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bracesport DLG v3

bracesport

Well-known member
#1
I decided to move this DLG from the 'homage to Flyboa' as it is starting to move away from the intent of that thread - this version is more in the style of a production DLG that can handle launch stresses but is made on a budget - if that is possible! :D

Specifications
Wing 1.5m - 13 deg dihedral - foam board core - carbon tow skin - sine wave spar.
Wing foil - modified AG03 - flat bottomed foil (easier to make without bagging).
Fuse - 1 piece - carbon braid over foam - remove foam after moulding.
Tail - bottom mounted (for better pull string control at launch).
Tail construction - hollow - carbon tow - 3D printed mould Experimental).
Servos - 3ch - in fuse aeleron and elevator servos.

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bracesport

Well-known member
#2
The foam is cut ready for sanding (after the Coronavirus lockdown) - I made the foam blank in two parts over a 5mm bright steel rod to help keep the fuse straight during the sanding and moulding process - I 3D printed a light wing saddle that has nuts pre-inserted - once sanded I will pull a carbon braided sock over the fuse and wrap it with clingfilm during moulding - it is similar to what they do when making fishing rods - I will 3D print an external former to press in the wing mount area which is a negative indentation of 13deg. :D

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bracesport

Well-known member
#4
Wing construction - firstly I wanted to build a full carbon DLG - it sounds complex, but I think it should be as easy as fibreglass, but a tad stronger - the construction has been rattling around in my head for a while and is not fully formed, but essentially I will attempt a one-piece wing with included dihedral.

What is a sine wave spar - in simple terms it is a vertical spar section that tracks along the wing in the shape of a sine wave - when the top and bottom skins meet the spar it forms a strong and light spar - well that is the principle anyway!

my plan is to use the same handheld hot wire technique I used on my other DLG wings which actually creates a quite a nice foil.

1- I need to make a dihedral jig at 13deg and about 20cm wide.
2- I will first cut four blanks from FB (slightly oversize in the TE) and join one set at the dihedral (paper removed) and hand sand the underside LE into the wing.
3- then I will epoxy the underside CF skin of the wing on the upside-down jig (with an extra CF strip along the spar line).
4- after that, I will lay the wing into the jig right side up and hotwire the TE.
5- having the CF on the bottom surface will allow the hot wide to cut more easily at this point.
6- then I will hotwire the top blanks individually and laminate them to the main wing.
7- I will pre-form the spar between foam board that will be hotwire cut into the sine wave shape and protected with packing tape to prevent sticking to the foamboard while curing.
8- once cured the spar will be inserted into a sine wave shape slot down the wing and epoxied into place.
9- once cured and sanded back to the top surface of the wing I will sand the TE back to the underside skin of the wing and add the top CF skin.

well thats the plan anyway!

In reality, there will be more steps! :D
 
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Wildthing

Well-known member
#5
Wing construction - firstly I wanted to build a full carbon DLG - it sounds complex, but I think it should be as easy as fibreglass, but a tad stronger - the construction has been rattling around in my head for a while and is not fully formed, but essentially I will attempt a one-piece wing with included dihedral.

What is a sine wave spar - in simple terms it is a vertical spar section that tracks along the wing in the shape of a sine wave - when the top and bottom skins meet the spar it forms a strong and light spar - well that is the principle anyway!

my plan is to use the same handheld hot wire technique I used on my other DLG wings which actually creates a quite a nice foil - I need to make a dihedral jig at 13deg and about 20cm wide - I will first cut four blanks from FB (slightly oversize in the TE) and join one set at the dihedral (paper removed) and hand sand the underside LE into the wing - then I will epoxy the underside CF skin of the wing on the upside-down jig (with an extra CF strip along the spar line) - after that, I will lay the wing into the jig right side up and hotwire the TE - having the CF on the bottom surface will allow the hot wide to cut more easily at this point - then I will hotwire the top blanks individually and laminate them to the main wing - I will pre-form the spar between foam board that will be hotwire cut into the sine wave shape and protected with packing tape to prevent sticking to the foamboard while curing - once cured the spar will be inserted into a sine wave shape slot down the wing and epoxied into place - once cured and sanded back to the top surface of the wing I will sand the TE back to the underside skin of the wing and add the top CF skin - well thats the plan anyway!

In reality, there will be more steps! :D
You done yet?
 

bracesport

Well-known member
#8
my last foam wing with paper mache weighed 115g - so I think the Carbon version should be lighter and stiffer if I keep the epoxy light - I have some carbon tow fabric that is 0.8k (80g/sqm) and I have been told to pre-impregnate the carbon between two sheets of plastic using a roller to push out the excess epoxy.

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