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Author Topic: Tern Free, composite TLG  (Read 8839 times)
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OZPAF
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« Reply #25 on: October 06, 2014, 03:22:18 AM »

Very interesting - I can't wait to see this thing fly.
John
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F3KBlake
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« Reply #26 on: October 07, 2014, 03:58:41 PM »

Ployd6

In an attempt to save weight we decided to face the LE with a 25g/m□ fiberglass strip. The stab and fin came out at 3.4g  Wink


As for moment dimensions, not 100% sure, we going with trial and error . Our starting point= nose to wing LE 187mm Chord is 124mm and 470mm from wing TE to stab LE.

Blake
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Re: Tern Free, composite TLG
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Ployd
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« Reply #27 on: October 07, 2014, 05:20:21 PM »

Thanks Blake, looking good. Nose length is on the money but would suggest reducing the moment arm down to 410mm (16.15").

Ployd in OZ
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sweepettelee
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Simplicate & add more lightness. Keep sanding!



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« Reply #28 on: October 07, 2014, 07:34:03 PM »

Blake,

I respectfully disagree with my good buddy Ployd re TMA.
I suggest you leave it long at your dimension of 470 mm.
Reasons are:
1. Most 1 meter TLGs in USA seem to be over 18 TMA, with Spin F1N of Stan B & Tim B 18.5 to 18.63, wing TE to stab LE. (~470-473-mm)
2. If you decide during flight testing that boom is too long(maybe transition or gust recovery from stalls is not to your liking), then it should be easy
to shorten the boom.  That is the best solution, since adding material makes fixes difficult to say the least...Big OOPS! Shocked

Leeper, aka Sweepettelee  Grin
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Leeper
F3KBlake
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« Reply #29 on: October 10, 2014, 07:07:41 AM »

Dylan and I are ready for first flight tests this wknd. The test model has come out at 103g balanced and ready to fly. We should be able to get to 90g on the next one but durability will be the determining factor.

Regarding moment arm/boom length, would you guys mind elaborating on what to expect in the transition and or gust recovery phase when the moment arm is to long or to short? Im sure there will be tradeoffs here but I have no clue what they are.

Blake
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Ployd
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« Reply #30 on: October 10, 2014, 07:08:41 PM »

Hi Blake

Leeper and I will respectively agree to dis-agree on the moment arm question but my take is simple and it is tied into the physical dimensions of the boom you are using for the fuselage (and there is a difference between indoor and outdoor use).

I use an Avia sports graphite kite boom (8mm down to 6mm diameter for a 32" (813mm) length) and initially I started with a MA of 17.5" (445mm) which does give an arrow straight climb in calm conditions but in gusty or turbulent conditions boom flex caused me problems during launch so I did a trade-off and reduced the MA to 410mm to reduce the flex. The climb and glide were un-affected. Ideally a larger diameter boom would be the way to go, say, 10mm down to 6mm (which if I remember correctly is what Mark Benn's used).

I would be interested to know what our American cousins are using.

Ployd in OZ
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« Reply #31 on: October 11, 2014, 10:09:37 AM »

From the photo of the V-tail portion of the Y-tail group on reply #22 it looks like the tail plane area is not extremely large, so maybe it would be Ok to start out with a somewhat longer tail moment. The photo(s) of Ployds model(nice looking TLG by the way) make the V-tail look somewhat large(?).

Do you have the plans for Mark Benns Spin Up 42?
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julio
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« Reply #32 on: October 11, 2014, 12:28:19 PM »

Re asymmetrical planforms, there is a flight video(U Tube I think) of a Japanese FF TLG which has lots of right tilt.
This appears to me to be due to the wing dihedral layout: left wing has one break about 3" from tip, whilst right wing
has two breaks, plus more overall d'dral. Hence, the need for more right tilt to compensate. The launch & recovery 
are among the best I have ever seen, with no obvious wiggle-waggle of boom & Y-tail group.
This fact alone seemed to result in a high & nearly straight left climb, with clean recovery.
Maybe a search would allow the astute online users to see what I mean.
A link or info on the Nippon flyer would be most appreciated...

Sorry to be late Sweepettelee. The flyer is Mitsuru ISHII (Japan). There is plenty of info, videos and plans at the following link.

http://www.hippocketaeronautics.com/hpa_forum/index.php?topic=2669.msg22347#msg22347

'2 panels on one side of the wing and 3 on the other...'

Julio
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« Reply #33 on: October 11, 2014, 05:54:50 PM »

I think I rushed to post the above reply...It refers to an indoor free flight TLG, but it was so close to the description posted by Sweepettelee (asymmetric dihedral, japanese model and flyer) that I didn't realized this thread was at the outdoor free flight forum. My apologies.

Julio
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sweepettelee
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Simplicate & add more lightness. Keep sanding!



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« Reply #34 on: October 11, 2014, 08:35:15 PM »

Ah yes, that is correct. Ishii's video was indoor.
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« Reply #35 on: October 12, 2014, 03:12:56 AM »

Ployd

Thanks for your reply. It makes sense. Dylan n I will be doing a one piece fuselage and boom to increase rigidity at some stage. It will be done in such a way that we can layup boom only as well. Elliptical in section and tapered. Maybe we should start composite fuse/boom builders lounge?

John

I have the spin up 1000 plan. Not sure if the spin up 42 is the same thing?
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Ployd
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« Reply #36 on: October 12, 2014, 11:59:31 PM »

Hi Blake

A one piece fuselage will only work if the mode of DT is effective and sofar a tip-up boom has been the most effective method to date and easy to engineer.

