Scale Soaring UK

As I recently posted on the "who's building what" thread I am about to scratch build a Pilatus B4 to 1/4 scale. Why do that when there are lots of kits about I hear you ask. The answer is "just because I can and I want to". This will be a relatively slow build as my name isn't Williams but I hope to fly the model later this year. The build started with drawing the plans (old school pencil and paper) and there should be a couple of pictures attached. Other than the plans the only part of the model which is complete is the retract mechanism which I built a couple of years ago.
The first real construction job will be to produce all the fuselage formers. These have been designed with Devcad and the printouts are currently being attached to ply sheet ready for the jigsaw.
Brian.

You can do it Brian - go go go

looking forward to this. thinking I may what to build a pilatus or salto one day??? will be following.

Thanks guys for your comments. I am sitting happily with a cup of coffee in the workshop as the snow comes down outside. My fingers are gently vibrating as I have been cutting formers this morning with my dremel jigsaw. I do so much love cutting wood!
Brian.

As it was a lousy wet, snowy day I spent the best part of it in my cosy little workshop. The results of my labours can be seen in the attached photo - all but three of the fuselage formers and all of the up-stands for my fuselage jig. The remaining three formers will be cut from the 1/4 birch ply which will be arriving from Balsa Cabin some time this week. You might notice that I have added temporary horizontal reinforcement to three of the formers to stop then bowing inwards during construction and before the planking is added.
Brian

Brian, I'm trying to send you those canopy pix and dimensions but struggling with the message system. PM an email and I can get them to you.

I said this wasn’t going to be a fast build! While I waited for my timber and other materials to arrive I set up the fuselage jig. There was lots of measuring and re-measuring and adjusting before I got it all right.
I increased the thickness of former 6 to 5/8 inch with balsa both sides of the plywood as this would be the point where the rear sheeting would join the front planking. And once the carbon fibre arrived I cut the 14mm main spar tube and the 12mm Joiner bar to lengths. Then I did the same with the 6mm incidence tube and the 4mm incidence rod. The boxes for the joiner and incidence tubes were the formed onto formers 7 and 8 with 1/8 ply and balsa reinforcement.
Finally this afternoon I was able to get all the formers mounted on the jig and the spruce longerons all glued in place to form the fuselage skeleton.
I started work on the fin, mounting the rudder post and attaching some of the internal bracing. I was feeling pretty good about the progress when I took a couple of check measurements and discovered that the rudder post was set at the incorrect angle to the fuselage. After a few minutes and several choice words the embryonic fin was deconstructed. I will start afresh later in the week.
Brian.

Sorry to hear about your fin Brian. This kind of thing happens!

Build looks good - following with interest.

Rog

Despite all the care and attention things do go wrong. I had been congratulating myself that the basic structure had gone together rather well till I noticed the lines round the middle of the cockpit area. The culprit was former 4 which was drawing the longerons inwards a little too much creating a coke bottle effect. After checking and rechecking I realised that my drawing (CAD) was a little out. I redrew and cut a replacement former, which when fitted, still wasn’t correct. I then repeated the process once again and thankfully the third former appears to be just fine and the flowing lines are restored. Anyone want to buy a couple of slightly used plywood formers?
I made up some stiff cardboard templates from the fin drawings and used them as I rebuilt the fin inner structure. This time I also remembered to punch holes in the ribs for the elevator servo cable as the servo is going to reside in the top section of the fin.
Brian.

I completed the fin basic structure and sheeted one side then began the elevator installation in the uppermost bay. I soon realised that in order to make the elevator linkage to the correct length I would require a tailplane. A couple of days saw a tailplane constructed but I soon realised that I also needed the elevator. One thing led to another and I ended up with a fully finished, covered, hinged and with a control horn, tailplane assembly. However that allowed me to set up the push rod geometry and check that the elevator surface movements were going to be sufficient. It was then a simple task to sheet the other side of the fin. You will notice that I built in an access hatch for the servo as well. This will have a little moulded cover over the servo when complete.
I was very happy to find that the finished tailplane sits at -3 degrees to the proposed wing datum line.
The next job will be to start on the fuselage sheeting and planking.
Brian.

