@CthulhuJon I tried your idea of sharpening the blade, but it did not work too much for me. Maybe the sandpaper I had was a bit rough. Anyway, I was able to get some more. Would you guys use toothpicks or bamboo skewers to hold the rubber bands for an airplane this size? Can I just glue them to the edges of the uprights in the fuselage?
building a glider
- Thread starter hello183
- Start date
You mean like this?
I snipped the image from this thread:
https://forum.flitetest.com/index.p...-kit-604-rubber-power-to-rc-conversion.59521/
I never thought of designing that. Can the longerons do for it instead? maybe could I use a screw to attach the wing to the fuselage?
I snipped the image from this thread:
https://forum.flitetest.com/index.p...-kit-604-rubber-power-to-rc-conversion.59521/
I never thought of designing that. Can the longerons do for it instead? maybe could I use a screw to attach the wing to the fuselage?
quorneng
Master member
hello183
For a light weight you would be well advised to stick with rubber bands to hold the wings on.
With a rigid wing mount it only takes a wing ground touch to do serious damage. The only way to avoid this would be to build the wing and fuselage structures so strong that it would shear a nylon bolt before it did any damage. Not really applicable in your case.
The ideal is to use rubber bands that are just strong enough for the flying load they have to hold. In any sort of crash they allow the wing tip to move backwards quite easily. In a more extreme crash they actually slip off the pegs likely releasing the wing completely.
An example.
RC, electric powered, aerobatic, bigger and a lot heavier than your glider but the foam wings are still held on by bands. Only one band in the picture but normally 3 are used. It has saved quite a bit of damage over the years.
For a light weight you would be well advised to stick with rubber bands to hold the wings on.
With a rigid wing mount it only takes a wing ground touch to do serious damage. The only way to avoid this would be to build the wing and fuselage structures so strong that it would shear a nylon bolt before it did any damage. Not really applicable in your case.
The ideal is to use rubber bands that are just strong enough for the flying load they have to hold. In any sort of crash they allow the wing tip to move backwards quite easily. In a more extreme crash they actually slip off the pegs likely releasing the wing completely.
An example.
RC, electric powered, aerobatic, bigger and a lot heavier than your glider but the foam wings are still held on by bands. Only one band in the picture but normally 3 are used. It has saved quite a bit of damage over the years.
@quorneng thanks for telling me this, I was actually considering using a normal metal screw so that would have been worse. I did not consider making a wing saddle in the design. I would not like to glue one on top of the longerons because I wouldn't want it to look that way.
Could I glue one kabob stick on the centerline of the fuselage and use a rubber band that slides over from the front of the center of the wing, to the back of the center? It is difficult to explain but it is used in the sailplane linked below. You can see it in the photo gallery.
http://airfieldmodels.com/gallery_of_models/builders_gallery/william_rahiser/br1_sailplane/index.htm
Could I glue one kabob stick on the centerline of the fuselage and use a rubber band that slides over from the front of the center of the wing, to the back of the center? It is difficult to explain but it is used in the sailplane linked below. You can see it in the photo gallery.
http://airfieldmodels.com/gallery_of_models/builders_gallery/william_rahiser/br1_sailplane/index.htm
quorneng
Master member
Hello183
Note also the reinforced covering at the wing centre where the bands sit. You will probably need something (card?) as well
With rubber bands it is easy to insert thin packing under the wing leading or trailing edge to give the required incidence. You are very likely to find that what ever you build it at it will need adjusting after a few test flights. When you are happy with the way it flies just glue the packing permanently onto the fuselage.
Also remember rubber bands degrade in sunlight and over time. Always take plenty of spares!
Note also the reinforced covering at the wing centre where the bands sit. You will probably need something (card?) as well
With rubber bands it is easy to insert thin packing under the wing leading or trailing edge to give the required incidence. You are very likely to find that what ever you build it at it will need adjusting after a few test flights. When you are happy with the way it flies just glue the packing permanently onto the fuselage.
Also remember rubber bands degrade in sunlight and over time. Always take plenty of spares!
I cut some notches in the fuselage sticks for the kabob stick to fit on, then used some superglue with it, then wrapped threads around it and used superglue again. Also, sometimes the superglue gets a bit gel like now and it wasn't doing that before. Does that mean it's old?
quorneng
Master member
hello183
Just a point. With the fuselage tissue? covered how are you going to get the bands on the centre line kabab stick?
Wont the band tension put a considerable load on the balsa cross pieces?