An elliptical boom is an interesting approach but think that a tear drop cross section maybe better. It is lateral bending of the boom during launch that has to be minimized not longtitudinal.

Ployd in OZ
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« Reply #37 on: October 24, 2014, 10:54:43 PM »

John

I have the spin up 1000 plan. Not sure if the spin up 42 is the same thing?
Blake, ...not sure if the 42 plan is the same as the 1000, but it seems logical as the 42 builds up to an essentially 1 meter glider.

Have you had any maiden flights?

...also, Ployd makes good point about the pop-up tail boom as the contemporary means of D/T, and it also allows for effective and easy incidence adjustment on the field.
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dylan1024
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« Reply #38 on: November 10, 2014, 11:03:45 PM »

We had some good weather yesterday and put in some flights. ... we think the declage was a bit much after some repairs. Also the launch tip side is a lot heavier than the other tip.  Will post again after we get another session in

Watch "Ternfree launch2" on YouTube - Ternfree launch2: http://youtu.be/tp_pwC5kJX4

Watch "Ternfree launch" on YouTube - Ternfree launch: http://youtu.be/zCPqxqswhX8
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Rewinged
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« Reply #39 on: November 11, 2014, 12:13:04 AM »

Glider videos look great--should be fantastic with final launch trim and good recoveries, since the glide looks great!

Re launch tip heavier--some of this is OK, even helpful, since it aids thermal-seeking by offsetting the turn from the rudder/skew.

--Bill
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« Reply #40 on: November 11, 2014, 07:17:34 AM »

An elliptical boom is an interesting approach but think that a tear drop cross section maybe better. It is lateral bending of the boom during launch that has to be minimized not longtitudinal.

Ployd:
If the major axis of the ellipse is aligned with the lateral plane, the stiffness will be maximized for TLG launch. I think some of the RC DLG guys who are fabricating 1-piece composite fuselages are doing this ... I've lost track as I haven't been following RC DLG in the last year or so.

-Dave
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« Reply #41 on: November 11, 2014, 08:30:28 AM »

The model is excellent. I get the impression that he could do more to climb. There should be only slightly reduce the difference of angles. Transition will be much better.
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MarkCovington
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« Reply #42 on: November 11, 2014, 10:13:27 AM »

 How much skew do you have in the V-tail?

 Mark C
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dylan1024
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« Reply #43 on: November 11, 2014, 10:38:39 AM »

Zero stab tilt and zero skew.

We cant find a decent illustrated explanation of tilt and skew and their corresponding directions... so we left it zero zero
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« Reply #44 on: November 11, 2014, 04:08:33 PM »

 L.E. of stab at centerline should be about 1/16 (1.5mm) left of T.E. at centerline. No stab tilt needed. That change would make launches and transitions much better. Looks pretty good as is.
If you don`t want to add the skew, try some tip weight on the right side. This is just my opinion though.

 Mark C
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Ployd
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« Reply #45 on: November 11, 2014, 04:58:49 PM »

Like the videos and the model makes a definite whistle on launch  Smiley

I do not use either stab tilt or skew on any of my models and have found no reason to use it. When the Morris Dancer was designed way back on the SFA forum (2006) stab skew was unknown until the first kits were seen in OZ but by then it had become common knowledge in the US and has appeared on all subsequent published and kitted designs.

As regard to one wing tip heavier than the other, I statically balance the wing by adding lead to the opposite tip (built in) then add an additional piece of lead to the tip to make it slightly heavier (right hand circle, right hand tip) then file away that lead piece until there is just enough weight to drop the inboard wing into the glide...gets rid of the stall as it transitions into glide mode. Sometimes a bit of rudder tweaking is required.

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If the major axis of the ellipse is aligned with the lateral plane, the stiffness will be maximized for TLG launch

Agree with you on this thinking but on a F/F TLG it means making a wider nose pod so that a "broken back" DT can be fitted.

Ployd in OZ
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OZPAF
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« Reply #46 on: November 11, 2014, 05:33:15 PM »

Thats a nice glide Dylan. I have no experienc with TLG but a bit with CLG and I suspect i would be trying a bit of built in right rudder and tail tilt for the glide.
It certainly has potential.
John
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« Reply #47 on: November 12, 2014, 07:45:47 AM »

If the major axis of the ellipse is aligned with the lateral plane, the stiffness will be maximized for TLG launch

Agree with you on this thinking but on a F/F TLG it means making a wider nose pod so that a "broken back" DT can be fitted.[/quote]

Ployd:
Apologies if my previous post was impertinent ... of course you're aware of this. I think the problem was with how I interpreted what you meant by "teardrop" ... I think I get it now.

Warm Regards-
Dave
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« Reply #48 on: January 13, 2015, 05:37:39 PM »

Hi Dylan and John,
that's a real fantastic piece of work, my warmest compliments.
Just some question, how do you prepare the rohacell core? I tried cutting with hot wire, no chance, so I had to sand it. Do you mill it Huh
Secondly, probably you heat the mould slightly (40-50°C) during curing. We had a lot of trouble because of the different thermal expansion coefficient of aluminum against a carbon structure with near to 0 coefficient. How do you tackle this matter?
A warning about russian carbon, it has the same stiffness but only half the tensile strenght in comparison to "our" western carbon. Actually I thing the two spar caps would benefit from beeing made from high modulus UD fibre.

That's just my 2 pence worth.....

Urs
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dylan1024
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« Reply #49 on: January 15, 2015, 01:35:45 PM »

Hi Urs

We mill the rohacell.
So far the expansion issue has not proven to be a problem.

We play with all sorts of carbon. The Russian is HM as far as i know.


Thanks for the kind words
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