6 x 3 GWS Hyper Drive on the Witch most of the time but if I want to replicate rubber model performance (i.e. fastish spiral climb for a minute then glide) I put a GWS 7 x 3.5 on, which ups the current to around 6 amps plus. For this reason I have a 10 amp ESC in the Witch. However, in the current build, the Sportster, being a smaller model I will be using either a 5 x 3 or 6 x 3 Hyper Drive prop and have therefore installed a 6 amp controller to save a bit of weight. Personally I would think your Ajax, being smaller than the Witch, would be fine with a 5 x 3 or 6 x 3 (my choice would be the 6 x 3) and hence the 6 amp ESC.

Re servos; the BRC GS3707 is absolutely identical to the Blue Arrow S0361 ones I am using in the Sportster and very different to the Hobbyking one (check the dimensions). I have just put one of mine on the scale and it reads 3.6 grams, that is complete with lead, plug and a double sided output arm. However, an extra 3 or 4 grams isn't going to kill your Ajax especially if you are saving so much with the 1811 motor, so a couple of 5 gram ones would work fine I reckon.

Surprised you are having trouble with the balsa stripper, that sounds like exactly the same one that I have used for years and it works fine provided the blade is nice and sharp.
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Old Jun 09, 2012, 12:33 PM
The dog ate my clearance
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Joined Jan 2004
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Hi Colonel,

The Ajax looks like a good subject, especially as you've built one in your youth. Should be a fun build, and I'll be following along.
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Old Jun 10, 2012, 11:02 AM
*jj
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United Kingdom, Birmingham
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Quote:
Originally Posted by Colonel Blink View Post
Any photos? I'm happy for anyone to post photos of their Ajaxes here for inspiration!!!!
Zum befehl, herr Oberst:
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Old Jun 10, 2012, 12:40 PM
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Ajax, Ontario, Canada
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Nice models *jj

Weeds need treatment ......
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Old Jun 10, 2012, 02:41 PM
Sticks, Tissue & old Diesels
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France, Centre, Amboise
Joined Nov 2011
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Here's one

My Ajax, still flying well in proper KK colours and brushless (6 strands of Pirelli).
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Old Jun 10, 2012, 02:48 PM
I like real wooden aeroplanes!
Sundancer's Avatar
South-west France
Joined Sep 2007
4,773 Posts
Well, those three should have inspired you Colonel!!
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Old Jun 10, 2012, 03:37 PM
So I'M meant to be in control?
Colonel Blink's Avatar
Ilkley, West Yorkshire, UK
Joined Nov 2008
3,615 Posts
Well, here's a funny thing.......

Well, having given up on the idea of using the 20g motor I already had - I'll use it in a KK Snipe - or a Vic Smeed Ballerina - or....or....or...., I have realised that I'm going to need to spend some money on this project . Being smaller than anything I have done electric before, I'll need motor, servos, ESC, Lipo, prop, piano wire, wheels, connectors and especially given my poor performance on the balsa stripping front, this may even involve a 25 mile round trip to the nearest model shop for the purchase of some 3/32" square strip. Given the small amounts of wood that I will require, minimum postage charges of nearly seven quid from online balsa emporia although understandable, arent really economic.....

Anyhow, some preparation needed to be done, so having searched RCG for 'Ajax', I found a post a couple of years ago where Applehoney of this parish had mentioned he had scans of the printwood, so a hopeful PM was sent off into the ether... this was promptly and very helpfully answered in the affirmative, so then email contact was made. Result! - at least this would mean no approximation on the aerofoil front, or endless discussions on whether a NACA3627 or an RAF81634 or ClarkYOY would be best - any of which would end up tadpole shaped after I'd plotted, marked, cut and sanded the ribs......

So, having been given leave to disappear into the loft while Lady Blink downed a Pimm's or two, I cut out my versions of F1 & F2 using some firm 3/32" sheet I already had. Simple though it was, I thoroughly enjoyed the task. I left the lower halves solid, as there would be no potentially explosive overtightened rubber in this fuselage. Also, as the Lipo and ESC are likely to be somewhere around the space between them, a bit of extra solidity wouldn't harm.

The following morning, I decided to climb deeper into the eaves in search of a box of scalpel blades I knew I'd bought more years ago than I have toes on me feet. Digging into a box by the light of a torch shaped like a hippo (really must get some batteries for the Maglite), I found a KK Achilles kit I knew I had, a KK Invader kit I now remember I had, and................a KK Ajax kit I genuinely didn't know I had!!!! Even now, I find that fairly spooky....

Well, this is the MkIII kit from the 90s(?) with a fairly soulless plan (but it actually shows a 'typical rib'), diecrushed ribs and printed sheet for the other parts. But it did have the wire & tubes for the u/c, the wheels and the stripwood. Most of the strip seems usable - a couple of the 3/32" arent completely straight (but nor are the longerons) and only one seems so soft you could bend it double. If I can just sort out four that are of similar stiffness for the longerons...... That is my biggest fear at the moment!

I went to send an email to Applehoney to say panic over, but found the email with the promised scans - and the top guy had spent time tweaking the scan so I could pick out the rib shape on the die cut sheet. Thanks again, Jim - I know how much you help so many people and I feel guilty about causing you unnecessary work.

So at the moment, I am sort of considering a build using the kit wood and parts - I'm not a kit collector, and don't consider this kit of a collectable age. It solves some of the logistical issues I have concerning the marshalling and purchasing of parts for the build. Plus there is a bit of the nostalgic 'we used to build from what was in the box' attitude here!!!

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