Helicopter Design

[bjt4888]

This is a question from another forum posting here so that more can see discussion.

After looking at Bill Silins helicopter I was wondering if theres a way to pitch the entire rotor upwards as he did and if it would even work bc our helis are supposed to be heavier?

Helicopter asked about is here: Indoor News & Views; search word "helicopter". Bill Silin's helicopter is not a Science Olympiad heli. It is a much lighter, very high performance AMA rules heli. Some design ideas can possibly be borrowed from helis like this. The student is asking about the upper rotor dihedral angle.

Brian T

[bjt4888]

This is a question from another forum posting here so that more can see discussion.

After looking at Bill Silins helicopter I was wondering if theres a way to pitch the entire rotor upwards as he did and if it would even work bc our helis are supposed to be heavier?

Helicopter asked about is here: Indoor News & Views; search word "helicopter". Bill Silin's helicopter is not a Science Olympiad heli. It is a much lighter, very high performance AMA rules heli. Some design ideas can possibly be borrowed from helis like this. The student is asking about the upper rotor dihedral angle.

Brian T

Here is my reply: Called dihedral angle. As with a wing, adds lateral stability. Most of the lateral stability is provided by the top vane.

[bjt4888]

Here’s the link: https://indoornewsandviews.com/?s=Helicopter

[NEonGhOsT]

Hi coach brian,

The question I was asking was how would one make a dihedral angle on the top, right now I plan to use small gussets and have the top rotor fixed in a similar way the ffm 2024 model with gussets and the supports, is there any suggestions you could give me on the construction of it? also to ensure the bottom rotors have more thrust, I need to increase the rotor area on the top right? as it is on a 8 degree dihedral which may have made the rotor slightly less on the top.

thank you,

[bjt4888]

Hi coach brian,

The question I was asking was how would one make a dihedral angle on the top, right now I plan to use small gussets and have the top rotor fixed in a similar way the ffm 2024 model with gussets and the supports, is there any suggestions you could give me on the construction of it? also to ensure the bottom rotors have more thrust, I need to increase the rotor area on the top right? as it is on a 8 degree dihedral which may have made the rotor slightly less on the top.

thank you,

NE,

If, for example, your rotor spar were .039" carbon rod, I would probably put a 1/16" or 1/8" thick x .125" tall x 2" long hard balsa (18-20 lb cu ft) "dihedral brace" on each side of the rod like a "sandwich". The area at the center of the braces could be filled with 1/32" hard balsa to create a solid section for the shaft to be mounted throughThere would most likely need to be a flat spot on the bottom of this bracing so that mating with the thrust bearing is good. Or, if plastic tube is used to house the shaft, that would work too. Very accurate and straight shaft placement through the dihedral will also be important.

I'd be inclined to make dihedral equal on top and bottom rotors. Do you know if the J&H has equal dihedral? Top rotor area could also be equal to bottom. As this is complete custom designing, you can try equal area and also more on the top if you like. Again, I like copying successful design ideas when initially testing something new. Have you looked at the Dave Aronstein NFFS design and the J&H design that both use dihedral?

See this outdoor free flight plan (lower left corner) for what I mean by "dihedral brace". Of course the braces on this outdoor airplane are very big and are plywood and yours will be small, thin and hard balsa: https://aerofred.com/search.php?search_ ... taj5454l65 but this will hopefully help.

Brian Turnbull

[bjt4888]

Click on the aerofred plan itself then click "download" to see a detailed copy for the dihedral brack.