Logo
Builders' Plan Gallery  |  Hip Pocket Web Site  |  Contact Forum Admin  |  Contact Global Moderator
March 22, 2019, 12:49:17 AM *
Welcome, Guest. Please login or register.
Did you miss your activation email?

Login with email, password and session length
 
Home Help Search Login Register
Pages: 1 2 [3] 4   Go Down
Print
Author Topic: 2019 Elastic Launched Glider  (Read 4124 times)
0 Members and 1 Guest are viewing this topic.
bjt4888
Silver Member
****

Kudos: 5
Offline Offline

United States United States

Posts: 216



Ignore
« Reply #50 on: November 02, 2018, 11:53:26 AM »

Jdp,

My teams use a 6” loop of 1/16” thick Tan SS for the typical school gym ceiling height (25 ft to 30 ft).

I have used a 6” loop of 1/8”, stretched to my full arm span, successfully in a low Category III site (72 ft ceiling). Of course, the glider for this site is built for this extra force. I fly Bill’s Category II record holder for this higher ceiling; an excellent glider that I would highly recommend.

Brian T
Logged
jdpsloflyer
Bronze Member
***

Kudos: 3
Offline Offline

United States United States

Posts: 65




Ignore
« Reply #51 on: November 02, 2018, 04:30:35 PM »

Thanks Brian,

Any other pointers about coaching the launch?  It's been two years since I did this and cannot remember where I saw them.

Do you have a plan of the glider with the elliptical wing (the "El Gordo") that I saw on one of the threads you posted on?  I did not see it in the Gallery.  I have a copy your other one.

Jerry
« Last Edit: November 02, 2018, 04:43:28 PM by jdpsloflyer » Logged
bjt4888
Silver Member
****

Kudos: 5
Offline Offline

United States United States

Posts: 216



Ignore
« Reply #52 on: November 02, 2018, 09:21:29 PM »

Jd,

You’re welcome. My launching notes are in the thread, “Flapper CLG for 2014” in the earlier page of this thread. Mostly in my post #4. Let me know if something in these notes is not clear.

Sorry, I am not remembering the El Gordo design. However, I think that semi elliptical is the way to go as all of the top designs and record setting designs are of this platform.

Brian
Logged
Olbill
Titanium Member
*******

Kudos: 59
Offline Offline

United States United States

Posts: 2,470

Topic starter


Ignore
« Reply #53 on: November 03, 2018, 12:03:52 AM »

Jdp,

I have used a 6” loop of 1/8”, stretched to my full arm span, successfully in a low Category III site (72 ft ceiling). Of course, the glider for this site is built for this extra force. I fly Bill’s Category II record holder for this higher ceiling; an excellent glider that I would highly recommend.

Brian T

Former record holder.
Logged
jdpsloflyer
Bronze Member
***

Kudos: 3
Offline Offline

United States United States

Posts: 65




Ignore
« Reply #54 on: November 03, 2018, 07:12:46 PM »

Jd,

You’re welcome. My launching notes are in the thread, “Flapper CLG for 2014” in the earlier page of this thread. Mostly in my post #4. Let me know if something in these notes is not clear.

Sorry, I am not remembering the El Gordo design. However, I think that semi elliptical is the way to go as all of the top designs and record setting designs are of this platform.

Brian


Sorry, the El Gordo was from dslusarc post #46 in 2016-Elastic launched glider.  I am "throwing one together"  today to see if mine works as well.  Then use it as a demo.  Using foam in place of balsa for flaps.  3/32 light balsa (sanded) and carbon rod fuselage.  All new for me, wet finger design and build, hope it works.

Jerry
Logged
bjt4888
Silver Member
****

Kudos: 5
Offline Offline

United States United States

Posts: 216



Ignore
« Reply #55 on: November 03, 2018, 08:36:09 PM »

Jerry,

Hope it flies well.

