Flaps on poly-dihedral wings (simple soarer)

[clolsonus]

Or if you're like me and stubbornly back in the dark ages with no computer aided anything, do a flight and try to enter a high stabilized pattern for landing ( hands off everything except for turns) Play with flaps and trim there because you will have better 3 D references like light poles, trees, whatnot and you can actually see the results. The idea is practice your landings and see which settings make it go farther, since farther is the measure of efficiency. Finally, unless the stalls are non events, don't fiddle with any settings lower than maybe 10-20ft. This will make your landings even better.

Flying faster is not necessarily draggier and most people generally fly too slow. I still take my gliders to stall with up trim then add a couple three or more of down trim clicks until it sinks noticeably then back one up click.

If you rigged up some sort of telemetry altimeter, you could also just time a decent with a stop watch at different trim speeds and flap deployments (presuming fairly calm conditions.) It would still be tedious but you could probably start to work out the best configuration without getting too nerdy. But I agree with your main point ... with some experience, you can kind of just feel when a plane is in it's happy relaxed place ... doesn't have to work hard, but still fairly responsive. If you get there you are probably a click or two of trim from fairly optimal.

I'm not a drag expert, but there are two types, induced and parasitic. Parasitic drag increases with speed, and induced drag decreases with speed. Your speed for minimum sink will be different from the speed that gives you the best lift/drag (L/D) aka glide ratio.

From wikipedia:

Edit: I found this link and it seems pretty accessible. The subject matter is technical and complicated of course, but they definitely are trying to present the material in a way that doens't require a phd to understand, yet still covers the most important stuff in pretty good detail:

https://www.faa.gov/regulations_pol...s/aircraft/glider_handbook/media/gfh_ch03.pdf

 

[Piotrsko]

I used to know best rate formula, something like 1.3 times the stall speed, but that's useless without accurate airspeed.

Volkers et all talk endlessly about dynamic parameters that they can't accurately measure and obsess about wing profile measurements that they plot to have lumps. Hughes from the '70s says "Proper airfoils don't have lumps" . It's a nice warm fuzzy paper, but the best summary I got from it was where they determine flaps position on launch determines height achieved but imho, that wasn't relevant to duration which they didn't address. Would have been nice if they determined what profile they were looking at and shared that info, but recognize that data is relative to only their conditions.

 

[duckduckgoose]

If you rigged up some sort of telemetry altimeter, you could also just time a decent with a stop watch at different trim speeds and flap deployments (presuming fairly calm conditions.) It would still be tedious but you could probably start to work out the best configuration without getting too nerdy. But I agree with your main point ... with some experience, you can kind of just feel when a plane is in it's happy relaxed place ... doesn't have to work hard, but still fairly responsive. If you get there you are probably a click or two of trim from fairly optimal.

I'm not a drag expert, but there are two types, induced and parasitic. Parasitic drag increases with speed, and induced drag decreases with speed. Your speed for minimum sink will be different from the speed that gives you the best lift/drag (L/D) aka glide ratio.

From wikipedia:

View attachment 196290

Edit: I found this link and it seems pretty accessible. The subject matter is technical and complicated of course, but they definitely are trying to present the material in a way that doens't require a phd to understand, yet still covers the most important stuff in pretty good detail:

https://www.faa.gov/regulations_pol...s/aircraft/glider_handbook/media/gfh_ch03.pdf

Fantastic. Exactly what I need, I am more of a visual cause and effect learner so thatgraph makes a lot of sense (as a general understanding). I tried a glide again today in similar conditions (thee was a very slight breeze) without using flaps and the results were ever so slightly better. I think I possibly could go longer because the breeze kicked up slightly towards the end of the flight. My guess is that the planes 'sweet spot' is at a quite low velocity, so the parasitic drag isn't as obvious but the lifting drag is probably losing me some altitude. I'm currently building a longer (2.4m) wing and I might not bother with flaps for the 1st flight.

 

[duckduckgoose]

Just smashed my previous record of 9 mins 33 scs with a 19 mins 49 sec glide! Unbelievable, I suspect a thermal was at play because there was an eagle hanging around doing the same, but it is totally clear to me now how much drag the flaps add. Thanks to everyone and their advice, im super pleased with this plane!

 

[Piotrsko]

You'll know you're in a thermal when the tail comes up or the nose drops , but you dont sink

 

[duckduckgoose]

You'll know you're in a thermal when the tail comes up or the nose drops , but you dont sink

Yeah ok. I maidened the 2.4m wing today (no flaps) and managed a 20:25 min glide from a starting altitude of probably 2/3 of the usual starting altitude. It actually GAINED altitude so I must have been in a thermal (I was too high to properly gauge the orientation of the nose). Then as it began drifting too far away from me (in big lazy circles) , I gently steered it back and it was like the spell was broken and it began slowly losing altitude again. This has opened the door of possibilities I thought I couldn't achieve with foamboard.