Well done Brian.
Looks very neat so far & you’ve even started the covering

Thanks for the nice comments Peter.
I have now started on the sheeting and planking of the fuselage. It is pretty straight forward at the back because the fuselage is a straight forward ovoid cone shape with no compound curves. I have been able to cut the 1/8 balsa sheet to a long triangles, moisten the outer surface and glue and pin it into place. I have resorted to traditional planking going towards the top of the fuselage where the curve tightens. The front of the fuselage will all be planked to cope with the compound curves there.
If I keep going at this pace I will be keeping up with Chris Williams! (in your dreams Brian!!!)
Brian.

This afternoon I have got the sheeting and planking to the point where the fuselage is rigid enough to allow me to remove it from the jig. Thanks Robbie, once again your jig design has left me with a perfectly straight and nicely aligned fuselage structure. The fuselage is now sitting upside-down in a couple of foam cradles on the workbench ready for me to start on the underside planking.
Brian.

Hi Paul...
Yes it's a great tool and easy to build and use. Designed by Robbie Bridson and details are available - this is where Cliff Evans can step in with the Info.
Brian

Damn you Brian!! There is basic info here: viewtopic.php?t=2486

Just to add to Cliff's post, my original was 50 x 50 ali angle and was spaced with M8 studding. Bear in mind you will need four nuts and washers per spacer. You could use bolts but studding is probably cheaper.

All the hardware for mine (minus the jig base) came from B&Q: the angle brackets were perfect for the job...

I have made a bit more progress in the last couple of days. The fuselage is now completely sheeted and planked except for the upper surface in front of the cockpit, This is being left open at the moment to get easy access to the whole of the cockpit area. The planking on the outside of the front of the fuselage was given a rough sand followed up by a thin layer of filler all over to close up any holes and gaps that there might be between planks. The filler I use is Ronseal multi-purpose wood filler (natural) as I find that it sets fairly hard but is easy to sand and gives a good surface finish.
I then cut out panels of 390gm/m2 glass cloth using card templates and glued them into the various bays using Bucks Composites finishing epoxy resin.
I have also added the balsa leading edge to the fin and have rough sanded it to section.
Brian.

Looking very nice Brian.
Nice even planking.
Are you preparing to fit a fixed mainwheel or retract?

Peter

Thanks Peter. The wheel will be retractable as in the photo of the full size on page 1. As I said at that point I made a retract mechanism a couple of years ago from plans on this forum and have been looking for an airframe to put it in. There is a photo also on page 1.
Brian.

Brian,
Now that you you have reminded me, I remember the comment about the available retract mechanism.
I look forward to seeing it finished before too long.
Peter

Things are very busy for me at the moment despite “lockdown” so I’m only managing one post per week on average. So here’s what I’ve done in the last week.
The fin has been finished off and a rudder built, hinged and temporarily mounted. I created ply outlines for the nosecone and glued them to the fuselage. I find that I can get a much better final nose profile when I do this. The quarters were then filled with of-cuts of balsa and planed to a rough outline before final sanding to shape. I think it looks Ok!
Brian.

I stole another hour in the workshop this afternoon and have now got the retract mechanism sitting happy in its little home. It did take a little fettling of a couple of lower formers which I had made a little too neat but is now fitting in quite snugly. The fuselage is now going to be set aside for a while.
I now require a couple of wings and the wing supermarket is closed at present. What will I do? Perhaps I should build them from this pile of wood I have stacked in the corner. Watch this space!
Brian.

Slec are still open and delivering!

I have made a little more progress, this time on the wings. Once again I have made a bit of a rod for my own back. The inner section of each wing is parallel chord so I was able to make a 1/16 ply template and cut each rib individually using that. However the outer section is tapered so each rib is of course different. In the past I have used the sandwich method of producing the ribs but have never found it entirely satisfactory. This time I printed out a copy of each individual rib from Profili, tack glued it to the balsa sheet and cut out two copies. Very time consuming but I now have all my ribs exactly the correct size (in theory).
You will notice that I have cut each rib with building tabs on the upper surface. This is because I am going to build the wings upside down. The reason being that the top surface of the wing is completely flat and the thinning of the wing due to the wing tip taper happens entirely on the lower surface. Hopefully this will not provide me with too many problems during the build.
Next job? Splicing and tapering spars!
Brian.

Dear oh dear oh dear.

