RE: F27 STRYKER -Way Past the Limits Part 6 -Go deeper in to the Dark Side...

RE: F27 STRYKER -Way Past the Limits Part 6 -Go deeper in to the Dark Side...
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RE: F27 STRYKER -W... - 5/1/2008 7:54:01 PM

Posts: 2041
Joined: 7/11/2003
From: Charlotte, NC, USA
Status: offline

This post will be edited later to point to various info in thread.

< Message edited by Gryphon -- 5/1/2008 7:55:04 PM >

(in reply to Spid)

RE: F27 STRYKER -W... - 5/1/2008 9:42:07 PM

Posts: 166
Joined: 5/30/2007
From: Norwalk, CA, USA
Status: offline

hi,

My Stryker is all stock but i reinforced the airframe with clear duck brand packaging tape all around except the middle underside where I reinforced/stylized with blue and neon orange duck tape. I added a servo in front of battery bay to control steering on nose landing gear. (Fixed

) landing gear is heavy duty, not very aerodynamic, purchased at hobbycity per a previous post of mine. I opted for this heavy duty landing gear because when i was about to put in some 2mm wire retracts, yall advised me its too wimpy to handle the stryker landings. all in all my Stryker tips the scales at 32.9 oz. Some of the extra weight comes from gorilla glue securing front nose gear mount, three thin (useless?) strips of carbon fiber embedded from the belly and reinforcing the middle of the plane , and 12 small neodynium magnets securing the removable nose, and also the battery hatch. Stock motor, stock prop, stock 11.1v 2200 mAh lipo. Center of gravity is very nose heavy.

Its been sort of windy in southern california and i am waiting for docile weather to maiden my plane. Can you experienced pilots tell me if my plane is too heavy for the stock electronics, what to expect for this nose heavy plane, and do you think it will still glide well especially on landings.

Check out ma pix!

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< Message edited by iamman711 -- 5/1/2008 11:31:05 PM >

(in reply to Gryphon)

RE: F27 STRYKER -W... - 5/1/2008 10:19:17 PM

Posts: 262
Joined: 7/14/2006
From: N. Richland Hills , TX, USA
Status: offline

iamman711, yes, that is heavy. Have you a watt meter? You can get some idea of performance you might expect if you can determine the power the motor/prop is producing. Here are some suggested power needs:

50 - 70 watts/lb = min for light park flyers
70 - 90 watts/lb = trainer and slow flight
90 - 110 watts/lb = sport aerobatic & fast scale
110 - 130 watts/lb = advanced aerobatic & high speed
130 - 150 watts/lb = light 3d and ducted fans
150 - 200+ watts/lb = unlimted 3D

Looks as if you will want at least 200 watts.

(in reply to iamman711)

RE: F27 STRYKER -W... - 5/1/2008 10:53:40 PM

Posts: 166
Joined: 5/30/2007
From: Norwalk, CA, USA
Status: offline

Hey jumper, cool i've never before seen the relationship laid out like that. i bought an eflite power meter but it didnt come with any plugs so its been collecting dust as i haven't decided whether to stick with the blue EC3s or the dean ultra plugs. can you guys help me make my mind. leaning towards ec3 as i own all parkzone products so far like the parkzone charger, 3 lipos, etc. i figure if it aint broke, dont fix it so i didnt bother to swich over to deans but then again i dont know what i am missing.

the good thing about my current landing gear is that it is removable. the nose gear screws off, and the rear gear is secured with clear packaging tape and velcro.

< Message edited by iamman711 -- 5/1/2008 11:00:53 PM >

(in reply to jumper666)

RE: F27 STRYKER -W... - 5/1/2008 11:19:35 PM

Posts: 262
Joined: 7/14/2006
From: N. Richland Hills , TX, USA
Status: offline

I bet someone will pick apart using the watts/lb suggestions, but they are just that....suggestions.

My preference is Deans on everything.

< Message edited by jumper666 -- 5/2/2008 12:03:52 AM >

(in reply to iamman711)

RE: F27 STRYKER -W... - 5/2/2008 2:05:55 AM

Posts: 2041
Joined: 7/11/2003
From: Charlotte, NC, USA
Status: offline

Here is a way of picking apart some numbers.

Well, more like analyzing numbers, etc...

I took the data for the 3S packs from Don's site and tried to figure out a way to come up with an equation.

http://www.donsrc.com/cart/index.php?act=viewProd&productId=12

I decided to see if I could find an equation that would give me some value, if I had a second value.

So how do I get RPM if I know amp draw?

(For 3S in the 23A to 34A range)

RPM = - 347.2 X (Amp) + 32389

Test for 27A: RPM = -347.2X27+32389
RPM = -9374.4+32389
RPM = 23015

Actual RPM from site = 23000 RPM
Difference of 15 RPM

***No all numbers come out as close. Equation results give from 320 RPM too high to 220 RPM too low. As an average those values are within 120 RPM which is not bad at all.

