Re: Perfect Pitch ... WTF
Posted: 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.
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.
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.
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/
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.
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.
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/