Martin Harris - Moderator
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Posts posted by Martin Harris - Moderator
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I’m waiting on a video of my experience on Saturday. I’ve obviously got a significantly more rearward CofG than during my previous extensive flying of the model but the model showed no sign of excessive pitch sensitivity during the flight and inverted flight still required a positive push. If it had been a model of unknown origin, I wouldn’t have had any concerns - and as I’ve done extensive test flying of clubmates’ models of all types and provenance over the years, I’m no stranger to flying models with rearward CofGs!
Was the response to the gust CofG related? To be honest, I’m not sure and I’m hoping the video will give some clues. What I do know is that conditions were deceptive and increasingly gusty for all pilots present that afternoon.
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A problem for home mixers in the UK is that nitromethane is classed as an explosive precursor and you need to hold an Explosives Precursor and Poisons licence to obtain or store anything from 30% content upwards.
This requires checks on the applicant and intended uses and a fee for issue and subsequent renewals.
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17 minutes ago, Peter Jenkins said:
I just can't screw up the courage to stick a contact lens in my eye!
I said the same for decades and then for some reason suddenly decided to give it a try. I haven’t looked back since…if you’ll forgive the inappropriate metaphor! -
Beware of the lightest weight cloths - some just have a more open weave and therefore take a greater percentage of resin/fibre to fill the weave making the result actually heavier than using a nominally heavier cloth.
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Regarding the problem of prescription sunglasses, the best solution for me 25 years or so ago was to bite the bullet and overcome the cringe factor in trying contact lenses. Finally, light drizzle is no problem, I have a free choice of sunglasses and I feel that my distance vision is better than with glasses - especially when they would collect dust and fingerprints etc.
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I’m assuming that second Ian is Payneib, of the current Pegasus Hurricane thread? Looking forward to hearing about its maiden - if your field ever dries out! At least the wind should help there…
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Duplicate photo removed.
All the information regarding the record suggests 3000m - or an average climb rate of just under 10,000 feet per minute.
Perhaps the builder of the model made an error in his signwriting?
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For more clarity, the main sponsor of the full size was the Oracle IT corporation and the full size aircraft was a one off called the Turbo Raven. If you’ve been searching for information about an aircraft called an Oracle, this explains your lack of success!
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Ah - it looks like that is a scale model of the full size record holder - I’ve found photos showing similar wording on different models. The sponsors shown on the rudder are American based companies.
This article may be of interest - although it suggests the 1 minute 9 seconds was to 3000 metres - possibly a typo somewhere?
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Don't forget that these instructions were written before modern synthetics were widely available. Back in the day, Neil Tidey only recommended castor for Lasers...
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I'm guessing height rather than distance? Something in the region of 3000 fpm isn't a bad climb rate...
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I judge my approaches by attitude rather than (ground)speed but gusts in ground effect can add significant transient energy! Flying today was probably my biggest error although conditions appeared reasonable enough for the flight.
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Welcome to the forum Slater. Some pictures would help! Was this a Wren turboprop powered Turbo Raven? Maybe even this one?
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An awful long way back - the engine's out!
More seriously, about 3/4 of an inch behind the plan point. I don't think it had anything to do with today's hiccup - the rest of the flight was perfectly stable in pitch.
Hopefully I can find a compatible engine mount to avoid making more holes in the firewall. Other than rewiring one of the retract units, the only other repair work will be the undercarriage mountings.
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Wish my idle would have crept up...
Today's experiment was a bit of a mixed bag in a moderate to fresh gusting wind. I taxied out without a moment of drama, turned into wind, started the take off run, brought the tail up, balanced nicely on the main wheels, came off into a steady climb out, raised the gear and found more performance than ever before, with half a pound of lead sitting on my workbench. No sign of wing drops with tight turns, waffled happily at tickover with the stick hard back and still a reasonable push needed while in (non-scale) inverted flight.
Full of confidence, trundled down the approach, settled into the flare, waiting for the speed to bleed off and the engine cut...at the same time a crosswind gust hit and the model ballooned a few feet - with no energy reserve and no engine, despite immediate relaxation of the elevator the nose dropped uncontrollably and the poor old girl flopped onto her spinner, breaking the swiss cheese (from several engines over the years) engine mount (firewall seems fine) and hammering the undercarriage, popping the mounts out of the foam. Nothing more and nothing terminal - unlike most ARTFs these traditional builds are pretty resilient - but annoying as all the comments from the peanut gallery were of how good she'd looked in the air and sounded amongst the plethora of electric models and EDF jets flown at our club today. Maybe, given the earlier stall test, I'd overdone the elevator movement reduction but given the circumstances, probably a simple stall?
It was recorded on video but I'm not likely to get a copy before next week so further analysis will have to wait.
And Man City nicked a goal at Wembley...😢
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Surprising how it mounts up. Hope all goes well when she takes to the air. When do you plan to maiden her?
