Scratch Built SE5a

[Greyhead46]

Thank you all for the replies, hope you enjoy todays offering.

 

Grahame

[Greyhead46]

The fuselage consists of a substantial front end with a rear section framework from ⅛" square spruce; I’ll complete the front section of the fuselage, as far as practical, before attaching the rear section thus alleviating the need to swing a 3-foot fuselage around in the confines of the workshop; always a recipe for damage!!

Although the current trend is for interlocking “Liteply” formers I still prefer to use birch ply for these high stress areas. The formers are “notched” to key into the fuselage side doublers; this greatly increases the strength (even though the fit isn’t up to the standard found in CNC cut kits!!).

 

·         F2 has a hole cut to suit the fuel tank and consists of 4 pieces glued together for extra strength at the front cabane and front undercarriage mounting points.

 

 

The rear undercarriage mounting cross member is also made from 4 pieces of ply.

 

Ply doublers will “tie” the formers together to form the front section.

 

[Greyhead46]

The front section assembled.

 

 

The “engine” bearers are glued and screwed directly to the side doublers; the engine will be mounted on a Paxolin plate, which in turn is bolted to the bearers. This method gives great rigidity to the front of the fuselage and also makes changes to the thrust line easier if required.

Showing how the undercarriage will be attached.

 

The front position for the undercarriage mounting is fixed by F2; this has to be accurately positioned because it is also the mounting for the front cabane struts. Having built the undercarriage first it was an easy job to make any adjustments to the position of the rear mounting cross member (in practice it needed to be about 1mm further to the rear than I’d drawn on the plan). Done the other way round, bending and silver soldering the piano wire to fit the fuselage, would have been a lot more problematical!


Showing “engine” bearers.

[Greyhead46]

The radiator consists of 2 separate units joined by pipes, the top pipe also incorporates the filler cap, the intervening gap has a metal cover plate; as I intend to use the radiator cap as a convenient fuel filler point I needed to model the 2 header tanks. When trial fitting them I realised that the cover plate would have quite a “double curve” to fit to the rear radiator former (see photo "Showing how the undercarriage will be attached") and this didn’t seem right. Checking photos showed that in fact the rear radiator former should have a flat top, the transition to curve taking the entire length of the cowl.

Luckily the former wasn’t glued in place so a replacement was made and the plan changed.

 

The grills are made of aluminium mesh from a car accessories shop, stretched to open the slots to more closely resemble the true hexagonal shape of the original. I’ve not yet decided whether to cut the former out behind the mesh or just paint it dark, I my compromise and cut out the top section, which shows above the radiator shutters, and paint the rest.

 

 

This shows the undercarriage front fixing; it’s recessed up into the fuselage to allow the front flying wires to pass through the fuselage sides via dummy attachments and be tensioned inside using turn buckles.


 

The “bullet” at the cross over point of the undercarriage wires (correct name acorn, thank you Barry) stops the wires chaffing. In the full size to prevent wear and possibly failure but for the model it’ll prevent metal to metal contact which can cause interference with the radio signal.

Edited March 9, 2023 by Greyhead46

[Geoff S]

The 3rd model I built (after a Precedent Electrafly and a 40 size trainer) was a Flair SE5a.  I didn't like their engine mounting method and opted to a similar system to Geyhead's - a paxolin plate for the OS52 Surpass I'd chosen.  However, the Flair SE5a has considerable down and right thrust, which I kept (this was back in 1996).  I don't see any downthrust here but, as the model has actually flown it's not a problem. I converted my SE5a to electric last year and kept the same thrust angles as the original.

 

Once more some stunning work.  I'm learning a lot.

[Greyhead46]

Hello Geoff

 

The Paxolin plate method goes back many years, I can’t remember where I heard about it. If down thrust had been needed a few washers under the plate to determine how much then a couple of wedges for permanent adjustment and the jobs done but most of all I like the strength it adds for a very modest weight gain.

 

The SE5a has the tail plane set with positive incidence, I used 5 degrees and that does the job, did the Flair SE5a have the tail set neutral?

