CDScaleDesigns Sopwith Pup

[Simon Chaddock]

BEB

What an interesting aileron mechanism!

I would agree that in principle connecting two servos to the same control surface is not ideal but one has to assume that CDScaleDesigns would not have used it if it did not work.

 

In theory the thin rods between the ailerons could actually be replaced by cables.

 

I suspect the turn buckles on the top wing linking cable will need careful adjustment to ensure both servos centre easily, in fact you may find it works best with the cable almost slack at the neutral position so one servo cannot pull at the other.  

[Biggles' Elder Brother - Moderator]

Thanks for that advice Simon. It certainly does look interesting as a mechanism. I have been in touch with Chris Davies, the designer, to seek his thoughts on this. He tells me that its based on a mechanism he saw in a model in Radio Modeller a number of years ago. He put it in because he had had some issues with "dropping" upper wing ailerons on an earlier designed Camel. He definitely views it as an "option" and not essential. So I shall give the matter some thought. As you say Simon putting it in would mean I could have very scale like cables rather than tie-bars (however fine) between the upper and lower ailerons. We'll see.

 

OK upper wings are now finished - at least as far as the basic woodwork is concerned, but they still require leading/trailing edges shaped etc. and this "semi-closed loop" system installed if I want to use it.

 

Here's the centre section with the wing support wires in place...

 

And here is the assembled upper wing...

 

I have a choice now - I could move on to the tailplane and fin/rudder etc. or build the cabane strut assembly. No contest - cabane struts! I'm dying to see the fuselage with both wings attached!

 

BEB

 

PS By the way Chris tells me CDScaleDesigns are back upto date with deliveries and so the website is back up ready for orders. If you would like to drool over some very tasty scale models take a look here

[Biggles' Elder Brother - Moderator]

Back again. Been doing lots of flying over the weekend enjoying the rare sunshine! (and a bit of rain!). So, today I'm "picking up the reins" as it were.

 

The next job is the cabane struts - because with them we can mount the new upper wings and centre section just finished. But aligning the struts is always a trial with a biplane - but Chris Davies has a neat solution, he provides a jig to assist in fitting the bracing wires to the cabanes. Cool! So, first step - assemble the jig. Its obviously important that this goes together as square as possible...

 

The jig is made from 4mm lite-ply and is laser cut like the rest of the kit and so it fits together excellently. Once the two cross pieces have been installed we can add the fourth side...

 

Cut outs in the gig allow the fitting of hardwood strips which will been in the correct locations as on the fuselage itself...

 

So this is the jig complete and the cabane strut wires can naow be formed according to the plan and then fitted to the jig ready for soldering up the bracing wires....

 

Soldering starts tomorrow!

 

The other thing I've been doing is pouring over the plans and trying to decide what engine to use. I've drawn up a list of requirements

 

1 4 Stroke

2. Approx 0.8-1.0HP output

3. Preferably entirely contained within the cowl

4. Able to spin a 13-14" prop (14" would be exactly scale size - but I'll settle for 13"!)

5. Preferably able to provide space for the Williams Bros Le Rhone model engine.

 

Weight is not really a problem - the original had an OS FS60 apparently - not the most powerful of engines and no light weight! Given the usual problems with short nosed, rotary engined, bipes being tail heavy and bit more weight on the engine side will not hurt!

 

Currently I'm considering a RCV CD58. This meets most of the requirements. But I'm having an issue with the location of its mounting lugs and how I'm going to bring the prop shaft onto centre-line. So, its back to the plans and pencil and paper to see if I can work out a solution...

 

BEB

[Biggles' Elder Brother - Moderator]

Work continues on the cabane struts. One of the excellent things in this kit is a fret of etched brass fittings to help with the rigging...

 

As can be seen these are excellent quality and make the task of anchoring all the various wires very much easier. I understand that CDScaleDesigns will sell this fret separately from their kits. If your building a biplane it has to be worth considering.

