Andy Blackburn
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Posts posted by Andy Blackburn
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> not sure what you mean by ‘slight pull towards the canopy’ - I would say a successful CG dive test is one which has a gradual unassisted pull out
Yes, same thing - been round power models too long...
What I do for balancing is to get hold of a couple of used matchsticks and (for a low-winger) tape them to the top of the wing, aligned spanwise, at the required c.g. position. Then I turn it over and balance it on fingertips - it's not going to be more than a millimetre out either way.
What I'll do (later in the week) is to move the c.g. on the plan to the 78 mm position with a note to say that it should probably be optimised using the dive test.
Edited By Andy Blackburn on 21/07/2020 08:51:45
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OK then, that all sounds very reasonable; I have my hands full for the first part of this week but will try and get some updated files to Phil before next weekend.
I take it that we are all certain that 7 mm (85 mm - 78 mm) is the correct amount to move the c.g. forward? If you do a dive test (useful as a general reference even if you don't really believe in it) then there should be a slight pull towards the canopy...
A.
P.S. - hoping to get up to the Orme before the end of the year, Covid and accomodation permitting...
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> I will check the decalage before the next flight and add some more weight to the nose.
Hi Jez - all that would be really helpful; I did move the c.g. forward from the original plan (partly because I have my c.g. on the smaller one fairly far back anyway), but obviously not enough.
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Well, this is - frankly - shocking. One just can't get the staff.
My apologies to Jez for the unnecessary excitement. I'll make the appropriate changes to the CAD files and re-issue the plan to Phil. It'll take me a week or so because I have my hands full at the moment...
A.
P.S.
Pete - you built the first JP, did yours need the c.g. moving forwards as well?...
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Nicely done...
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I hadn't noticed that (or the glass) - well spotted. I might try that technique...
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Top planking tips, particularly liked the one about "Nobody likes planking. Well that is nobody who has done it before likes it! Regardless of what people may say it's not therapeutic! It's tedious, time consuming and will draw blood!".
I've never had the blood but everything else is right.
. Helps if you put the radio on and kind of get into the zone.Speaking persoanlly, I use medium CA (new bottle) to glue the planks to the formers and Titebond for the plank-plank joints, so I don't have to bother with pins much. I think I tend to slightly over-sand the chamfer on the plank (by feel, with a permagrit block) so I don't get any gaps.
In the past I've tapered the planks so that they're narrower at each end, which means that you can use wider planks but that's another 2-minute process added to installing each plank. Might use the parallel-plank method on this one.
I've never had a twisted fuselage but then I've always planked when the fuselage halves are already joined, adding each plank on alternate sides - by the time the top half is done, it's more-or-less completely rigid.
(Can't start my F-86 yet, just doing a Peanut. Shouldn't take long, though...)
Edited By Andy Blackburn on 12/11/2019 08:22:08
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Like the colour scheme.
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Posted by Peter Garsden on 27/10/2019 19:00:19:Posted by Andy Blackburn on 25/10/2019 19:50:35:Posted by Peter Garsden on 23/10/2019 20:13:47:
Sorry Andy - have now covered the wing. I can weigh everything though if you wish?
OK, no problem - if you could maybe weigh the covered parts without the radio, that would be great. I can make allowances for the covering (Oracover, I assume?)
Just weighed it at 65.8oz or 4ilbs 9 oz. Here is a picture so you can tell how much solarlilm there is. There are 2 servos in the wings but no servo or battery in the fuselage. Will now look up the surface area of the wing to work out the wing loading - it is 3.8 square feet which is 17.8oz per square foot - bit more to take account of the rest of the solarfilm and the battery.
Edited By Peter Garsden on 27/10/2019 19:08:39
That's looking pretty good - it's only just over 4lb so let's call the final weight about 4.5 lb, maybe 4.75 lb with a bit of nose weight, so even though it's about 60" span I'd say you're probably looking at 19-20 oz/sq ft.
Perfect!
A.
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> Things have moved on a bit since then and I am wondering what model would be best for very light wind (12mph or less) slope soaring.
Well... 12 mph isn't really what I'd call "very light", and it depends whether you want to build something in the traditional manner or assemble some glassfibre parts.
- If the former, I'd drop a line to Phoenix Model Products to see what they recommend.
- However, if you want to assemble something glass then I'd try a Mini Ellipse - they're really good on normal slopes, will fly in a few (single digit) mph and are ballistic if ballasted.
If neither of those floats your boat, almost any DLG will be fine (but might be expensive if you buy new) but unless they can take quite a bit of ballast they are unlikely to offer the same overall performance as a Mini Ellipse.
Just my two penn'orth...
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Posted by Peter Garsden on 23/10/2019 20:13:47:
Sorry Andy - have now covered the wing. I can weigh everything though if you wish?