Brian, what is going on? Wonkey tops, bottles not standing up to attention - really poor show - must do better.

Very nice work Brian, reminds me of my Fauvette build with all that planking. I cut my planks to 3/8" width bevelled each side, yours look to be thinner which in hindsight mine should have been as yours looks a neater/tighter finish requiring less filling.

Will you be risking this on the slope with that retract?

Robbie, I will cop to the wonky tops but the upside down bottle is me getting the very last dregs of epoxy out of the bottle (I'm a thrifty Scotsman don't yo know).
Stephen, most of my planks were either 1/2 by 1/8 or 1/4 by 1/8 on the tighter sections. I also bevel the edges of each plank to get a better fit. I also soak the planks in water to get them round the trickier curves. Most of my flying is on the slope but the retract is there for the occasions that I aerotow. I also have one slope which has a (very) small, neat grass, landing area where I drop the wheel if my approach looks right.

I have made a start on the wing construction this afternoon and so far so good. Everything has fitted together quite well with no major fiddling and fettling. The carbon joiner tube fitted quite snugly and appears to be at the correct angle. I am pretty content with my afternoons work and feel I have almost achieved “Williams” pace!
I will probably leave the whole assembly to set and settle overnight before fitting the bottom main spar and starting on the webbing between the spars.
Brian.

settle overnight That's where you're going wrong

So much for building at “Williams “ light speed!
The amount of progress I have made has been frustratingly slow, mainly due to a lack of foresight on my part. However all spars are glued in place and all the webbing on the main spar as well so the wing feels quite stiff. The 3/32 balsa sheeting was applied to the underside back to the rear spar and then to the upper surface forward of the main spar and also the leading edge sheeting.
At that point I hit a problem. I had to install the electric airbrakes before I fitted the rest of the top sheeting. Did I buy the airbrakes? Can’t remember! Turn the workshop up and down and the only thing I found was my original materials list which didn't have the airbrakes crossed off. Oh Bother - Never mind – Phone Gliders and buy a set. Blast they are all on back order! However a tinterweb search got me a set from RC World.co which arrived this afternoon. Thanks guys – great service. I can now get on with the rest of the wing sheeting.
Brian.

Nice work as usual Brian. Just to give you some encouragement, here is a full size in distress. The Main spar failed during aeros after the pilot overstressed the aircraft. He bailed out safely

Thanks for that Vince, just the encouragement that I needed while building wings!

I have now added the trailing edge of the wing. The lower surface has a 1/16 ply strip ½ inch wide attached to the balsa sheeting to provide a tougher edge. It also allows me to sand the trailing edge down to a fine edge (photo one)
The upper surface is 3/32 balsa with the rear underside sanded to a fine taper. This allows me to replicate the fine undercamber of the HQ3.5/14 wing section (photo two). The upper and lower trailing edges are clamped together between two steel straight edges which should give me a good straight structure when the aliphatic glue sets.
I have added a photo of my workshop as just I have left it which should dispel some of my super tidy image. This is how things usually look while I'm working and before the daily tidy up.
Brian.

Utter carnage. You should be ashamed.

If I post a picture of mine, I think you'd probably suffer some sort of seizure Brian...

Jolly Roger wrote: ↑30 Apr 2020, 15:53 Utter carnage. You should be ashamed.

Agreed, but at least the pins in the wing are colour co-ordinated (and no doubt Brian will be on any time soon with a logical explanation for that).

No Problem Robbie!
The pink/purple pins are old and a little blunt and bent. There are not enough green pins to place one in each rib, therefor the blue pins have been used to fix the sheet to the spar. However there are not enough blue pins left to complete the job therefor the new yellow pins were used to hold down the centre of the sheeting to the ribs. Schimples!
Brian.

I knew I shouldn't have asked........................

The left hand wing is now complete but I am just waiting on a wood delivery before I start on the right hand wing. (must Remember – Right Hand, Right Hand......)
This morning I have installed the mounts for the rudder and aerotow release servos. I cut and joined two chunks of orange/pink foam for the canopy moulding. That was then temporarily fitted to the fuselage and then attacked with a large rasp. Using a selection of less and less abrasive sand papers I have now reduced the foam to something approximating the finished canopy shape.
Also bearing in mind that I have also planted my peas and sown cabbage, Brussels sprouts and kale for next winter, that’s not a bad mornings work.
Brian.

