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Old Oct 10, 2012, 11:15 AM
Sure it'll work
Flyextreme's Avatar
United States, CA, Torrance
Joined Nov 2005
4,271 Posts
Discussion
Is Launch preset "always" necessary?

At this point of my noobness, not having alot of time at the field, not yet getting things completely dialed in, and not having relocated my momentary switch to the left side, I have not been launching with a preset. Also, I've been thinking at this point to keep it as simple as possible so I can concentrate on keeping the plane in the air, and in one piece. It seems to be working fairly well so far.

I've been launching 3 different planes, and each launches a little different from the other.

Just to keep my question simple........

Does anyone "not" use preset?

Thanks, Bill
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Old Oct 10, 2012, 11:33 AM
Will fly for food
davidjensen's Avatar
Bellevue WA,
Joined Dec 2003
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In winds over 8mph the preset is almost unnecessary for my DLG's however YMMV
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Old Oct 10, 2012, 11:42 AM
Launch high. Fly low.
United States, CA, Lake Elsinore
Joined Aug 2003
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I always use it. Always.

Soar!
Jun
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Old Oct 10, 2012, 11:50 AM
G_T
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Joined Apr 2009
5,711 Posts
Always. To not do so is rather inefficient use of launch energy. It also encourages a person to launch at a substantial upwards elevation angle. That is ok, but incurs risk of tip strike and plane destruction. High angle launching should be avoided, particularly by inexperienced pilots. Also, if something goes wrong, the lack of up elevator increases the odds of the plane impacting the ground, or people out a ways in front of you, at high speeds. After all, you go from having one control - elevator on a switch - to no control at all, until you can get your hands on the sticks.

I've used launch preset to dodge midairs on launch before. When it is the only control at your hands, use it.

Gerald
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Old Oct 10, 2012, 11:55 AM
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United States, MD, Baltimore
Joined Feb 2007
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Is it necessary to get the plane in the air? No. Is it necessary for a competetivley high and consistent launch? Absolutely!

On a properly tuned aircraft lauch preset will proved your rotation to the desired angle of climb. This angle will change based on the wind conditions. A little better than 45 degrees into the wind or almost vertical in dead air. After this rotation has occured and the preset is released the model should fly arrow straight until you push over. If it continues to pull up you are wasting valuable energy and need to retrim your speed mode for no recovery at high speed. Thus if you launch a properly tuned aircraft without preset the plane will continue at whatever angle you released it at. Usually less than 20 degrees.

If you are not concerned with lauch height keep doing what you are doing but it is really fun once you start launching correctly and pick up the extra height. I do not know anyone with a competetive launch that does not use a preset. There are two if not three very different phases of launch that need to be accuratly programmed for in order to make them the most efficient.

Austin
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Old Oct 10, 2012, 12:00 PM
Registered User
USA, NY, Jamestown
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If I may add a question... So a preset adds some up elevator? Release the preset switch and elevator goes to neutral? Thanks
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Old Oct 10, 2012, 12:13 PM
sewing machine thumb
United States, CA, Palo Alto
Joined Jul 2001
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Quote:
Originally Posted by JoeR View Post
If I may add a question... So a preset adds some up elevator? Release the preset switch and elevator goes to neutral? Thanks
Yes. You can also experiment with some rudder offset to counter yaw from launching.
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Old Oct 10, 2012, 12:25 PM
Sure it'll work
Flyextreme's Avatar
United States, CA, Torrance
Joined Nov 2005
4,271 Posts
First of all, I suppose I need to make certain my planes are properly tuned. Then, I need to relocate my momentary switch, or add a button.

I have been attempting to throw level which gives me about 10-20 degrees at release, and 2 of my planes make a fairly smooth arch into around 70-80 degees at the top before pushover. One almost wants to start a loop at the top.

Generally in the afternoon (when I get there) at my field, there is almost always some wind. This may be why it's gone fairly well so far.

The hardest part for me is finding time to get in the air enough to smooth out the wrinkles on all levels. So far, I've only go the planes flyable.
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Old Oct 10, 2012, 12:32 PM
G_T
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It sounds like you have the trim / CG well off optimal. Some tuning may be in order...

CA has a number of DLG folk - it might be good if you can get together with an expert pilot for a little work/advice.

Gerald
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Old Oct 10, 2012, 12:52 PM
Sure it'll work
Flyextreme's Avatar
United States, CA, Torrance
Joined Nov 2005
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Quote:
Originally Posted by G_T View Post
It sounds like you have the trim / CG well off optimal. Some tuning may be in order...

CA has a number of DLG folk - it might be good if you can get together with an expert pilot for a little work/advice.

Gerald
As I suspect trim wise. I will be also be focusing one one plane at time from this point on.