 

The first step in building the cabane strut framework is to solder the appropriate brackets from the fret onto the wires. Once this is done we clamp the wires in the jig, being careful to check that they are central and the right way round - the front and back are at a slightly different angle -

 

we then commence fitting the cross bracing wires. One end is hooked onto the bracket taken from the fret and previously soldered...

 

whilst the other is bent to line up with the piano wire strut, bound with wire and then soldered. The picture below shows the current status with the job about halfway.

 

The big arrow on the side of the jig is to remind me which is the front - I actually soldered one wire up the wrong way round before I added this aid

 

I am continuing to consider the engine question. The only engine that satisfies all the requirements is the RCV - but...there is something rather odd about this engine. Careful examination of the dimensioned drawing and the on-line manual reveals that the mounting lug lower faces (ie the ones that contact the bearers - are 3mm below the prop shaft centre line. Because the bearers in the model are much wider spaced than any engine mounting lugs I will have to fit a plate. But, and here's the rub, the bearers in th model are 4mm above the desired propshaft centre line. As the engine will be fitted inverted that leaves just 1mm between the lower faces of the engine lugs and the bearers - clearly not enough for a sufficiently thick plate. I could try an make a steped plate - but its very messy and even then it would only leave 1mm of material over the bearers - I wouldn't be happy with that.

 

The other candidate engines are;

 

The OS56FS-a good looking engine, OS are an excellent make. Meets all the requirements except it would stick out of the cowl at the bottom by about 2mm - which is acceptable. One nice feature is the new system OS have whereby oil is extracted from the crankcase, up the push rods, into the cylinder head, through the inlet valve and burnt! Thus less oil in the cowl! It weighs in at 461g and typically costs £215.

 

The Saito 56 a well established engine. Slightly less powerful than the OS (0.9HP versus 1HP - but to be honest you have to be careful with this as neither manufacturer specify fuel/prop etc when the power was measured). Its taller than the OS and would stick further out of the bottom of the cowl - about 5.5mm, still not too bad. Its quite light, weighing just 414g, and costs typically £190.

 

Laser don't do a 56 but their 70 is quite small for its capacity. Laser engines have a excellent reputation (having powered many top scale models in competition). Its height means it would stick out of the cowl by just 2.5mm - so that's comparable with the OS. One advantage of this engine is its weight - at 560g it by far the heavest and is very close to the 550g weight of the OS60FS which powered the prototype model. As I said yesterday extra weight in the nose is a benefit to a rotary engined bipe! Cost for the Laser is currently £200.

 

There are numerous other possibilities; the ENYA 53 4C TN, the SC 52 FS MkII, the Thunder Tiger 54S, the Magnum XL 52RFS and the ASP 52FS being the ones I have considered. But all these have at least one, and in many cases more than one, unacceptable failure in my criteria list.

 

So, it seems to come down to the OS or the Laser, or maybe the Saito if I want to save a couple of quid and add more lead to the nose! Anyone got any thoughts? 

[Biggles' Elder Brother - Moderator]

Took a half day off work - so decided to spend it working on the Pup. The weather here is perfect for flying - but our club has electric only on Thursdays so I'm grounded  Still I think my time has been well spent - as I hope you will agree!

 

Started off by finishing the cabane cross bracing. All the main joints are wound in 15amp fuse wire and then soldered...

 

Here it is finished and looking rather good, though I say so myself. I know a lot of modellers don't like soldering - even ones that fly electric and may be happy making up some cables still baulk at "structural" soldering. Having spent a number of years making 'O' gauge model railways and building locos out of brass kits soldering now comes fairly natural. The 'secret' of a good solder joint is getting everything really clean, having plenty of heat and really good flux. I use a fibreglass scratch pencil to clean up the surfaces before hand, then I try hard not to touch them again. These joints were made with a 50W Antex thermostatically controlled iron set to very close to its max temperature of 450C, and finally I use a liquid flux containing 9% phosphoric acid - and plenty of it. Using this kit, with most joints, the solder just "flashes" over the joint in an instant.