The canopy glazing tool is now ready to be sent off to Sarik to have a couple of canopies pulled. The mottled appearance is due to me making minor adjustments to the shape by judicious skims of filler followed by careful use of various grades of wet and dry paper. I spent a lot of time going over it filling tiny pin holes. Final sanding with 400/800/1200 wet and dry paper has given a nice smooth finish. I suspect that there will probably be a few minor imperfections in the final pulled canopy but as they say “at 500 ft who will ever notice”.
I have also received a very nice 3D printed instrument panel from Cliff Evans (thanks Cliff) which will adorn the finished cockpit.
Brian.

I have now started the build of the right hand wing. The completed left hand wing was built inverted on the plan of the right hand wing therefore logically the right hand wing is built inverted over the plan for the left hand wing. Straightforward right? No Left? Confusing isn’t it?
Brian.

Looking good Brian,

Thanks Terry, its nice to be back working with wood once again rather than messing about with foam, glass and filler.
Brian.

The build of the right wing continues. The joiner reinforcement, bottom main spar, the ply and balsa webbing and the balsa false leading edge have all been added. I have now added the underside, leading edge sheeting. No real dramas and I even managed to arrange the pins tastefully.
On the other bench I have the rear underside sheeting cut, scarf joined and glue drying ready to be stuck in place once the aliphatic has set on the front.
Brian.

This afternoon I tackled the bit that I dread when I am building wings – fettling the joiners. I fitted the main joiner into the completed left wing and the right wing shell before mounting them on jigs that would hold them both at the same angle of incidence. Then the right hand incidence peg tube was slipped onto the incidence dowel. Low and behold – it fitted perfectly! Well actually no it didn’t.
There then followed a good half hour of sanding, filing, paring back and cursing before I finally got everything fitting and sitting square. The incidence looks right, the angles all look right and it comes apart with only a little persuasion.
I took it outside my workshop to show my wife who was working in the garden. She saw it propped up against my workshop and was appalled by the size – so I must have got it right then!
The next job is to build all the gubbins into the right hand shell before finishing the sheeting.
Brian.

You clearly need to go to third scale then Brian to keep her satisfied

Ray

I tried that a couple of times Ray and earned myself the really grumpy treatment.
Brian.

Both wings are now fully sheeted and sanded and have the root ribs fitted. The next job will be to cover the wings and fuselage with 25gm/m2 glass cloth and epoxy resin. However before that I took the opportunity to assemble all the bits to check out the fit and see what the finished machine would look like.
I have to say that I am quite happy with it so far!
Brian.

I started on the covering of the airframe this afternoon. Everything on the airframe is being covered in glass cloth except from the tailplane and elevator which have been covered in Oracover previously. The glass cloth I am using is plain weave 25 gm/m2 cloth from East Coast Fibreglass which I have found to be very good in the past. I am using the EL2 Epoxy Laminating Resin from Easy Composites which goes on very nicely and usually sets nice and crisp within 24 hours. I always mix too much resin on the first batch and I have managed to cover half the fuselage, half the fin, half the rudder and the top side of both ailerons and still had some resin left in the pot.
Brian.

Something always goes wrong! Last night I trimmed all the parts that I had glassed then turned them over and glassed the other sides. Today I checked them out only to find I had put 2 coats of glass on the left side of the rudder and none on the right. Duhhh!
Brian.

Now I would NEVER do anything like that. says the man who falls off seats.
You could just glass the other side twice too (I have this thing about symmetry). I’m sure the rudder could use a little extra glass, with the usual slope side wear and tear. I reckon the second layer of glass adds less than 3g at the back.

I really don't need another 3gm at the tail end Rog!
Brian

Signs of old age creeping up. Don't worry as it only gets worse

In the last few days I have tackled the wing roots and fairings of the fuselage. My workshop is not large enough to have both wings attached to the fuselage and still have room to work round about it so proceedings were transferred to the dining room table (with the kind permission of Mrs S).
The airframe was assembled with the wings resting on two large boxes and the fuselage hanging between. An incidence meter was attached to wings and tailplane and this showed a decalage angle of 2.2 degrees (quick nod to Antonia) which will do quite nicely thank you. Once fuselage, wings and tailplane were all squared up the inner wing root ribs were attached to the fuselage with epoxy and thin ply forms. Once disassembled and back in the workshop the gaps between the ribs and the fuselage were blocked in with balsa then covered in “Epol” filler before lots of careful sanding. I am quite pleased with the finished result.
The next job will be to wet and dry the glass on the whole fuselage and then the wings – not a job I am looking forward to.
Brian.

