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New 78" Vulcan for twin 90mm DF

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Tony Nijhuis26/09/2015 00:42:25
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600 forum posts
225 photos

Ok so here's the last in the size range of Vulcans I set out to do more than 4 years ago and not off to a great start......a before and after photoimg_3391.jpg

img_3392.jpg

I never did like the phrase 'non destructive testing' All I can say is the model when it was flying was superb and cant wait to build the second prototype as the size, simplicity and performance made this a winner...

happy days

Ian Jones26/09/2015 01:01:25
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3218 forum posts
1397 photos

Oh dear that must have been disappointing Tony.

Bet there's lots of people waiting for Prototype 2 to succeed in anticipation of the finished design. Trad build twin 90mm fans plus the Vulcan's distinctive good looks, got to be a winner.

Hard luck and good luck with the next one!

Ian

Piers Bowlan26/09/2015 07:47:38
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1867 forum posts
44 photos

Ouch! A very sorry sight, at least the outboard sections of the wings appear to have survived unscathed - small consolation. Any idea what went wrong, so that it is not repeated?

What span is this 90mm fan version, 78in?

Tony Nijhuis26/09/2015 10:57:31
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600 forum posts
225 photos

Only a slight disappointment Ian.....there is always a greater risk when test flying a design without any sort of covering applied. Of a model this size, one would glass cloth epoxy the structure which locks in great strength. Part of the reason for failure was no covering was applied so i was asking a lot of the balsa. The other reason was too much 'on the hoof' redesigning (cutting & carving) which had weekend the structure

What is useful is now i have the wreckage to analyze, i can see where the problem are. There is always a positive to any disaster

Yes Piers, 78inch span

ChrisB26/09/2015 13:03:49
1219 forum posts
34 photos

Certainly looks an impressive model Tony. What was the weight?

The picture looks like a grass strip. How did it perform off grass?

Cheers

Chris

Tony Nijhuis26/09/2015 14:02:11
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600 forum posts
225 photos

AUW was 18lbs and although the runway was quite boggy on the first test flight, after the last few days of rain and the grass covered the wheels (54mm dia), she fairly raced along and was airbourne in no time. Each fan is capable of 10lbs of thrust so ground power is good...soon as she's away you cut the throttle to two thirds and she climbs away with gusto!...after that, haft to a third throttle is all you need, until you want the 'Vulcan climb'!!!!!

Former Member26/09/2015 16:18:30
1322 forum posts

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ChrisB26/09/2015 16:37:39
1219 forum posts
34 photos

Thanks Tony, certainly looks the part. Yet another top model on my list!

Tony Nijhuis29/09/2015 23:16:54
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600 forum posts
225 photos

David, on delta's, tip stalling is not a problem so no washout is required.....What washout does is reduce the wing tip lift and bring it inboard.....QED if the lift is reduce at the tips, the chance of tip stalling is reduced. With the Vulcan wing and the fact delta's do not tip stall, the AVRO designers actually made the tips a flat bottomed high lifting section so the payload carrying capabilities of the Vulcan could be vastly increased with still no chance of tip stall....

Now redesign and the part being cut for a new one........and strangely looking forward to buildsmiley

Former Member30/09/2015 16:00:17
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Ian Jones30/09/2015 16:19:35
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3218 forum posts
1397 photos

With that degree of positive thinking it's bound to be a success.... as usual. Wathcing with great interest.

Ian

Matt Jones30/09/2015 17:31:19
1186 forum posts
1 photos
David, I've got a 72" one with the scale section, i.e. LE droop for the outer half of the span. It has very different characteristics in pitch with different speeds which I'm convinced is due to the unusual section. I reckon if Tony can do without them and give a more stable model then all good.
Former Member30/09/2015 18:43:36
1322 forum posts

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Matt Jones30/09/2015 20:38:27
1186 forum posts
1 photos
David, it's from the South Herts Models plan, by far the most accurate plan that's out there, and for PSS off the slope. The characteristic is that if you put the nose down even slightly the model accelerates rapidly and becomes incredibly pitch sensitive with a tendency to tuck if left unchecked. I've tried a variety of CG positions without change. It's quite nice to have to 'fly' a model and really focus on what you do but odd none the less.
Former Member30/09/2015 21:42:54
1322 forum posts

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Matt Jones30/09/2015 21:59:28
1186 forum posts
1 photos
Absolutely no idea, would have to weigh it.
Former Member30/09/2015 22:39:04
1322 forum posts

[This posting has been removed]

Tony Nijhuis30/09/2015 23:05:49
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600 forum posts
225 photos

Interesting point Matt about pitch sensitivity and tuck under....if the wing geometry of your Vulcan is incorrect especially when introducing the under cambered wing profile towards the wing tips (as per the real Vulcan) you are in danger of too much lift behind the CofG. The consequence of this is when you put the nose down the the main inner wing section produces less lift but the out part is still lifting well behind the CofG.....QED as a result the model will pitch down and accelerate and then tuck under....its a vicious circle and only carefully up elevator control (a throttle) can retrieve the situation from desaraster!!!

However when the Vulcan wing is in normal level flight or climbing the wing is extremely stable and delivers very high lift characteristics, which is exactly what a bomber had to do.

To descend a Vulcan you need to reduce power and keep the nose level then raise the nose slightly and the aircraft descends The rate of decent is check with engine power.

On my Vulcan designs I tried to make the wing a little more forgiving so the under camber was not included and so pitch sensitively is not a problem, nor is tuck under. The purist may say its not scale but the idea is to make something that works well rather than a 'scale' hand full in the air....

Former Member01/10/2015 13:20:06
1322 forum posts

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Former Member01/10/2015 17:12:25
1322 forum posts

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