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The Big Guff.

My Winter Build.

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Limobob03/06/2020 07:45:05
52 forum posts

Just to let you know, further info on sourcing vinyl decals. Yesterday evening i searched for a supplier and came up with Lettresadhesives.net. I’ve ordered one wing sized decal and two smaller, ‘Barnstormer 72’. With postage the whole order was 16 euros which i thought was pretty reasonable delivered to my door with no chasing about. They promise a rapid turnaround so i will report back when they arrive with my conclusions! I’m in the Haute Vienne, nearest largish town is Bellac. I have visited B2M several times and note your very good facilities and thriving membership which is good. I know your president Francois and also the Dutch chap Gerard, both of whom are very pleasant and friendly. Not sure about the runway, looks a tad short but doesn’t seem to stop any competent fliers and probably just a bit of a learning curve. Very nice situation though away from habitation with, if i remeber correctly, just an adjacent farm.

David Davis03/06/2020 09:48:09
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3764 forum posts
719 photos

Yes it's a friendly enough club. Gerard and Francois are on the committee as treasurer and vice treasurer respectively. I've been to several inter-clubs (fly-ins to non French speakers) run by the other Creuse clubs but I have to say that ours has the best catering. We were planning to hold an inter-clubs in May but that was postponed owing to the Covid 19 epidemic. If further restrictions are relaxed we may be able to hold a fly-in later in the year, so if we do please come over and introduce yourself. I will be flying the Big Guff or the Laser V Twin-powered WOT 4 XL dependent upon the weather conditions.

You think that our runway is too short? I think it's 80 metres long by 10 metres wide. What do you fly jets? That said, my landings have improved immensley since I joined B2M and it's considered a point of honour to land your model "sur la piste."

runway lourdouiex st pierre mac.jpg

As you live in the Haute Vienne do you know George Stringwell? He was British and Irish Glider Champion in the Seventies and used to write for one of the magazines. He mostly flies electric vintage and scale stuff these days. He lives near Rochechouart.

I've made a note of your vinyl supplier for future reference, **LINK** but I have to go into Gueret soon to reclaim tax paid in England so I'll pick up my vinyl at the same time.

We brazed the undercarriage together yesterday so we'll see how that holds up to the stresses of my take offs and landings. If it fails I'll buy a big soldering iron! Checking the centre of gravity a couple of days ago was carried out without the receiver battery installed so I may me able to move it back a bit by fitting the battery a bit further to the rear.

Only the painting of the wheels and undercarriage left to do now, then roll her out and run up the engine. The weather is forecast to be rather stormy here over the next few days but on Wednesday 10th June winds are predicted to fall light. I plan to maiden her then.

David Davis05/06/2020 06:16:54
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3764 forum posts
719 photos

The Big Guff saga is nearly over!

The next job will be to weigh the model split down tho three seperate components as it's far too big to fit onto my kitchen scales. After that, a final cg check and an engine run up.

I was going to maiden the model next Wednesday 10th June 2020 but I've just had a look at the weather forecast and Sunday afternoon, 7th June looks possible.

Watch this space.

David Davis05/06/2020 07:20:57
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3764 forum posts
719 photos

PS. I have just weighed the model. The fuselage with all of its equipment weighs 2441 grammes, the undercarriage and wheels 653 grammes and the wings 795 grammes giving a total of 3889 grammes or 3.889 kgs.

The Imperial equivalents are 86 ozs, 23 ozs and 28 ozs respectively giving a total weight of 137 ozs or 8.56 lbs. A little heavier than I would have liked but part of that is down to the very heavy Dubro wheels which can be replaced with lighter ones if necessary.

Given that the wing area approaches 10 square feet, the wing loading should be about 14 ozs per square foot so I'm not particularly bothered.

David Davis06/06/2020 08:34:32
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3764 forum posts
719 photos

The weather in central France has been unseasonably wet and windy over the last couple of weeks but tomorrow is forecast to be dry with light winds. I intend to maiden the Big Guff.

David Davis06/06/2020 18:35:05
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3764 forum posts
719 photos

Big Guff roll out and engine test in the back garden.

I decided to dodge the raindrops and run up the engine on the Big Guff this afternoon. All good.

Fun and games with the wheels this morning but the problem was solved with some brass sleeving. There is a one metre rule alongside the fuselage which gives you an idea of how big it is.

Maiden flight tomorrow afternoon.

big guff roll out  and engine test (2).jpg

big guff roll out  and engine test (3).jpg

big guff roll out  and engine test (4).jpg

big guff roll out  and engine test (5).jpg

big guff roll out  and engine test (1).jpg

Ron Gray06/06/2020 19:19:30
2186 forum posts
942 photos

Best of luck for tomorrow David, make sure lots of photos and vid (if possible)!

Dwain Dibley.06/06/2020 20:31:48
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1508 forum posts
1487 photos

The B.G. is looking tres bon David, as above pics and vid Matey.

Bonne Chance

D.D.

paul d06/06/2020 21:21:48
186 forum posts
22 photos

Superb David, a first class job sir, best of luck for the maiden, love the script on the elevator!

David Davis08/06/2020 07:21:59
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3764 forum posts
719 photos

On the morning of the maiden flight, Sunday 7th June 2020, I made a change to the Laser 70’s slow running settings The previous day I had started the engine in the model, on my Best Mate stand. I thought that the engine was running a bit rich at low speed so I resorted to the old trick of finding a clean piece of fuel tubing and blowing into the tube while progressively closing the slow running needle until you could only just blow in to it and hear air escaping. Then I left things alone.

I arrived at the flying field at 2pm to find myself the only pilot there. I assembled the model and took it down to the runway and pushed it up and down the tarmac. I was dressed in brand new red overalls especially for the occasion! Roger Aubard, the club’s president turned up after five minutes with his camera. He saw my exertions on the runway and pronounced, “Ah ca va aller je pense!” (I think that will do!) A few minutes later, the club’s treasurer, Gerard van der Meulin turned up, another camera enthusiast. I expressed a concern about having the centre of gravity somewhat forward of the recommended position. The receiver battery was held in place with velcro on the fuselage floor but I had added more velcro further to the rear just in case a more rearward balance point was recommended. Having agreed that it would be better to move the receiver battery backwards, I took off the wings and repositioned the battery. This had the effect of bringing the centre of gravity closer to the 40% chord position as recommended in the instructions.

I had been told that modern Laser engines like to run on a fuel containing 5% nitro. I didn’t have any but I had some 10% and I had some “straight” so I mixed the two into a large pink plastic bucket and poured the mixture back into their original containers which where then marked “5%” with a permanent marker.

So there was now nothing left to do but to fuel up with the 5%, switch on the radio, fit the glow igniter and fire up the engine. To switch on the radio on my model you have to open the door! The Good brothers had their switch mounted in the nose.

The engine started “in a quarter of a turn” as the French say. Turning a 13 x6 prop it gave plenty of power at full revs and at tick over it appeared to be running like the proverbial Swiss watch but much more slowly! By now there were several clubmates on site and one of them, Gilbert Kohler offered to carry my transmitter down to the runway while I carried the model.

I am not normally that nervous on maiden flights but I was on this occasion. I had to remind myself that I was an experienced r/c pilot, a qualified club-level instructor in two countries, an A Certificate holder in both England and France and I’m even qualified to fly at public events in France! There was no wind, the model was the straightest model I’ve ever built, so what was I worried about. I was imagining all sorts of unpleasant possibilities as I checked the controls one last time, peaked out the engine then stood aside as I advanced the throttle.


David Davis08/06/2020 07:22:51
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3764 forum posts
719 photos

The model rolled off down the runway and suddenly deviated from my intended track but it was soon airborne, flying slowly straight into wind. I reduced power and turned with the wind. The model still climbed, I added down trim. Roger Aubard was at my side snapping away. Observing the model he advised more down trim. I had already decided that this was what I was going to do and I reduced power yet further.