Looks really smart Brian. What's your wing joiner?

Hi Rog. It's a 14mm carbon rod in 16mm carbon tube. This should be more than man enough for a 1/4 scale model, even taking into account my occasional hooligan episodes.
Brian.

B Sharp wrote: ↑10 Jun 2020, 17:36 Hi Rog. It's a 14mm carbon rod in 16mm carbon tube. This should be more than man enough for a 1/4 scale model, even taking into account my occasional hooligan episodes.
Brian.

Yeah, that should do the job! I found it impossible to break a 12mm carbon rod in a 5kg, 4m model by aerobatics alone. I needed a hillside to do the job properly.

So you should have a decent margin. In theory a 14mm rod is nearly 60% stronger than a 12mm rod, as section modulus goes up with the cube of diameter.

Rog, section modulus is a term I haven't heard or used since my early 20s and at college.
Brian.

I’ve been focusing on some of the fiddly bits today. I started with the canopy frame as I am expecting to get my newly pulled canopy mouldings back from Barry at Sarik in the next few days. It’s constructed from 3.5mm ply, held in place at the front with a 6mm dowel and at the rear with 4 x 10mm button magnets. The instrument binnacle has been shaped with balsa block and has then had 0.7mm plasticard wrapped round the shape to give a good flat surface and a slight overhang to the instrument panel.
I have started on the undercarriage doors by bending a piece of 1.0mm aluminium sheet round a form to achieve the curve of the bottom of the fuselage. I have created lips inside the fuselage front and rear of the opening so that the ali sheet sits flush with the fuselage surface. Once I have formed the hinge seats inside the fuselage I will cut the ali sheet in half to create the two doors.
Brian.

Very nice Brian

Its been a couple of weeks since I was able to show any progress on the B4. In the background I have wet & dry sanded the fuselage and the wings following the glass cloth and epoxy session.
I have also fitted the canopy glazing to the frame and painted it up. It is just as well that I ordered 2 canopy mouldings as I made a right pigs ear of fitting the first attempt! The trimming and fitting process went ok and it all looked good. However I used “canopy glue” to attach the glazing to the frame before taping it down securely – I THOUGHT! When I undid all the tape it was a right mess. Bits of the glazing were coming away from the frame, some sections had pulled squint and I ended up ripping it all off. I decided to use good old Evostik contact glue for the next attempt and it worked just fine.
I have a bit of cockpit detail still to do but I can see “PAINTING” approaching quite soon and I’m not looking forward to that.
By the way the more observant of you may have noticed that I have installed a new worktop to my workbench. I had to use Plywood as I couldn’t get hold of 18mm chipboard anywhere. Is chipboard the new toilet paper?
Brian.

Is chipboard the new toilet paper?

I really hope not..............



BC

Life is rough Barry!
Brian.

I see that my last post was at the end of June so I am due an update. Plenty has happened with the build since then but not a lot of progress. I shall explain!
The wings and fuselage were covered with glass cloth and epoxy and all sanded back with 120 and 240 wet and dry. I was very happy with the finish as it was nice and smooth with very few blemishes. I applied a coat of white primer to everything and that’s when things started going wrong. The primer showed that although the surfaces felt smooth in fact the cloth weave was showing through. In addition there were masses of pin holes in the finish. Stupidly I applied a second coat of white primer and that didn’t improve matters one small bit. At this point I suspect that if Chris Williams is reading this he will be shaking his head and having a chuckle.
I bit the bullet, got out more 240 wet and dry and started rubbing down once again. When all the primer was gone I re-coated the whole airframe with another thin coat of epoxy followed by more rubbing back. This time when I resprayed the airframe with white primer there was no weave showing at all but there was still a lot of pin holes – out with the filler! There then followed several days of fill followed by sand back and gradually the number of pinholes was reduced. Finally I applied a further coat of primer followed by three coats of white gloss. By this time my right bicep was bulging and my shoulder aching.
In the last week or so I have got the ailerons fitted and servos installed. The elevator servo installed and a small moulded hatch created to cover the hole in the fin. It had to have a moulded bulge to clear the servo arm. The rudder was added and the servo installed in the fuselage. I have also created in interior for the cockpit including a natty little seat. This afternoon I have inserted the sockets for the wing retaining system and also the hinges for the undercarriage doors.
All photos below!
Brian.

