Posted by Dparture |
Apr 20, 2016 @ 04:33 PM | 7,392 Views
Dec 11, 2007, 01:15 AM
LBMiller5
Use the Force!
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San Marcos, CA
Joined Jan 2005
2,179 Posts
aireze,
There is a very complicated formula for determining the load factor of a propeller, but in it's most simplistic form, for a 2-bladed prop, the load that a prop places on a motor is equal to the diameter cubed times the pitch or D x D x D x P. For a 2 bladed 10x6 prop, the load factor would be 10 x 10 x 10 x 6 or 6,000. For a 12x8 prop it would be 12 x 12 x 12 x 8 or 13,824.
The more complete formula, which takes the number of prop blades into account is D x D x D x P x Square root (N-1), where N = the number of prop blades. For a 2 bladed prop, the square root of (2-1) is the square root of 1 which is 1, so the term just drops out of the equation.
For a 3-bladed prop, the correction factor is the square root of (3-1) or the square root of 2, which is 1.414.
For a 4 bladed prop, the correction factor is the square root of 3, which is equal to 1.732
So if you have a 3-bladed 9x7 prop, then the load factor is 9 x 9 x 9 x 7 x 1.414, which is 7,216, and this would be roughly wquivilent to a 2-bladed 10x7 prop, which has a load factor of 7,000.
If you had a 4-bladed 12x7 prop, then the load factor would be 12 x 12 x 12 x 7 x 1.732 or 20,950 This would be roughly equivelent to a 2-bladed 14x8 prop, which has a load factor of 21,952.
In the end, if the load factor of 2 props is the same, you will get similar RPMs from the two props, and similar performance.
So there you go, hope that helps!
Lucien
Posted by Dparture |
Apr 10, 2016 @ 07:32 AM | 5,026 Views
Battery specs:
- One of the UK dealers was kind enough to advise that:
"... recommended is a 3s 1800mAh. As there is plenty of room inside the model most customers are fitting the larger 3s 2200mAh packs"
- From the photos in the linked review, it looks like the ESC/batt connector is an XT60:
https://www.centuryuk.com/docs/rcmw%20stol%20500.pdf
Posted by Dparture |
Apr 02, 2016 @ 11:20 AM | 31,826 Views
http://www.stefanv.com/rcstuff/qf200203.html
Measuring Pitch
"Most propellers are labeled with their pitch and diameter, but it is possible to determine both given an umarked prop. The diameter is straightforward to measure of course.
Measurements needed to determine the pitch of a propeller should be taken 3/4 of the way from the hub to the tip.
Measurements needed to determine the pitch of a propeller should be taken 3/4 of the way from the hub to the tip.
To measure the pitch, lay the propeller flat on a table, measure 75% of the way from the hub to the tip, and draw a line across the propeller blade. Measure the width of the blade at this point, along the surface of the table (i.e. the width of the blade’s shadow if there were a light on the ceiling overhead). Next, measure the height of the front and the back of the blade, and compute the difference between these two to determine the height.
The pitch is then given by the formula:
pitch = 2.36 diameter height/width
There’s nothing magical about the number 2.36; it’s just 75% of π (pi), because we’re measuring pitch at the 75% diameter mark.
The reason we measure pitch at 75% of the diameter is two-fold. Generally, the pitch of a propeller is not completely constant, varying somewhat from hub to tip to optimize it for the different linear speeds at each point along the blade. The pitch at 75% corresponds roughly to the average effective pitch of the propeller. Secondly, the propeller is
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Posted by Dparture |
Mar 20, 2016 @ 01:03 PM | 4,899 Views
Interesting link which shows effect of glue gun temp on bead...
http://www.instructables.com/id/Make...ue-gun-cooler/
Posted by Dparture |
Mar 14, 2016 @ 08:46 PM | 5,564 Views
Documenting the dimensions here...
Stuart's build video indicates that the outer wing panels can be removed -- but hoping someone can tell me whether you feel would really be viable to routinely remove the outer wing panels for transport, or would this put too much wear and tear on the joiner tube, thumbscrews, etc.?
And as part of this I'm looking for:
1) the length (span) of the outer wing panels,
2) the length (span) of the center wing module (and
3) how much the joiner tubes stick out beyond the center wing module if I were to leave them in (think I read these are 36cm, so do they protrude by 18 cm?)
4) distance from the nose tip to wing leading edge and approx wing chord.
1) 19 1/2"/495mm
2) 19"/483mm
3) 14"/356mm overall length, can be removed
4) 13"/330mm and 10"/254mm wing cord
5) 43 1/2"1105mm nose to tail
Wing tip are easily removed, that is why they used the system they have with the thumbscrews.