 

[danskis]

How, excellent!!! - It's time to put your name and phone number on it! Invasion stripes on the bottom of the wings and a bright color on the nose will help orientation.

 

[duckduckgoose]

How, excellent!!! - It's time to put your name and phone number on it! Invasion stripes on the bottom of the wings and a bright color on the nose will help orientation.

Haha yeah definitely need some stripes, although at a certain point it just turns into a silhouette. Might put a small fpv cam onboard. I live in the Australian outback so if I lose it, it's a gonner.

 

[Piotrsko]

. I live in the Australian outback so if I lose it, it's a tonner.

Two quick comments: #1:. Old full-size glider rule.. if it isn't going up the air is probably going down except on no lift dead calm days.

#2 that is why I said spoilers were worth their weight in money.

Oh and thermals cycle off the source. If you can stay put you may catch the next one before you need to land.

 

[quorneng]

duckduckgoose
The air in even a weak thermal rises at 2 or 3 ft/sec which is likely to be at least equal to a light model glider's sink rate.
Even if you just fly straight across a thermal you are likely not to loose any height and will gain some if the thermal is reasonably strong.
The trick of course is to judge where the thermal is and to circle keeping within it. Not easy as the air tends to rise fastest at the centre so it will tend to "spit you out".
You don't actually want to be able to fly fast in a thermal in fact the slower the better but remember everywhere there is thermal activity there will also be areas of sink as the rising air draws down the cooler air . You can find any height gained can be just a quickly lost. This is where the 'speed' performance of a glider pays dividends to get you to the next thermal as fast as you can without loosing to much height.

 

[duckduckgoose]

duckduckgoose
The air in even a weak thermal rises at 2 or 3 ft/sec which is likely to be at least equal to a light model glider's sink rate.
Even if you just fly straight across a thermal you are likely not to loose any height and will gain some if the thermal is reasonably strong.
The trick of course is to judge where the thermal is and to circle keeping within it. Not easy as the air tends to rise fastest at the centre so it will tend to "spit you out".
You don't actually want to be able to fly fast in a thermal in fact the slower the better but remember everywhere there is thermal activity there will also be areas of sink as the rising air draws down the cooler air . You can find any height gained can be just a quickly lost. This is where the 'speed' performance of a glider pays dividends to get you to the next thermal as fast as you can without loosing to much height.

Looks like I need an onboard fpv cam with altimeter on the osd so I can tell when I've found one.

 

[clolsonus]

Looks like I need an onboard fpv cam with altimeter on the osd so I can tell when I've found one.

I think (but I don't know for sure) that frsky offers an altimeter telemetry module and the transmitter can beep at you like a variometer to tell you if you are in sink or lift. Someday I'd like to learn more about soaring ... in the warmer months we definitely get thermals around here. But mostly I just find the sinks so my few tries so far have been pretty unrewarding.

 

[Piotrsko]

I think (but I don't know for sure) that frsky offers an altimeter telemetry module and the transmitter can beep at you like a variometer to tell you if you are in sink or lift. Someday I'd like to learn more about soaring ... in the warmer months we definitely get thermals around here. But mostly I just find the sinks so my few tries so far have been pretty unrewarding.

Pay attention to when it looks like it's going up and match those conditions. I have flown thermal for maybe 40 years before we had telemetry, so I know its possible. Heck i flew thermal before I had RC equipment (can you say Jetco thermic?) and that bittersweet moment knowing you hooked a big one and that was probably the last time you'd see that plane ever again.

 

[duckduckgoose]

Pay attention to when it looks like it's going up and match those conditions. I have flown thermal for maybe 40 years before we had telemetry, so I know its possible. Heck i flew thermal before I had RC equipment (can you say Jetco thermic?) and that bittersweet moment knowing you hooked a big one and that was probably the last time you'd see that plane ever again.

Yeah, i'm pretty fortunate to live out on a rural property, with some good open fields, so in the middle of a warm still day id say there would have to be some thermals (although we are now just heading towards winter), but i really need to go and do some research on them. i never worried about them before now. do they get stronger up higher?

 

[Piotrsko]

On a proper adiabiatic day, as the surrounding air gets cooler, they get better. Not sure how, technically, but they expand and the rate goes up a bit.

You get small thermals even in the winter on calmer sunny days, AND, I have been known to fly the A/C exhaust on the local school gym. A friend noticed once that in farm country, if you can smell the pasture it's a good day for thermals

 

[OlliePackman]

Flaps should work just fine on it. I believe @OlliePackman put flaps on his.

I did indeed! 👍Works great.

 

[duckduckgoose]

I did indeed! 👍Works great. View attachment 196563 View attachment 196563 View attachment 196563 View attachment 196563 View attachment 196564 View attachment 196565

That is one good looking soarer!