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I am building a custom/scale project.How do I determine if there is adequate clearance between the main and tail blades?
|01-16-2017 07:25 PM|
Morgan Hill, CA. USA
Use a tape measure?
Turn the main and tail rotor blades until they are at their closest point.You could get fancy and use a piece of string that is the same length as the main blade and see if the main and tail blade's arcs intersect
|01-16-2017 07:41 PM|
ok, sounds straight forward, but I thought there was more to it than that.So....If I'm looking at my heli from above, and see an imaginary line outlining the circumference of the main blade tips, as long as tips of the tail blades don't touch that line, I'm ok?I'm experimenting with different swash types, and I'm thinking I read that going to a DFC style head (which usually has a shorter mainshaft, putting the mains closer to the boom in a downward direction), made the tail blade selection more critical. Or were they possibly referring to boom strikes?These 900mm blades are $$$....
|01-16-2017 08:18 PM|
Costa Rica, Central America
From the sideLook at the heli from the side with the main blades parallel to the boom and tail blades at the closest point to the mains in their arc.
|01-16-2017 08:48 PM|
Boom strike depends on dampeners and height of head and how loose the blade grips are . So a low head with soft dampeners and loose blades is a guarantee of a boom strike
spending time, paying attention
|01-17-2017 01:52 AM|
Richmond, VA, USA
The rigidity of the DFC heads allowed for shorter mainshaft length without a boom strike. Of now experience has proven you can nix the DFC and still use a short mainshaft, have no boomstrike concerns, and avoid the pitfalls of DFC. You can get away with some overlap of tail blades and mainblades IF you have adequate mainshaft height and don't make a habit of hard landings mixed with aft cyclic.Ben Minor
Team Synergy Team Futaba Team Kontronik USA
|01-17-2017 03:02 AM|
Also of consequence relative to blade/boom strikes is the tightness of the blades in the blade grips. The tighter the better. In fact, if one tightens them just enough so that when you turn the heli on its' side and shake it, the blades to not move. Then hover the heli and let the rotor stop on its' own. Do NOT stop the rotor with your hands. This will ensure the blades remain in their "in flight" lead/lag position in the blade grips.Then tighten the blade bolts a bit more. Now you will have very little chance of having a blade/boom strike.What causes most boom strikes, is the blades leading or lagging excessively through a change in rotor speed, while simultaneously giving a command that entails a lot of collective and/or cyclic pitch.To understand this. While on the bench, move the blade in the grip to give about 20 degrees or so of lead or lag. Now rotate the head at zero pitch....the blades do not come close to the boom. Now do the same with full down collective. Rotate the head and see how your blades now contact the boom.
|01-17-2017 07:07 PM|
| Dan Minick|
I have been thinking about how you could actually measure this. Jogged my memory back to high school geometry.http://ncalculators.com/number-conv...ras-theorem.htmYou know A and C, solve for B and cut your boom. Make sure you cut B a few MM longer than was needed
Team Synergy, Team FBL Rotors---Formerly Dyecocker1-------if its not broke...it will be!
|01-18-2017 01:26 PM|
Silver Spring, MD by way of Sidney, Ne - USA
I checked my helicopters...stock Trex500 and 800 have about 1.5inches of horizontal space from main to tail blades. Maybe just me, but I would not overlap them. I really don't know how much coning I am getting and what a punchout would do.I would love to watch some video of hard inverted punchouts when the blades are overlapping.
|01-18-2017 06:48 PM|
42½ N, 83½ W
Nothing complicated.Measure the straight line distance from the center of the rotor head at the spindle to the center of the tail hub at the tail shaft.That distance must be greater than half your rotor disk diameter plus half your tail disk diameter.If you want to avoid boom strikes, keep your rotor speed up and/or don't punch out inverted too hard.
|01-23-2017 01:06 AM|
|Andy from Sandy|
I would imagine the flyer of a scale model will not be looking to punch out inverted.To avoid a blade strike just make sure there is no overlap whatsoever and then they can never touch.It was curious to me after a few years of flying my Logo 500 that I notice the blades overlap by quite a bit but they have never touched.
|01-25-2017 05:29 PM|
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