____________________

Here is how you can do your own numbers:

In Excel spreadsheet line up Amps on left column, line up corresponding RPM on next column.
Highlight the whole thing and then click on scatter chart to get a plot.
On plot double click on the points to get them highlighted, then right click and choose add trend line, see which one of the options comes out closer or close enough with the simplest equation.
Make sure to check the box that will display equation while still in the trend line menu.
In the case above I chose linear because things lined up pretty well, otherwise I guess I would have chose 2nd or 3rd order polynomial.

Gryphon

< Message edited by Gryphon -- 5/2/2008 6:37:43 AM >

(in reply to jumper666)

RE: F27 STRYKER -W... - 5/3/2008 12:09:13 AM

Posts: 142
Joined: 6/19/2007
From: Corona, CA, USA
Status: offline

quote:

ORIGINAL: iamman711

hi,

My Stryker is all stock but i reinforced the airframe with clear duck brand packaging tape all around except the middle underside where I reinforced/stylized with blue and neon orange duck tape. I added a servo in front of battery bay to control steering on nose landing gear. (Fixed ) landing gear is heavy duty, not very aerodynamic, purchased at hobbycity per a previous post of mine. I opted for this heavy duty landing gear because when i was about to put in some 2mm wire retracts, yall advised me its too wimpy to handle the stryker landings. all in all my Stryker tips the scales at 32.9 oz. Some of the extra weight comes from gorilla glue securing front nose gear mount, three thin (useless?) strips of carbon fiber embedded from the belly and reinforcing the middle of the plane , and 12 small neodynium magnets securing the removable nose, and also the battery hatch. Stock motor, stock prop, stock 11.1v 2200 mAh lipo. Center of gravity is very nose heavy.

Its been sort of windy in southern california and i am waiting for docile weather to maiden my plane. Can you experienced pilots tell me if my plane is too heavy for the stock electronics, what to expect for this nose heavy plane, and do you think it will still glide well especially on landings.

Check out ma pix!

Hey Man,

Nice work. One word of caution... You have the main gear pretty far forward so there is a possibility that the prop might hit the ground on take off. Have you seen at what angle nose up that the plane of the ground crosses the circle of the prop? That is, turn the prop so it is oriented up/down, place the plane on a flat table, then pivot the plane on the rear gear and note the angle when the prop just touches the table. As long as you don't get near that angle on take off it should work well.

I forgot to ask, or if I did forgot the answer. What kind of field are you going to launch. Dirt or pavement or?

~Bub

_____________________________

Fly it like you stole it

(in reply to iamman711)

RE: F27 STRYKER -... - 5/3/2008 12:18:50 AM

clovus

Posts: 1838
Joined: 9/27/2004
From: B, AUSTRALIA
Status: offline

Hey Guys, You have probably answered this 100 times before, but for those of us on dial up (gasp!) I would take all day to find the answer.....

When you are setting up the Stryker which way does the prop face, writing forwards, or writing facing the back?

Cheers

clovus

_____________________________

<insert witty comment here>

(in reply to BubbleGum)

RE: F27 STRYKER -... - 5/3/2008 12:25:59 AM

Posts: 2041
Joined: 7/11/2003
From: Charlotte, NC, USA
Status: offline

Only the stock F-27B's push on type prop has the numbers facing back.
I don't know the stock prop that comes with F-27C motor.

Almost all of the regular props have the numbers face forward.
The props turn in the direction that has the smooth (thick) edge of the prop cuts through the air first.
If standing in front of plane (at the nose) and facing the motor, the prop will be turning counter clockwise.
If standing behind the plane and looking forward, you will see that the prop is turning clock wise.

Example APC E 6X4

___________________

Very few props are called "PUSHER" props they still have the writings face forward, but are meant to turn in different direction that above props due to having reverse pitch (the prop is twisted the other way).
Again you will see that the smooth wider edge of prop will be cutting through the wind first.
Some of those will be like APC EP 6X4. (The P means pusher and cost more than prop above).
____________________
For a twin, ideally you would want one of each prop of same specs turning different directions.
(1) APC E 6X4 and (1) APC EP 6X4 each turning in different directions to cancel torque effects.
____________________

Strykers have a pusher motor so why do we usually put on regular props even though our motors are mounted in rear?
Because we have a LOT MORE variety to choose from, availability, and price.

With brushless motors we simply control the direction of rotation with swapping any 2 of the 3 motor wires.

