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Member postings for Andy Blackburn

Here is a list of all the postings Andy Blackburn has made in our forums. Click on a thread name to jump to the thread.

Thread: CAA registration consulation
29/04/2019 18:16:31
Posted by Peter Christy on 29/04/2019 16:53:44:
Posted by MartynColes on 29/04/2019 12:23:30:

I think these guys are friendly to us. See link below to the "All-Party Parliamentary Group on General Aviation" They already challenged the CAA over airspace grabbing and managed to get a change in the law to stop CAA from not consulting properly in future.

They list the BMFA as a sponsor too, so they ought to be listening to us.

I have already written an e-mail to them this morning (no reply yet) but it may be a good idea for as many people as possible to request their help.

There is nothing to lose asking them to look into this problem, they may not be all that aware of it!

See "contact us" in link **LINK**

That's a good spot, Martyn! I notice that one of their "partners" is the BMFA. I wonder if, instead of us all contacting them individually, the BMFA might like to take it up with them? Any comments, Andy? Keith? Anyone?

Had a very bland reply fom my MP today, referring me to a load of government waffle - sorry, "statements" - on the subject. She clearly hadn't read any of them herself.

Ah, well, I wasn't going to vote for her next time anyway!



I also wrote to the All Party Parliamentary Group on GA, and within an hour had received an encouraging response from James Shipp; I think they are on our side. He finished by saying "...I would urge you and your colleagues to respond to CAP 1775 to make sure the CAA is aware of the strength of feeling on this issue". So it probably will make a difference, I think.


29/04/2019 15:46:45

I've written to my MP using ; it might or might not do any good, but it made me feel better.

Edited By Andy Blackburn on 29/04/2019 15:47:18

26/04/2019 19:43:54

I've also filled-in the consultation document (politely but firmly).

Thread: Wash out
26/04/2019 08:51:02
Posted by Nigel R on 26/04/2019 06:55:07:

Interested to know why the washout is there by design on a cub. A rectangular plank wing inherently stalls root first I believe.

I've certainly never put washout in anything I have built with a plank wing.

I assume that it's there to control how sharp or soft the stall feels to the pilot (I assume you're talking about the full size)?

25/04/2019 20:13:45
Posted by Don Fry on 25/04/2019 19:52:56:

Why not speak to the bloke who owns DB Sports and scale?

Good idea.

But if I were you, I'd do exactly what it says in the instructions. If you don't put the washout in, you'll effectively be increasing the wing incidence which is not what the designer intended.

BTW, I think you'll find that the full-size J-3 is normally rigged with about 1.8 - 2.5 degrees of washout...

Thread: JR resurrection?
04/03/2019 13:33:39

I agree with what's been said; given the competition I'd balk at paying half the proposed asking price. I think the problem is that JR was seen as a premium (and expensive) brand but they're not a premium brand anymore, unfortunately.

Thread: Andy Conway Bae Hawk
03/03/2019 20:16:05

I've built three of these with several wing sectons (can't help myself), and they're very, very nice. In my experience, they do need either a) washout, or b) the wing fences installed.

Thread: PSS Jet Provost
12/11/2018 10:47:16

> I was wondering if the washout on the JP could be 'blended' into the tip tanks to make it look more scale-like ?

Yes, that's what was done on the small one - the tip tank is (or should be!) at the right angle for scale, the washout isn't noticeable.

> I don't think the plan is 'Ron Collins' but, it is a Mark 5. Target weight was around 3-4 lbs if I remember the magazine article correctly. Does this seem ok for wing loading ?

If it's 48" span, then bearing in mind you said that you wanted a "light, but strong airframe that can be ballasted" then 3 lb is probably OK, at a guess. It also depends what slope you fly from - if it's a brick lifter then I wouldn't worry too much, but if you fly from a more normal slope then I'd aim for a wing loading of 15-16 oz/sq ft. You might well have to use some light wood to get that, though.

10/11/2018 12:25:25

> On the slope, I'm wondering about a Selig 7055 or Eppler 205 /374 section ?

Depends on the size, and on what you want. The small Jet Provost wing section is Selig S7055 which works well at that size, it thermals and climbs well but the wing section seems to limit the top speed. Eppler E205 is faster but seems to require a decently-sized wing chord to work properly, I hesitate to speculate but I'd say something around 8-9 inches chord would work well. E374 is similar but a bit faster, and hasn't got a nearly flat rear profile so it can't be built flat on the bench.

One other thing, though - the small JP has a little bit of washout (a degree, from memory) and it normally behaves itself in the tip-stall department; I urge you to at least consider the possibility that a little bit of washout might be a good thing...

(P.S. If it's Ron Collins' plan for a JP Mark 5 that you have, I think it's Eppler 374...)

Thread: Slowing down a Boomerang II trainer
08/11/2018 09:02:40

There's not a lot wrong with a Boomerang as a trainer.

However, many trainers are set-up with a forward c.g. (particularly if one has erred on the side of caution), one side-effect of which is that they may tend to fly a little fast once they're trimmed for the glide (as it's electric and you're thinking it's a bit fast, I'm guessing that the throttle will be closed for most or all of the approach).

I suggest, therefore, that you experiment with moving the c.g. back a little bit at a time - nothing bad will happen because it has a nice, square wing. If you move it back far enough you'll notice the elevator is a bit more sensitive, but you can reduce the throw slightly to compensate, and carry on.

