Wright Stuff C

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klastyioer
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Re: Wright Stuff C

Post by klastyioer »

thanks sm bjt
it's not about the medals; go out there and have fun. make progress, learn a few things and have one heck of a time; that's all that matters.

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Re: Wright Stuff C

Post by bjt4888 »

K,

Also, in Hip Pocket Aerodynamics under Indoor/F1D,F1L, etc., you will find threads like “P/D Ratio” and propeller design with contributions from the experts of the day.

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Re: Wright Stuff C

Post by klastyioer »

thanks again bjt

this is gonna sound like the dumbest question ever but what does moving the cg foward and backward from the planes cg without a ballast do
my old coach always taught me to try to move it up but i never understood why
and with wooden props that gives more weight for the ballast, but idk what to do with the cg since one of our planes has so much ballast weight
it's not about the medals; go out there and have fun. make progress, learn a few things and have one heck of a time; that's all that matters.

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Re: Wright Stuff C

Post by bjt4888 »

K,

More rearward CG generally allows less decalage angle which can reduce drag and reduce climb rate. However, more rearward CG reduces static stability margin (pitch stability) which means the airplane is not as good at recovering from upsets like bad air or ceiling hits.

Usually, I pick a safe stability margin between 15% and 20% as a starting point and then try more extreme trim after getting this safe trim to fly well. However, the tandem design allowed by this year’s rules makes this extreme testing a little different. So, the bottom line is to try a lot of trim combinations and let the stopwatch decide.

And, of course, propeller and rubber are the most important factors, with trim following. Lots of variables this year.

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Re: Wright Stuff C

Post by Rossyspsce »

besides too low density being too flimsy and high density too heavy or stiff during forming, what are the effects of density of wood used for wood props?

Also, how do others make forms for props?
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klastyioer
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Re: Wright Stuff C

Post by klastyioer »

Rossyspsce wrote:besides too low density being too flimsy and high density too heavy or stiff during forming, what are the effects of density of wood used for wood props?

Also, how do others make forms for props?
idk how to answer your first question
but i form mine on metal coffee containers so cylinder props cause i mean they function well for our purposes and theyre easiest to make that way
you just set your angle on a str8 line to 15-20 degrees to the left and rest your blades along the angle line bake around 200 degrees for like 8 mins or so but i do mine in a toaster oven cause im lazy for like 12 mins and you take it out and rest
i dont use rubber bands to hold them down but i use masking tape just make sure its good tape cause otherwise the adhesive will soak into your blades and leave a sticky residue
i might start prop blocks soon but we will see when the time comes
it's not about the medals; go out there and have fun. make progress, learn a few things and have one heck of a time; that's all that matters.

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Re: Wright Stuff C

Post by bjt4888 »

Rossy,

Lower density wood may be to fragile for a hard landing and will also flare a little. 7 to 8 lb cu ft 1/32” thick wood would probably be best; c-grain, if you can get it.

I’ve made my own prop forms using a method similar to that found in the Hobby Shopper EZB article.

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Re: Wright Stuff C

Post by coachchuckaahs »

We were fortunate enough to buy some C-grain contest grade from Sig in the fall. In the old days, "Contest" meant 4-6 pound, now it is 4-8# at Sig. Our 1/32" came in at about 7#, but for SO this is just fine.

We form our blades on a prop block, though we have used conical bowls and cylinders in the past. We simply wet the blade briefly, wrap on the form with a cover of some scrap 1/16" (also wet), and microwave for 4 minutes on level 4 (your micro may vary). This steams the blades to shape.

With the heavy weight of SO planes this year, the stock 1/32 7# wood was more than adequate. For LPP we sanded to 0.025" thickness, but this is just not needed on SO.

Unfortunately, Sig had a fire last winter, and they are currently out of C-grain and lightweight 1/32 and 1/16. No ETA. National will sell you lightweight but will not do grain selection. Easy Built Models is all out of Contest weight (4-6#) C grain, though they have some 6-8# in 1/20th and 1/16, not in 1/32. Probably still good for SO. Note the sheet sizes are small too (18"). Specialized will cut to order, including weight and grain. But, 100% surcharge for grain, and 100% for weight.

All that said, go to your local hobby shop and look through their bins. Note that I mean "look" with a scale. Much of the Midwest wood will be 10-15#, but you can sometimes find a gem. Prioritize C grain over weight for props for SO.

For SO, you have so much weight budget, you can probably make prop blades from 10# wood without messing things up. Just move your clay back to compensate. The planes this year are building up around 6g, so adding half a gram at the prop means you still have 1.5g ballast.

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Nationals Results:
2016 C WS 8th place
2018 B WS 2nd place
2018 C Heli Champion
2019 B ELG 3rd place
2019 C WS Champion
AMA Results: 3 AAHS members qualify for US Jr Team in F1D, 4 new youth senior records
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Re: Wright Stuff C

Post by Rossyspsce »

For coach chuck: did you guys build co-axial helis from scratch or from kit two years ago?
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Re: Wright Stuff C

Post by coachchuckaahs »

From scratch. Unfortunately, that year our high school kids did not make nationals.

We have not done any kits, as our regionals are in January. We stay flying right after the rules come out.

Coach Chuck
Coach, Albuquerque Area Home Schoolers Flying Events
Nationals Results:
2016 C WS 8th place
2018 B WS 2nd place
2018 C Heli Champion
2019 B ELG 3rd place
2019 C WS Champion
AMA Results: 3 AAHS members qualify for US Jr Team in F1D, 4 new youth senior records
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