 

Having made up the cabane cross braces I had the interesting experience that I couldn't get them off the jig! Effectively they had been built around the jig so couldn't come off. Its like when you build a piece of furniture inside a room - then discover it wont go through the door! So the jig had to be cut sadly in order to release the assembly. Because of the aggressive flux I use it then all had to be rinsed under running water or the acid will eventually corrode the steel wire!

 

Once it was dried the next step is to fit it to the upper wing centre section...

 

The fixing brackets come off the brass fret again. At this stage the screws aren't fully home as I will want to remove this again at some stage. I may decide to eventually expoxy it in place as well as the screw fittings.

 

Well, there's only one possible thing you can do now isn't there? Where's that fuselage?

 

Wow! Its not all screwed together - its just a trial fit - but doesn't she look beautiful

 

All work stopped for the day - serious drooling and daydreaming session coming on....Ah those barmy summers evenings. A graceful Sopwith Pup pottering around in the twilight sky. The only sound being the soft purr of a 4-stoke...

 

Ah, yes, 4-stroke, that reminds me. I'm still no nearer to a decision on the power plant...must decide soon I need it to finish the front end. As I say, views on the engine choice are welcome - see previous post for details!

 

BEB

[Ed Darter]

Hi BEB,

I can recommend the RCV if you can find a way of fitting it. I have one in my SE5a and its lovely. Too much power form my model tbh, but sounds lovely bimbling along at low revs and has a more poppy / throaty sounds than some other 4 strokes. Also - it seems to run cooler than some other engines as well. I'm basing this only on the fact that a clubmate did an SE5a about the same time as me and fitted an OS 40FS and suffered quite a bit of engine overheating in his. I did follow a slightly differnt route to him for ducting etc and it could be down to this but I do like the fact that the engine is physically smaller, requires less maintenance etc etc than equivalent 'conventional' 4 strokes.

 

Just a thought - can you not mount it on the upper side of the mounting lugs ? would that give you the headroom for the plate ?

It is odd that they have designed them that way though - I think its the single biggest drawback of using them tbh.

Ed

[Biggles' Elder Brother - Moderator]

Well, much pouring over plans and sliding about paper cut-outs of engines has been going on. But at last the decision has been made. Following great thought you'll be pleased to know Ed...I'm going with the RCV!

 

Thanks for the push Ed it definitely helped. I am going to have to fit a ply plate across the top of the engine bearers, add two "inner bearers" to the underface of the ply, face those inner bearers with some grp plate and with the RCV's 3mm offset between the mounting lugs and the prop shaft I should be there! Simple really - oh yeah, just what I need. But at least its do-able and will give me an engine that fits entirely within the cowl.

 

So, onward we go. Next task fit the engine bearers...

 

Next we need the plate. I was looking for some 4mm lite-ply (4mm will be thick enough because of the combined bracing effect of the actual and inner bearers) when my eyes fell on the jig used to assemble the cabane struts. Sure enough its made from 4mm lite-ply! So I carefully "unglued" it...

 

Then I had a real "bonus" - it turns out that the end pieces from the jig (the two on the right in the picture) are exactly the width of the distance over the outside of the bearers - to within a millimetre

 

So, triming the lugs off one of the end pieces gives us just what we want.

 

Could have been made for it!!! Tomorrow we will start shaping this to take its place over the bearers.

 

BEB

[Ed Darter]

ah - what was it that sold it to you in the end then ?

TBH - on the SE5a I changed the design in a similar way. Its the Flair one and I had a bearer come up either fus side that a ply plate is then glued to. This plate is U shaped with a cutout for the engine. Works a treat ! Because i was using 5mm ply I removed a layer of ply where the engines lugs sit to bring it down a bit. wasn't the whole way but as I was making my own front end for it anyway it was easy enough to engineer it to all look right - I figured that 1-2mm out on the height of the engine thrust line would not be that critical on a slow Bipe such as this.

