Glue

[himlynx]

I tried 3M's high strength 90. Too thick! save your money. I like 77. Consider this as spray paint. When you are done, invert the can and spray for 2 seconds. (OUTSIDE)

I really like Titebond III for balsa "butt joints".
It slow to set but extremely strong, so do not use any more than is necessary. I say use half as much as you think you need and normally that will be too much.

For CA glue, I have the builders put a tiny drop of glue on the duller side of aluminum foil. Then coat just the area of the stick that needs to be joined by a light touch and possibly a swirl. Old CA is not any good, so start with tiny drops and throw it away after say 3 minutes. For most, it works out much better than even micro dispensers and costs a lot less.

Being a retired chemist, I did not like blue or purple glue, so mixed them in a nearly empty bottle until I got the consistency that I liked. TLAR method--That Looks About Right.

It must work OK because the MS teams and HS teams blew away the competition at state in towers.

Gorilla glue and I do not get along well.

Thanks Retired1. I'm also retired and Sc Oly brings me to 2nd childhood. I worked with balsa more than half a century ago and the world has changed.

[jander14indoor]

PVA has its place, but if for outdoor or wet, you need the weather resistant formulations from hardware stores/big box home centers like titebond II or III.

Note, I'm an indoor flyer where the whole plane might weight less than half a gram and .001 grams can be important, so I don't normally use CA for flying things, it is too heavy. BUT, the SO rules have been written to NOT be that critical (though you'll find they are critical to 0.1 gm or less) and the reduced building time is so valuable until the students are hooked that it is not a significant penalty if you are careful.

Jeff Anderson
Livonia, MI

[retired1]

Last year I started the students out with a thin coat of diluted Ambroid and then a coat of slightly diluted. Put on with a brush. It did not add much weight. It was superbly strong. Time was killing us, so we switched to the mixed CA glue.
It takes a while for new model builders to figure out how much glue is enough and then how much is too much. The first is a weak or failed joint and the second is added weight. For boomilever, I think that 0.2g is going to make a significant difference in positions. Same with glider. Great gliders only weigh 2g.

[himlynx]

PVA has its place, but if for outdoor or wet, you need the weather resistant formulations from hardware stores/big box home centers like titebond II or III.

Note, I'm an indoor flyer where the whole plane might weight less than half a gram and .001 grams can be important, so I don't normally use CA for flying things, it is too heavy. BUT, the SO rules have been written to NOT be that critical (though you'll find they are critical to 0.1 gm or less) and the reduced building time is so valuable until the students are hooked that it is not a significant penalty if you are careful.

Jeff Anderson
Livonia, MI

Wow ! A whole airplane weighing less than half a gram ! What is the wingspan ? What is the material you use ? Balsa ? Carbon fiber ? Do you use a magnifying glass while building ? Any videos on Youtube ?

[himlynx]

Last year I started the students out with a thin coat of diluted Ambroid and then a coat of slightly diluted. Put on with a brush. It did not add much weight. It was superbly strong. Time was killing us, so we switched to the mixed CA glue.
It takes a while for new model builders to figure out how much glue is enough and then how much is too much. The first is a weak or failed joint and the second is added weight. For boomilever, I think that 0.2g is going to make a significant difference in positions. Same with glider. Great gliders only weigh 2g.

With an efficiency of 1000, 0.2 gms makes a difference of 200 gms. Yes, we always have to aim for gold, even if we are finally happy with doing our best.

A 12 inch wingspan glider capable of withstanding the launch force and yet weighing only 2 g is going to be a tough call. Thanks for letting us know what to aim for.

[jander14indoor]

For the stuff I build, just balsa (CAREFULLY selected) and very thin mylar film.

The planes I'm referencing are called Ministicks (7 inch span, capable of flying 15 minutes or so) and EZBs (12 inch span, capable of flying 20 to 25 minutes). See http://www.indoorduration.com/ and dig around the site for more information on these.
Here's an EZB flying: http://www.youtube.com/watch?v=PCO8eXfN-tQ
Here's a Ministick: http://www.youtube.com/watch?v=BNhbAP3AgiY

Note, there's a level of craziness beyond this. F1Ds weigh about a gram, 55 cm span, and fly 30 to 40 minutes on a rubber band. These are mostly balsa and mylar, but do use some exotic stuff like .003 diameter boron wire. Dig around the Indoor Duration site above for F1D info and for some beautiful videos of these at the recent world championship see: http://www.indoorduration.com/

Comment on the recent world champs. Two of the US Seniors, and both juniors got started in this hobby through Science Olympiad Wright Stuff!

Jeff Anderson
Livonia, MI

[retired1]

I am definitely no in the same league as Jander. Hopefully the students will be able to get close to the 2g. Weight is the most important factor for a glider followed by trim. They will not get there on the first tries. Will be saving the really good wood for later versions.

[himlynx]

For the stuff I build, just balsa (CAREFULLY selected) and very thin mylar film.

The planes I'm referencing are called Ministicks (7 inch span, capable of flying 15 minutes or so) and EZBs (12 inch span, capable of flying 20 to 25 minutes). See http://www.indoorduration.com/ and dig around the site for more information on these.
Here's an EZB flying: http://www.youtube.com/watch?v=PCO8eXfN-tQ
Here's a Ministick: http://www.youtube.com/watch?v=BNhbAP3AgiY

Note, there's a level of craziness beyond this. F1Ds weigh about a gram, 55 cm span, and fly 30 to 40 minutes on a rubber band. These are mostly balsa and mylar, but do use some exotic stuff like .003 diameter boron wire. Dig around the Indoor Duration site above for F1D info and for some beautiful videos of these at the recent world championship see: http://www.indoorduration.com/

Comment on the recent world champs. Two of the US Seniors, and both juniors got started in this hobby through Science Olympiad Wright Stuff!

Jeff Anderson
Livonia, MI

Thanks, Jeff. I've had a quick look. What is the boron wire used for ?

[jander14indoor]

Boron fibers are used for local stiffening. Typically a couple on either side of the motor stick to stiffen, and now on either side of the wing spars to stiffen. Allows use of a wider range of wood for the spars as the stiffness comes from the fibers, not the wood so much.

Note, for SO, we've tried to write the rules to specifically keep boron OUT of use.

Boron has some unique handling hazards we didn't want to risk with students. When you cut it, it is so stiff and hard it tends to shatter throwing splinters a long way if not done properly. These are very sharp and painful if you get one under your skin. Almost impossible to see and remove, the pain stays until your body eventually encysts the boron and spits it out. Not really life threatening as the boron is pretty non-reactive, but very uncomfortable.

If you want more details, dig around the indoor duration site and the Yahoo Indoor Construction group.

Jeff Anderson
Livonia, MI