Why 1.5 meters? - Page 2 - RC Groups
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Jan 02, 2018, 02:18 PM
1 revolution and throw!
Quote:
Originally Posted by Thermaln2
Jon,

The comment that a 2M will launch lower has a bit of tunnel vision in it. The extra .5M probably won't make as much difference as you expect. The added weigh would be relatively insignificant but the AR would give quite a bit more in performance. So I have to really disagree. If HLG/DLG had be allowed to evolve as it was really trending in the day, that is the only limitation being that it had to be hand launched, we might see planes that are quire different than we have today.

As for smaller, one had to look at the intent of the designs, not their performance in comparisons. Often spans and weight are imposed to just get people to compete, and sometimes it is to remove the expense. Obviously that is not the case in our DLGs, but in freeflight contests, look at pennyplanes, EasyB as opposed to the f!ds.
Have you seen or tried it? i've seen both 2m and 2.5m dlg thrown by f3k pilots and the way you rotate to throw it is totally diffrent , especially the 2.5meter glider launched very low , somewhere around 20meter i think it was , while the same guy launches a 1.5m dlg to 70m+
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Jan 02, 2018, 02:19 PM
God Created me to Create
The_Builder's Avatar
Quote:
Originally Posted by jfinch
Seems odd to me to say competition is the reason DLGs are 1.5 m and at the same breath mention smaller planes. Nothing in the rules exclude a plane with a smaller span than 1.5 m. You could compete at the next F3K contest with a 10" javelin launched plane if you want.

I agree with Tim (and Kristoff).
How is that odd, A larger plane has an advantage and 1.5M is the largest size allowed. That equation seems pretty simple to me, nothing odd about that at all. A 1.75M or a 2M plane would not be allowed so the rules do indeed limit the planes to 1.5M. True the rules do not say a smaller plane cannot be flown but as a few of the folks on have said, why would someone spend all the time and money to attend an event to fly a 1M plane.

I mentioned the smaller planes to point out there are other sized DLG's but they will not been seen in competition very often. Once again, the rules dictate that 1.5m is the largest wing span allowed so that is the size people will fly because they can stay up longer than the smaller planes.

The past two years I have flown the same event and flown a smaller plane. Had a ball but was not really there to compete at all. I was there to have a good time, laugh with some friends and maybe even fly some toy airplanes. If was there to compete I would have flow a larger plane, something more akin to the maximum size the rules allow.

If you notice the rules keep coming up as to why the planes are 1.5m, nothing odd. It seems pretty simple to me, FAI makes the rules and anyone who is into competition flies a plane, within those rules, that will give them the best chance of winning.

However if a person has no interest in flying an FAI sanctioned event they could fly whatever sized DLG they wanted.

See, No rules, No size restrictions.....Rules, Size restrictions.
Jan 02, 2018, 02:26 PM
God Created me to Create
The_Builder's Avatar
Quote:
Originally Posted by krikkens
Have you seen or tried it? i've seen both 2m and 2.5m dlg thrown by f3k pilots and the way you rotate to throw it is totally diffrent , especially the 2.5meter glider launched very low , somewhere around 20meter i think it was , while the same guy launches a 1.5m dlg to 70m+
I am a mere 5'8" on a good day and I could not imagine spin launching a 2.5M.. That had to be something to behold.
I have some 2m wings in the shop for a different project and even they look huge to me but I primarily fly 1M when it comes to DLG's.

I bet both a 2M and 2.5M DLG would be fun to fly.
Jan 02, 2018, 02:30 PM
Registered User
I've been throwing a BAMF at around 224g's and it is so easy to launch at that weight that I'm having to alter my throw to get some power into it.
So I would say that there is room for more span as far as weight goes.
I have no aerodynamic design experience but cannot help wondering what a 1650mm or 1700mm BAMF might fly like.

But as others have said, it could never be used in competition so why would Thomas bother to design and test slightly larger spans.

Paul.
Jan 02, 2018, 02:41 PM
Registered User
I wonder what might be achieved if the rule was altered from 1500mm to 1800mm (even 1700mm)?

Could we see a 1800mm plane that both outlaunched and out flew a 1500mm plane?

Could be an interesting new adventure.