 

 Incidentally 5 degrees seems to be universal for the SE5a; wing and tail incidence and dihedral. 

 

Grahame

 

[Greyhead46]

The next thing I want to do to the fuselage is to fit the cabane struts, but I don’t like to put my trust in geometry for this critical job, especially if it’s my geometry!

This means that before I do this I’ll make the top wing centre section, hold it in position with a temporary jig and then fit the cabane struts thus ensuring that the wing incidence etc. is correct.

If I’m fairly confident that what I’ve drawn on the plan will translate into the actual part when built then I usually make a “kit “of parts.

 

The 2 outer ribs are 1/16th ply the others 1/16th balsa made using the “sandwich” method and then the inner ribs are shortened to fit the trailing edge cut away.

The hardwood blocks have a hole for the wing location wires drilled at 5º  to give the correct dihedral and grooves routed to fit onto the 1/8 x 1/4 spruce spars. The yellow “pegs” are in fact snake inners tapped 2mm that will have grub screws to lock onto the wing wires to hold the wings in place.

The build starts with the trailing edge.

 

The centre section is at the stage ready for the fitting of the cabane struts, the top and bottom sheeting will be added later. The carbon fibre leading edge really adds to the torsional strength; the wings with carbon fibre leading edge and carbon fibre spars should be as stiff as a board!

 

The hard wood wing retaining blocks / spruce spars have had a few wraps of carbon fibre tows, very little weight but tremendous increase in strength for this crucial area.



The cap head set screws will be replaced with grub screws before the top sheeting is added; these are just for a test to make sure that they will hold the wing in place and they certainly will. They only need to be “finger tight” to make the wires solid so a “nip up” with an Allen key and the wings will be going nowhere!

 

Now the jig to design and get the cabane struts fitted.



 

Edited March 10, 2023 by Greyhead46

[Basil]

Just WOW!!!!!

[Greyhead46]

Hello Basil

 

Thank you for the reply, it’s always nice to know someone is reading what I’ve done!

 

Grahame

 

This post is actually a reply to a couple of questions that were asked when I did the original build thread (I’m only including my own posts in this thread) but if anybody has any questions about the build just ask and I’ll do my best to answer.

When cutting the large “square” holes in the ribs (see last post) I stuck Selotape on both sides of the rib because the cut is very close to the edge, this helps to hold the wood together whilst cutting, after carefully removing the tape I apply some thin cyano which really strengthens the wood. You can cyano the wood first but this makes the cutting a lot more difficult.

I should have included this tip in the post but you tend to assume that everybody knows these things; another thing I realised is that I blithely said, “using the “sandwich” method”.

Basically this means using the 2 outer ply ribs as templates for the inner balsa ribs, which are cut as blanks, held between the outer ribs and sanded to shape using sand paper attached to a suitable piece of straight timber. Possibly not really worth it for the centre section but for the wings with 60 ribs it certainly was and I photographed the process and that will be detailed later on in the thread.

Edited March 11, 2023 by Greyhead46

[Greyhead46]

The jig is mainly made from ¼ square balsa using plenty of braces to ensure stiffness; it’s got to hold the centre section rigidly in place whilst the cabane struts and bracing wires are fitted.

 

The jig in position on the fuselage. It will be held more securely for the final fitting.

 

The initial fitting of the cabane struts is the check that they will actually line up with the fixing points.

 

 

Having confirmed that the lower fixing positions are correct the cabane struts are cut in half. It’s far easier to do the bending and drilling for each end of the struts separately then any discrepancies can be catered for when the two halves are joined, I don’t kid myself that they’ll be perfect first time!

 

The lower tube has a short length of smaller tube soldered into it to form a spigot for the top tube. The pin through the joint isn’t primarily to strengthen the joint but to stop the balsa cladding, which will be used to streamline the cabane tube, from twisting but it also makes sure that the inner tube will stay in place as the top tube is soldered to it.