Very clever fish in your part off the world Brian

(chuckle, chuckle)

My Pilatus B4 build is now complete!!!
I have been working away quite steadily for the last few days on the installation of the undercarriage, the aerotow release and radio gear.
This morning I was able to assemble the model and check that everything waggles correctly and in the correct direction. The CG positions were recalculated and the model mounted on the balancer. I say positions (plural) as I always start with a “safe” slightly forward CG position for the first flights and then gradually move the CG rearwards until I get the aeroplane handling the way I want. I calculated the forward CG position using a static margin of 15% and a rearward CG position using a static margin of 10%. This placed the two CG locations 12mm apart on the wing root. A total of 473gm in the nose was required to achieve the forward CG position. However 130gm of lead can be removed incrementally to move the CG back to suit my flying taste. The total weight of the model came out at 5.20 kg – 11 lbs 6oz in old money.
I am rather pleased with the finished model and now only require a suitable day for the maiden flight.
Brian.

Looks great Brian except, for the 4th pic!

Looks very nice Brian - the model that is

Looks superb Brian, Should fly well. Thanks for a brilliant build thread, very informative and entertaining.

Looks brilliant Brian, look forward to seeing it in person, got to bring it to Buckminster

Thanks for the nice comments boys and girl, they are much appreciated. As I said before this is one model which has been dragged, kicking and screaming into the world - it's been a difficult build at times. There is still the buttock clenching maiden flight to deal with.
Hopefully, all being well, the B4 may make it's first public appearance at Buckminster (see you there Antonia, but no cuddles this time!). As to the last photo, that is only a cardboard cut-out - I am much prettier in real life! Honest!
Brian.

Well goodness gracious me, IT FLIES!
This afternoon the weather was perfect for the maiden flights of the Pilatus B4. The wind was a steady 18mph gusting 22mph, directly onto my local west facing slope, and as a bonus the sun was shining.
Despite my worries the first flight was a total non-event; I have seldom had an easier first flight. The elevator required four clicks of down trim (to compensate for the four clicks of up trim I had added “just in case”), the other trims needed no adjustment at all. After ten minutes I landed and increased the aileron differential to 60%, reduced the throw on the elevators as well as the volume of brake/elevator mixing. I also took a 36gm chunk of lead out of the nose.
On the second flight the model was flying as if on rails and responding well to patches of thermal lift. The stall was straight as a die with no tip stall what so ever. Turns could be made wide or pulled as tight as I liked. Landings were easy and I was able to park the model exactly where I wanted.
On the third flight my hooligan instincts took control and I can report that the B4 is very capable of all the usual manoeuvres and I was pleased to see that the model carries loads of momentum.
I am now looking forward to my next visit to the slope with my Pilatus!
Brian.

Good job, Brian...!

Well done Brian.
I’m glad all went well

Top job Brian.

Wel done Brian, it looks gorgeous
It must have been national Pilatus B4 day, Mel's B4 got an outing the same day, first time in three years

Fantastic - congratulations!

Fantastic job Brian, up to your usual high standard.

Love the colour scheme and the upholstery, but where's the pilot?

Thanks very much for that generous round of applause, it is very much appreciated. It doesn't have a pilot as yet as I am a rubbish sculptor and too mean to buy one of the expensive dolls that are available. (I can buy the materials for a new model for the price of a good pilot figure!).
I am considering making a profile figure of me to stick in the seat so that the cockpit looks filled whilst in the air.
Brian.

Brian, your a star, I can always rely on you to come up with the goods

Brian take a look at this for proportions for a pilot.
http://design.data.free.fr/RUCHE/docume ... REYFUS.pdf
Then you only have to carve or mould a head from an existing figure in another model.

Its a link I put into one of the scale newsletters I do for the STC - had many positive comments from people who don't want/won't pay stupid prices for pilot figures.

John M