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Perfect Pitch ... WTF

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DartBoard
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Re: Perfect Pitch ... WTF

Postby DartBoard » Thu Jan 19, 2017 4:51 am

Here's the wing straight out of the vac bag. The leading edge didn't need any touching other than to clean it up with 400 grit.

Image

Because I wanted to get the foil section as close to the 63-412 outline I made the wing in 3 sections. Each half wing had the foil section traced on it and I sanded just the root and tips down as close to the outline as I could.

Image

Because the wing does not have any compound curves in it, just straight lines it was easy to use a belt sander mounted upside down to sand the rest of the material away. The completed ends can be used like guides and you are only ever sanding straight sections, no difficult curves so its easier to make it accurate.

I cut 30mm wide section for middle with the sides cut with the right anhedral angle on them ( used a drop saw so that the angle on both sides would be identical) and then 5 min epoxy glued the pieces together.

Image

Although the wood was hardwood ( yep, from bunnings) I selected a very low density piece. Its much more like the typical density of Paulownia (so easy to sand) and so its role is less about providing strength than it is about providing shape. I built it up to about 2.5mm of glass ( 6 x 10oz each layer of glass being about 0.4 mm). Hit a reef with it first session ( go me!!) and it laughed it off.

There was less than an hours work in getting it ready to glass and so I'm going to make a few wings with different foil sections and see how different they feel. Maybe a thinner one.

BTW I came across a really useful bit of free ware for generating NACA foils.

http://tracfoil.com/

DartBoard
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Style: Surf Foil
Gear: RPMs, Switch, Homemade TT, Homemade Foils
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Re: Perfect Pitch ... WTF

Postby DartBoard » Mon Jan 30, 2017 9:33 am

Very happy to report that I managed to solve the mystery of the high pitch noise that the new wing set was causing. I tried a couple of things ( sanding with finer grit paper and squaring off the trailing edge) and it reduced the noise a small amount. But as I looked much closer at the stabiliser I realised that there was a very slight twist in it. It was about 2-3mm difference in the height of the trailing edge tips. I swapped the stabiliser for the one off my original foil which was about the same area ( slightly smaller) but with more sweep in the leading edge. Problem solved. No noise!!! Obviously the twist was enough to set the rest of the kit vibrating. The pitch was very high even though my speed was very modest so maybe there was some resonance going on as well. Happy days!!!

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NYKiter
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Re: Perfect Pitch ... WTF

Postby NYKiter » Mon Feb 20, 2017 1:00 pm

Is this a 1" square alum fuselage? can you explain why you went with these dimensions if true?

DartBoard
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Style: Surf Foil
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Re: Perfect Pitch ... WTF

Postby DartBoard » Thu Feb 23, 2017 10:28 pm

Hi,
It's 20mm square 6061 T5. My first fuselage was 1" square but it felt like overkill. I just wanted try smaller for the sake of weight and although I was hoping to get T6 temper my local supplier didn't have and could track any down.

The risk was it may bend but after a lot of use and few big hits no damage. Any smaller and I was worried that I'd weaken it too much around where i drilled the holes for connecting it to the strut.

Cheers

max
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Re: Perfect Pitch ... WTF

Postby max » Thu Feb 23, 2017 11:12 pm

DartBoard wrote:Hi,
It's 20mm square 6061 T5. My first fuselage was 1" square but it felt like overkill. I just wanted try smaller for the sake of weight and although I was hoping to get T6 temper my local supplier didn't have and could track any down.

The risk was it may bend but after a lot of use and few big hits no damage. Any smaller and I was worried that I'd weaken it too much around where i drilled the holes for connecting it to the strut.

Cheers
Where did you get the aluminium from? Not Bunnings :)

DartBoard
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Re: Perfect Pitch ... WTF

Postby DartBoard » Sat Feb 25, 2017 8:14 am

:) no. Next door to Bunnings!

Lev737
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Re: Perfect Pitch ... WTF

Postby Lev737 » Wed Mar 22, 2017 11:54 pm

DartBoard wrote:
Tue Jan 17, 2017 1:59 am
Finally got to tune my new wing/fuselage yesterday. I was amazed to find that changing the AoA on the rear wing from zero to - 3 degrees was transformative. All of a sudden it was so stable I could ride with my feet together and even switch my feet while up on the plane, something that I was never able to do on the old one. Stoked to say the least.

Setup is 550mm span, 600cm2 area, AR 4.9, NACA 63-412 (moth) foil section, hardwood core and 5 layers of 10 oz stiched e-glass. 43 cm between TE of wing and LE of tail plane. 20x20mm 6061 T5 aluminium fuselage. Zero degrees of front wing and -3 on the tailplane. All bolts at M6.

Image

Its not a canard design, it just has a straight leading edge so that I could wrap the LE and have the glass joint at the trailing edge. My previous wing had the join at the leading edge and in the course of shaping I thinned it too much and after a hitting a few sand banks it split along the join and eventually failed.

One problem it has picked up is a high pitch ringing at intermediate speeds. The noise goes away when edging hard and higher speeds. I'm using it on my existing strut and with the old wing/fuse there is no noise so its something related to the new wing/fuse set. I find it pretty unnerving because the sound is right in the key of Tiger Shark so I'm keen to make it stop. Any suggestions on the cause or things to try to work out the source of the ringing ?


Thanks
Matt
Hello DartBoard !
Thanks for sharing your experience..
What about the stab's size?
Span, area(S),AR ?
Cheers,
Lev :jump:

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rogerm
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Location: Switzerland

Re: Perfect Pitch ... WTF

Postby rogerm » Mon Mar 27, 2017 2:08 pm

DartBoard wrote:
Thu Feb 23, 2017 10:28 pm
Hi,
It's 20mm square 6061 T5. My first fuselage was 1" square but it felt like overkill. I just wanted try smaller for the sake of weight and although I was hoping to get T6 temper my local supplier didn't have and could track any down.

The risk was it may bend but after a lot of use and few big hits no damage. Any smaller and I was worried that I'd weaken it too much around where i drilled the holes for connecting it to the strut.

Cheers
Hi folks
I made my fuselage out of Aluminium 25/15 mm and it seems to be strong enough. I weigh only 60 kg :)
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bisdremis
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Re: Perfect Pitch ... WTF

Postby bisdremis » Sun Jul 09, 2017 9:28 am

NICE work ! Did you embed any tail fin angle to your fuselage or you gona shim it later on? how much it weights?

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tegirinenashi
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Re: Perfect Pitch ... WTF

Postby tegirinenashi » Tue Jul 11, 2017 9:41 pm

I just can't help comparing it with LF Happy/Rocket foil. The later features the same fuselage height (25mm) but it is 30 mm wide. The weight come as 1.2 kg. Granted LF is almost round, so not exactly twice the weight of rogerm's design, but I would expect 25 x 15 would be around 700 grams. As for me, I'm certainly tempted to grind/cut off the sides of LF, especially at the tail section (which bears less load). Any suggestion of the tool to make it clean job?


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