Posted by Dparture |
Mar 10, 2016 @ 08:14 AM | 4,627 Views
My eBay reputation particulars as of 3/10/16 [click to enlarge]
Posted by Dparture |
Jan 18, 2016 @ 10:44 AM | 5,337 Views
I was looking for the dimensions for the Apprentice S 15e floats, noticed a closed thread where others were looking for this so thought I'd post what I found from E-Flite:
Float Set: 15-Size
Product Specifications
Length: 32.4 in (820mm)
Weight: 11.5 oz (326 g)
http://www.e-fliterc.com/Products/De...ProdID=EFLA550
Posted by Dparture |
Jan 29, 2015 @ 06:38 PM | 6,880 Views
"For those of you that like the idea of DLG, but aren't very athletic, or get dizzy easily, you might want to try my "SLG" method, or "Sling Launched Glider" method.
I taped a 15 foot length of sewing thread to the left wing tip.
I start out with about 3 feet of string, and start whirling the glider around with my hand over my head. I adjust elevator trim until the glider has only a very slight amount of nose-up tendency. ( note: I always fly gliders with the CG as far aft as I can stand it).
As I whirl the glider around my head, I gradually let out more string, until I have the thing going whistling fast, then release the string.
With Discus launch, the velocity achieved depends on how fast you rotate, and the length of your arm.
With the Sling Launch method, the only things limiting my launch velocity is the strength of the glider, and control surface flutter.
But then again, the UMX Radian was never intended for such high speeds. Since my poor bird is about worn out, I'll be building a purpose-built Sling Launch glider, probably a "plank" style with a bird-like planform, ala "Alula" style.
But the Sling Launch method was definitely getting the little Rad much higher than I could ever throw it, that's for sure.
All you need is thread and tape to try it. I'm not inclined to discus launch myself, so I came up with this lazy man's way to "git 'er done".
Just don't release if your elevator trim isn't right, or you'll either dive into the ground or loop around and hit yourself in the back of the head, all the while wondering "Where did it go"?
Instead of taping the thread to the wing, you can fashion a simple hook from paperclip wire and tape that to the wingtip. Tie another paperclip to the string. Attach a small streamer to the string, when you release, the string falls off, ala high-start style. " -- from dayhead
Posted by Dparture |
Dec 30, 2014 @ 12:06 PM | 5,706 Views
I was wondering if these might work, perhaps with addition of a bit of padding -- stackable spice rack shelves (they come in pairs but stack arbitrarily high).
Probably most useful for wings-on transport of smaller gliders/sailplanes, parkflyers which can fit into the rear deck of the car. Some kind of nose hold-down might be required, particularly for transport. A bit less appropriate for storage due to the need to unstack, or at least pop out a leg or two, for access
Depth = 10 3/8"
Width = adjustable from 7" to 17"
Inter-shelf Clearance ~ 3.5" or 5" depending on which legs are used
Commonly available -- search AMZN for:
Spicy Shelf Patented Spice Rack and Stackable Organizer
Posted by Dparture |
Dec 28, 2014 @ 03:14 AM | 5,130 Views
Was hanging some Christmas decorations using 3M Command hooks.
This got me wondering if the smaller hooks might be useful as a removable tow hook -- enabling Hi Start or catapult launching, while also being removable in a non-destructive manner...
http://www.command.com/wps/portal/3M...mmand/Command/
Posted by Dparture |
Dec 26, 2014 @ 04:42 PM | 5,531 Views
For completely unrelated reasons I came across the PowerUp paper airplane power module, at the same time I happened to be looking at a free flight toy foamie.
The PowerUp 3.0 power module performance with a paper airplane is pretty impressive:
http://www.poweruptoys.com/
So I took a closer look at the small Guillow free flight toy foamies, like their Space Shuttle and Sky Raider:
http://www.guillow.com/spaceshuttle.aspx
http://www.guillow.com/skyraider.aspx
And I began to wonder about doing a mashup between the two... need to check out the approx. length of the PowerUp module vs. the length of some toy foamies, but it could be a bit of a hoot to have a Bluetooth-phone controllable powered Space Shuttle glider.
For the Shuttle, my initial thought would be to mount the PowerUp module inverted along underneath the Shuttle fuse, as this would provide for a bit of COG flexibility plus a low VCE for the small, black 'rudder vane' on the power module -- and perhaps thereby enable the Shuttle to bank despite the stubby delta wings -- who knows I might even luck out with something approximating coordinated turns...
