A go at a Foamie

Idling my time away looking round the forums I came across a few posts about RC conversions of the FX707S Albatros. The main appeal of aeromodelling for me is building them, after all I haven't done much flying, & also balsa etc is much nicer than polystyrene.
However I thought that at £20 for the basic kit its not going to break the bank, it only amounts to two after-work sessions at the club, (when I packed in work I was advised to try & keep some regular routines)  so I ordered one & it came this morning.
It was as I'd expected & a good platform to try out some new techniques.
Questions already;
1. There's a small fault on the side of the fuselage, not really enough to justify sending it back, which looks more like a manufacturing fault that in-transit damage. How could I fill it in? Or is it not worth it? I suppose some paint would cover it.
 
2. To flap or not to flap? It appears that the ailerons are close to the fuselage & the outer markings are just for show. Q has used the ailerons as flaps & made his own ailerons further out. The outer markings straddle the dihedral which makes hingeing difficult. If the ailerons only went up to the dihedral would this be sufficient?
I like the idea of Crow Braking!
3. How necessary is the rudder? I've seen a post where its not used. I suppose it could be retrofitted.

 
 
 

What are these for on the underside?
 

Magpie
If you want to do without the rudder the suggestion is to place the ailerons well out towards the wing tips. You can then use differential aileron action (more up than down) to reduce or even eliminate the normal adverse yaw ailerons create. This will make a rudder unnecessary unless you want to do extreme aerobatics! The weight saving can be useful too.

Yes. Outboard ailerons will cross the outer dihedral kink. I actually very carefully used some heat and bending massage to virtually eliminate it. With ailerons you don't need the polyhedral of the chuck glider.  
On my first FX707S I set the ailerons only on the very outer wing portion but they do end up rather small with limited control power. Still adequate except when in turbulence!
Despite it being a "ready to fly" you will have quite a bit of "building" to do particularly if you add a motor. There  is quite a bit of hollowing out required in the cockpit area, the canopy and even under the wing depending on where you place all the bits.
If you add a motor I will be very interested in the total weight you end up with.

My flapped FX707S with its five servos weighs 347g (12.25 oz) complete with a 1000mAh 2s..
 
 A small battery but I actually flew it this afternoon for a full 20 minutes.     

What level of heat are you talking about?
A heat gun? Hot towels, like hand cleaning towels in a restaurant?
I guess a covering iron would be too direct? But over a damp towel?

Aerobatics aren't a goal. Keeping it in the air would be an achievement!
 

I used a hair dryer. It had a lower enough temperature not to damage the foam.
The trick is to locally heat the top and bottom surfaces then slightly "over bend" the wing letting it cool down at the same time. The natural springiness of the foam means it will spring back a bit but if the over bend is correct it ends up with no dihedral.
To avoid permanently damaging the foam it can take several tries.
On mine there is still a very slight dihedral but I left it as I did not want to risk any permanent damage to the otherwise excellent wing mouldings.

Note. On both my conversions I added extensions to the 3mm thick trailing edge to improve the wing's aerodynamics so it went down to a 1mm trailing edge.
From this

To this
 
Probably a bit "overkill" but as a byproduct it does increase the area of both the ailerons and flaps without cutting any more wing foam away.    

I have experimented abit with the wing held flat on the bench & the wing tip pressed flat without any heat.
I guess a gentle heat so not just the surface is warmed then holding it there while it sets.
Then the important part is that the ailerons have three points in a straight line for the hinges.
 

If I build it without the rudder then I only need a single control rod for the elevator.
Could this be fed through the fuselage carbon tube stiffener? I've measured up & there looks to be sufficient room at the tail end to fasten to the control horn. But I cannot find anyone who's done it & I cannot see where the stiffener ends up at its forward end without cutting into it.

Magpie
I am not sure if a control rod will run freely through the carbon stiffener but I note it exits very low down into the space under the wing. From there it might be difficult to effectively couple the rod to a servo. On my first FX707 for convenience I have actually run the 35 Meg aerial through the stiffener.
 
The two channels moulded into the top of the fuselage are intended to hold snakes to control the elevator and rudder. They are positioned at a suitable height to easily couple to servos mounted in the space under the wing.
I hope this helps.   

Measuring it off aginst the fuselage it reaches up to the back of the square hole in the plastic wing mount which you have covered over. At a guess the polystyrene is solid there which would mean carving it out from underneath but I wondered if I could glue a 3mm drill bit in the end of the stiffener tube & drill through into the cut-outs for the servos where you have the receiver. If it worked it would make a nice tidy job.
The bore of the stiffener is 3mm, I'm sure a 2.5mm rod would slide freely.
As usual the carbon fibre is quite cheap but the delivery bumps the cost right up. There is a relatively local firm at South Shields stocks it but that is still a 50mile round trip.

