SE5a CONSTRUCTION BEGINNING TO . . .

[Guest]

An absolutely beautiful job and a pleasure to watch traditional modelling techniques used throughout.

Thanks for the postings.

[Guest]

Just had a Browse to keep me up to date,

This one is just getting better and better as it goes along, a real credit to Grahame.

Keep up the good work and looking forwards to the next installment.

Regards..........Mark.

[Guest]

keep up the good work

its looking good already

[Greyhead]

A Change of Plan


I decided that I’d 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!!


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 post #29) 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. Wonderful thing hindsight! Now I know the shape of the radiator it’s quite clear on the 3-view drawing, what a difference that thin line makes when you realise what it is!


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.





I’ve also made a correctly dimensioned “bullet” at the cross over point of the undercarriage wires. The SE5a certainly took streamlining quite seriously, the undercarriage bungy cords are encased and the pilot foot holes have cover flaps.

[wonwinglo]

Grahame,I had no idea that you flew helicopters ? the correct term for the bullet a la WW1 style is Acorn,these prevent singing of the wires with the subsequent chafing.

Nice work as ever and the radiator grill looks good,amazing how much there is to think about with a model like this.

If you are learning to fly helicopters then this is the best way ever to sharpen up your rudder skills for your old timers !

[Greyhead]

Barry

The helicopter is a small electric “indoor” model called the Humming Bird that my son bought from a trader at our annual club air show in June this year; I have to admit that helicopters don’t really interest me that much.

On the box it reads in large print:

1. Open the box

2. Charge the battery

3. Fly your Humming Bird

If only it were that simple!! It’s now more carbon fibre tows and super glue than original model.

My son can now fly it for about 20 seconds before he “loses it” and has to make a quick landing but I still can’t get it safely off the deck. These things are certainly for the young with quick reflexes, but I suspect that as with most things aeronautical small equates to more difficult to fly.

[wonwinglo]

A friend passed his Humming Bird onto me Grahame,could not get the thing to fly for love or money,finished up making my own blades for her in the end,she would resonate on the ground with barely enough power to get off.

My Twister Bell 47G flies like a dream by comparison.

[Greyhead]

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 [ EDIT: information received later suggests that the correct dihedral angle should be 3º 20’. I hope to be able to modify the model accordingly. Information received even later suggested that the dihedral angle was indeed 5º; because of this conflicting information I decided to leave things as I'd first designed] 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.

[wonwinglo]

Centre section layout,everyone has their own way of doing things and very interested Grahame in your own approach,temporary jig is the only way forward as you are preparing here,have tried different versions one version is two templates fitting saddled to the upper portion of fuselage,the forward one governs the wing incidence whereby the centre section ribs fit,I have tried fitting piano wire frame first locking this to the centre section ribs via the overhead jigs,the jigs can be torn free once everything is set up,should you need removeable centre section then flattened brass tubes can be screwed into ply side pieces and ply outer centre section ribs,the usual balsa cladding is then added fore and aft,Don Stothers had some great ideas for his lovely biplanes and used self tappers with head removed and drilled out for rigging wires,on his large models he used lots of car bundy tubing with suitably flattened ends,all ideas to be food for thought.

But no doubt you will have a good mental picture in your mind of the way you are tackling the centre section strutting,no easy task whichever way that you choose.

[Greyhead]

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, but first a few days away in the caravan, complete with electric glider of course.

[wonwinglo]

Very strong and practical Grahame,you have crammed a lot of practicality into a small space.

Can I ask where you obtained your carbon fibre tow material plus the rods ?

Also where the rods enter the centre section do these go just into the timber or is this area sleeved as well ? so the grub screws just sit screwed into the hardwood block ready to wind down,very clever,have I got that right ?

[Greyhead]

Well the break in the weather means the caravan is on hold for the time being.

Barry

I got the carbon tubes from www.carbonology.com and I must say they were very helpful; the tows are available from our local model shop. I haven’t sleeved the wood blocks because when the screws hold the wires there will be no movement hence no wear, I hope! You’ve got the idea correct, once the top sheeting is in place the only visible evidence of the grub screws will be four 1mm diameter holes and similarly for the bottom wing.

Grahame

[Greyhead]

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.

[wonwinglo]

***Details have been added to the Modellers Resource Directory under Carbon Rod & Tube supplies.

Well the break in the weather means the caravan is on hold for the time being.Barry

I got the carbon tubes from www.carbonology.com and I must say they were very helpful; the tows are available from our local model shop. I haven’t sleeved the wood blocks because when the screws hold the wires there will be no movement hence no wear, I hope! You’ve got the idea correct, once the top sheeting is in place the only visible evidence of the grub screws will be four 1mm diameter holes and similarly for the bottom wing.

Grahame

[wonwinglo]

I like the whole setup Grahame,just out of interest how much upper wing incidence will you add ? just at a guess I would say 3 degrees decalage.

This lost jig technique can be used on any biplane model and certainly takes all of the guesswork out of everything.