The 'rudder vane' seems pretty stout so it would seem to stand a chance of protecting the prop on landing.
So, before I spring for a $50 power module... what are the odds that something like this will fly?
Posted by Dparture |
Dec 21, 2014 @ 09:11 PM | 6,317 Views
>> Constrained Beach Venue/New Ka-8
The good news -- Picked up a new PZ Ka-8 last week, and my nearby venue is a smooth, sandy seacoast beach which is often deserted in the Spring and Fall.
The bad news -- I only have about 200' to waters edge at dead low tide, and less than 50' at high tide, with a breeze that's usually onshore... so seems very tight for a Hi Start, and the glider would be feet-wet at release -- something which seems to pose some considerable LOW risk while learning to Hi Start -- and I've yet to see a float option for the Ka-8.
Another option would be to try a shortened Hi Start based perhaps on the heavier duty version of the Great Planes Up -Start -- would need to limit flying to fairly low tide and the Up-Start would need to be shortened considerably, as even the Up-Start appears to be designed for a 300' setup.
>> PLAN B: Quadcopter Tow, or Lift & Release?
Another thought I've had for this venue, is to use a stabilized quadcopter to aerotow or lift the Ka-8. Most of the Youtube vids that I've seen have been a bit horrifying -- usual approach has been to drag the glider up vertically by the nose with a 'drop' release from pure hover. Best outcomes have been flyable but only after a big loss in altitude due to recovery needed... and then there's the crash risk (this has happened) from entanglement of the towline in the quad's blades.
I expect it might take a fair amount of practice for a team to establish a nice aerotow
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Posted by Dparture |
Dec 16, 2014 @ 03:11 AM | 5,774 Views
The attractive qualities of the Parkzone Radian include its simplicity, light weight, and easily removable wings. However, a common and desirable mod also seems to be the addition of spoilers or air brakes to facilitate landing -- something which can add weight, be complicated, and also make the wing removal process a bit more of a hassle.
In the 'crazy but simple' idea category... passive spoilers:
Wondering if the Parkzone Ka-8 spoilers (see below) could be adapted to the Radian in a simple,
passive way by modifying the spoilers with a spring clip/latch (I'm thinking that some small cut-down nylon tweezers glued in the right place. might work) to enable deployment and locking in the raised position simply by doing a loop -- allowing gravity to pop the spoilers with the clip/latch locking them in position.
The clip or latch could be mounted on the leading edge side, so pressure on spoilers would be helpful in moving them into the fully locked position. Small canopy magnets might be an even simpler alternative to a mechanical clip/lock (if they can hold the wing on a Champ they can probably keep the spoiler raised). Also there might be some ideas or parts associated with positive locking mechanisms for landing gear that are worth considering
The spoilers would be lowered manually after landing by resetting the clip/latch. Obviously, at least when flying with the passive spoiler equipped wing-set, inverted flying must be avoided until you want the spoilers deployed -- but this seems reasonable for simple soaring or thermal hunting flights.
This way all that would be needed is mounting of the modified Ka-8 spoilers in the Radian wing... and hey, if nothing else, flying the "spoiler deployment loop" should be kind of interesting...
Posted by Dparture |
Dec 09, 2014 @ 01:05 AM | 6,589 Views
Interesting approach to squeezing a Tactic rx in the Kunai...
http://m.youtube.com/#/watch?v=rvHnURsewD8
Posted by Dparture |
Jun 06, 2014 @ 01:36 PM | 6,080 Views
As a newbie, I thought I'd keep a "Ground Zero" log of my learning process in the hope that it might help others get down the curve a bit faster with fewer mishaps...
Had a successful maiden flight, and then a couple more short flights, with my Hobbyzone Duet before getting overconfident and flying up against a roof, knocking about an inch of the nose off, argh. (Note to self -- take a time-out to reflect on your successes and near misses before barreling right along.
)
So, after practicing on some foam "popcorn" to get calibrated (3rd attempt worked well), I did my first foam-safe CA repair to re-attach the nose cone.
All the advice re using CA and kicker sparingly was right on -- particularly the caution to spray kicker from 4-6" away. I did try to drag the CA 'drops' in a line to ensure more surface area coverage and that seems to have worked well.
I also covered the break in some high stretch (curve-conforming) 3M yellow tape, which nearly matches the factory decal treatment, to smooth out some ruffles in the foam and for a wee bit more structure. As part of this, I also found it was helpful to cut a strip of paper, the same width as the tape, to do a 'dry fit' and see how the tape might wrap around the nose, before committing to applying the tape.