In the conventional set up the band loads are taken by stout dowels running across the fuselage.
https://www.vintagemodelcompany.com/keil-kraft-ajax.html
Just a point. With the fuselage tissue? covered how are you going to get the bands on the centre line kabab stick?
Wont the band tension put a considerable load on the balsa cross pieces?
In the conventional set up the band loads are taken by stout dowels running across the fuselage.
https://www.vintagemodelcompany.com/keil-kraft-ajax.html
I just got the tissue. and I made a test piece for it as well. I tried an Elmers glue stick in the test but it isn't waterproof so on some parts it lifted, but for the most part it shrunk well. I am planning on using thinned out wood glue for the actual airframe.
@quorneng
1. I actually wasn't going to cover the bays in the fuselage where I would need to put the kabob stick.
2. It probably will, but to test it, I have already assembled the entire thing and left the wing on for a few hours, and everything was fine. It might be different in flight though; in which case I can always redesign something better. Also, thanks for sending that website.
@quorneng
1. I actually wasn't going to cover the bays in the fuselage where I would need to put the kabob stick.
2. It probably will, but to test it, I have already assembled the entire thing and left the wing on for a few hours, and everything was fine. It might be different in flight though; in which case I can always redesign something better. Also, thanks for sending that website.
the vertical stab covered. The wood glue worked fine, but when I shrunk it earlier this morning, it tightened like this, but drooped back a couple hours later, so I did it again, and it shrunk well again soon later (the picture you see now) but it might come back again. I don't use too much water, so maybe I will have to do the process several times before it shrinks tight enough.
In the night, the stabilizer's tissue still drooped back a bit, so I brushed it with water again, but in the morning, it drooped back again. So, I figured I didn't cover it tight enough and then redid the covering process and tried again, and it tightened great as usual, but drooped back soon later. Does anybody know why it is behaving this way? Maybe it is because it is a sheet surface? On the test piece it works fine, and I did the same process on the vertical stabilizer, and it is still wrong.
Tench745
Master member
I haven't had this problem, so I'm not sure... How tight are you applying the tissue to begin with?
I have had tissue sag if it gets some dew on it when flying, or over long periods of time when humidity changes significantly.
On my last model I coated the tissue with a light coat of water-based polyurethane. The tissue sagged like crazy when applying the WBPU, but then tightened up pretty well and became semi-rigid when the polyurethane dried.
quorneng
Master member
hello183
In general untreated tissue is very sensitive to changes in humidity and temperature. Thus water shrinking is really only the first stage. Tissue has to be 'fixed' and made almost waterproof with an air drying lacquer like a water based polyurethane. However there are other acetate based finishes that have both better filling and shrinking properties under the generic title of 'dope'.
The quality and density of the tissue is also is a significant factor in the final appearance. To achieve a good tissue covering requires its own degree of skill.
Bigger heavier planes use self coloured heat shrink plastic film which of course gives a truly water proof gloss finish.
I hope this helps.
In general untreated tissue is very sensitive to changes in humidity and temperature. Thus water shrinking is really only the first stage. Tissue has to be 'fixed' and made almost waterproof with an air drying lacquer like a water based polyurethane. However there are other acetate based finishes that have both better filling and shrinking properties under the generic title of 'dope'.
The quality and density of the tissue is also is a significant factor in the final appearance. To achieve a good tissue covering requires its own degree of skill.
Bigger heavier planes use self coloured heat shrink plastic film which of course gives a truly water proof gloss finish.
I hope this helps.
Thanks @Tench745 & @quorneng for telling me this. I decided to shrink the wrinkled parts of the control surface with a mix of mostly water, and a slight bit of wood glue. Now several hours later, it has shrunk and is attached to the balsa, so there are not many wrinkles as there were before. Also, both of you mention coating the tissue with water-based polyurethane to seal it. I think I have that. But I don't have an airbrush. Won't it be a bit heavy if I just brush that stuff on? I have also heard of Krylon spray. I might get that though.
My idea of baking soda and wood glue for covering the nose block didn't work. I think I will try mixing foam shavings from sanding and glue next.
My idea of baking soda and wood glue for covering the nose block didn't work. I think I will try mixing foam shavings from sanding and glue next.
I recovered the center section of the horizontal stabilizer. I might be getting a hang of covering with tissue. The patch might leave a mark. All I care about is that there are less wrinkles.
Also, all I have is oil-based polyurethane, not water based. Could that work? How can I apply it? I don't have an airbrush so I still might get the Krylon spray bottle.
Also, all I have is oil-based polyurethane, not water based. Could that work? How can I apply it? I don't have an airbrush so I still might get the Krylon spray bottle.