I actually used the long wing stiffener to drive the rear fuselage stiffening hole through to the under wing space so in a straight line that's were it will come out. I then withdrew the long stiffener and put it the intended one. I actually pushed the tail stiffener about 1.5" further in as my glued on tail plane added significant stiffness to the last couple of inches of the fuselage.

Quorneng
Like you I used the long stiffener to bore through to beneath the wing and excavated enough to be able to get a 9g servo in to pick up the end of a CF rod run inside the stiffener. If I can use 2mm diameter it will connect with the servo arm using a nylon clevice. As CF is quite stiff I'm hoping it will slide in the 3mm stiffener bore without any problems.
 

On the RCME forum someone has removed the hatch on the bottom of the fuselage. I started to do it but not knowing the layout of the inside I got nervous about messing it up so gave up.

On your FX707 you have used an LE2204 motor so I have ordered one with a 12A ESC.
As usual none of the sellers give a full specification. They obviously all just copy the Readytosky site which itself doesn't give the shaft diameter. Elsewhere someone has given 3mm. Does this match your motor?
Until I am sure about this I can't order the prop. As I have lost a couple of props on the Slider & the Albatross doesn't have wheels I want to use a folding prop. I think you ended up with a 5x3. Aliexpress have some 6x3 and 6x4. Where did youget the 5x3? Was it just from your Aladdins Cave?

Looking at the Lipo, there is a 3S 850mAh Overlander which is a neat fit in the cockpit.
I see on one of your posts you have opened up the cockpit well but then had to wedge the battery in. If I only partly cut away the sides so the EPO held the battery plus some velcro underneath I would get some ventilation.
 

Magpie
Yes the LE2204 motor does have a 3mm shaft. It is quite long. I had to shorten mine to fit the folding prop with it spinner spinner.
The reason I opened out so much of the cockpit was simply I did not know what battery or ESC I was going to fit or where they might be required to obtain a good CG. As I was after the lightest possible plane using ballast was out of the question. 
An 850mAh 3s will give quite adequate power so if you are happy with its position it would make sense to hollow out the cockpit to specifically fit the battery.
I did originally flew mine with a fixed 6 x 3 prop. I soon fitted a similar 6 x 3 folder to both improve the glide and to reduce the chance of a breaking the prop or damaging the motor mount. So far this has proved to be the case.

My flapped XF707 conversion uses a 1500mAh 2s with a slightly bigger 6.3 x 3.3 folder. The battery is 17% heavier and the full power thrust is slightly lower but it is still quite adequate however it does of course give a significantly longer "cruise" duration. 32 minutes is the current record.

I understand that if you use a "normal" 28mm out runner its extra weight will preclude placing the battery in the cockpit hence the markings for a battery hatch on the underside although I felt such a large opening would do nothing for the fuselage strength & rigidity.     
. 
 

The Overlander 850mAh 3S is a nice fit width & depth wise in the cockpit well plus there is room to move it back & forward to help the CG.
When I first looked at hollowing out underneath the wing I also thought it would weaken the fuselage at that point but after a couple of squeezes I thought the plastic wing fixings would give it enough strength but then when I started I felt I was digging in the dark so had a change of mind.
So now I'm waiting for some CF rods & the LE2204 before I can do anything further.

My next questions are about adhesives for foamies, I think someone has just posted something so I'll follow that up.
There are various openings around the model, is it worth filling those in & if so what with?
There was something else but its gone now!

Magpie
As I was after the best possible glide performance I filled the channels on the underside of the wing with lightweight filler. The biggest "fill" was the V gap and the servo position on the inboard ailerons which I filled with bits of 6mm Depron carefully cut to fit.
 
I also added bits to the wing trailing edge to bring it down to 1mm rather than the 3mm as moulded.
As I did not test the wing "unfilled" beforehand I have indication whether any of the "filling" or trailing edge extensions actually improved the glide ratio by any measurable amount. The added wing area from the trailing edge extensions likely made the biggest difference. 

The question that got lost was about all the little burrs on the surface. Do I just sand them off with a fine sandpaper?

What do you recommend for painting? Will water-based acrylic be OK?
Do I need a sealer, like a variety of Modpodge?

I found your post on adhesives. It took some searching on ebay to find the correct colour, I'll order some this morning.

It appears we are not allowed to post EBay links so here's a pic.