Paul.
Jan 02, 2018, 03:17 PM
Oleg Golovidov
olgol's Avatar
It would be great to see an 'unlimited' hand launch class.
For most (all?) other soaring classes, a bigger span is always an advantage.
For hand launch, at certain size the launch starts to be affected, and going to a larger wing span will not help. So (for a given pilot height and strength!) there will be an optimum wing span where the launch is still near the maximum potential, and the increased span would help with the glide performance (a lot!). This unfortunately means that taller and stronger pilots would get an even greater advantage over smaller ones, by using a larger span model
I imagine we would probably develop different launch techniques. Like maybe spinning twice before release, to get to a much higher speed.
Just interesting to think about what could come out of it.
Jan 02, 2018, 03:39 PM
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The_Builder's Avatar
Quote:
Originally Posted by olgol
It would be great to see an 'unlimited' hand launch class.
For most (all?) other soaring classes, a bigger span is always an advantage.
For hand launch, at certain size the launch starts to be affected, and going to a larger wing span will not help. So (for a given pilot height and strength!) there will be an optimum wing span where the launch is still near the maximum potential, and the increased span would help with the glide performance (a lot!). This unfortunately means that taller and stronger pilots would get an even greater advantage over smaller ones, by using a larger span model
I imagine we would probably develop different launch techniques. Like maybe spinning twice before release, to get to a much higher speed.
Just interesting to think about what could come out of it.
They already out launch the average guy by 50' so it may not make much difference at the end of the day....LOL, LOL The top 10 guys are always flying against the top 10 guys.

As a whole this all sounds like it would be fun. I also agree with you Oleg, 100% about there being an ideal size plane for each pilot.
Jan 02, 2018, 03:50 PM
Registered User
Thanks Oleg, thanks Paul.
Hadn't really thought about the taller guy advantage thing.
I'm only a short-arse ( 5'8 or so), would be interesting though to see at what span things really get tricky on launch.

Paul
Jan 02, 2018, 04:33 PM
New at this whole life thing
Cfiimei's Avatar
I think it would be awesome to have an open class in F3K where there are no size restrictions at all. I wonder what would eventually dominate... not sure what that would be, but bet it is not 1.5...
Jan 02, 2018, 06:01 PM
1 revolution and throw!
Quote:
Originally Posted by Cfiimei
I think it would be awesome to have an open class in F3K where there are no size restrictions at all. I wonder what would eventually dominate... not sure what that would be, but bet it is not 1.5...
i'm pretty sure it would be close to 1.5meter ! like Oleg described above one can match the span to the pilot but the optimum would not make huge diffrences i think, like between 1.4 and 1.6 meter maybe?) this would mean half of the pilots can go with the optimum span as per rules now

if you need to make 2 turns to get at least a bit of a descent launcheight you are screwed against todays good pilots in a turnaround task with normal 1.5m dlg .

i strongly doubt anyone could launch a +1.5m dlg higher then a 1.5m dlg bt i'm pretty sure some would launch a -1.5m dlg higher then a 1.5m dlg....
Jan 02, 2018, 08:07 PM
ThomasLee's Avatar
Quote:
Originally Posted by pabloh
I'm only a short-arse ( 5'8 or so)

Paul
I'm 5'7

I did fly several contests with a 1m in 2017 though, got silver in two contests, 95% at The Bruce, and I forget what % in Japan. Not everyone goes to contests to get gold, for me I go have fun, socialize, have a few drinks with everyone, and show off my new designs... it doesn't matter what span I fly (as long as it's within rules) to meet all 4 'requirements'.
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Jan 02, 2018, 08:30 PM
A reluctant beekeeper ...
Tower_City_Woody's Avatar
Quote:
Originally Posted by Thermaln2
.... we lost out on a lot of experimentation and aerodynamic advances because rules were imposed. ....
Personally, I see two sides of rules - they stymie and encourage experimentation and advances at the exact same time.

Woody
Jan 03, 2018, 01:18 AM
Registered User
I can see how someone stronger could throw higher, but how so for a taller person?
Jan 03, 2018, 01:42 AM
Adam
xStatiCa's Avatar
Longer arms maybe... Oh... and they gain a few inches higher off the ground
Jan 03, 2018, 02:33 AM
In F3J size does matter!
roydor's Avatar
It all depends on the rules and conditions. If you need to fly the same taskes and the weather is good, a 1.5 m model would allow you to make full times so a bigger model would not give any advantage. If the conditions are not as favorable, a model with better performance will be more important and here lies the big question, what is the correct balance between launch height and performance?
Iím assuming it has a lot to do with the achievable height which a function of physical ability of the thrower. If you get 20% more L/D but 20% Less height I would still favor the height over the performance. If you traded 10% less height for 20% more L/D I would prefer the L/D. So it really matters the balance.
I expect models with grater span would be designed with very narrow wings so to get more height and reduce the drag at the outer tip during the spin which would translate to altitude. This introduces some structural challenges and may limit the amount of performance gain by keeping the Reynolds from growing much where they can do good. Maximum launched mass would not grow as it seems it is a physical limitation which supports the assumption that narrow, low area, high aspect wings would be favorable for a wider range of conditions (ballasted wing loadings canít go down by much).

I think for most pilots, around 1.5 m would stay the optimum, maybe grow to 1.6 but not much over. For others with different physical abilities, even 2 m may be good but I think that would be the top limit.
A 1.6 m DLG should cost similarly to a 1.5 (assuming there is enough of a market to pay back for the tooling) a bigger model would be more expensive due to material costs and more expensive tooling and I expect a smaller market.
The most practical size today is the 1.5 because it would be easier to resale...


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