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If mine survives the CofG experiment it will have flown in my care for over 21 years with no real handling problems in the air. There’s a lot of wing so hopefully it will carry the extra weight of your engine.
There’s an outside chance of a wing drop with your higher wing loading so you might consider setting a little up aileron at neutral to provide some washout effect for first flights. I did once manage to induce a spin off a turn at low level over trees in turbulence - a handily placed large blackthorn bush added some more weathering but saved the model from serious damage.
P.S. Are you sure about the weight? With your forward engine location and CofG in the plan position, I’m wondering where another couple of pounds has crept in?
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My old girl pictured in 2006 with a temporary engine - an old OPS60 that I bought for a never completed Mick Reeves 1/6 scale (80") Hurricane before I stopped model flying in favour of full size gliding. Imagine expecting a 60 2 stroke to power an 80" warbird these days - but in 1977 it was a monster engine! It was wearing both the Mick Reeves concealed "silencer" and an add on Pitts style in order to get below 82dB. It just seemed the "right thing" to use the never flown OPS in a Hurricane while I was waiting for some bearings to arrive for the now venerable SC90FS that powered it before and after to this day. The weathering was originally faked but is now even more authentic!
I've taken another 4 oz out of the Hurricane’s nose, reduced the elevator movement a little and managed to squeeze in some 1/2” larger wheels while I was at it. Hopefully taxying will be a bit better - and the stability won’t be too much affected…at least with a full tank!
I did try 3" wheels but they were too close to the leading edge for the depth of the wheels. Did you use very thin ones Payneib?
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In this case, we’re looking at a solution for the ground handling difficulties which seem to plague some models - and the Hurricane in particular.
There’s no magic about a CofG position marked on a plan - we rarely know whether the designer has marked it there as a result of practical testing, calculation or even guesswork! Then we also don’t know whether it’s been chosen by personal preference or with safety in mind. In fact, if the plan shows a CofG range rather than a single point, I’d have more confidence in the designer’s aerodynamics competence.
In this case, I’m carefully conducting a test of combining more rearward positions with reducing elevator movement based on Jon Harper’s experience with similar warbird models. This may not correspond with full size movements but perhaps scale effects e.g. Reynolds Number, start to become significant on control effectiveness with models of 1/6 or smaller scale?
I have also provided a “taxi” switch (non latching) which gives a higher rate for taxying and initial stages of the take-off run. This carries over from pre-experiment times.
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Flight tested today.
4 oz. of lead removed from over the engine. CofG 1/2” back from plan position - elevator reduced to plan specified (3/8” up and down) amount.
No apparent reduction in stability (it’s some time since I last flew the model) but still eager to nose over. Grass freshly cut but quite damp and draggy for the little 2” wheels. Inverted flight required definite push so I’ll be removing more lead.
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A club near ours lost its longstanding flying field on what was apparently the whim of the farmer's wife. It seems that she'd contracted Lyme's disease and as a consequence, suffered long term mood swings.
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Returning to the subject...
As mentioned earlier, I bought mine at a swapmeet in early 2003 (looking quite elderly even then) and I've just remembered that on the included plan, it shows torque rod operated strip ailerons. I see yours has, like mine, scale position inset ailerons and split flaps. Were these detailed as an option in the build notes or were later plans/kits modified?
Anyway, I've removed some lead to bring the CofG back about half an inch from the plan position and reduced the elevator movement. The grass has been cut today so, fingers crossed, I'll start putting Jon's advice to the test tomorrow...
P.S. I see the Pegasus website illustrations show strip ailerons...
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How strange for Paul - using a fuel with no castor!
I can't say that I've noticed any sign of overheating but my version (91) sits in the front of a very vintage (re-engined several times) circa 1982 Stearman, nicely exposed to the breeze between the dummy cylinders. I hesitate to say this but I promised the old boy who "gave" me (I managed to persuade him to take some money) the model when he was downsizing, that I would use the several gallons of Duraglo 10% (6% castor/9% synthetic) that came with it which was "the one and only" fuel recommended by the distributor before Westons (oddly, one that they distributed) and have largely honoured the pledge. The old boy used to bore (and often exasperate) club members by constantly harping on about this recommendation. Strangely, once Westons took over the engines, their fuel became the only suitable one!
Could he have had a point?
The idle seems quite normal and I don't recall 58s having problems - perhaps they redesigned the carburettors at some time?
There shouldn't be too much problem arranging good cooling in the Pup, Lindsay, as long as you don't fall into the trap of thinking the wide open spaces of a rotary's cowl will provide it. Rather counterintuitively, what actually happens is that hot air pools in the cowling around the engine and any airflow takes an easier route. A dummy engine or suitable blanking plate to encourage air to flow over the cylinder and head, coupled with a suitable exit should do the job. It looks like BEB was mounting it inverted so a good exit should be easy to arrange.
Galaxy/Pegasus Hurricane
in All Things Model Flying
Posted
A thousand words…definitely semi symmetrical: