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The Big Guff.

My Winter Build.

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David Davis26/07/2019 10:09:14
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3757 forum posts
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It was a Brown Junior originally but I believe that the Good brothers used other engines in the model post war.

Don Fry26/07/2019 10:18:08
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54 photos

Paul has recent knowledge. I would also think of using what you have already got.

Just remember, if you go the dope route, it needs fuel proofing. A straight tex finish does not. Decisions, decisions.

David Davis26/07/2019 20:57:43
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3757 forum posts
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Posted by paul d on 26/07/2019 09:08:46:

I've been using "eze dope" just lately, water based so no smell etc.

Just out of interest what engine did the original use? I'm guessing Brown junior?

How does it work with a water-based dope paul?

With cellulose dope I'm told that you brush on 2-3 coats onto the fuselage, then you apply the tissue damp and work thinned dope or even just thinners through the tissue. This melts the dope on the fuselage and the tissue sticks to the balsa.

David Davis23/09/2019 15:35:15
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3757 forum posts
718 photos

I have just finished building the fuselage. As I type this some filler is setting. Weight of the bare fuselage is 919 grammes or 2lbs 3 ozs. I am building the Big Guff's fuselage pretty well as Walt Good built his: 1/4" sq (6mm) frame, balsa block from the nose to the firewall, 1/16" (1.5-2mm) sheet from the firewall to the trailing edge, grain vertical and 1/32" (0.8mm) balsa sheet over everything, grain running horizontally. I only differ from Walt's method of construction by using the 1/32" sheeting with the grain running across the fuselage top and bottom, rather than in line with it.

The pictures show the fully sheeted port side and the starboard side awaiting it's sheeting.

port side of the fuselage.jpg

starboard side of the fuselage yet to be sheeted.jpg

It's the first time I've used 1/32" balsa in sixty years. It splits more easily of course than thicker wood but generally I've been getting on well with it. I glued it across the fuselage on the underside using aliphatic glue. Sometimes the water in the glue caused the fibres in the wood to swell so the underside has a slightly rippled appearence. I'm hoping that it will sand out. Sometimes the sheeting lifted in one or two places but I wasable to stick it down again using cyano. I had no trouble with the 1/32" sheet on the fuselage side or on the top of the fuselage but having found a tube of Evostick impact adhesive in my glue box, I tried that! It was remarkably successful and I may use it on the forward part of the starboard fuselage. The structure is very strong and rigid already. Incidentally, a note to French residents, I am finding the aliphatic glue sold by Top Model to be very good.

Apologies for the untidy workshop.

Dad_flyer23/09/2019 20:48:37
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315 photos

Re: covering for sheet balsa in the earlier posts. I started with water based dope last year. It was OK, but felt very like a one-shot process. The dope is water based, so doping and wet shrinking the tissue are a single thing. Then when the dope cures it is set (on your brush as well). I tried 'real' dope on tissue this summer. It is a very different process, and it is particularly nice that the dope softens with thinners, so you can re-activate it (and get brushes ready to use again). It also dries really quickly, so you can see what you are doing, and get on with the job. I have not yet tried shrinking over an open structure with it.

Specifically for the question of strength of covering sheet balsa, I did tissue and real dope on a 36" model, over mainly 1/16 and 3/32 balsa sheeting. A much smaller model than yours, but the surface that I got is really nice and feels as though it has a lot of strength and ding resistance.

The downside is somewhere to do it that is well ventilated (outside...), dry, not windy, not dusty, not too sunny.

David Davis30/09/2019 13:00:51
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3757 forum posts
718 photos

I have finished the basic fuselage construction of the Big Guff. The engine is simply placed on the bearers just to see what it would look like. It is not bolted in place. I should be able to move it backwards a little. Sorry about the untidy workshop, typical of a creative personality I'm told! I have built the door for the starboard side but cannot find it in the mess! 😛

completed fuselage port.jpg

completed fuselage starboard.jpg

What I did manage to find was several sheets of red tissue. I don't know where I got them from but I was tempted to cover the fuselage in tissue. That would mean ordering dope. Nitrate, butyl, water-based? Do I give it a coat of sanding sealer first? Covering the lot in Solartex would be much easier!

David Davis01/10/2019 08:18:46
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3757 forum posts
718 photos

The balsa sheeting on the fuselage is not quite as smooth as the photograph suggests, there are one or two ripples in it so I think I'm going to cover the fuselage in the dark green Solartex. It's matt appearence would do a better job of hiding the ripples! Besides I've just seen my bank balance and I recieved my Taxe Fonciere bill yesterday so the cost of buying sanding sealer, cellulose thinner, brushes and dope is now out of the question! Moreover, I haven't used tissue for sixty years so I could make a horlicks of applying it and as the Big Guff is such an important project to me, I think I'll stick with the Solartex. I'm thinking of building a Guidato at some stage. I'll reserve the red tissue for that. **LINK** I may even use it over mylar!

P.S. Found the door. It was inside the fuselage all the time!

David Davis27/11/2019 13:01:43
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3757 forum posts
718 photos

We all do this don't we?

Amongst the chaos of my workshop the construction of the Big Guff makes progress.

fuselage and tailplane.jpg

David Davis21/12/2019 12:59:43
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3757 forum posts
718 photos

Basic construction of tail surfaces now complete. Packing tape is just holding the elevator in place for the picture. I will either top-hinge the elevator using Solartex or I will use Magic Hinge. No further progress will take place until the New Year as I'm going back to Blighty for Christmas and the New Year.

tail surfaces complete (1).jpg

tail surfaces complete (2).jpg

David Davis11/01/2020 09:02:37
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3757 forum posts
718 photos

The construction of the Big Guff continues. I have covered the tail surfaces in Red and Antique Solartex. I intend to cover the fuselage too and to move both of them into the guest bedroom while I attend to smaller models requiring servicing or repair before the flying season starts in earnest. The tailplane is over a yard wide (94cms) and could have been easily damaged in storage in its uncovered state. Building the tailplane with its "eggbox" system of construction has been good practice for the wings which are built in a similar way. The assembly weighs 8.5 oza or 241 grammes. I have not yet glued the hinges in place nor the fin to the tailplane.

Picture below. I don't know why it is on its side but it's not the only one. Mods can we do something about this?

tail surfaces covered.jpg

francois and his prize.jpg

David Davis02/02/2020 10:22:32
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3757 forum posts
718 photos

I have started the construction of the Big Guff's wing.

As I may have stated before I am following the original "egg box" method of construction using the materials supplied in the kit. The plan shows that the first three ribs, from the centre rib outwards, are spaced at 3", 2.5" and 2" from the centre rib ( about 7.6 cms, 6.5 cms and 5 cms respectively.) Then there are eleven ribs spaced at 3" centres.

wing construction (1).jpg

wing construction (2).jpg

I carefully marked the spars and cut slots in the relevant positions to take the ribs. Whilst the first few ribs line up fairly accurately, the further out towards the tip you go, the marked postions on the plan become less and less accurate. I have consequently ignored the plan and worked to my own markings. I suppose that the plan has stretched or become distorted with repeated photocopying.

wing construction (3).jpg

wing construction (4).jpg

wing construction (5).jpg

wing construction (6).jpg

wing construction (9).jpg
Each rib is marked at the position of the spar and you have to cut out a slot in each rib half the height of the rib at the spar position. In a couple of cases I made the spar slot too tight and broke the rib when fitting it. Lesson learned for the port wing. I note that the trailing edge is simply a piece of 1/4" x 1" strip not TE as I expected but this is not a problem. The spars are resting on 1/8" (3mm) scrap because of the undercambered wing section.

David Davis27/02/2020 06:34:45
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3757 forum posts
718 photos
 
Construction of the Big Guff continues. I have built the starboard wing but I am waiting for one of my trainee pilots, a qualified engineer, to make up the four little metal brackets which connect the two wing halves together before sheeting the leading edge, centre section and wing tips. I found the wing tips particularly problematic and a considerable amount of cutting, shaping, filing and general fettling was required to get the wing into its current state. Further planing and sanding is required. The plan was not much help because it had become distorted with repeated photocopying. We are holding a static display of models in a local community centre over the weekend of 6th-7th March. I plan to display the Big Guff in its half-built state.
 
starboard wing.jpg
David Davis19/03/2020 14:16:01
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3757 forum posts
718 photos

Still a long way to go but we all do this don't we? wink Metre rule in the first picture gives you an idea of the size of the model.

still a long way to go but we all do this dont we (1).jpg

still a long way to go but we all do this dont we (2).jpg

David Davis02/04/2020 08:51:26
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3757 forum posts
718 photos

It's been exactly a year since I started this build. This is as far as I've got...

awaiting wing sheeting.jpg

...and I've found out that you can fold the wings which will make storing and transporting a model of this size easier.

they fold.jpg

I am awaiting the delivery of some nuts and bolts before I start sheeting the wings.

David Davis03/04/2020 09:23:53
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3757 forum posts
718 photos

Well I found enough little nuts and bolts for one wing and managed to get the top wing sheeting onto the starboard wing yesterday. It's amazing how even 1/32" balsa sheet makes the wing so much more rigid. There's identical sheeting to go onto the underside of the wing too.

have i used enough pins (1).jpg

have i used enough pins 2.jpg


Do you think I've used enough pins?

David Davis12/04/2020 12:39:48
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3757 forum posts
718 photos

Once I have finished fitting the 1/32" sheet to the port wing, it will be time to think about covering the underside of the wings.

The Big Guff has an undercambered wing section and I haven't covered an undercambered wing since I built my Junior 60 in 1988! However, thinking about it, I must have covered a Junior 60 wing at least three times because originally it was covered in Neutral Solartex, a sort of translucent white and now it's orange. I built another one for electric power. It's the red and yellow pictured below alongside my first one in its orange scheme. I regret that I do not have a picture of the Junior 60 in its original olive drab and Neutral colour scheme. Probably just as well! wink

I cannot recall having a problem getting the Solartex to stick to the undercamber of a Junior 60 but others have suggested coating the ribs and spars in Covergrip or thinned PVA white glue first. Another suggestion has involved using cyano to glue the Solartex in place when the underside has been covered. What do you think?

The views of the cognoscenti are, as always, keenly sought.

j60 in winter.jpg

junior 60 2.jpg

Outrunner12/04/2020 13:22:24
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83 forum posts
27 photos

David. I recently recovered my Junior 60 using tissue over doculam. I used balsalock around the edge of the ribs and spars, it stuck as good as the original Solartex but much lighter. We went into lockdown before I managed a test flight.

Enjoying your Big Guff build, should be ready for when we can fly again.

Stay safe.

Phil.

David Davis13/04/2020 07:51:53
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3757 forum posts
718 photos

Hi Phil

I'm out of Balsalock and Solarfilm Sales are not trading until the Covid 19 restrictions are lifted. I'll send off for some Covergrip. It won't do any harm.

Stay Safe.

David

David Davis14/04/2020 13:38:07
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3757 forum posts
718 photos

Gentlemen,

The Big Guff Build.

After 54 weeks since I started to build it, the last piece of wood has been glued into place! Time for a celebration!

Stay safe

last piece of wood has been glued into place.jpg

David Davis03/05/2020 11:06:34
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3757 forum posts
718 photos
I've been a bit distracted by other projects so work on the Big Guff had stopped until the day before yesterday when I began to glue the elevator hinges into place. That's when I noticed that one end of the elevator was at least 3mm (1/8" higher than the other and nothing I could do with heat would make it flat. In the end, heating the covering caused the leading edge of the elevator to deform. There was nothing for it but to remove the covering, cut away the leading edge of the elevator and replace it with one made from slightly thicker and harder balsa. Once the glue had dried I removed it from the building board. It was still not flat!

I hit upon the idea of adding 3mm square diagonal braces between each of the ribs. I have a SLEC balsa stripper but didn't bother to get it out for this little job, just cutting 3mm strips from scrap balsa supplied with the kit using the TLAR principle. Having cyanoed them into place I found that I had fitted them incorrectly. The diagonals on the outer bays for example were sloping in the same direction not in opposing directions! Oh how I laughed! A major Homer Simpson moment! blush

I removed the offending article from the building board and it still reminded me of a Texas Longhorn but all was not lost. I pinned the offending article to the board using lots of my new plastic headed pins and added cross bracing to those braces which were already installed.

It's flat now.
 

Edited By David Davis on 03/05/2020 11:08:37

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