[Biggles' Elder Brother - Moderator]

Hi Ed, in the end the shear pleasure of having the engine entirely within the cowl was irresistable! That and what everyone (except one person) tells me about the sound they made - which they seemed most impressed with. The one exception was one friend who described the sound as "like a bag of hammers"! Well, we'll see!

 

So, on with the implementation of this masterplan. First we cut the ply sheet to shape - the idea is get something which is a push fit onto the bearers...

 

Here is the plate with the mounting holes marked so as to ensure the prop driver plate will be the correct distance from the cowl front. Next we try the plate in place...

 

This view is taken from below with the fuselage upside down. To me this looked just a bit too flimsy so I decided to add an extra bearer across the back. This will enable me to put a couple of extra fixing screws in and offer a bit more gluing area - thus making the whole plate more rigid...

 

And with the plate pushed in again...

 

Finally here's the engine in place...

 

And from the front, with the picture inverted so as to show what it will look like "right way up"!

 

Now measuring carefully, the propshaft will come out about 1mm high of dead centre. But as

 

1. I am convinced this won't be detectable with the naked eye

 

2. As Ed says its not likely to make much difference to the handling of the plane (its hardly a precission aerobatics pattern-ship!)

 

I'll live with this!

 

Next I have to fix in the plate, add the stiffening lower (inner) bearers, trim the fire wall a bit (I'll explain why in a future installment!) and drill the engine mounting holes and we're done!

 

BEB

 

 

[Biggles' Elder Brother - Moderator]

Hi,

 

progress is slow at the moment, fitting the engine has prooved to be a pig of a job. Having solved the probelm of the 3mm vertical offset of the mounting lugs I hit a second problem - the mounting holes on the RCV are much further apart (along the axis of the engine) than on a conventional engine. This meant that when the drive plate of the engine was placed in the correct position the rear bolts fell smack in-line with the firewall! This means I will have to "nibble" away at the firewall to get the bolts in and enough room to fit the nuts. This nibbling could compromise the security of the engine mounts (its very close to the fitting points) so the plate mounting will have to be "beefed up" to reinstate the strength of the front end.

 

First of all lets look at the plate...

 

As can be seen, as well as the four engine mounting holes, we now have six countersunk holes for screws which will locate and fix the plate in the plane. Ultimately the plate will be both screwed in and epoxied to the bearers. With the 10x5mm spruce stiifeners fitted to the plate epoxied to the bearers, the plate itself expoxied to the bearers, the extra bearer in the back and the whole thing screwed in - I think it should be strong enough

 

Above is the firewall in "mid-nibble". The lower surfaces have been partially cut back (later this cut was widened to provide "finger room" to get the nuts onto the mounting bolts) the firewall above the mounts is about to be "nibbled" where marked out.

 

The picture above shows the plate installed. The plate has been made to be a nice tight sliding fit in the front. It is not glued yet - I need to be sure I can the engine in and out without removing the plate before I fit it perminantly. You can see how the rear mount holes clash with the fire wall in this photo.

 

Now to put the engine in. Front bolts - no problem. Rear bolts...Grrrrrr! An hour later and much fiddling I finally managed to get them fitted in!

 

View with the fuselage upside down...

 

And finally the view with the fuselage the right way up...

 

This shows the spruce plate stiffeners and their role alongside the main bearers. It also shows the expanded cut of the firewall necessary so that I could get my sausage like fingers in to mount the bolts!

 

This installation will eventually have to be taken apart, the plate epoxied and lock nuts fitted - but not just yet - my patience wouldn't stand it!!!

 

BEB

Edited By Biggles' Elder Brother on 20/03/2010 21:00:39

[Biggles' Elder Brother - Moderator]

No chance to do very much today - sadly. But I decided I wanted to see what she would look like with the cowl and prop in place.

