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Old Sep 05, 2001, 10:23 AM
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Arlington,VA USA
Joined Jan 2001
1,862 Posts
GWS props less than 10" are wimpy

I have a number of GWS orange props and notice that the difference between the widths of the blades towards the center of the hub is great.

On all props less than 10", the widths "drop off" by about 50% for the 9" prop (vs the length is only a drop of 10%). The trend continues on down for the 8" prop also. The 9" prop is so weak being that it has about half of the plastic that the 10" has at the hub that the blades break off with the slightest of resistance....even an otherwise "normal" landing of a 9 oz plane will snap the prop if it gets caught on the slightest amount of grass (most all the time for non-wheeled models).

Does anyone have pointers on how I can "trim-down" the lengths of the 10" props to a 9" or 8" prop?

Many thanks,

Pullin'
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Old Sep 05, 2001, 10:37 AM
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mattk17's Avatar
Dallas,TX
Joined Jul 2001
1,656 Posts
I have no experience with trimming props but will agree with you on 9" and less GWS props being weak. I've had 9" props bend on my tigermoth from a routine grass landing.

One idea that was brought up is to use the APC 9x6 prop. I have one and it works great but doesn't fit the motor shaft so you either have to use an adapter or other idea. Another ezoner had an idea of using rubber tubing as a makeshift spacer to use the apc prop on the lite stik type motors. I've tried it and it works great except the prop tends to start slipping over time.
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Old Sep 05, 2001, 11:00 AM
Old age is not for sissies
Azarr's Avatar
Dayton Intl, Ohio, United States
Joined Jan 2000
7,805 Posts
You might want to take a look at the APC Slow Fly Props, they're available from 7 to 11" diameter. I also have a prop adaptor that fits the GWS gearbox.

Azarr
www.azarr.com

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Old Sep 05, 2001, 03:46 PM
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Walled Lake, MI, USA
Joined Feb 2000
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Picked up an APC 8x6 at the LHS this lunch hour, and was surprised by the composite hub adapters packaged with it. The APC 9x6 that I previously bought only had two adapters, both for fairly large shafts. The 8x6 I bought today had four adapters -- the same two larger sizes plus two smaller ones. The smallest looks as if it may fit the GWS gearshaft. I don't know if only the smaller size APC props offer four adaptors, or if this is a running change for all of the APC slowflyer props to fit the smaller gearshafts that are becoming more common with the smaller motors. Both the APC 9x6 and 8x6 slowflyer props have much more meat at the base of the blades where they meet the hub than the smaller GWS props. The APCs are also much stiffer than the GWSs.
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Old Sep 05, 2001, 07:18 PM
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United States, VA, Chesterfield
Joined Mar 2001
5,322 Posts
One way to avoid breaking the orange GWS 9 inch prop is to make your own landing gear wire for the TM with .061 music wire and make the struts about an inch longer (more scale like) and use Trexler air wheels. That way you won't hit the prop on the ground or blacktop when landing.

Pat
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Old Sep 05, 2001, 08:59 PM
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Walled Lake, MI, USA
Joined Feb 2000
11,182 Posts
Pat, I have to agree with you about the longer landing gear and/or bigger diameter wheels with the 9x7 prop. At this point, however, I'm interested in trying the 8-inch prop experiment.

APC prop update: After getting it home, I found that the 8x6 APC prop has a smaller hole than the 9x6 APC. The 8x6 will take a slight reaming out for Azarr's prop adapter to fit into it. The smallest of the four adapters that comes with the 8x6 is slightly small for the GWS gearshaft, and the next largest one is slightly too big. So, obviously, APC was not thinking about people using their props on the GWS geared motors. Oh well, doing it yourself is half the fun, right? I'll try to patch something together to fly this weekend and report back.
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Old Sep 06, 2001, 12:27 AM
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Walled Lake, MI, USA
Joined Feb 2000
11,182 Posts
I have broken far too many GWS 9x7 props, and will not purchase another. I tried flying outdoors on the GWS 10x4.7 this weekend, and it was fine. I also tried a GWS 8x6, which pulls the Tiger Moth around a lot better than I thought it would. It looks just as weak as the 9x7. But the shorter length has kept it from snagging and breaking -- so far. My next experiments will be with the APC 9x6 and 8x6. I prefer using a smaller diameter prop where possible, and since the GWS 8x6 works well, I'm hoping the APC does, too.