Brian
Logged
Maxout
Titanium Member
*******

Kudos: 91
Offline Offline

United States United States

Posts: 2,708


WWW

Ignore
« Reply #56 on: November 19, 2018, 09:06:05 AM »

I've been getting a lot of emails from far and wide about trimming for ELG contests, so I put together some notes for a guy who noted that he doesn't learn easily from videos. I still haven't gotten feedback from him on this, but if you scroll down this link a little, you'll find my article on trimming. Hopefully someone will find this helpful:
http://jhaerospace.com/resources-for-science-olympiad-competitions/
Any feedback would be appreciated. I'm getting a little overwhelmed with the number of people coming to me for help.
Logged
Olbill
Titanium Member
*******

Kudos: 59
Offline Offline

United States United States

Posts: 2,470

Topic starter


Ignore
« Reply #57 on: November 19, 2018, 11:11:48 AM »

Josh
My only comment is that I never touch the stab on catapult gliders. I think Jim Buxton was the source of that info for me. If I remember correctly his reasoning was that any adjustments to the stab will have greatly magnified effects at launch speed.

For heavy gliders in typical low ceiling sites this may not be a big concern but it is a rule that I follow.
Logged
Maxout
Titanium Member
*******

Kudos: 91
Offline Offline

United States United States

Posts: 2,708


WWW

Ignore
« Reply #58 on: November 19, 2018, 01:29:50 PM »

Josh
My only comment is that I never touch the stab on catapult gliders. I think Jim Buxton was the source of that info for me. If I remember correctly his reasoning was that any adjustments to the stab will have greatly magnified effects at launch speed.

For heavy gliders in typical low ceiling sites this may not be a big concern but it is a rule that I follow.

Since I'm flying a model with a fixed wing mount and pultruded carbon fuse, that's not really an option, but I'm really curious what he's using instead. On outdoor gliders I use gurney flaps on the stab and rudder and the adjustments hold for years without significant changes. Jim is in a different league from me anyway...I couldn't replicate his stuff if my life depended on it!
Logged
jdpsloflyer
Bronze Member
***

Kudos: 3
Offline Offline

United States United States

Posts: 65




Ignore
« Reply #59 on: November 19, 2018, 02:18:24 PM »

I like the explanation Olbill had in 2013, I used that learning and coaching my students.

My standard system:

Adjust the glider for the best glide.
Throw hard straight ahead and observe.
If it dives add incidence, retrim the glide and repeat
If it has a steep climb remove incidence, retrim the glide and repeat.
When you have a level flight that slows down into a normal glide OR a slight climb and good transition to the glide you're ready for catapult testing.
Go slow at first with low power and a shallow launch angle.
Increase power and launch angle in small steps and watch what the glider does at the top of the climb.

I always set up low ceiling gliders for a right turn in the glide and launch with a right bank. The amount of bank and the launch angle are both critical and need to be worked out with experimentation. If you're using my setup you will see one of 3 possibilities:

1. Everything is perfect. Fly it until the launch is committed to memory and then put it away.
2. The glider will be in a right bank at the top of the climb and lose altitude before it starts the normal glide or it will spin in. Use less bank.
3. The glider will stall at the top and either lose a lot of altitude or spin in to the ground. Use more bank or a shallower launch angle or both.

If the glider spins in when you think it shouldn't then add incidence. This will also call for more nose ballast so don't change it much. I always try more flap deflection as a first try when I need more incidence.

I think a lot of flap deflection gives a safer model because the flaps will give you more incidence in the glide. The WIF7 has about 1/4" of flap deflection.

As for carbon rods, I have experimented with adding a small pylon to the rod and one to the wing so we can move the wing a small amount for trimming purposes (both for CG and incidence).  This has proved to be easier than glueing the wing directly to the rod.  The trouble I am having is finding pultruded rods that are straight, ones that are slightly bent need to be aligned carefully to avoid yaw and pitch problems.  I'm thinking balsa fuselages are the way to go.


BTW what is a gurney flap?

Jerry
Logged
DavidJP
Titanium Member
*******

Kudos: 42
Offline Offline

United Kingdom United Kingdom

Posts: 2,654




Ignore
« Reply #60 on: November 19, 2018, 02:58:52 PM »

Came upon this topic by chance and much amused by the copyright issues.  Your laws on the matter seem rather different from ours in the U.K.  I like the “cease and desist” letter.  An example of lawyers fondnes for using two words when one will suffice. 

Copyright actions here are very very costly. 

My feeling is that my response would be two words.  Ascendo tuum. (Latin of course).

