wonwinglo

Where struts vanish into the fuselage like this can be a real problem area,but you have tackled it just the way that I would have done,there is just no other option available,glad that you remembered that Micropore,it really locks up rock hard once the cyno touches it,and once more can be easily wound and stretched slightly,as you say Grahame a thin soaking in thin cyno will make the filler solid as it soaks in.

__________________
'And there I was oil on my goggles from a broken pipe,then I looked at the altimeter,all I could see was the makers name !'
www.wonwinglo.scale-models.net/

Greyhead

The top of the fuselage is covered in 2 pieces, first all the decking and then the stringers to just behind the cockpit, so the rear decking has 2 layers of Solatex. If I say that covering the decking was a challenge you’ll get the idea, I certainly envied the full size where the struts and bracing wires are removed before covering.



I’m now ready to start on the next section, the fin, skid and rudder but before I do I compare the actual model to the plan. This is for 2 reasons, firstly the plan is amended for those things that didn’t work out exactly as I’d envisaged and secondly it ensures that the next bit will fit what has already been made.

wonwinglo

Grahame can you explain why you used two layers of Solartex on the rear decking ? no doubt you have good reasons to do so knowing your precise and well planned approach to building.
Thank you.

__________________
'And there I was oil on my goggles from a broken pipe,then I looked at the altimeter,all I could see was the makers name !'
www.wonwinglo.scale-models.net/

Greyhead

Barry

The decking is in 3 sections with one of the joints just aft of the cockpit at the “break” point (SE5a CONSTRUCTION BEGINNING TO . . .); this would seem to be the place to end the decking covering but it would create an obvious weak point so the covering is taken back to the end of the decking. The “stringer” covering is taken forward over the decking because the decking is a different length on either side of the fuselage. Done this way there is a neat join between the coverings, which is further strengthened by a frayed tape.

A little extra weight but I wouldn’t want the decking to “spring” open on a less than perfect landing; where strength isn’t an issue I save every gram I can but there’s no point building so light that you’re for ever having to repair the model.

wonwinglo

That makes good sense Grahame to do what you have done,a weak spot can wreak havoc into a structure like that,any cockpit opening is a weak point as well,it is a difficult decision especially as the aft centre of gravity build up of weight can be a real issue.
The S.E.5A has such appeal as a model subject and I can see now why you picked it as your current model subject.

__________________
'And there I was oil on my goggles from a broken pipe,then I looked at the altimeter,all I could see was the makers name !'
www.wonwinglo.scale-models.net/

Phoenix

may sound stupid but what is aft centre of gravity

is it just the centre of gravity of the plane?

Greyhead

Iain

Firstly there is no such thing as a stupid question, only a question you don't know the answer to.

The centre of gravity (CG) is the point at which the aeroplane physically balances, it is always marked on the plan and it is very important to get the model to balance correctly. A model that is nose heavy will usually fly reasonably well but a tail-heavy model can be literally unflyable. The CG is always some distance in front of the aerodynamic balance point to ensure stability.

On all the planes I know there is more model behind (or aft) of the CG than in front, in the case of the SE5a there is 10" from the CG to the nose and 34” from the CG to the tail so it needs 3.5 times the weight in the nose to balance weight at the tail. The length of the nose is calculated to allow the weight of the engine to balance the plane but as our engines tend to be light compared with the full size counterpart it is important to build as light as possible behind the CG to minimise the “dead” weight required in the nose.

So to actually answer your question, to read it correctly “aft centre of gravity” needs that next four words added to make sense which are “build up of weight”.

Hope that all makes sense!!

Grahame

Greyhead

Before I start on the construction of the fin itself I want to be sure that the tail plane incidence adjuster will work so I’ve made that first.

The fin post is a carbon fibre tube through which the adjuster rod, a snake inner, slides; the 2 attachments for the bracing wires are made from closed loop adapters and brass wire.



The lower attachment has a 2mm cap head bolt that will do the actual adjustment by screwing in or out of a length of snake inner firmly fixed to the fin post; I used snake inner for this as it acts like a large “Nyloc” nut so won’t alter the incidence as a result of engine vibration.

Any adjustment required will be made using an Allen key through a small hole in the base of the tailskid fairing.



This is the position it will be fitted in, at this setting the adjustment is about central and can be altered approximately 7mm either way.

wonwinglo

Grahame this little feature is so important,and it surprises me that more modellers do not use it,no matter how well calculated the tailplane incidence nearly always needs adjustment to enable the model to fly properly.
I really like the idea of the snake inner put to use in this way,by the way this material also makes ideal cowling screw fastener inserts,you just push a flared piece through the wood and attach with a dab of cyno,the flare can be made with a hot metal butchers skewer quickly pushed into the snake inner,another flare on the outside takes care that it is not pushed through the wood,the job is best done during construction of the model.
Full sized aircraft utilise a screw jack arrangement for ground adjustment by the engineer.

__________________
'And there I was oil on my goggles from a broken pipe,then I looked at the altimeter,all I could see was the makers name !'
www.wonwinglo.scale-models.net/

Greyhead

The fin is made using “core and half ribs”; for those not familiar with the method it is a simple way to make strong but light structures, especially if the outline is “curvy”. It is my preferred method even for simple shapes such as the SE5a fin, rudder and elevators; the tail plane may have to be a fully built up construction because of the cable and pulley elevator linkage, I’m not decided as yet.



To start the core is cut to the shape of the finished item, the usual material is 1/16th balsa but I’ve heard of the use of thin ply for extra strength or even Depron if weight is an issue. The positions for ribs etc. are marked then one side constructed whilst the core is pinned to the building board, thus ensuring a straight structure. After leaving plenty of time for the glue to fully dry the process is repeated for the other side.