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Re: Elastic Launched Glider B
Posted: February 9th, 2015, 4:49 pm
by bjt4888
drcubbin wrote:
I saw on one of the Launched Glider videos that an "accelerant" is used to dry the CA glue much more quickly. Does anyone know where I can buy that (without having to order and wait since we are in a bit of a rush?) I thought they said it is sold at Walmart, but I couldn't find it there. And are there any types that are preferred?
In my experience having coached quite a few students through construction for the glider event (and about 50 years of model airplane building), accelerant is unnecessary. If you are referring to the Kurt Krempertz video on the AMAGlider website, he uses accelerant for instant setting of super glue (CA) for all joints.
My students for the last couple of years also constructed the Stan Buddenbohm Littl Sweep kit as their first glider and all construction was done with fresh, good quality, super glue (ZAP Medium is my favorite) and joints set in about 60 seconds with this glue. All joints were simply held together for this short amount of time till set. The only joint we allowed a little more setting time for was the wingtip dihedral. We held these joints together temporarily with masking tape just as Kurt demonstrates and applied glue and propped the wingtips up to the correct dihedral angle and put a small weight (a 1"x2"x4" piece of wood) on the wing center section until the joint set for about five minutes. One tip dihedral is set and glued at a time. Then we carefully added four or five more drops of super glue along the joint.
All glue is applied with an applicator, not the bottle, the bottle usually allows the glue to flow too quickly and gets way too much on the joint. The "applicator" is simply a short stick of 1/4"x1/4"x4" balsa with two pins inserted through one end at very shallow angles (opposite each other) so that the points form a sort of a "pincer" that will pick up a drop of glue by capillary action from a bigger drop of glue sitting on a piece of wax paper.
Good luck and good flying,
Bjt4888
AMA member since 1972
Re: Elastic Launched Glider B
Posted: February 10th, 2015, 7:21 am
by slytherin
Do you guys have any good plans for ELGs that will fly for around 10 or more seconds? Or websites that I can use to find some plans?
Re: Elastic Launched Glider B
Posted: February 10th, 2015, 9:41 am
by jander14indoor
Check back up the chain for a number of suggestions and links. One page back should do it, two at most.
Jeff Anderson
Livonia, MI
Re: Elastic Launched Glider B
Posted: February 10th, 2015, 10:29 am
by bernard
This is the reply he is referring to.
Re: Elastic Launched Glider B
Posted: February 10th, 2015, 1:31 pm
by slytherin
bernard wrote:This is the reply he is referring to.
THANK YOU SOOO MUCH!!!!!!!!!!!
Re: Elastic Launched Glider B
Posted: February 14th, 2015, 1:19 pm
by bernard
The glider I'm working on isn't transitioning well. I'm using a flapper design. I originally had problems with it nosediving when launched at a positive angle but I added ballast to the front and it doesn't happen anymore. I think it isn't dealing well with the fast launch speeds. Has anyone else had issues with this?
Re: Elastic Launched Glider B
Posted: February 14th, 2015, 2:30 pm
by bjt4888
bernard,
Nosediving on launch is usually caused by inadequate decalage angle. It is odd that adding ballast to the nose corrected this. Please supply much more information so that I can help you better. Example: what design are you building? What is the amount of flap droop? What are the flaps made of and how thick are they? What is your wing incidence angle or amount and what is your stabilizer incidence angle or amount? If you are not building a design that I can review the plan for on the internet, please include a full description of all measurements (and a couple of pictures would be good too). What is your center of gravity (distance along the wing chord from the leading edge)? What does you glider weigh? What is the quality of the wood you are using (ex. is the fuselage good stiff wood and are the wings reasonably light and the stabilizer and rudder light and stiff?
Thanks,
Brian T.
Re: Elastic Launched Glider B
Posted: February 14th, 2015, 2:45 pm
by bernard
bjt4888 wrote:bernard,
Nosediving on launch is usually caused by inadequate decalage angle. It is odd that adding ballast to the nose corrected this. Please supply much more information so that I can help you better. Example: what design are you building? What is the amount of flap droop? What are the flaps made of and how thick are they? What is your wing incidence angle or amount and what is your stabilizer incidence angle or amount? If you are not building a design that I can review the plan for on the internet, please include a full description of all measurements (and a couple of pictures would be good too). What is your center of gravity (distance along the wing chord from the leading edge)? What does you glider weigh? What is the quality of the wood you are using (ex. is the fuselage good stiff wood and are the wings reasonably light and the stabilizer and rudder light and stiff?
Thanks,
Brian T.
Here are some links to images of my glider.
Entire glider
Nose
Wing
Empennage
Broken glider
Re: Elastic Launched Glider B
Posted: February 14th, 2015, 3:01 pm
by bernard
bernard wrote:bjt4888 wrote:bernard,
Nosediving on launch is usually caused by inadequate decalage angle. It is odd that adding ballast to the nose corrected this. Please supply much more information so that I can help you better. Example: what design are you building? What is the amount of flap droop? What are the flaps made of and how thick are they? What is your wing incidence angle or amount and what is your stabilizer incidence angle or amount? If you are not building a design that I can review the plan for on the internet, please include a full description of all measurements (and a couple of pictures would be good too). What is your center of gravity (distance along the wing chord from the leading edge)? What does you glider weigh? What is the quality of the wood you are using (ex. is the fuselage good stiff wood and are the wings reasonably light and the stabilizer and rudder light and stiff?
Thanks,
Brian T.
Here are some links to images of my glider.
Entire glider
Nose
Wing
Empennage
Broken glider
Here are more photos. The thickest part of the wing is about 1mm. The lowest point of the leading edge is about 5mm above the fuselage and the trailing edge is about 2mm above the fuselage. The whole glider is about 3grams.
Fuselage - about 31cm
Wing chord - about 6cm
Wingspan - about 25cm
Wing - leading edge 5mm, trailing edge 2mm
Re: Elastic Launched Glider B
Posted: February 14th, 2015, 6:33 pm
by bjt4888
bernard,
Good job of documenting your current glider. It appears that the pylon that attaches the wing to the fuselage is not very substantial. This is an area that you want to be quite rigid so that the wing does not flex or change incidence angle too much during launch. Also, I'm not sure why you are building a shorter span wing than the allowed 32 cm? If I were you, I would build the a 32 cm wing and build to the required minimum weight of 4 grams. I am also noticing that your fuselage is quite thin. A thin fuselage can be stiff enough if it is reinforced with carbon, but I'm thinking that your fuselage may be too flexible. It would be a very good idea to build a glider from a proven design to minimize the potential issues (or, at least to construct a new, stiffer fuselage and more substantial pylon for your current glider). I have notes earlier in this thread describing how to modify the design we used last year for the current year rules. Much more detailed notes regarding construction and trim of this glider are written on the Hip Pocket Aeronautics website.
Thanks and good luck,
Bjt4888