 

The cowl is a fairly thin polycarb type moulding - but with excellent surface detail.

 

So lets remove the centre. First drill a series of small holes around the centre disc to be removed....

 

and then with a small cylindrical grinding stone fitted in the mini-drill we just "join the dots"....

 

Using the same grinding stone the edge can be smoothed off and taken back to the appropriate line - have to be very careful doing this as the stone cuts through the plastic like a hot knife through butter. I tend to use an Opti-vision magnification headset - the eyesight isn't what it used to be! Here's the finished item....

 

Well in reality its no where near finished as a number of cut outs (as per prototype) are still needed and somehow it has to become "metallic" - but it finished as far as this central cut out is concerned at least!

 

Now we can try it on the model. At the moment I haven't fitted the cowl locating ring so its just "resting" on the fuselage and is a little bit further back than it will be eventually - but you get the idea...

 

(One of my fuzzy photo again I'm afraid  - I really don't know why that happens!) Anyway, as you can just about see that the engine fits without any cowl cutting on its behalf. But you can also see the gapping big hole that the lack of an dummy engine leaves us with - hence why I am so keen to get the Williams Bros Le Rhone model in there if at all possible - and its looking distinctly possible with this RCV engine  If so it will have been worth all the trouble it has caused in fitting it. That prop is a 12x6 which I will use to run-in the engine on the bench. Once run-in if possible I'll switch to a 13x5 which is nearer scale size.

 

BEB 

[Terry Whiting 1]

BEB,

 

Check out     www.parkflyerplastics.com   they just might have a substitute for the Rhone.

 

Terry 

[Biggles' Elder Brother - Moderator]

Hi Terry,

 

thanks for that link it looks really interesting and may well provide me with an alternative if the Williams Bros engine is proving hard to fit. I was particularly impressed with the sort of "styrene" moulded engines - they would be easy to fit. I was amused by the classic H&S warning on the website "It is not recommended to fix these engines to the propshaft"

 

Bit of a delay at the moment - I want to do the stabiliser and fin next but I need 0.8mm by 3mm balsa strip to laminate up the edges. I've had a go at stripping this by hand from 1/32 sheet - not a sucessful experiment I'm afraid  - in fact it was a total waste of wood .

 

So I've ordered a balsa stripper from SMC yesterday and I am awaiting its arrival. This will enable me to do the job much better - I hope. Once its here "normal service" will be resumed! I have been dreading this next operation since I started the build. The strip has to be soaked in water, bent around some very tight looking formers and then glued up in a triple lamination.

 

Wharra mean! "Piece of cake"!!!! We'll see....

 

BEB

Edited By Biggles' Elder Brother on 25/03/2010 00:08:59

[Biggles' Elder Brother - Moderator]

Those splendid chaps at SMC have come up with the goods - delivered 36 hours after ordering. Excellent

 

First step is to cover a wooden board and the lite-ply formers we will shape the laminations over with cling-film to stop the laminations sticking to them. The formers are then nailed down to the board...

 

These formers will allow us to make laminations for both the the stabiliser and the elevator at the same time. We need to use both formers twice - one pair for the upper surfaces and one pair for the lower.

 

As I said in the previous post the laminations are supposed to be made from 0.8x3mm strip. In imperial that more or less 1/32 by 7/64! I had a go at cutting these by hand from 1/32 sheet using a 1 metre steel straight-edge - that didn't work too well  So I ordered the balsa stripper. I've been meaning to get one of these for ages - but never got round to it - wish I had, they're brilliant! The one I've purchased is the Master Airscrew one, simple to set up. The screw has a pitch of 1/32 per turn - so for this job that's three and a half turns. You just pin down the sheet, put the stripper against the edge of the wood and draw it along. Simples

 

The result is great, lots of strips generated in no time and all exactly the same size. You can get carried away - I did! Its very therapeutic!

 

Beautiful, I'm a happy boy

 

Now I think for a first for the forum - a picture like you've never seen before!

