Help with tow hook position - RC Groups
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May 01, 2005, 10:37 PM
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bilbobaggins's Avatar

Help with tow hook position

Hello everyone, I want to convert a 2 metre slope soarer to a flat field bungee launch but am unsure of where to put the tow hook. Can you help please.
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May 01, 2005, 11:40 PM
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Vince inTX.'s Avatar

12-15 degrees ahead of the CG. Measure this with the plane upside down. place a protractor on the bottom of the wing (now the top) and place the "focal" point of the protractor on the CG. Now draw a line on the side of the plane forward (towards the nose) 12-15 degrees from 90. Where that line crosses the bottom plane of the fuselage is where you put your tow hook. This method works nomatter how tall the fuselage is.

This is a good starting point and should get you straight and stable launches. If the launches are not steep enough for your liking you can do one of two things. either move the cg forward (easy but not recomended) or move the tow hook back. I would not move the tow hook back any more than 1/4 to 1/2 inch at a time. As the tow hook gets closer to the CG your launches will become steeper but they will also require you to be much more active on the sticks.

May 02, 2005, 04:50 AM
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bilbobaggins's Avatar
Hi Vince, many thanks for helping so soon.
Kind regards
May 02, 2005, 11:00 AM
Deletedfor proving Nauga wrong
Note. some slope models the wing is very close to the bottom, and that can create a stability problem on launch.

Some people compensate with a "bridle" (2 hooks spaced out on the wings and about 2 ft of line with a snap-clip in center to lock the bridle onto the towline) The fixed distances of the 2 lines to the wngs formng a triangle adds a little roll stability.

You can also compensate by launching more level and letting the model build speed before pulling for climb. (usually they nose-up on thier own... but with a low wing, the hook may not be low enough to pull the nose up for you.)

Its simply that there's no distance between hook and center of drag to make the hook help control the aircraft's attitude. Bungee launching a Zagi for example is a "fun" project if you don't know to watch for this.

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