Wright Stuff B

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smartkid222
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Re: Wright Stuff in Division B!!!

Post by smartkid222 » November 13th, 2008, 2:46 pm

planesarefun52 wrote:when you have weight left over wthout being over the minimum, how should you add it?
If your plane is under minimum weight you should add ballast to the center of gravity.
If it's extememly underweight, consider a design change.
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Re: Wright Stuff in Division B!!!

Post by carneyf1d » November 13th, 2008, 11:04 pm

you only know you are at level 3 when you know how to cure microfilm :)

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Re: Wright Stuff in Division B!!!

Post by jander14indoor » November 14th, 2008, 8:54 am

bob3443 wrote:This is not my best event but I would say add some glue to the joints.
Nooo.... not glue...

OK, there may be an advanced trick where adding glue is useful, but be careful with it. Smearing a THIN layer of balsa cement along both the top and bottom of a spar MAY stiffen it a little, but don't use so much as to get over the minimum weight. Doing one side only will cause it to warp. This doesn't work so good with super glue as its very difficult to control the weight gain.

For most, the first step if only a little under, say .5 gm or less, is to add just enough clay to get to the minimum and use it to adjust balance. Part of the trimming for best flight time.

IF you have more wt to work with, add clay and fly the heck out of that plane paying attention to where its breaking or bending excessively. Then build new parts using slightly heavier (and stronger) pieces. Places where you may want to add wt are where its breaking most often. Commonly the wing posts first, then the wing spars. The next spot is the motor stick, especially if it bends a lot due to the rubber band. Trick there is to use same density wood, but a thicker piece, not more dense wood. Last place to add weight is to the tail boom or stab spars, unless they are too fragile, or worse, floppy. Hardly ever to the ribs.

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Re: Wright Stuff in Division B!!!

Post by Iceman » November 14th, 2008, 1:31 pm

Adding ballast is usually best way. There is all ways odd circumstances where doing something else might be better. For instance, if your extremely under weight say by nearly two grams rebuilding a component to make it stronger would be best solution.

About double gluing, That is what I do for planes and did for towers by the way. Understand need to double glue depend on what type of glue and or mixture with acetone used. My preferred method is with ambroid or duco mixed with good portion of acetone this allows glue portion to penetrate wood, yet dry light wieght. The second coarse is straight duco or ambroid with only little acetone mixed in but often just straight glue. The reasons for double method are it will be lightest method, the under side of joints on my building board wouldn't get "proper even" gluing with it and it is arguably strongest/lightest method.

Again, depending on the glue used the reason joints sometimes are weaker after second gluing is because acetones in glue have weakened first gluing. The mistake was second gluing
used less cement and probably pentrated the wood deeper than first or the glue wasn't given enough time setup fully.
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Re: Wright Stuff in Division B!!!

Post by bob3443 » November 15th, 2008, 4:44 pm

How long should the rubber be? should it be a little longer than the motor stick or the same size when not stretched?
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Re: Wright Stuff in Division B!!!

Post by andrewwski » November 15th, 2008, 6:52 pm

As far as I know, it should be exactly the same length as the distance between your rear hook and prop hook. Any longer will result in slack that won't give you turns.

You will theoretically get more power if you stretch it further, but at the expense of turns. You'd be better to get thicker rubber if you need more power.

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Re: Wright Stuff in Division B!!!

Post by gh » November 15th, 2008, 7:08 pm

I don't see how using more length would be wasted. Sure, torque would be reduced, but more rubber is more energy. The slack itself shouldn't make a difference until the winds are almost all spent. I always used as much length as 2.0 grams allowed. Thicker rubber isn't practical because it would give you more torque and more height, so you'd be hurting flight times in lower ceiling sites.
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Re: Wright Stuff in Division B!!!

Post by bob3443 » November 15th, 2008, 7:35 pm

Another question: How do I reduce the friction on my propeller? Pictures would help. Also isn't the maximum weight of the motor 1.5 grams?
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Re: Wright Stuff in Division B!!!

Post by andrewwski » November 15th, 2008, 8:25 pm

gh wrote:I don't see how using more length would be wasted. Sure, torque would be reduced, but more rubber is more energy. The slack itself shouldn't make a difference until the winds are almost all spent. I always used as much length as 2.0 grams allowed. Thicker rubber isn't practical because it would give you more torque and more height, so you'd be hurting flight times in lower ceiling sites.
I was recommending thicker rubber if you need more torque, instead of using a shorter, stretched motor, which also gives more torque.

If your rubber sags when it's relaxed, you've got a lot of winds that either aren't going to unwind, or are going to do so very slowly. I used to adjust the length of the hooks so that the 2.0 g motor would be the same length as that distance.

In regards to the prop...use a good thrust bearing and some very straight wire (I used to get the Ikara/attachment from Harlan). I suppose a little graphite between the thrust bearing and music wire would reduce friction, but probably negligibly if you've got a good fitting prop assembly.

The max motor weight may be 1.5 g...I'm not sure as I'm not in B...but for the past long time when it was a C event it was 2.0 g, which is what you'll see a lot of people mention.

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Re: Wright Stuff in Division B!!!

Post by Iceman » November 15th, 2008, 9:36 pm

Any person that has set a indoor rubber powered airplane record in short ceiling heights with various model classes will tell you a thicker loop will provide longer flight times. It is true you will back off full torque to avoid hitting ceiling but more energy will be used than longer loop.
To long of loop will result in landing with excessive turns left over. It's like not using all gas in your car or carrying around dead weight. The more involved reason is long loop in short ceiling doesn't provide enough torque per turn to power propellar fast enough. Resulting in
plane falling way to fast even though propellar is turning.

What ever you do use full amount of rubber allowed. Short ceilings need thicker motors and tall ceilings longer motors.
Doug Schaefer
Northmont
Ohio

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