Polyhedral DLG

[bracesport]

... so here we go again - my mate Pete has flown the new YODA and was impressed enough to order one - so I decided to build one!

Here is some progress - I plan to make a carbon fibre wing and fuse of my own design based on the BAMF wing and the YODA polyhedral - I have tracked down some carbo-weave cloth and am researching my hot wire options while getting the CAD done - the poly wing moves us from 4 servos to 6 servos, but we get the crow braking.

I took some pictures of my BAMF wing and researched the SYNERGY II wing foil making a modified version to suit my needs - my first try using 3D printed foil templates worked pretty well.

@thenated0g - I remember your hot wire trick with the wire on a pivot point - simple and effective!

it will be an interesting project.

 

[bracesport]

Some progress on the polyhedral jig - 8 deg outer panel, 3 deg inner panel - so far so good!

 

[bracesport]

given there will be aileron servos in the wing - how do we all feel about putting two more in the wing for the flaps - I know that means we will need nose ballast given we are not using the servos up front, but it would be easier to remove the wing - thoughts?

 

[Konrad]

As I recall there was a move towards the 4 servo wing in the distant past. But they went back to the dihedral and 2 servo wing for weight, drag and efficiency issues. But as you have a polyhedral wing I think a 4 servo wing is worth the hit for the added versatility. Also the X06 makes this much more practical

 

[Wayne]

Think you could have. single flap servo in the fuselage.

I'd love to see an F5K model with this layout.

 

[bracesport]

we Would loose full span ailerons, but maybe they are not needed with a poly wing?

 

[Konrad]

A rough rule of thumb is that the inner half of full span ailerons only contributes 15% to the rolling power. Proper polyhedral and rudder sizing can make a very effective turning model.
You will have to nail down what you are looking for as to roll control. But yes, I too would think that the weight saving (6 to 8 grams) from a single flap servo wouldn't be worth the loss of control flexibility.

 

[Wayne]

You could still have just 2 servos and some messy "Y" linkage with the servo out near the outer panels. Just saying.. At the weights of these planes, I really don't think Crow is needed. I just like the handling of a Poly. Kind of dig the look too.

 

[Konrad]

DJ Aerotech had a 4 panel Monarch aileron ship that used a "W" ABS insert (flex joiner) between the flaps and aileron panels. Effectively making these a single full span control surface.

 

[bracesport]

Chipping away on the new fuse moulds - basics are roughed out - now I will model the male and female moulds to print - the green section is the main mould, and given the wing has camber at the TE there is a undercut on the mould - I am planning to have the inner mould with a breakout section to allow the surface under the wing to release - the outer mould will be in two pieces to achieve its release - I am using the old pool cue again for the boom.

 

[bracesport]

At the moment I am leaning towards 6 servos simply because I like the idea of full control using Open TX - depending on the weight of the wing I will decide on four or two servos in the wing - four up front will be better for weight distribution, but four in the wing would be an easier build - can I build this under 270 with six servos... time will tell!

 

[bracesport]

Here are the male and female moulds for the main section of the fuse/boom - the internal parts can break inwards after the pool cue is first removed - the outer parts will easily split off the mould.

 

[bracesport]

The first prints are done for the internal fuse moulds - two of the tail end sections failed so I am reprinting them at the moment - nevertheless the parts all fit pretty well - once moulded the this slivers should be able to be prised out and then the top and bottom halves can be removed - this allows me to have undercuts (one of note is the heal of the wing as it seats against the back wall) - before moulding these pieces will be covered with a shrink film or cling wrap.

 

[Nigel]

I know it's going to be a DLG and everything... but I feel like this could be a really interesting F3K-similar ship (I think that's the right class). You could do an even lighter layup, and if you increased the wingspan to maybe 2.5M you could probably offset the weight of the 6 servos and power system. Having something that could thermal like a DLG with full glider mixing capabilities would be fun to explore.

 

[bracesport]

@Nigel - if the moulds work out OK I will make a couple of fuses - same for the wing, it would be easy enough to make a bigger one! I have made the fuse body a bit bigger than my last one - I am hoping it will give me a bit more 'landing' strength!

 

[bracesport]

I reprinted the end section and also the first outer mould - the outer mould has a split to allow for expansion and compression onto the wet carbon fibre.

 

[bracesport]

carbon braided tubes have arrived too!

 

[bracesport]

I finished the top and bottom outer moulds and everything seems to fit pretty well.

I have managed to find some 50mm polythene flat bags to use as shrink wraps (waiting on that before proceeding) - in the meantime I am recycling some 3K 5mm braided sleeve as tow - I also measured (roughly) my glass cloth @30 g/sqm, my 50mm braided sleeve @40 g/m, and my 25mm braided sleeve @20 g/m.

Carbon ship - 270g target - 68g fuse - 140g wing - 15g tail feathers - 32g 6 servos - 5g receiver - 10g battery

 

[bracesport]

@Doc James Hammond @Wayne @thenated0g @Konrad @Nigel - apart from the foam I have mostly what I need to build this puppy - any last advice welcome!

 

[Konrad]

You are in a different league with those 3D printed molds. I'm looking to you to learn a thing or two.

All the best,
Konrad