Vasek .F Posted September 2 Share Posted September 2 Hello there, I'm trying to make an autogiro as a school project and I'm in the progress of the making the blades. Due to available material, I glued 4mm and 2.5mm Balsa sheets to obtain the thickness of the blade, and then glued an 8mm pine leading edge. The total width of the blade is 45mm and I haven't set the length yet, but currently the blades are 500mm long. I was wondering on average how heavy should the blades be? I've just sanded the blades to their profiles, and they weigh approximately 17g. Is this an acceptable weight? I'm aiming for the model to weight between 500 - 800g. Kind Regards, Vasek .F 1 Quote Link to comment Share on other sites More sharing options...
Vasek .F Posted September 2 Author Share Posted September 2 Sorry I tried to attach a photo of one of the blades to the previous post (the link is invalid) Quote Link to comment Share on other sites More sharing options...
Richard Harris Posted September 2 Share Posted September 2 Vasek, Welcome to the forum. The only real test to know for sure that your blades will function ok is to fly them. However, in my experience I think that 17g per blade is a bit too light for an autogyro weighing 800g if the mass is evenly distributed evenly along the span. If it were me I would add some tip weights, start off with about 5 grams and see how the autogyro feels, this should stiffen up the rotor disc for a more controlled flap and reduce the coning of the blade disc. Let us know how it goes? Rich Quote Link to comment Share on other sites More sharing options...
Vasek .F Posted September 5 Author Share Posted September 5 Hi Richard, Thank you very much for your advice with the wing tips! I will definitely consider using them. I am planning to wrap the blades in an iron on Vinyl to strengthen the blades for the final step. The one I bought will give an estimated extra 13g to the total weight of the blade, as well as the pieces of plywood I need to glue to the ends of the blade. Do you think that this would make on the other hand the blades too heavy (1 blade weighing 35g each with the vinyl)? The Blade profile I am using for my blades is the NACA 8-H-12 profile. Does it matter how much I cut off on the end of the blade where they are connected to the delta hub? Should I stick to cutting out a triangle with dimensions of something like 80mm x 30mm? The model I have so far is a temporary prototype. It uses a 1000KV 12V motor with 10' x 4.5 Propeller. I'm hoping this will provide sufficient thrust. Will keep you updated with the project Kind regards Vasek Quote Link to comment Share on other sites More sharing options...
Vasek .F Posted September 9 Author Share Posted September 9 Hello, does anyone have any tips for covering the blades? I'm trying to apply Iron on Vinyl to cover the blades and I'm not too certain on what's the best method to use. I've tried using a Iron and a heat gun. Any tips would be much appreciated. Kind regards Vasek Quote Link to comment Share on other sites More sharing options...
Paul De Tourtoulon Posted September 9 Share Posted September 9 I use either the vinyl for industrial signs, Oracover or the HK cheap stuff, or my favorite is, tissue paper, cellulose dope then painted. Quote Link to comment Share on other sites More sharing options...
Cuban8 Posted September 9 Share Posted September 9 Just normal white heatshrink film from my odds and ends box and applied with a modelling iron works well for me. Quote Link to comment Share on other sites More sharing options...
Paul De Tourtoulon Posted September 9 Share Posted September 9 1 hour ago, Cuban8 said: Just normal white heatshrink film from my odds and ends box and applied with a modelling iron works well for me. Kyosho used it on their wooden helicopter blades, that didn't last long under the french sun. Quote Link to comment Share on other sites More sharing options...
Richard Harris Posted September 10 Share Posted September 10 Another option that I have used several times is covering with adhesive backed vinyl which is readily available over here in the UK. One point worth making is that which ever method you use be sure to make your overlaps are facing towards the trailing edge (just like covering a wing). Quote Link to comment Share on other sites More sharing options...
Vasek .F Posted September 10 Author Share Posted September 10 Thank you all for the feedback! Just a quick question, when you apply the covering, how do you tighten the fabric or vinyl to minimize wrinkles and air bubbles? Quote Link to comment Share on other sites More sharing options...
Paul De Tourtoulon Posted September 11 Share Posted September 11 5 hours ago, Vasek .F said: Thank you all for the feedback! Just a quick question, when you apply the covering, how do you tighten the fabric or vinyl to minimize wrinkles and air bubbles? You can't !, it's tricky to put on, and use a pin to make holes in it to free the air bubbles. Quote Link to comment Share on other sites More sharing options...
Engine Doctor Posted September 11 Share Posted September 11 Could you not use heat shrink tubing as used on batteries etc for covering blades ? No seam to come undone , very tough and quick and easy to apply. Loads of sizes and colours available on internet. 1 Quote Link to comment Share on other sites More sharing options...
Vasek .F Posted September 29 Author Share Posted September 29 I've decided to try using the tissue paper method. I managed to find two different colors so I can identify the top of the rotor from the bottom. Unfortunately, after I applied the tissue (with dope and later some varnish) one of the blades slightly bent itself. Is this still acceptable or is there some way I could straighten it out again? I've also been careful to get rid of as many of the air bubbles through poking holes as recommended. The total weight of each blade turned out to be 20g (415 x 45 x 6mm). To balance the blades before covering I inserted some air gun pellets to the blades as needed: I later tried a very primitive test to see if there is any autorotation when I power the model underneath the blades. There was some autorotation as the blades didn't slow down and kept spinning. However, they were spinning rather slowly than expected. Are my blades then still too light? Would I then have to add some wingtip weights as recommended? Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.