OK, no problem - if you could maybe weigh the covered parts without the radio, that would be great. I can make allowances for the covering (Oracover, I assume?)
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Looking good, impressed with the dashboard.
Any chance you could weigh all the structural bits before you start covering, please...?
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Where Eagles Dare (because it's a rip-roaring yarn)
Kelly's Heroes ("Mulligan!!"..."Did you lose my aerial photographs?"...)
Saving Private Ryan (no explanation necessary)
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I don't suppose you've weighed it yet, have you?...
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Very nice, particularly the cockpit. Good luck with the maiden, and let us know how it goes.
A.
P.S. - you've probably noticed this already, but you've lost the starboard engine starter fairing...
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Martin - in order to save the rest of us doing some experimentation, can you please tell us a) how wide your planks were (10mm?) and b) whether you'd use different width planks if you built another one?
Edited By Andy Blackburn on 13/10/2019 15:16:09
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If the ply plate is fixed to the wing, then if one wingtip hits first and the wing bolt snaps, the wing will pivot in the horizontal plane and the ply reinforcement will remove part of the wing seat on its way out.
What you could do to try and manage this is to add a chamfer to the edge of the ply plate to try and persuade the wing to move downwards as well as sideways during the crash.
Edited By Andy Blackburn on 11/10/2019 18:54:32
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Posted by Peter Garsden on 06/10/2019 13:42:58:
Good point Andies (is that the plural of Andy?) or a type of hand tissue? Because I forgot the hard balsa inside the wing, I added a piece of 1/64 ply, then carbon bandage and resin, then the covering piece of 1/16 as on the plan - probably should have put the ply on first! - so I think I probably have enough of an edge to snap on a heavy landing?
It's not so much an edge that you need, it's as short a length of unsupported bolt as possible. Hence the filling-in below the bolt plate...
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> ...the fuselage seems to weigh quite a lot...
To be honest, I wouldn't worry about it; it's a much bigger model than the 1/12 scale version, the wing is operating in a much better regime as far as Dr Reynolds in concerned, and people used to fly ~60" Warbirds (Brian Taylor Tempest, P-47, etc.) that weighed 6 or 7 lb off the slope and they flew really well. So the chances are that it'll be fine.
Of course, if your wood selection has been a little, shall we say, "conservative" (the plan has something to say about this as well) then it'll be a bit more advantaged in the momentum department than one might have expected. However, that's not necessarily a bad thing.
(BTW, one of the updated notes on the latest version of the plan (which you have) talks about filling-in the area underneath the wing bolt plate with hard balsa so that in a crash, the wing bolt is persuaded to snap/shear cleanly and allow the wing to come off properly rather than just bend, which would damage the wing.
You might get away with another piece of 1/8" ply or very hard balsa positioned flush with the bottom of F14. It's not mandatory (depends how often you crash!) and you can always do it afterwards.)
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Posted by Peter Garsden on 02/10/2019 17:26:28:
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Incidentally, have you any idea what the wing area is in square feet to save me working it out?
Yes, it's 3.80 square feet including the optional <ahem> high-performance plug-in rounded wing tips.
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Posted by Peter Garsden on 01/10/2019 21:17:32:
...I noticed that there was quite a twist to the fuselage so it was important to pin down the fuselage to the work top over the top view of the plan. I used T pins as it was under quite a lot of pressure. Difficult to know how to avoid this.
Pete, I think this must be happening when the fuselage sides are glued to the battery box assembly - if they're not straight and square at that point (sight along the fuselage from the jet pipe forwards) then they'll twist when the ends are drawn together.
If the fuselage sides weren't square when glued to the battery box and the glue has already set, you'll have to live with it and try to carve/sand out most of the misalignment, but if you catch it before the glue sets then - with care - you can usually twist everything straight and nobody will be any wiser.
I'll add an extra clause to the fuselage instructions on the plan.
If its any consolation, most of my models end up with a small amount of fuselage twist, to the accompaniment of some bad language...
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Parts files for F6 and F7 are now updated.
However, in a rare victory I should point out that the wing bolt plate hole is (or should be) correct because a) not all spiked nuts project into the hole, and b) some people prefer to invert the T-nut on top of the wing bolt plate and fix it with a good helping of epoxy; this has the advantage that - for an accurately made T-nut - the wing bolt will then be properly square to the wing bolt plate.
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Nice. Watching with interest.
I assume that the reference to 70-90 size engines is for four-strokes...?
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FYI, what I've done on the latest version of the plan is to remove the top (thinner) part of F16 (the part above the spruce spar) because, on reflection, it's just not required. All the other changes that people have identified have already been incorporated, so I'm hoping that'll be it.
Jet Provost 1.5metre Andy Blackburn PSS Plan
in PSS Build Blogs
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It's done. My conscience (such as it is) is once more as clear as can reasonably be expected.
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