Yes, there are plenty of guys here. Most are early morning people, I am not. So most are gone when I get there.....when I finally do get to go. It seems to take forever to do the simplest things. I should have 2 planes dialed in by next summer at the rate I'm going

I also put in a click or two up for launch (very little).



Bill
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Last edited by Flyextreme; Oct 10, 2012 at 12:57 PM.
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Old Oct 10, 2012, 02:07 PM
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Re launch preset. At the moment my model set up feels about right in cruise ( flat wing ) and thermal mode ( down 3 mill ) With a tad down trim on launch pre set I get 50-60 deg launch angle, but releasing as flat as I can, deliberately not throwing up ( tho i probably still do at times ) Any other flyers with down pre set on launch or have I screwed up somewhere.
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Old Oct 10, 2012, 02:27 PM
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USA, WA, Seattle
Joined Oct 2005
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Quote:
Originally Posted by Flyextreme View Post
...Then, I need to relocate my momentary switch, or add a button.
It doesn't have to be momentary or a button (although they do have their advantages). I just use the normal toggle switch on my tx and I know others that do this as well. Works fine for me (although I do sometimes consider changing it).
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Old Oct 10, 2012, 02:29 PM
I have a DLG problem...
Scrib's Avatar
United States, NC, Southern Pines
Joined Aug 2011
450 Posts
I'll add my 2 cents here. Given that DLGs can fly decently at a range of CG locations - depending on your preference for pitch stability, or not - and that some folks are taller and some shorter, there may be more than one way to skin a cat. So to speak.

I have my DLGs setup with a forward CG (cause I suck at flying) making them a bit more stable in pitch, this also requires carrying a bit more up elevator trim to maintain a reasonable flight speed. The up elevator trim at high speed (launch speed) is enough to pitch the plane into a nice ascent angle.
I'm also a little on the tall side and tend to throw more upwards than some do (I can get away with a little more up angle without tip strikes), requiring a little less pull-up from the plane to get into launch tragectory.

That being said, the top launchers use a launch preset in most conditions.
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Old Oct 10, 2012, 02:55 PM
a.k.a. Bob Parks
Glendale, AZ
Joined Jun 2008
2,283 Posts
A DLG reacts differently at high launch speeds versus cruising speeds. I believe that is why GT & others suggest a dive from high up, to pick up speed and then determine CG and elevator trim positions.

If it is taking down elevation trim at launch speeds, it may have too much up elevator at normal speeds. Time to re-read GT's initial DLG setup posts.

http://www.rcgroups.com/forums/showthread.php?t=1441098

BP
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Old Oct 10, 2012, 03:07 PM
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United States, MD, Baltimore
Joined Feb 2007
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OK first a disclaimer. I am not the highest launcher in the group but I am definitly in the top 1/4. This it the way I do it and have helped many sportsman gain 10-15 feet by 5 min of radio tuning using this technique.

1st off CG has nothing to do with launch. Set your cg by feel or dive test in cruise mode. After this is done you will need to set up your launch modes.

2nd "preset" lasts well less than 1 second and only is used to achive desired climb angle.

To explain, there are two different phases of launch that need their own radio programming.
Phase 1 (rotation) From when you start spinning through when you release and until the model has reached its optimum angle of ascent
Phase 2 (Zoom) ballistic part of launch after rotation until push over.

Phase 1 Mix will include:
1. UP elevator
2. (Speed mode) The cleanest air foil possible (this will vary depending on the model usually reflex or even with the tab)
3. Possible rudder correction however newer tail designs and proper technique eliminate this need.)
Phase 2 will include
1. (Speed mode)The same clean air foil as described in Phase 1 properly tuned with elevator compensation that will result in an arrow straight path after Phase 1 is complete.

To achive a well tuned speed mode you will utilize a "Dive test" after and independently of your "CG Dive Test" in this test you will set the camber to the cleanest air foil ie. speed mode and dive. Trim your elevator until the plane will folow a straight line all the way to the ground if you let it. The reason for this is that any change in pitch after your rotation is creating drag. You are only using the angle of attack to creat lift at this point and if the elevator is pitching the plane up you are losing speed for no reason.

You may chose to keep this as your only speed mode as I do. (It is a very high pilot work load at this trim setting used to creat speed then switch back to cruise) Or you may have a secondary trimmed for running home.

Once this speed mode is set up all you need to do is add a momentary switch with up elevator. The amount of up is personal preferance based on how fast you like you model to rotate. I have a very aggresive rotoation and have to get off the Phase 1 preset quickly.

The timing will take some getting used to but you will be able to adjust launch angle based on how long you hold the momentary switch.

G_Ts comment on airframe control while your other hand is busy is also crucial at times.

Hope this helps.
Austin
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