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Old Feb 04, 2010, 07:39 AM
Halifax Electric Flyers Assoc
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Halifax, Canada
Joined Jan 2008
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That lacing seems like a great idea.

I drilled holes in my firewall as well and PU-glued some toothpicks into the foam for extra strength. I found, however, that the holes in the wood firewall compromised its strength. On the maiden flight I tried a hand-launch and it bounced off the ground 20 feet ahead of me, not too hard, but enough to break the mount right along my two holes. Your lacing method looks to me like it would avoid that problem.

Speaking of Turnigy power alternatives I've been very happy with the 2213-20/1050kv. I suspect it's not a huge upgrade in power from the Rimfire but it's been beautifully balanced, vibration-free, quiet and strong. My Seawind is in fact outfitted with HobbyCity electronics from stem to stern, with a Supersimple 30amp ESC, HXT900 servos, HobbyKing T6A radio gear and Turnigy 3S 1300mah packs, and it has all been very reliable.

Water's hard but the Seawind is a lot of fun in fresh snow.

Dave
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Old Feb 04, 2010, 08:26 AM
We shall serve the Lord
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Originally Posted by va3mw View Post
#2 will be to use 2 servos for the aerilons instead of 1. This will allow for better tuning and who knows, maybe flaperons.
With the ailerons extending to the wing tips, you may want to consider using reflex instead of flaps to slow down the Seawind. The full scale Seawind reflexed the ailerons up and the flaps down. If you droop the ailerons, you are creating "washin" and the wingtips will be the first part of the wing to stop flying and stall. Aileron droop could cause some nasty slow speed snaps and stalls.

If you use the two servos, it would be easy to program in both functions on a 3-way switch. Then get up high before you try the flap or reflex positions.

McD
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Old Feb 04, 2010, 07:59 PM
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With the ailerons extending to the wing tips, you may want to consider using reflex instead of flaps to slow down the Seawind. The full scale Seawind reflexed the ailerons up and the flaps down. If you droop the ailerons, you are creating "washin" and the wingtips will be the first part of the wing to stop flying and stall. Aileron droop could cause some nasty slow speed snaps and stalls.

If you use the two servos, it would be easy to program in both functions on a 3-way switch. Then get up high before you try the flap or reflex positions.

McD
Thanks, you are right, with the ailerons that large, it could kill the lift. Reflex sounds interesting. I did some quick searching on it, but can you tell me more to help clarify it?

thanks again...
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Old Feb 04, 2010, 08:55 PM
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It's not that the ailerons are so large that downward deflection would kill the lift, its that downward deflection near the wing tip would cause the early onset of tip stalls. Check out the terms washout and washin in reference to wing tip design.

The short version is that if the rear edge of the wing tip is higher than the rear edge of the center of the wing, then you have washout. This design will cause the center of the wing to stall first while both wing tips are still producing lift. This results in the nose of the plane dropping straight ahead and the plane continuing to fly. Imagine holding the plane up with a finger under each wing tip. That's what the air would be doing.

Washin would be where the rear tip of the wing tip is lower than the rear tip of the center of the wing. This results in the wing tips stalling before the center of the wing resulting in a snap stall depending on which tip stalls first. Imagine holding the plane up with both fingers under the center of the fuselage.

Reflex just refers to deflecting the ailerons upward. Hope this helps.

McD
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Old Feb 04, 2010, 10:30 PM
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Originally Posted by kingsflyer View Post

Reflex just refers to deflecting the ailerons upward. Hope this helps.

McD
That is what I guessed it was about. Thanks for taking the time to explain it to me. I really appreciate it. I was looking at the wing just now and trying to find some epoxy mixing sticks to extend the mounting holes for the aerilons.

I also did some testing with 2 different 8x6" props (an APC and the one that came with the Seawind). On the 924kv Turnigy's, they both spun up to 8000 rpm drawing about 150 watts on the bench.

I do need to build a thrust gauge and see which one is pulling better.
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Old Feb 05, 2010, 06:58 AM
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With that motor, you may want to try a 9x6E prop. I know the clearance it really tight, but that lower kV needs a larger prop. I'm using a 9x6E on an 1100 kV at about 200 watts on a 2200 30C 3-cell Lipo. It's great fun!
McD
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Old Feb 05, 2010, 10:37 AM
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With that motor, you may want to try a 9x6E prop. I know the clearance it really tight, but that lower kV needs a larger prop. I'm using a 9x6E on an 1100 kV at about 200 watts on a 2200 30C 3-cell Lipo. It's great fun!
McD
I tried a 9x6 as a test on the 924kV motor.

It only made it to 7000rpm/155 watts and the motor got to 35C after about 3 minutes. I didn't measure the thrust as I have to build a jig for my test motor mount.

I'm just starting to play with motor/prop combinations. I appreciate that a lower KV motor provides more torque.

I had a 9x6 on my last one, but it sank when the motor departed!
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Old Feb 05, 2010, 05:48 PM
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I'm still building my new one Seawind.