Thread: Canberra by Andy Blackburn PSS
24/10/2018 09:03:32

That's really great news Pete.

+1 for pictures.

08/10/2018 08:26:13

Pete, that looks really good.

> What is the wind range Andy?

I've not found the wind speed limits yet, because every time I've chucked it off a slope it's flown OK.

All slopes are different of course and will provide different amounts of lift with the same windspeed, so it's difficult to give any hard limits. However, it will fly higher in the same lift than my light-ish 2nd Jet Provost (silver and dayglo) and Hawk T1a (the grey one, SD6060 wing) so if a JP or Hawk will gain height, then the Cranberry should do too. I've chucked the first prototype JP (slightly lighter) off the Orme in a lot less than 10 mph and that took a bit of concentration, but it did gain height.

Having said all that, though, you really need a decent amount of lift for a maiden in case you need to sort things out so I'd just go with what you're happy with.

04/10/2018 09:50:26

I've used JR and then Spektrum, but I suspect that you use Futaba(?) so this might not make all that much sense, but on my Tx you can either do it using end point adjustment, or on the Tx screen where the dual rates are set-up - you can set-up different amounts of movement for up and down elevator by holding up or down stick whilst adjusting the movement.

I'm afraid I did it on end-point adjustment - something like 100% down and 80% up ...

03/10/2018 08:58:50

On the prototype I had the model set-up with two elevator servos exactly as Phil describes above; the only time you need to use a Y-lead is if you haven't got enough channels.

BTW, I also used one channel per aileron so that it was easier to adjust them, so there were a total of 5 channels used:

  • Left Aileron
  • Right Aileron
  • Left Elevator
  • Right Elevator
  • Rudder

+ a small amount of aileron-rudder mix as described in the original article, and I think I had about 2:1 aileron differential. Also a small amount (~10%??-ish) of expo to get all the surfaces back to a linear movement with the sticks. Might also have had a little bit extra expo on the elevator because you don't need very much movement at all - it's quite a short-coupled airframe.


01/10/2018 08:23:58
Posted by Peter Garsden on 01/10/2018 08:12:23:

Thanks Andy - I did all of this apart from gluing the wing root to the fuselage, which was a bit obvious when I think about it, and would have helped a lot. Just goes to show how just a small obvious missed step can make all the difference.

Ah! smiley ... Well, that might do it.

Colour scheme starting to look very nice indeed, BTW.

30/09/2018 11:27:48
Posted by Peter Garsden on 30/09/2018 07:40:34:


The handy balsa trimming tool Andy made and shows in his article works really well - a blade glued between 2 pieces of 3mm balsa, but I think you could us 2mm? What did you use Andy?

I just CA'd a new scalpel blade to the bottom of a piece of thick balsa (like, 1/4" or 3/8" ) so that it could be easily held, then just ran the resulting tool along the wing surface (that is, the blade is in contact with the wing surface) so that it cut through the soft balsa that had been stuffed into the gaps.

BTW, I'm a bit puzzled by the problems you're having with this bit, I thought it might be the worst part but - for me - it turned out to be quite straightforward. Here's what I did, from memory:

  • Tack-glue the ply root facings to the inside of the wing ribs with tidy dots of CA or balsa cement - can't remember which.
  • Install the wings on the fuselage and glue the root facings to the fuselage where they touch the fuselage.
  • There'll be a gap at the trailing edge, stuff a small (but sightly oversized) bit of medium balsa into the gap (wrap some sandpaper around the fuselage to get the right curvature so that you have about 6-9mm of balsa supporting the TE of the ply root facing.
  • Cut the bit of supporting balsa to the right profile using the tool.
  • From now on it should be plain sailing because all you do is repeat the following until there are no big gaps left: find a short (2-4 inches) gap, sand a chamfer on a slightly oversize bit fo soft balsa, stuff it in the gap (squashing with fingers if necessary), tack glue it to the root facing (because we don't want glue mess on the fuselage), cut it to profile with the tool, then glue it in place properly.
  • Run a new blade between the wing root and ply root facing to separate them, and then remove the wings.
  • Fill in the inevitable small gaps with filler.
  • When dry, sand and cover quickly in case one of your mates comes around an makes an unkind comment about all the filler.





Edited By Andy Blackburn on 30/09/2018 11:28:15

30/08/2018 15:23:41

That does look like a nice set of turbine blades!

However, bear in mind that my engine intakes were flat so would very probably have had lower drag, if you find it's an issue then I recommend the use of an acetate disc with a small circular hole cut in it for the starter fairing - you'll still be able to see the intake detail but the air won't.

Thread: Government Consultation on Drone Flying in the UK.
23/08/2018 14:31:50

I've done it; took a while because I used my own words in the "Why?" parts. Which, BTW, you do not have to fill in.


Thread: Austerity BF109G
21/08/2018 11:37:25

Does Mrs Scotty know about the illegal and provocative use of the kitchen table? smiley


Thread: Canberra by Andy Blackburn PSS
15/08/2018 09:04:45

> So question Andy - is my maths correct?

Without checking the numbers, the principle is correct - apart from the middle bit of the fuselage that's parallel, the ends of the planks taper in the same ratio as the former size. Just don't forget to chamfer the edges a bit so that if there is a gap between planks (perish the thought!) then it's on the inside and will be filled with glue.

However, you don't have to be dead accurate with the planks because you can always make a couple of odd-shaped planks to get everything back to where it should be.

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