Have fun,

Gryphon

< Message edited by Gryphon -- 5/3/2008 12:46:43 AM >

(in reply to clovus)

RE: F27 STRYKER -W... - 5/3/2008 12:53:36 AM

Posts: 36
Joined: 6/22/2003
From: Willoughby, OH, USA
Status: offline

quote:

Here is a way of picking apart some numbers.
Well, more like analyzing numbers, etc...
I took the data for the 3S packs from Don's site and tried to figure out a way to come up with an equation.
http://www.donsrc.com/cart/index.php?act=viewProd&productId=12
I decided to see if I could find an equation that would give me some value, if I had a second value.
So how do I get RPM if I know amp draw?
(For 3S in the 23A to 34A range)

One way of estimating power needed on a prop is to use the cubed relationship. If I have a prop spinning 25000 rpm at 300 watts, to spin it 29000 rpm you will need: 300 watts * (29000/25000)^3 = 468 watts minimum to spin the higher rpm. Generally though you will need moore watts as the motor efficiencies drop as the watts get higher, but it gets you in the ballpark. Also thrust goes with RPM^2. So if you have 16oz thrust at 20,000 rpm at 130 watts, then go to 23,000rpm, expect 16*(23/20)^2= 21.16 oz of thrust and 130*(23/20)^3= 197.7 watts to do it.

Don

(in reply to Gryphon)

RE: F27 STRYKER -W... - 5/3/2008 12:59:46 AM

Posts: 288
Joined: 2/18/2007
From: Novato, CA, USA
Status: offline

quote:

ORIGINAL: iamman711

hi,

My Stryker is all stock but i reinforced the airframe with clear duck brand packaging tape all around except the middle underside where I reinforced/stylized with blue and neon orange duck tape. I added a servo in front of battery bay to control steering on nose landing gear. (Fixed ) landing gear is heavy duty, not very aerodynamic, purchased at hobbycity per a previous post of mine. I opted for this heavy duty landing gear because when i was about to put in some 2mm wire retracts, yall advised me its too wimpy to handle the stryker landings. all in all my Stryker tips the scales at 32.9 oz. Some of the extra weight comes from gorilla glue securing front nose gear mount, three thin (useless?) strips of carbon fiber embedded from the belly and reinforcing the middle of the plane , and 12 small neodynium magnets securing the removable nose, and also the battery hatch. Stock motor, stock prop, stock 11.1v 2200 mAh lipo. Center of gravity is very nose heavy.

Its been sort of windy in southern california and i am waiting for docile weather to maiden my plane. Can you experienced pilots tell me if my plane is too heavy for the stock electronics, what to expect for this nose heavy plane, and do you think it will still glide well especially on landings.

Check out ma pix!

iamman711

I helped a guy the other week at the field with a similar setup as yours, this is what I had to do to make his Stryker balance correctly:
* Removed all duct tape in front of COG-dimples
* Replaced the frontwheel with a Light-Weight alternative that I had laying around
* Replaced his stock 6x4 prop to a 5.5 x 5.5
He later used spray paint to the areas where the very heavy duct tape had been...

Good luck

Stryker Viking

_____________________________

~~~~~~~~~~~~~~~~~~~~~~~
- - - Altitude is still my best friend...

(in reply to iamman711)

RE: F27 STRYKER -W... - 5/3/2008 1:34:07 AM

Posts: 288
Joined: 2/18/2007
From: Novato, CA, USA
Status: offline

New experience...

Though somewhat out of topic I still feel the need to share this with you all...

I maiden my Zagi 5C that I built quite a while ago down at a extremely cool and steep sloope down the coast the other day.

For you who don't know about this plane: It's a 48" flying wing made out of a extremely strong spongie type of foam (EPP) reinforced with CA, only spray glue is used and the whole thing comes together very quickly. It can be motorized but is generally used as a slope flyer...

Being a total virgin in this type of flying I prepared myself and tossed the wing over the edge, and thats when the magic started. It just took off and quietly climbed and climbed without any input what so ever... To make a long story short, 30 minutes later the struggle started to get her down, that's right - the problem is NOT to get this type of bird up, it's to get them down...

It was a blast, and I can highly recommend it as a complement to all Stryker Pilots of the Dark Side, it's great practice that will enhance your skills, and after all our Stryker started as a slope glider they say...

Will now try my motored setup next time.

Cheers to you all

Stryker_Viking

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_____________________________

~~~~~~~~~~~~~~~~~~~~~~~
- - - Altitude is still my best friend...

(in reply to Stryker_Viking)

RE: F27 STRYKER -W... - 5/3/2008 3:46:43 AM

Posts: 166
Joined: 5/30/2007
From: Norwalk, CA, USA
Status: offline

quote:

ORIGINAL: BubbleGum

Nice work. One word of caution... You have the main gear pretty far forward so there is a possibility that the prop might hit the ground on take off. Have you