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Jun 25, 2019, 07:09 AM
So I'M meant to be in control?
Colonel Blink's Avatar
Thread OP
Build Log

EAR - Keilkraft Invader x 2 - 80"


Well, as the Early Age Revisited was sort of my suggestion, it would probably be churlish not to enter oneself, innit?

For those not of these hallowed shores, perhaps a few words of background about the design would not go amiss....

The designer was Albert E Hatfull - yes, he who later designed the ubiquitous Junior 60. The Invader was in fact AEH's first kitted design; as a teenager at Technical College he had turned up on spec at the gates of Keilkraft and had spoken to Eddie Keil himself who had said he 'could have a go at designing a glider, and if he [Eddie] liked it he would kit it' - which is exactly what happened. The Invader name came about because it was around the time of the Invasion of Europe in WWII. It's popularity was and is unquestionable - it is part of the 'new Keilkraft range' being offered by Ripmax around 75 years later. For a potted history about Albert Hatfull and his designs, I point you to Chris Jenkins' thread entitled appropriately Albert Hatfull

The EAR credentials are that in my earlyish years (I would have been about 12, perhaps 13 I suppose - being a mere whippersnapper this would have been the early seventies) my elder brother had been given the Invader kit one Christmas - he had built the fuselage and I think the empennage but not the wing; the part built model had languished under his bed for some months before I offered to complete it. I am not sure to what level my skills had risen at this point, but it must have been pretty low as I remember the virtually square leading edges and virtually no shaping being carried out on the tip TEs which were laminated from 3 strips of 1/8" square balsa. I remember that the wing and tailplane were covered in yellow Modelspan; the fus and fins I have a feeling may have been red .... or may have not have been. Age is a funny thing isn't it?

No matter the speculative standard to which it was built; it flew reasonably well as I remember, and was I believe pretty strong by dint of most stripwood being 1/8" square - in comparison the similarly sized KK Gypsy's fus was made of 3/32" square, and that needed to withstand the tension of a Wakefield-power rubber motor. I do remember one summer's evening the model circling over my head after dropping the towline and I could hear a quiet creaking - after it landed, investigation showed that the spars had both cracked on one wing allowing the tip dihedral to change by over an inch at will. It had happened in an earlier prang, but apparently there was still enough integrity to stand a gentle tow - though it did explain why it suddenly always wanted to veer to the left on towing...

Right, that's dinnertime over so I need to do my employer's behest; next post will be the design ethos behind what terrible liberties I am going to take with the design.

A quick note - John Woodhouse's videos of his Invaders - especially his impressive 'wobbly wing' 80" version - have had several airings around here recently, so there is probably no need for anyone to post them again. But just to ring the changes, I will certainly not be making the wings on my incarnation anything else than rigid, and held on with rubber bands!!
Last edited by Colonel Blink; Jun 27, 2019 at 01:37 AM. Reason: Removl of annoying exclamation marks
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Jun 25, 2019, 10:07 AM
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Larry Jolly's Avatar
A really lovely Classic Glider. Looking forward to this one. L
Jun 25, 2019, 11:04 AM
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kkphantom's Avatar
Well I hope you make a better job of this model than the usual tat you turn out....
Gary
Jun 25, 2019, 11:19 AM
B for Bruce
BMatthews's Avatar
CB, were you thinking of making the wings pivoting as pitcherons as was done in the other recent thread? If you are you'll want to do a bit of extra work on the joiner rod socket to provide inner and outer sleeves as bearings. Otherwise when the joiner rod flexes under load it could lead to a lot of binding in the hinging and high loads on the servos. Done well though the whole control system could be hidden and it would simply look like the wings plug on and the model is purely a free flight model. Even the activator for the pitcheron function could be hidden in the wing root.

I'm busy as blazes for the next week. But when I get back I could do up a sketch of what I'm thinking about if you like.
Jun 25, 2019, 01:51 PM
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kkphantom's Avatar
'Hidden control system?' That's a laugh...bet he pikes the servos out through the fuselage sides!����
Jun 25, 2019, 02:29 PM
So I'M meant to be in control?
Colonel Blink's Avatar
Thread OP
Quote:
Originally Posted by BMatthews
CB, were you thinking of making the wings pivoting as pitcherons as was done in the other recent thread?
Hmmm. I refer the honourable gentleman to my initial post...............

Quote:
Originally Posted by Colonel Blink
A quick note - John Woodhouse's videos of his Invaders - especially his impressive 'wobbly wing' 80" version - have had several airings around here recently, so there is probably no need for anyone to post them again. But just to ring the changes, I will certainly not be making the wings on my incarnation anything else than rigid, and held on with rubber bands!!
Quote:
Originally Posted by kkphantom
'Hidden control system?' That's a laugh...bet he pikes the servos out through the fuselage sides!
Aaaaaaahhhhh shaddap!!!!!!!!
Jun 25, 2019, 04:48 PM
Registered User
In "Flying Models" 3/56, in an article about designing built up fuselages, Bill Dean seems to have drawn a tidied up Invader. Slimmed down, upright spacing more regular, curves smoothed, messy bits around the tail fixed, single rudder, but basically an Invader. Perhaps the article should have been called "Look and learn Albert" and my build log for "Bill Dean's Captain" should have been called "Bill Dean's New Invader".
Jun 26, 2019, 01:34 AM
So I'M meant to be in control?
Colonel Blink's Avatar
Thread OP
Now to me, that looks a whole lot more like an enlarged glider version of the Ace - or maybe a sportier Chief - rather than a development of the Invader...........
Jun 26, 2019, 01:55 AM
So I'M meant to be in control?
Colonel Blink's Avatar
Thread OP

You're going to do what....???