Today I replaced the 1 aileron servo with 2 after making a new mounting plate out of an expired security card. I then redid the linkage so that is now doesn't not touch the backing plate for the wing.

I also notched the wings so that the aileron control doesn't bind with the wing. The servos are just test fitted. I might not punch a hole in the bottom of the wing but rather just have the wires exit where they are.

The picture should tell the story.
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Old Feb 05, 2010, 08:54 PM
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Nice looking install. You might want to round the edges of the CF wing dowel. It will make it easier to install the wing.
McD
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Old Feb 06, 2010, 07:18 AM
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Nice looking install. You might want to round the edges of the CF wing dowel. It will make it easier to install the wing.
McD
Good point, I haven't gotten to that yet. Since the dowel takes some abuse, I might just reinforce it by sliding a 'rod' through it to the wing between the servos. Fortunately I left enough room to do that.

I happen to have a spare wing, I might try to modify it for flaps using the same design as the ailerons (or, I could go to 3 servos). I would then only have 1 servo for ailerons and 1 for flaps. The trailing edge of the wing at that point is pretty substantial. Would it have enough effect at low speed for a take off. When the water is chopping, it seems take longer to get off the water.

Being foam, this makes it fun to hack around with.
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Old Feb 06, 2010, 01:25 PM
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I think using that area for flaps would work fine. You may even want to consider making them "split" flaps. That way the top of the wing surface and the aileron torque rods remain unchanged and the flaps could actually be larger and extend farther forward under the wing. Sound like a good idea to me.
McD
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Old Feb 09, 2010, 08:18 AM
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I've got this wing finished with both servos. I can now run flaperons or the opposite. It will be interesting to test how it flys (or falls).

I've also reinforced the carbon wing pin by extending it between both aileron servos (you can do that with a tooth pick) and glue it in place. I've had that break free in a crash (maybe that isn't a bad thing).

I've mounted the receiver in the rear compartment about 1cm off the bottom.

Ailerons are HS55's and the Rudder and Elevator ar HS65's. The ESC is a Turnigy 18a with the battery smart leads. I'm going to stick with the stock 8x6 or an APC 8x6. I still need to do some thrust tests.

Before I hit the water, I will punch a drain hole in the bottom rear so that water drains in flight (it is just impossible for fully waterproof this thing).

I've got corrosion block on all electronics (ESC, receiver and servos).

Once I get my old broken back from the cottage, I'm going to modify that wing for flaps by cutting them just behind the current seam in the wing that the control rod for the aileron travels.

More to come.
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Old Feb 09, 2010, 12:49 PM
Halifax Electric Flyers Assoc
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Hi va3mw -- I for one am following your reports with interest.

In terms of props I recall someone earlier in this thread thrust-testing several options. I believe he concluded that the stock prop performed significantly better than other 8x6 options, attributing the difference to the back-angled prop tips. Have you settled on the 924kv motor?

Dave
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Old Feb 09, 2010, 10:03 PM
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Hi va3mw -- I for one am following your reports with interest.

In terms of props I recall someone earlier in this thread thrust-testing several options. I believe he concluded that the stock prop performed significantly better than other 8x6 options, attributing the difference to the back-angled prop tips. Have you settled on the 924kv motor?

Dave
Funny you ask... I just finished some testing with my 'thrust gauge', which is a piece of 3/4" dowel on a plate that is attached to my scale. The setup has the motor push down on the scale. Works well for about the 15 minutes it took me to build it (not including the 20 minute trip to Canadian Tire for the doweling).

You be the judge. They are all pretty close. If you need the power, then go with the 3 blade Parkzone 8.7x6".

The APC looks like the most efficient with 5.81 watts/oz of thrust, so this should result in longer flight times.

The stock Seawind produces more thrust than the APC at 663g vs. 645g.

My Turnigy 2213 22turn 924kv 17A Outrunner got pretty warm when running anything bigger than 8". After about 45 seconds, it got to over 40C, but that would be due to the fact I was drawing about 17A at full power.

Kv: 924rpm/v
Operating Current: 6A ~ 14A
Peak Current: 17A
Suggested prop: 11x5.5 E-prop
Suggested Battery: 1300~2200mAh 3S1P
Weight: 59g

Hope that helps.

My next series of tests will be to see what speed/thrust/wattage level is more efficient for each of the 4 props.

Mike
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Old Feb 10, 2010, 11:08 AM
Halifax Electric Flyers Assoc
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Halifax, Canada
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Those are very interesting results va3mw. Did you find you were drawing 17A across all four propellers?

If I'm reading the chart correctly it seems to me the PZ 8.7x6 3-blader is the winner. You seem to achieve a 35% thrust improvement over the stock prop at a cost of only a marginally lower thrust-per-watt ratio. Unless the amp draw was way higher on the 3-blader it seems like a good bet. I've always thought this plane needed a 3-blade prop anyway, for aesthetics alone....

I've only ever used the stock prop on my 20-turn version of your motor, but I have a Master Airscrew 8x6 3-blade on hand, waiting its turn. Maybe it's time to try it out.

Looking forward to the next round of testing!

Dave
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