 

Yes its a picture of the bath! A couple of inches or water, a dash of ammonia and chuck in the wood strips. SWMBO isn't too impressed - especially when I explained that they are there until tomorrow afternoon! But I have to get them soft enough to bend round the formers without breaking somehow!

 

So, with my wood in soak, that's it for tonight. Tomorrow I'll be trying to make the laminations for the upper surfaces of the stabiliser and elevator, wish me luck!

 

BEB 

[Terry Whiting 1]

Hi BEB,

 

Having fun, you should have used waterproof glue for boat building

 

A few years ago I built the Dennis Bryant SE5 A , and used the very same former technique, but no wood soaking.

 

I made it in a 5 layer lamination for the fin/rudder, and 7 lamination for the wing tips, The fin/rudder, stabilizer/elevators  lay up was 3  of 1/64" ply and 2 of 1/32" balsa.  Starting with ply and finishing with ply  ALL wood was cut cross grain, no soaking required.

 

The fin/rudder were made with 1/4" wide strips, the stabilizer/elevator was in 1/2" stips, and were strong enough to be bandsawn in half to make a mirror image.

 

Wing tips with 7 laminations but   1" wide, and bandsawn into 4 tips.

 I do use epoxy for laminating.  

 

Many of my models have laminated wing tips.     

Edited By Terry Whiting 1 on 26/03/2010 09:04:28

[Biggles' Elder Brother - Moderator]

Posted by Terry Whiting 1 on 26/03/2010 09:03:56:

Hi BEB,

 

Having fun, you should have used waterproof glue for boat building

 

 LOL  

 

Well I've retreived my wood from the bath - it feels like cold cooked spaghetti! The whole process seemed to go quite well - no drama really.

 

Basically just pin the first strip round, then removing one pin at a time and replacing as I worked round I glued the next strip on - then the next. Because the wood was wet (very!) I used white PVA as the adhesive. I can see the attraction of the method you used Terry, with your wood being dry you of course were able to use epoxy. But the PVA went fine.

 

It has to be left at least 24 hours now, maybe longer. What you see there is enough to deal with one surface of the stabiliser and elevator. Depending on the weather tomorrow I may start building the actual stab - so its ready for these bits while I bend the next lot up. "Er, luv can I use the bath for my wood again?"

 

BEB

[Terry Whiting 1]

BEB,

 

I have in the past read of this techniqueit, but have never fancied trying. 

Any of my builds with compound curves such as the fuselage of my  ME262 I resolved  by planking. Now that I do find therapeutic.

 

TW

[Biggles' Elder Brother - Moderator]

Well the laminating is proving to be a great sucess at the moment. As the picture shows below I have nice curved laminated strips...

 

The top one is cut ready to go on the stab starboard leading corner. The middle is as it comes off the former - not cleaned up yet to remove any surplus glue or any plastic sheet that may still be stuck to it - and the bottom one is the other part of the top one and will eventually form the two trailing edge corners of one of the elevators.

 

I'm assembling all the parts to build the stab but have been slowed down by some lack of clarity in the "instructions" - and for once, unusually, the drawings are not a lot of help. The problems (and the solutions I've come up with) have been;

 

1. The elevator spar is described as 6x2.5mm hard balsa - there isn't any. Measuring from the drawings suggests the width should 5mm, not 6mm. There is some 5x2mm hardwood strip that I can't see any other use for - so I'm guessing I use this. I became even more sure this was right because the spar cut outs in the stab ribs are only 2mm deep - not 2.5mm.

 

2. The false trailing edge of the stab is not made from the laminated material, but there is no mention anywhere of what it is made from! Taking measurements from the plan - and assumming it fits flush in height with the rear of the stab ribs - then it must be made from 5x2.5mm balsa. But there is no stock of that description in the kit. So I will make these strips up from 3mm sheet with new balsa stripper and gently sand them flush with the back of the ribs.