Azarr, I have one of your prop adapters, and I'm also the one who mentioned the idea of using tubing inside an APC prop in a GWS nuts-and-washers sandwich. I have not tried the Azarr adapter yet because I wanted to try a lighter weight solution first. Perhaps a way to reduce slippage with the tubing solution is with a couple of thin rubber washers between the metal washers on either side of the prop hub to provide more frictional grip. I'll have to try weighing all of the nuts, washers and tubing and see how the weight compares with Azarr's prop adaptor, which is fairly lightweight for being all metal. Certainly, Azarr's adaptor is the simplest solution, and I believe the performance of the APC props is going to be worth the effort to find the best APC mounting solution on a GWS gearshaft.

By the way, if anyone decides to order one of Azarr's prop adapters, I highly recommend adding to the order one (or more) of his small antennas. The performance is outstanding, and the absence of a wire dangling out the back of the aircraft is well worth the cost of the antenna ($10).

[This message has been edited by Dave Hederich (edited 09-05-2001).]
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Old Sep 06, 2001, 10:07 AM
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Walled Lake, MI, USA
Joined Feb 2000
11,182 Posts
Late last night I had great success mating the 8x6 APC prop with a DX-A gearshaft. First, I installed the largest of the 4 inserts provided by APC and inserted it in the hub. These cylindrical composite inserts press fit into the back of the hub. The insert with the largest hole (thinnest walls) makes the hole though the prop hub a consistent diameter from front to rear.

Next, I took a piece of soft plastic fuel tubing slightly longer than the depth of the hub and crammed it into the hole in the hub. Because the 8x6 APC has a smaller diameter hole than the 9x6, the tubing really has to be forced in. With the tubing squeezed tightly into the hole, it will barely fit over the DX gearshaft. In fact, it cannot be pushed on, but must be screwed on like a nut over the shaft's threads.

Of course, before screwing the prop on you need to install one of the standard GWS nuts and a flat washer. I used a #4 washer, which is slightly larger than the standard GWS washers. Once the prop is screwed tightly down to the nut and washer, finish off with a second #4 washer and standard GWS nut. Tighten down firmly to squeeze the small excess of tubing on each side of the prop between the two washers and you are done.

The fit is much, much better than with the 9x6. It fits so tightly that you cannot turn the prop on the shaft even when applying great force. Prop slippage should be non-existent. I'll have it up and running tonight, and will report back on the results.
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Old Sep 06, 2001, 11:25 AM
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Arlington,VA USA
Joined Jan 2001
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Pat, I hand-launch these planes (no place in the field for a strip)....extra weight and drag of landing gear is noticable.
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Old Sep 07, 2001, 02:04 PM
in persuit of low wing loading
Gordon Johnson's Avatar
Boston, Mass
Joined May 2001
6,428 Posts
Pat, thanks for the info. I was going to ask you what diameter wire you used. The other night I landed a bit too hard on my driveway (had a bunch of kids on my lawn and wanted to get it down fast without hitting anyone). Anyway, but some nice breaks in the cowl because it hit the ground when the landing gear flexed.

BTW, are you going to NEAT? I'll be there Friday only.

--Gordon
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Old Sep 08, 2001, 12:01 AM
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Walled Lake, MI, USA
Joined Feb 2000
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Went out at lunchtime to try the 8x6 APC, and the wind was far too strong and gusty to put a Tiger Moth in the air. In setting it up at home last night, I ran it up with the APC 8x6 prop and a new Sanyo 6-cell 120mAh NiCd pack (from a GE/Sanyo 9V). I wasn't prepared for the level of thrust at full throttle -- it almost pulled the TM out of my hand! It obviously has way more thrust than any of the GWS props I've been running on Rayovac NiMH 9Vs. It will take a little experimenting to determine what roles the new prop and new battery played in creating the additional thrust. Without even putting it in the air yet, I'm guessing that the 8x6 APC on 6 cells will be a winner.
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Old Sep 10, 2001, 02:35 PM
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Walled Lake, MI, USA
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11,182 Posts
Short update: In another thread, I mentioned that in back-to-back static testing with the APC 8x6, my strongest Rayovac NiMH 9V and the new Sanyo NiCd 120mAh 6-cell pack seemed to produce about the same amount of thrust and motor speed (by ear). Unfortunately, I do not have any test equipment to get more accurate readings. But it does appear now that it is the APC 8x6 prop that is responsible for the strong static thrust, and not the new NiCd pack. I'll post a flight report as soon as the wind and rain fully departs the Detroit area.
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