In the end I got the model down to a lower level so that the camera enthusiasts could take their pictures and I proceeded to fly left hand circuits with the throttle only one or two clicks above the lowest position on the transmitter with the trim back as far as it would go. I decided to land the model which I achieved by lining the model up with the runway and moving the throttle fully back. The model landed to spontaneous applause from the assembled company. With the model on the ground I hit the kill switch but the engine continued to rotate. My slow running adjustment of the morning was obviously having its effect! I stood over the model and asked Gilbert to get me a rag from the van. I tossed it into the prop to stop the engine.

I made a second flight later that afternoon which was much the same as the first but I made sure that the model could turn to the right this time! I found that I’m using 36% down elevator trim and nothing at all on the rudder. The running off course on take off I put down to a combination of my being unfamiliar with the model and of using a propeller with too much pitch. I have a 13x4. I’ll see what difference that makes. On packing up I was amazed at how clean the model was despite running on 15% oil. The engine exhausts through a Heath Robinson extension pipe made up of two different thicknesses of silicone tube and an aluminium pipe. Surprisingly it all stayed together!

So I’ve got to adjust the kill switch and make a better job of mounting the receiver battery but generally I’m impressed by the model and I’m especially impressed by the engine.

It’s not a model for aerobatics though doubtless some enthusiasts would try that, neither is it a model for breezy days but it’s forecast to be calm on Wednesday so I’m going to fly it again!

one mightily relieved pilot.jpg

Jonathan W08/06/2020 14:19:56
124 forum posts
11 photos

Great job, David!

It's amazing how these bulky vintage designs will go on the merest whiff of power. My Radio Queen climbs forever on little more than idle. Big diameter, low pitch prop is the way to go.

Control-wise, it's like steering a bus where somebody has gone around and loosened all the wheel nuts! My maiden of the Queen was swiftly aborted by a ground loop.surprise

But once aloft, it's lovely to watch these things puttering along on a calm sunny day.

paul d08/06/2020 14:25:32
186 forum posts
22 photos

Congratulations David, pleased but not surprised it went well.

David Davis08/06/2020 14:47:11
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3764 forum posts
719 photos
Posted by Jonathan W on 08/06/2020 14:19:56:

Great job, David!

It's amazing how these bulky vintage designs will go on the merest whiff of power. My Radio Queen climbs forever on little more than idle. Big diameter, low pitch prop is the way to go.

Control-wise, it's like steering a bus where somebody has gone around and loosened all the wheel nuts! My maiden of the Queen was swiftly aborted by a ground loop.surprise

But once aloft, it's lovely to watch these things puttering along on a calm sunny day.

Yes Jonathan, I once had a Radio Queen. I had an OS52 FS in mine but that was too powerful for it so I fitted a 48. Even that was a bit much for it! At that time the club chairman built one powered by an Enya 40 FS. I didn't think it would fly it but I was wrong.

I have two OS 52s and a Magnum 52 doing nothing and I'm sure that any of these would fly the Big Guff. Staying with the Laser for the moment for reasons of patriotism!

Jonathan has suggested using a 16 x 4 prop on it. I'm going to try it out on Wednesday.

David Davis08/06/2020 21:41:55
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3764 forum posts
719 photos

A few pictures of yesterday afternoon's maiden flight taken by our club's treasurer Gerard van der Meulin.

big guff maiden flight 4.jpg

big guff maiden flight 3.jpg

big guff maiden flight 1.jpg

big guff maiden flight 2.jpg

Dwain Dibley.08/06/2020 22:05:37
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1508 forum posts
1487 photos

Brilliant Mate, I thought it had all gone wrong when she veered off, but what a relief...it was all OK...Phew

Great write up David, Well Done.

D.D.

Dwain Dibley.08/06/2020 22:05:38
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1508 forum posts
1487 photos

Double post.. LOL...  I have a Great News, and as has been said it also flies on the merest phuff of throttle, a great joy to build and fly.

D.D.

 

Edited By Dwain Dibley. on 08/06/2020 22:11:53

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