Forgive my intrusion.
Logged
Maxout
Titanium Member
*******

Kudos: 91
Offline Offline

United States United States

Posts: 2,708


WWW

Ignore
« Reply #61 on: November 27, 2018, 07:43:24 AM »

Came upon this topic by chance and much amused by the copyright issues.  Your laws on the matter seem rather different from ours in the U.K.  I like the “cease and desist” letter.  An example of lawyers fondnes for using two words when one will suffice. 

Copyright actions here are very very costly. 

My feeling is that my response would be two words.  Ascendo tuum. (Latin of course).

Forgive my intrusion.

Just as a follow up, a friend of mine who keeps a patent attorney on retainer got me a legal opinion and I updated the listing on my site accordingly. Bottom line is that "fair use" dictates that I can describe the product as complying with Science Olympiad rules for Elastic Launched Glider and there's nothing they can do to stop that. As a double layer of insurance, the listing also specifies that I have no affiliation with Science Olympiad. And I haven't heard anything further from SO on the issue.

Most importantly, though, kids are flying the Protege gliders and having fun with them, which was the whole point anyway. The carbon fuselages seem to be the way to go on these models. Extremely durable.
Logged
DavidJP
Titanium Member
*******

Kudos: 42
Offline Offline

United Kingdom United Kingdom

Posts: 2,654




Ignore
« Reply #62 on: November 28, 2018, 09:16:26 AM »

That seems sound enough. But  in any event their loss or damage could not be very much at best so the costs alone (US Lawyers  to cheap either) would be prohibitive?  I have known a few folk who think mention lawyers and everyone will cower.
Logged
wlsguy
Bronze Member
***

Kudos: 1
Offline Offline

United States United States

Posts: 14



Ignore
« Reply #63 on: November 30, 2018, 08:07:08 AM »

You may want to reconsider use of the word “Olympiad” not because of a copyright but because it’s exclusive use is restricted to the National Olympic Committee by the Amateur Sports Act. Science Olympiad got special permission for its use after they were contacted by the lawyers.- John, Guru Engineering Tech
Logged
Ross J
Bronze Member
***

Kudos: 3
Offline Offline

United States United States

Posts: 77




Ignore
« Reply #64 on: December 21, 2018, 09:59:55 PM »

Thanks Bill, Josh and others for keeping this thread going. The trimming information provided in recent posts is proving true for my test models - launch is everything! I think success in competition will come from its of time in the gym learning to launch consistently.

My team is building a simplified WIF 7, with carbon rod fuselages and significantly enlarged tail surfaces. The wing looks a lot like the Protege wing, but with the flaps being slightly wider.The flaps are Down blue foam. I made some SO legal nose-hooks out of scrap Delrin, so all they have to do is slip them over the carbon rod and use a little CYA to affix them. Each hook weighs about 0.25 g. The wing pylon is a 1/32", 1/16", 1/32" vertical grain sandwich that is glued over the rod. I made a sanding jig that holds the fuselage/pylon and creates the correct incidence. Knowing how critical incidence is, i didn't want to leave this to chance. Huh I will also be building a simple jig for mounting the tail feathers. Is there any benefit in stab tilt? Huh

 Hopefully the student's models will be finished in the first or second week of January. They are doing a good job, much better than I expected. They love using a digital calipers to measure the thickness of the wings at various locations. One student has the wing on the fuselage, two others have the wings together with dihedral, the other five are still doing the last sanding on the wings. All of the models should be in the 3.3 - 4.0 gram range (without ballast) when they're done.
Logged
okboom1234
Nickel Member
*

Kudos: 0
Offline Offline

United States United States

Posts: 2



Ignore
« Reply #65 on: January 21, 2019, 03:34:41 PM »

Hello, I am new to gliders so I was just wondering what my airfoil should look like - currently, I am not sanding the bottom of my wings at all.
Thanks Smiley
Logged
Olbill
Titanium Member
*******

Kudos: 59
Offline Offline

United States United States

Posts: 2,470

Topic starter


Ignore
« Reply #66 on: January 21, 2019, 04:32:24 PM »

I you're building a flapper glider then the usual scheme is that the forward part of the wing is flat and the flaps have a considerable amount of camber. The result is an undercambered airfoil.