 

 

A small screw holds the cabane strut to the centre section, those hard wood blocks are definitely multi propose. The screw is only to hold things in position, the strength comes from the fact that they have a hole for the wing locating wires.

 

 

 

Edited March 11, 2023 by Greyhead46

[Geoff S]

I may part-copy this method when I build the Fokker DVIII I've ordered the drawing/CNC parts for from SLEC.  Getting a top wing in the right place is always tricky I find and the DVIII's wing is rather like the top wing of a bipe even though it's the only one.  Another master class.

 

Rather than soldering have you thought of using epoxy (EG JB Weld) because it's easier to adjust slightly before it sets hard - and isn't hot!  I'm pretty sure that in this application it's as secure as soft solder.

[Greyhead46]

Hello Geoff

 

Bending up cabane struts (or equivalent!) is never easy if at all possible I try to make them "adjustable". In the case of the SE5a they are made in two parts but with my Parnall Elf I made them truly adjustable as per the full size.

 

 

They look a lot better as well!

 

 

 

It all depends how the full size was made.

 

Grahame

[Greyhead46]

Before soldering the cabane struts together all the bracing wires need to be in place, in fact joining the tubes will be the very last job to be done.

When making multiple, or as in this case “handed” brackets, your computer is an extremely useful tool, first draw out the bracket, scan it in, copy and paste the image, after “flipping” it if “handed” brackets are needed then print out as many as required. For small brackets such as these I print them onto self-adhesive labels.
 

 

To make sure that the brackets will fit I made some test pieces from scrap Lithoplate, as this is dead easy to cut and bend, then the labels are stuck to the sheet material, in this case brass, for the final brackets to the cut.

 

 

 

The final shaping will be done with a combination of Dremel and hand files.

 

The brackets for the cabane bracing wires have been soldered to the top sections of the struts; all the bracing wires will be cut to the correct length and soldered in place with the centre section held by the jig.

This is a photo of one of the rear struts.

 

 

Luckily the end fitting for the side wires are hidden inside the cabane fairings with just the end showing so they can be simple tubes.

This shows a general view of how the struts and bracing wires will go together.

 

The front and rear bracing wires are a bit more complicated as the end fitting is visible. Once the wire is the correct length with both ends soldered in place the pin will be replaced with a short length of piano wire and the whole lot soldered together.

 

 

Edited March 11, 2023 by Greyhead46

[Greyhead46]

With the jig and centre section firmly held in position using various clamps the bracing wires are cut to correct lengths. Now would appear to be the time to solder the assembly together but there is a problem.

 

All those wires will make it very awkward to complete the fuselage top decking but if the decking is completed first it will then make the fitting of the cabanes more difficult!

I’ve decided on a compromise; I’ll finish the front section (the tank cover) as this has a lot of detail with straps, fasteners and the trough for the Vickers machine gun etc. and then finally solder the cabane assembly together before completing the decking back to the cockpit

 

The end fittings for the front and rear bracing wires are soldered to the wires because with the pins removed they easily take apart.

 

 

[Greyhead46]

My original idea had been to use 2 layers of 1/64" ply but I wasn’t convinced that I wouldn’t get some de-lamination at a future date and as this area will be covered in Litho plate it would be difficult to repair, so I opted to use 1 layer of 1/32" ply instead; this is still quite easy to bend, even if it takes a bit (a lot!) longer, so long as the bend isn’t too tight.

Paper templates are used to get the shape before the ply is cut slightly over size. The ply is then covered with boiling water (a good excuse for a cuppa!!) and left to soak for a while, it doesn’t need to be too long. The ply is then tightly bound to a former using masking tape, the former should be slightly smaller than the finished bend, I used a 4" diameter tin for a 2¼" radius bend. Cover the ply completely with the tape and if the former is porous cover that first with cling film then leave it overnight. The tape etc. keeps the ply moist; in fact it will probably still be damp in the morning. After removing the ply form the former hold it in its curve either using tape or pins while it finally dries if necessary.