 

3. Although not mentioned anywhere - its obvious that the stab leading edge is made up of a straight length of the laminated 0.8x3mm strip - so I've had to make up some straight ones as well as the soaked and curved ones!

 

3. There is talk in the instructions of 1.5mm ply templates (in the form of the ribs) to assist in sanding the central block on the stab which will eventually support the fin - but guess what? No 1.5mm stab ribs are supplied - surprise, surprise . So I've decided to make my own from an off-cut of 1.5mm ply from the kit by drawing round the balsa ribs. You can see this in progress below...

 

The original balsa rib is the lower one with the cut-out, while my "in-progress" ply template is the one above it. As you can see still some work to do on this and I have to make two - one for each side of the balsa block.

 

On top of this I still have another batch of laminating to do for the underside of the stab and elevator. I mention all this to explain why progress might seem a bit slow just now. Everytime I can't find a part it initiates a thorough search of all the kit, a long think, a pour over the "instructions", the drawings, the American biuld blog and then finally a decision to "do-it-yourself"! Things have been further held up by the fact that I managed to rip the undercart off my WOT4 on Saturday attempting a rather tricky cross wind landing - a big gust appeared just at the worse moment. So repairs there are occupying the workbench - as least some of the time.

 

But I am steadly getting there and I have most of the parts for the stab assembled in one place now...

 

Once I have my two ply templates (the only parts still outstanding) I think the actual stab will go together quite quickly.

 

BEB

 

 

[Terry Whiting 1]

BEB,

 

I have been puzzling my head over why your laminations were being fabricated so light, but now all is clear, a centre core build.

I was thinking a similar build as my SE5 which was all open framework, hence the stong laminate .

 

Hope you find those missing pieces.

 

TW  

[Biggles' Elder Brother - Moderator]

Hi Terry,

 

yes the real reason for these laminations is not structural - its scale. The Pup had a metal tube edging around both the tailplane and the fin/rudder. This was quite a noticable feature on the original so these laminated strips along the upper and lower faces will be sanded to a round profile and will (we hope) create the same effect once covered

 

I've given up looking for the bits - I find that in all kits (well the fully built up ones like this anyway) there always comes a point where you are pushed back onto your own resources - either because something isn't supplied or you break the one they give you!

 

BEB 

[Biggles' Elder Brother - Moderator]

Right, its build a stab time! (At last!)

 

The stabiliser went together well, no real problems - just some minor points I'll mention later...

 

The central block with the two holes in it still has to be sanded to the profile of the ply ribs either side (the ones we were making the other day) but we can't do this until the other side is done as we need a stable base for that.

 

As can be seen the laminated edges worked well - fitting perfectly. The balsa block was a slight problem and needed a bit of sanding and bodging to get it to fit and to make the two holes line up with those in the core.

 

Here is a close up of the stab...

 

The reinforcement blocks for the hinges - three each side - can be seen. The small square blocks with the holes in are hard points for the rigging attachment. These are made from 3mm basla faced with 0.8mm ply...

 

As can be seen they are pretty small. Its a sobering thought but these are all that will hold the entire tailplane assembly in place in the air. As I've mentioned earlier the rigging on this model is fully functional, so the tailplane and fin are not glued on. Instead they just sit on the tail of the fuselage located by two pins that pass through brass tubes in the two holes that can be seen in the central block in the earlier photos. These pins just stop side-to-side movement of the tailplane, its the rigging that holds it on! The wings are the same.

 

I don't think I'll be doing too many snap rolls with this model

 

More laminating underway and then the other side of the stab.

 

BEB 

Edited By Biggles' Elder Brother on 30/03/2010 23:13:34

[Terry Whiting 1]

BEB,

 

You will be surprised how rigid the tail surfaces will be,

I  used that means of fixing on the DB Scout when that model first came out which must be 25years+, my Club pals thought I was mad, but my answer was, if it works on the full size, it will a model.

