Strong wing construction Swift S1
 

Hi All,

Hope you have had a very good Christmas.

Recently I have been working on a few plans before my Autocad licence expires with help of BMathews. One of which have been a Swift S1 glider. Wing span is either going to be 1.8M or 2.3M but I think 1.8M to start with. I have been out of model building for about 10 years with most of my models being Balsa Kits. In terms of the fuselage, I was planning to use fiberglass as i think it will be stronger than balsa.

In terms of wings, I have questioned the typical rib set up and have leaned more towards foam/balsa sheeted wings. Am I mad?? I do not have any vacuum set up or have ever done anything like this but think that the finish would be better than a sheeted rib set up. What would be your opinions regarding this? Does balsa sheeted foam give a better finish to the typical rib set up?

Thanks in advance.





https://cimg9.ibsrv.net/gimg/www.rcu...3e7579f49c.png

I’m a big fan of foam. It can be as light or even lighter then built up. IMO the biggest advantage is you can do what I call transitional airfoils much easier. On my last design I used one airfoil at the wing root, a different one mid span and a third at the tip. All were symmetrical but ad different thickness percentages and I changed the location of the high point as well as LE radius. Being a sailplane for example you could start with an RG12 at the root and have an RG15 at the tip which could give better slow speed handling. Just an example, I know there are more modern airfoils available. A vacuum bagging setup is very useful and can actually be assembled with a small investment . Using vacuum to mold fuselages helps reduce weight while adding strength.

Thanks speedracemtrixie for you reply. You know I have never thought of the change in air foil. Very good point. Would be a nightmare with rib set up. Well I was going to use AG34 air foil to keep it simple but if there is a preferred one I can change it easily enough. As I plan to build more sail planes in the near future, I think a vacuum set up would be good to look into but at the moment i want to get flying. Can a industrial vacuum cleaner create enough vacuum to apply enough pressure than using weights? by letting the vacuum build up flow and suddenly pressing it against the check valve should in theory create more vacuum by inertia. Would this apply more pressure for gluing or would weights and tape be better? Probably stupid question.
Didn't even think of the fuselage for vacuum set up. How would this work? I was planning to carve the fuselage from foam and then make a mould of the fuselage. If there is a better method, im all ears.

Thanks for the reply

There is some good info on this build thread I did a few years ago. Covers wing sheeting and mold making pretty well.


https://www.rcuniverse.com/forum/rc-...n-biplane.html

Thanks for the link.

If I was going to go the vacuum bag route, would a tyre inflator modified be adequate?

Thanks

No, vacuum pumps are pretty available. A refrigerator compressor is common to use. A tank made from PVC pipe and caps, an automotive check valve. The only semi difficult part is the vacuum switch that gets installed on the tank. When the bag gets a desired vacuum the switch shuts the compressor/pump off. The vacuum drops and the pump turns on.

That said, using weights to sheet foam wings will work. Laying up a fuselage without vacuum will work. Things and be done a bit lighter using vacuum tecniques.