OK, so just to set my possibly rather contentious peg in the ground, here's what intend to do..........

Firstly, my Invader will have R/E/T control. The eagle eyed amongst us will have noticed the 'T' in there - for yes, my Invader will have electric power. This is for two main reasons - the minor being because I'm not going to run around with towlines nor do I live near a slope, but the main one being because I want to, so there. If you don't like it, then don't let the door slap you on the arse on your way out (I'm obviously getting crotchety in my old age ).

Secondly - as I have already touched upon above - for me, the robustness of some of the wood used is part and parcel of the look of the Invader, especially in the fuselage. As such I will be making the fus from 1/4" square; and anyone who starts bleating about 'twice the size is eight times the weight' will be metaphorically tarred and feathered and generally harangued, as I have made my thoughts clear on this attitude in my thread on the KK Ace (I really must chill, but I've noticed a slight increase in posts saying 'you will have to...' or 'you must.....' when possibly the poster means 'you could consider...' or 'if I were doing it, I might try....')

I am aiming for my Invader to be unmistakably an Invader and hopefully be a reasonably slow and majestic (or maybe ponderous) flyer. It is highly unlikely to be overpowered with what I have in mind!!
Jun 26, 2019, 03:56 AM
I like real wooden aeroplanes!
Sundancer's Avatar
So Colonel, you are going to grasp the nettle of the twin fins and dihedral tailplane head on, rather than craftily circumnavigating them as John Woodfield did. I'll be interested in following your solutions to these perennial problem areas. I'm particularly looking forward to this as the Invader was my first successful flying model built at the age of 6 years and 11 months, following an Achilles and Ajax which didn't - fly that is - and put me off rubber models for a year or two, so I have a considerable emotional attachment to the design. So don't bugger it up!!
Jun 26, 2019, 05:05 AM
Registered User
rchopper56's Avatar
This thread is going to be fun and long. But will survive my comments and end up eventually with a beautiful flying model.
Gene
Jun 26, 2019, 06:37 AM
So I'M meant to be in control?
Colonel Blink's Avatar
Thread OP
Quote:
Originally Posted by Sundancer
So Colonel, you are going to grasp the nettle of the twin fins and dihedral tailplane head on, rather than craftily circumnavigating them as John Woodfield did.?
I am - much as I love JW's 'wobbly wing' Invader (along with the rest of his fine work) it seems that in recent weeks/months it has become impossible to mention the Invader without it being assumed that one is going to do the same or that it is the only viable control method. I did consider for about a nanosecond making it an AMT and having the whole shebang tilt and turn but realised that would just look silly. No, I am a simple chap and I am going with the simple, traditional solution of rudders and elevators.

As it will very much be a gentle circuits or climb & glide model, even at 80" I don't think that there will be much in the way of aerodynamic forces on the control surfaces so I can get away with the lightest of servos - a 4g one for each rudder in the tailplane tips and a single 5 or 9g one for the elevators, probably under the centre of the tailplane or kept in the rear of the fus. The quick and dirty calculation is that the battery weight further forward will more than compensate for these; though it might be the wire which has more effect on balance than the servos! It might be that I have to run all three through the same negative lead, saving a little - but that may be more faff than it's worth. Finally, whilst we're on the subject of the tailunit, I will be making my fins built up as they are about 8" x 6" (200 x 150mm) and I will shave a few grammes off by making them partially air (probably with laminated outlines).

Quote:
Originally Posted by rchopper56
This thread is going to be fun and long. But will survive my comments and end up eventually with a beautiful flying model. Gene
Gene - you are correct, it will be long - interminably so! It may even end up as one of the first entries into the CAP2020 thread, especially as I now have the idea to include the conversion of the pink Viper to electric CL, purely for your benefit But I'm looking forward to your heckling and jibes
Jun 26, 2019, 07:54 AM
Registered User
rchopper56's Avatar
You'l get to the Goblin eventually, hopefully in my life time.
Jun 26, 2019, 07:56 AM
I like real wooden aeroplanes!
Sundancer's Avatar
You could use a common negative AND positive and end up with just five wires Colonel, but as you say some fiddly wiring would be required at each end. I have done it with two in my "V" tail "Simply the Best" E400 models and the saving was worthwhile, but they do have a very long tail moment, much more so than the Invader. Just depends if the saving will be worth the trouble.
Jun 26, 2019, 08:16 AM
Sticks, Tissue & old Diesels
brokenenglish's Avatar
Colonel, have a look at this pdf, posted by George (I think), a few years ago. Could it be a solution to your problems?


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