If you're making an all balsa wing then sanding in undercamber will remove a lot of weight. I think it might be hard to get down to the minimum weight with a solid balsa wing.
Logged
okboom1234
Nickel Member
*

Kudos: 0
Offline Offline

United States United States

Posts: 2



Ignore
« Reply #67 on: January 21, 2019, 07:38:43 PM »

Thanks!
Logged
fastdds
Bronze Member
***

Kudos: 0
Offline Offline

United States United States

Posts: 17



Ignore
« Reply #68 on: January 28, 2019, 10:02:06 PM »

What are people using for the Foam part of the flapper wing this year?  I had success with Durobatic foam in the past, but can't see to find any and went through my stash of ideal thickness material.  Hopefully there is a substitute that doesn't require sanding sheets down...


Thanks! 
Logged
bjt4888
Silver Member
****

Kudos: 5
Offline Offline

United States United States

Posts: 216



Ignore
« Reply #69 on: January 29, 2019, 08:04:36 AM »

Fastdds,

I have used Electrafly “Proformance” 1 mm foam from Great Planes. It does require sanding though. For example, flaps made for my Gowen Cat II glider were cut from a 6.125” x 2” piece of foam that weighed .412 g before and .309 g after. Sanding both sides evenly is required in order to remove the shine from both sides. I sanded with a block of 150 grit with five layers of masking tape wrapped around each end to theoretically sand to .025” thickness.

There may be better foam available, but this worked well for me. I have flown the gliders built with it and they complete all phases of flight very nicely.

Brian T.
Logged
Maxout
Titanium Member
*******

Kudos: 91
Offline Offline

United States United States

Posts: 2,708


WWW

Ignore
« Reply #70 on: January 29, 2019, 08:49:14 AM »

I'm using Vector Board exclusively now. Only source I've been able to find that will ship to the US is Lindinger.de. No sanding required. The 0.8mm and 1mm are in the weight range for ELG. I've even successfully used the 1mm for tail surfaces.
Logged
fastdds
Bronze Member
***

Kudos: 0
Offline Offline

United States United States

Posts: 17



Ignore
« Reply #71 on: January 29, 2019, 10:48:32 AM »

thanks BJT and Max.   I have used the electrafly type before, sanding is always a challenge.  I will try the tape instead of guitar strings method...
Logged
Maxout
Titanium Member
*******

Kudos: 91
Offline Offline

United States United States

Posts: 2,708


WWW

Ignore
« Reply #72 on: February 06, 2019, 10:39:15 AM »

This is a trick for flapped gliders that I learned from watching the videos of European F1N contests. It seems to work really well and makes the models easier to trim for a good glide transition while also improving glide performance. I saw a 25% increase in best glide time from the first model in this video by making that one change. Unfortunately the benefit doesn't show in the video because the humidity started rising and that model got really unhappy. The second model also showed a boost in performance, from a best time of 29 seconds up to 34 seconds. Unfortunately I don't have a way to measure the launch height, so I don't know exactly how high these were going. I think the second model was getting around 30 ft, but it could be more...or less...

https://www.youtube.com/watch?v=AzlLr5Thtks
Logged
AC01010
Copper Member
**

Kudos: 0
Offline Offline

United States United States

Posts: 3



Ignore
« Reply #73 on: February 11, 2019, 07:57:08 PM »

Hi,

I have a question regarding the thickness of rubber to launch at high ceilings. My next competition is in less than a week with a 40' ceiling and I'm worried that I won't be able to launch to the max height. Would looping the rubber (3/32") twice work or would that be too thick? I can get just over 1.1sec/ft in most Cat 1 gyms.
Logged
Olbill
Titanium Member
*******

Kudos: 59
Offline Offline

United States United States

Posts: 2,470

Topic starter


Ignore
« Reply #74 on: February 12, 2019, 09:21:06 AM »

I think one loop should be plenty for 40'. I use a loop of 1/8" to get over 50' with an 8 gram model. To be on the safe side you could make two launchers with a double loop on one. Make sure that two loops will work with the launch hook on your model.

Be careful about pushing your model past the point where flutter starts. Once you reach that point adding launch velocity will probably not increase your launch height and it can destroy your model.
Logged
Pages: 1 2 [3] 4   Go Up
Print
Jump to:  

Powered by MySQL Powered by PHP Powered by SMF 1.1.21 | SMF © 2015, Simple Machines Valid XHTML 1.0! Valid CSS!