The tank cover doesn’t continue all the way to the side plates. The front cabane struts go through the gap, which has a separate cover plate, so there will be no problem with the final soldering of the cabane assembly.

 

The gun trough needed a lot tighter bend but as it doesn’t really add to the overall strength just 1 layer of 1/64" ply was used.
 

 

Time for a little “metal bashing”; I love litho plate me!

The first job is to work out the positions for the “extras”, I draw these out, in this case onto the paper templates used to cut the ply decking. I don’t bother drawing to scale but add the necessary measurements then I know for sure where everything fits when I’m in the workshop.

 

Drilling Litho plate is about as easy as knitting fog, the only satisfactory way to make holes is to use a punch. As each strap has 8 holes and there are 4 straps it is easier to make a simple jig. 2 pieces of ply bolted together then holes drilled through, with the litho clamped in place the drill bit is used as the punch, turned the wrong way round and given a tap with a pin hammer (protecting the business end with another piece of ply).

 

With the holes done it’s a case of adding the “rivets” and then trimming to size

 

 

The 4 straps ready for final finishing.

 

With the straps, bottom strips and rivets added the finished plate is ready for fitting to the fuselage.

 

I don’t worry about the odd dent or scratch, I my opinion they just make the finished model look more realistic.

I well remember spending hours trying to get the aluminium cowling for my Albatros just right then finding out that in fact on the full size each panel was individually “hammered” into shape so everyone was slightly different with evidence of the manufacturing process clearly visible.

 

 

Just need to make the other side now.

Edited March 11, 2023 by Greyhead46

[Graham Davies 3]

Thoroughly enjoying this, Grahame!

[Greyhead46]

Hello Graham

 

Thanks for the reply, glad you're enjoying the thread.

 

Grahame

 

There must be more “recommended” ways to attach Litho plate than there are ways to skin a cat, they’ve all got their pros and cons, and I’ve tried them all! Purely by accident I’ve found what I consider to be the perfect adhesive for the job.

At work we needed some glue that dried clear for a project the students were working on, as I had some Pacer “canopy” glue in the car we tried that and it worked fine but some got onto the table which in turn got covered by a small tin foil container used to mix paint in. When it came to tidying up time the tin foil was stuck fast to the table, the old grey matter started to work overtime.

This glue is just the job for Litho plate, it’s like a mixture of PVA and Copydex; it’s thin enough to be spread thinly and evenly over the plate, which can be easily moved to position it accurately but within a short time it has good “grab” to hold everything in place. The icing on the cake is that it’s water based so a quick wipe over with a damp cloth before it’s really set gets rid of any sticky fingerprints etc.

 

The top panel has 3 distinctive parts; there’s a bulge over the fuel cap, the fuel cap itself and something that looks like a submarine conning tower.

Where the plates will overlap the edge of the under plate needs feathering in, even the thickness of the Litho plate would leave a noticeable step. For filling very thin depths such as this I think the best material is cellulose stopper as sold by automotive paint suppliers.

The bulge is first modelled in balsa and glued to the ply decking and given a coat of silver Solalac for both appearance and fuel proofing.

 

 

It is quite difficult to work Litho plate from a male mould so I cut an appropriate sized square in an off cut of 1/8th balsa and started to form the bulge from the inside working it into the cut out, when it was approximately the correct depth I transferred it to the actual model to finish it off.

 

A small ring of Litho plate and some rivets completes the top plate itself.

 

It is impractical to make this part from metal so I’ve used spruce and painted it with silver Solalac, when weathered it’ll look OK. When making small parts such as this it’s useful to keep them attached to the wood until they are as near to finished as possible. Sorry for the blurred photo!
 

 

The fuel cap is made from brass soldered together.

 

 

The result when the parts are assembled.

 

 

The gun trough was no problem; so that’s the tank cover finished and I must say it’s been an enjoyable few days.

 

The fuselage front section is now as complete as I want it; in a perfect world I would be able to work on the cowl and dummy engine, but before I do I want to fit the engine to ensure I don’t make things unnecessarily awkward for myself later, but in this non-perfect world I don’t have a spare Laser 70! So it’s time to start on the rear framework.