Sinse then any of my builds (which have been many) with tail plane flying wires, I use that method of fixing. 

On my 1&1/2 Strutter and Tomtit it was used to adjust TP incidence after their maiden flights. 

 

TW

[Biggles' Elder Brother - Moderator]

Sorry about the lack of posts for a few days. Work is pretty busy at the moment and the building board has been occupied with two repair jobs - one fairly extensive . Anyway, back to it.

 

I've been finishing the build of the stabiliser - completing the underside. First we have to tack a few 6mm balsa blocks to the upper face to support the stab while we work on the lower side...

 

The stab is then inverted and the previously formed second lot of laminations (which can be seen in the upper part of the photo above) are attached around the edges....

 

The central area of this lower surface is handled slightly differently than the upper face. Two ribs are fitted with undersized balsa doublers which act as a locating face for a 1/16 balsa sheeting. This is shown below...

 

This curved sheeted surface will sit on the tailplane mounting saddle at the rear of the fuselage. The photo below shows the completed lower surface with its hardwood spar, ribs, riblets, bracing gussets, hinge points and hard points added...

 

As Terry points out above the structure comes out stiff and commendably light.

 

Next up are the elevators

 

BEB

[Biggles' Elder Brother - Moderator]

The "Day Job" has been taking up a lot of my time over the last couple of weeks and on the few days I have free the weather has been just too nice not to fly. So the poor Pup has not been making much progress - but hopefully we have turned the corner and I'll be able to get back to things!

 

Well its on to the elevators now. These are built in a similar fashion to the stabiliser. We start by fixing the 3 piece pre-bent laminations around the edges...

 

And then we add the ribs and gussets...

 

So this completes one side of one elevator. The other elevator has also been assembled on one side. Next we will invert them both, fix them together and build the other sides, then it will be on to the fin and rudder!

 

BEB

[Biggles' Elder Brother - Moderator]

Time to join the elevators together. This is done via the common method of a metal torsion bar made from 2mm steel rod. This has to be bent up to high degree of accuracy because the cut-outs for the bar already exist in the elevators. This means that there is no opportunity to make the holes to fit the rod, instead we must bend the rod to fit the holes. I always find this difficult. One day I'll invest in wire bending tool - until that day I have to do it using the Mark 1 eyeball!

 

The picture below shows the prepared torsion bar....

 

In the picture the two part-built elevators from yesterday have been inverted and the cut-outs for the torsion bar can be seen. My first attempt at making the torsion rod was about 3mm too short. The consequence of getting this wrong would be that the two elevators will be too close together and so edges of the elevators will not line up with the edges of the stab - and that would look awful . So there is no choice but to do it again until you get it right! Also the torsion bar has to be straight - or we end up with "delta wing" elevators! - and "in line (as viewed from the end) - or we end up with one elevator higher than the other and the Pup will not fly straight! All this required a good deal of "fettling", bending and hammering! Fortunately my second attempt, which is the one you can see in the picture, was acceptable

 

Now we glue the bar in place using slow setting epoxy...

 

The clamps and pliers are just there to keep everything flat while the glue sets. Notice that the elevator assembly has had its leading edge lined up with one of the straight boarder lines of the drawing - to ensure that the mating face of the elevator assembly will be straight. My abortive first attempt at the torsion bar can just be seen near the top centre of the picture.

 

Now, with the torsion bar in place, we fix the laminated edges to the lower elevator surfaces...

 

Once the glue has set on the laminations its time to check if we have done all this correctly. Let's put the new elevator pair up against the stabiliser to see how it all looks...

 

(Big tailplane isn't it)

 

Not at all a bad fit. Though I say so myself I'm well pleased with this - the line up is fine. The gap on the left hand side is just because I haven't positioned the elevator hard up against the stab at that end - obviously the hinges are not installed yet.

 

The lower faces of the elevators now need their ribs and gussets added and the hinge hard points need to be added to both sides and then they are finished ready for profile sanding.

 

BEB