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        Question Foil for 60" DS plank wooden wonder

#1 taurineman Oct 12, 2012 02:08 AM

Foil for 60" DS plank wooden wonder
I was thinking of making a wing of solid Pauliwonia and then bagging it in glass, and I thought I would canvas some opinion on which foil I should use. First, my design brief:
- it will be a plank with semi-fuz, similar in planform to a Reaper.
- it will be 60"
- It will be made from two 30" pieces of Pauliwonia wood hand-planed into shape - so it can't have any real concave shapes (I realise self-stable foils require a reflexed trailing edge, and thus a transition from convex to concave on the top of the foil - but I will have to add the reflex with full-span elevons trimmed up a bit).
- Yes, i'm mad
- I don't need this thing to break records, i'm a relative newbie to DSing, but not to sailplanes. It needs to simple to set up and balance, be stable and can DS well enough to have good fun in 20-40 knots of wind, and track well.
- I guesstimate the AUW to be around 1.5-2Kgs.
- it will not be internally ballastable.
- I will run standard servos in it.
- the wood blank im starting with is 25mm/1" thick.
- be bloody tough!

What should I use?

#2 prodjx Oct 12, 2012 08:28 AM

If you can put some sand paper on a pipe you can get reflex in your solid wood wing. I did one of my first one's and it was an E-214 which has camber. This wing was for a glide recon that was eventually dropped from an F-15. The wing I built was for a 200% proof of concept and was flown as a sloper. The wing's were solid balsa. I used 3 carpenter's levels to get the shape . 2 to support the balsa and the third had rough sand paper on one flat and finer grit on the other. I did rough shape it using a 13 degree plane.

#3 prodjx Oct 12, 2012 08:30 AM

Oh I also had aluminum templates glued to each end and the edge's of the templates were Majic Markered so I would know when I was getting close with the rough sand paper.

#4 rothlisburger Oct 12, 2012 02:58 PM

If you're good enough at woodworking to have a sharp hand plane, you should be able to work a scraper. You can get curved ones to handle reflex curvature.



#5 josh18 Oct 12, 2012 05:10 PM

That plank sounds great! I agree with the others- use a proven plank airfoil like a pw 51 and work out some way to get the concave shape into it. I can imagine it will be pretty heavy though, with plank foils being on the fatter side. Good luck with it, it will be worth the work because the finished product will be almost bullet proof!

#6 taurineman Oct 12, 2012 06:17 PM

I'm a qualified cabinet maker - but haven't been in the trade for many years. So working with wood is 2nd nature - I just don't have to machine tools anymore :(

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#7 taurineman Oct 13, 2012 03:20 AM

I got one vote for the PW51 - any others?

I like the idea of a pipe with sand paper to get the concave on the top.

#8 ALEX HEWSON Oct 13, 2012 05:30 PM

My RT30 and RT28 were PW51, RT42 is PW98

I felt the 51 had better handling and nicer flying

#9 ReaperRob Oct 13, 2012 07:17 PM

Your plan sounds good. Have you seen this thread:


Might have some useful ideas for you.

#10 timbuck Oct 13, 2012 10:29 PM


Originally Posted by ALEX HEWSON (Post 22992614)
My RT30 and RT28 were PW51, RT42 is PW98

I felt the 51 had better handling and nicer flying

I agree with Alex.
The 51 is a good alrounder , frontside sloper and dser. Fly's well inverted and is good for turning.

The 98 is faster at low CL range , and doesn't like to be inverted.

Go the 51..:)

#11 taurineman Oct 15, 2012 03:20 AM

Ok, done - PW51 it is. Anyone got the co-ords file? What app do people use (free) to print out profiles to make the templates?

I have profile-22 and I have a 10% PW51 file not the original. What % is the original?

Also, I assume there is no wash-out on a plank of this sort?

#12 ALEX HEWSON Oct 15, 2012 03:25 AM

Use the search tool at the top. It is in a couple of places on RC Groups

#13 timbuck Oct 15, 2012 06:03 AM

Original is about 8.5%...just thin the one you have.

#14 BMtech Oct 16, 2012 05:06 AM

1 Attachment(s)
Take it down to 7.5% if the root cord is more than 250 mm & leave it at 8.5% for the tip

I have this on good authority;)

Here you go


#15 taurineman Oct 18, 2012 04:06 AM

Thanks guys. I will need to work it all out proper now :) Root chord of a 60" reaper is about 230mm, so I think it will be 8.5% the whole way.

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