[Greyhead46]

 For “runs” of rivets I use a dressmaker’s copy tool and a straight edge or curved template.

This one has had every other “tooth” removed to widen the spacing.



Mark the position for the rivets on the reverse side of the panel, hold the straight edge or template in place and carefully run along the edge with the tool; a couple of seconds to make a row of perfectly spaced rivets; what could be easier?

 

The screw driver and “sharpened” brass tube make screw heads and the ball point pen individual rivets.

 

[Greyhead46]

The first rear frame is built over the plan.

 

 

Using an open framework structure has advantages; it is quick and easy to build and very light but it is inherently weak compared to sheet material, to make matters worse the longerons have to be “broken” where the fuselage starts to taper towards the tail.

The strength can be greatly increased by the use of gussets, (apparently called “biscuits “in the aero industry, thanks Barry) as always it is a trade-off of strength against weight, I use 1/64th ply, which I consider to be a good compromise. One of the modelling magazines had an article that measured this increase in strength and amazingly even gusset made from brown paper made a significant difference.

 

The second frame is built over the first, which is covered with Clingfilm to stop any unwanted adhesions.

 

 

 

After gluing the rear framework to the front section the longerons are cut ¾ through at the “break” point and carefully cracked to allow them to be pulled onto the rear formers keeping the sides straight. On many aircraft, the Elf for example, the sides aren’t straight; they are pulled in at the rear and allowed to take up the natural bow imparted be the spring of the wood. I used a variation of the “3 pins method” to ensure a straight fuselage i.e. in this case the front formers had marks drawn on the centre line and a pin used in the rear former.

The framework is made from 1/8th square spruce; when working with this wood I’ve found that the glue takes a lot longer to set, even cyano takes its time!! So it’s essential to use lots of clamps and leave everything to set completely before removing them.



At this stage the rear fuselage is quite flexible, not to say fragile, but with a few more biscuits it’ll firm up.

 

Having added a few more 1/64th ply biscuits the framework was a lot stiffer, however I still wasn’t happy about the strength at the “break” line so I removed the cross braces and epoxied some carbon fibre tows over the joint.

Now that’s a lot stronger!

This raises the question why didn’t I do this in the first place? I go on at length about the virtues of carbon fibre tows and then I fail to spot this obvious application; must be something to do with age!

[Greyhead46]

In my opinion it’s never too soon to start on the instrument panel; they’re a mini project in their own right and whilst enjoyable to do it can be a bit frustrating because the model doesn’t seem to “grow” during the time spent on them, so I like to intersperse the work with the main build so keeping the interest going.

Here’s a photo to show what we’re aiming for, it seems a bit daunting but the idea is to concentrate on an instrument at a time.


I’ve made a start; that’s the easy bit!



This will be the final position.

 

It’s always useful to check that “Pete” will fit!


 

Tip of the day

Starting work on the instrument panel, which has several small pieces of ply and balsa, has reminded me to mention a very useful addition to the workshop.

Like everybody, I suspect, I have a draw (in fact 2 draws) full of “useful” sized off cuts but I also have this old ice-cream container into which I put any small off cuts.

Believe me, there will come a time when you need a piece of 1/16th balsa about 1” x 1” and all you’ll have is a 36” x 4” plank that you bought especially to sheet the leading edge, then you’ll wish you’d not put those little pieces in the bin.

[Geoff S]

Indeed. Even I have a box full of pieces of wood too small to be of further use 🙂   Despite that, they actually do get used.

 

Fantastic progress.  It seems fast but I know you're 'merely' posting after the model is complete.

[Greyhead46]

Hello Geoff

 

Even the fastest builder couldn't go at this pace!  It took me nearly three years to complete the original thread but I thought I'd better speed things up a bit.

 

Probably take me another couple of weeks to finish.

