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- This topic has 8 replies, 6 voices, and was last updated 14 years, 9 months ago by Anonymous.
06/16/2008 at 10:07 am #40887AnonymousInactive
Are there any changes you can make to a model to change the response to hook position ? Say you have a model that diverges due to the hook being too far back, can you modify anything such that the divergent response is alleviated ?
CHE06/17/2008 at 5:29 am #45947AnonymousInactive
Well, it sounds to me as though you have answered you own question. The hook is too far back…….move the hook forward. I have found that a location of 15-20 degrees forward of the CG is a good place to start. Make one change at a time and document the changes. You will find your answer will jump off the pages, right before your eyes. Then get out and practice, practice, practice.06/17/2008 at 7:52 am #45948AnonymousInactive
“The hook is too far back…….move the hook forward.”
Yes, I could do that. However, I would like to leave the hook where it is and change something else if possible. Any ideas ?06/17/2008 at 1:03 pm #45949DENNIS PHELANParticipant
I’d guess that increasing the fin area has gone through your mind?
Try adding a strip of wood to the front of the fin to increase area, or add a subfin?06/17/2008 at 3:47 pm #45950AnonymousInactive
I have to also agree with Dennis…..increasing your fin area will help reduce your problem. I prefer a fairly large fin back there. If you look at things as percentages of wing area…I believe my fin and rudder are around 1% and then I split that between the two something like 60/40. I’ll have to go back to my specs and let you know.06/17/2008 at 6:15 pm #45951AnonymousInactive
Checked my numbers and I’m at around 2%. If it’s a really short model, make it bigger.06/17/2008 at 8:24 pm #45952AnonymousInactive
As a power flier……..
Isn’t the hook positioned relative to the CG?
So move the CG back – and get some trim problems instead.
JB06/19/2008 at 10:41 pm #45953Jim FarmerParticipant
Right, move the cg back, but for tow only. Don’t know how you would do it – some kind of sliding or pivoting weight arrangement, or maybe a weight connected to the towline (illegal?).06/24/2008 at 3:07 pm #45954AnonymousInactive
Always good to make sure the basic set-up is correct. Most people use the bottom of the wing as the vertical CG position. For the standard F1A fuselage high, this is close enough– (I have found the actual vertical postion is actualy above the wing). Standard hook position is .6 to .8 inches fwd the CG (.7 inch a good start place). It is actualy better to measure the standard 17 degrees from vertical if you do have a “non-standard” height fuslage or a vertical cg that is not near the bottom of the wing. Also check the other basic set-ups are right– ie I was helping a flyer chase a tow problem when I saw the model had a large amount of stab tilt.
The current posts seem to to refer to “classic” type glider. If the model in question is an electronic model, then reducing the stab incidence in straight tow could be a solution. I have found that in calm condition, I can crank up the straight tow incidence to increase pull (line tension). However, in turbulence the model is prone to tip stall— one indicator is the tip stall can happen to either side.
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