 

Grahame

[Greyhead46]

This post will hopefully give you an insight into the thought and build processes that go into making individual instruments. I decided to start with the air pressure regulator, which is positioned lower left on the instrument panel.

First of all I make a rough sketch showing the main components, which I will include, there’s no way that I could make a true miniature.



Then find suitable bits and pieces, in this case some copper wire and tube to fit, three 14BA nuts, a 2mm crimp, a 2mm nut and some 2mm threaded rod, litho plate and 1/8th square spruce.



The wood has crossed holes drilled through and the wire soldered into position; the small tubes and 14BA nuts are then soldered on. The 2mm rod, nut and crimp are soldered together and the whole lot attached to the body using 5-minute epoxy.

When the glue has set the body is cut down and finally sanded to length with the Dremell a suitable hole drilled and the last "pipe" fitted.



The wire is bent around suitable drill bits and the back plate glued on, again with 5-minute epoxy.

The appropriate bits are then painted with silver Solalac.



Sorry about the blurred photo, taking photos this close really needs a tripod!

The finished regulator in position but not glued, I’ll leave that until all, or at least most, of the instruments are made.



The instrument panel has had a coat of stain as has all the wood that will be visible though the cockpit opening.

 

Another photo of the regulator in position.

Edited March 13, 2023 by Greyhead46

[Greyhead46]

The lower wing stubs are built individually; at this stage the front spars are "scrap" balsa and not glued. After leaving everything to thoroughly set they will be removed and the unit slid onto the spruce spars that go right through the fuselage.



Although not obvious from this photo the plans are drawn on tracing paper, this has a couple of advantages, firstly I’ve only had to draw one wing stub, for this one I’m actually working from the back of the plan and secondly it means that since I’m building both wing stubs from the same drawing they should be identical.

With the balsa spars removed the unit can be test fitted to the fuselage.



This shows the front spars and leading edge.


 

Waiting for the glue to set etc. whilst building the wing stubs gave me the opportunity to make the air pump selector; I chose this for no other reason than it connects to the regulator that I’ve already made, but before I go into the construction some general thoughts on instrument panels.

Having a good quality photo of the finished item is very useful and it might seem reasonable to scale the photo appropriately and stick that to the panel but I assure you it would look terrible. Take for example the regulator that I made earlier, it looks completely different from the front, side and top and there are an infinite number of variations between these extremes. A photo is 2 dimensional; our brains compensate to some degree when looking at a photo but put one into a “real” situation, such as a model’s cockpit and it looks just what it is flat! There are also shadows that move dependent upon the viewing angle; a very basic 3 dimensional representation will always look far more convincing than the most detailed photo (except for modern panels with "touch screen" control!).
 

Edited March 13, 2023 by Greyhead46

[Greyhead46]

The selector consists of 2 parts, the dial and the lever, so the first thing is to separate these, I do all the manipulation using Adobe Photoshop but I’m sure any photo editing software will do the job. There is an instant problem, some of the wording is missing, so failing more information I’ll make an educated guess and I think it is reasonable to assume that it is “FROM ENGINE & HAND PUMP”. Although I’m sure nobody will actually read the dial I feel that if at all possible the wording should be correct.

From the photo the dial is obviously aluminium, the illusion is created by the use of differing shades to simulate reflections, but once again these won’t work in real life. In the past I’ve used plain grey but it never looked very realistic, so this time I tried a different method and I’m really pleased with the results. I changed the grey to white, which of course doesn’t print out, reversed the image and printed it onto a transparency, when it was completely dry I painted the back with silver Solalac.



I had 3 failures before I managed to cut one good enough, this was then stuck onto 1/64th ply.

I had intended to use the lever as in “decoupage” pictures but it was too fiddley to work with in paper so I made the lever from shim brass, a 2mm washer and a dress makers pin, all painted silver, the spindle is a 14BA bolt and a brass nut.

The backing is a simple disc of 1/8th balsa with some copper wire and brass tube .

The finished selector.

 

Another shot.



Notice the shadow has moved to the opposite side of the lever. That's the 3D effect!