ALUMINUM prop......WOW!

[Shooter]

Well, I thought I'd try it for kicks. Run to run comparison resulted in favor of the Aluminum prop. I realize there are all sorts of variables (prop balance, sharpening, conditions, etc....), but the AL prop resulted in slightly higher MPH on the GPS. I took a pass with the Beryllium, swapped props, and took another pass with the Aluminum. So if anything, it didn't degrade the performance!

It makes sense that it would spin a little faster with less rotating mass (old car buffs used to reduce rotating mass under the hood.......crank, con-rods, etc...).

They sure are cool looking if anything. Our lake is extremely clean, so I don't have to worry about too many floaters that might cause damage.

I'm running a stock UL-1 with an AL X440 prop. So far, it's topped out at 43mph. If I could just get rid of the sponson dance, I could steel some more speed.

[Ub Hauled]

Have you seen the CNC props from CMDI?
Sharp as a razor and really light... good stuff.

[Drag Boat Bob]

Well, I thought I'd try it for kicks. Run to run comparison resulted in favor of the Aluminum prop. I realize there are all sorts of variables (prop balance, sharpening, conditions, etc....), but the AL prop resulted in slightly higher MPH on the GPS. I took a pass with the Beryllium, swapped props, and took another pass with the Aluminum. So if anything, it didn't degrade the performance!

It makes sense that it would spin a little faster with less rotating mass (old car buffs used to reduce rotating mass under the hood.......crank, con-rods, etc...).

They sure are cool looking if anything. Our lake is extremely clean, so I don't have to worry about too many floaters that might cause damage.

I'm running a stock UL-1 with an AL X440 prop. So far, it's topped out at 43mph. If I could just get rid of the sponson dance, I could steel some more speed.

What other props have you tried? Any 2-blades?

The x440 3 blade is very close to the load of a L40x57/3 and there are some who are reaching 50+mph with that prop.

In a previous post you said you were using the Hyperion 6500's. Is that what produced 43 mph?

Also, what is your setup: Strut, rudder, etc.

I ask, because I think you can go faster than 43mph with 6500 mAh batteries.

[eboat]

I wonder if the lipos were warmer for the second run vs the first run
You should try the two props again in the reverse order and see if you get the same results

On my hydro I have some weight added to help keep the front down and you can really tell when the lipos warm up it starts to lift because it is going faster (with the warm lipos)

Just a thought

[Shooter]

I'll have to check out CMDI.

D-Bob,
I agree. I was hoping for more speed with the batts that I bought. We will be at the lake again this weekend for more testing and I'm hoping for calmer waters. I really think that has a lot to do with the lower speeds. I'm running about 7/8" strut depth (bottom of hull to center line of prop) w/3° downward angle. The sponsons are dancing like mad. Thanks.

[Shooter]

No doubt I need to run more testing to increase the confidence in my findings. Good point about the lipo temp. The best test would probably be alternating props for at least 5+ runs each.

[Ub Hauled]

The bouncing around of the sponsons is inherent to the hull, most guy have/had that going on, each has a different cure.
The UL in racing trim I have seen people being successful with 642 or 445 even, all temps in check.
The 440 is a great prop for a day to day scenario, longer run times and less stress on the equipment.
To make sure that all variables are the same (except the prop) pre heat the lipos to the same temps to each different props and keep all the rest exactly the same.

[Drag Boat Bob]

I'll have to check out CMDI.

D-Bob,
I agree. I was hoping for more speed with the batts that I bought. We will be at the lake again this weekend for more testing and I'm hoping for calmer waters. I really think that has a lot to do with the lower speeds. I'm running about 7/8" strut depth (bottom of hull to center line of prop) w/3° downward angle. The sponsons are dancing like mad. Thanks.

Measure the strut depth with boat on tabletop with prop over the end (pic). The distance from tabletop to bottom of the boat is strut depth. This is just so we are on the same page.

3 degree downward angle? Is this a positive or negative angle (see pic).

I moved my batteries perpendicular to the boat (cross wise) and it helped when it got too loose. Not sure if yours will fit that way, but if so try it. It moves the CG forward a bit.

Also, if it remains too loose, drop the strut to 1" and see if that helps. It did me...

[Rumdog]

I'd suggest flattening out the strut. You may be getting too much lift in the rear.

[6S HYDRO]

Delta Force 26 = Funnest boat i've ever driven!

ME TOO!

[Shooter]

Thanks guys. Just for reference, I DID try lowering the strut a little (OK, more like a LOT) and her rear end got as squirly as a hound dog in a flea market!! ....and then of course the usual....turn into a kite and land like a rock.

Sppplaaaaash!!!

Back to some earlier questions. Drag boat - Yes, I've tried the X440, 2 blade prop.

I'm going to get some measurements tonight (flat on the table method) and see where I stand. I'll also flatten out the angle for the next run. I had a huge amount of downward angle (prop wash angled down into the water).

So far, I love this boat. Speeds are incredible. It's not nearly as stable as my Vegas yet, but I'm sure it will get there. Just need to sharpen my pencil a bit.

Once I get this thing dialed in, I'll repeat the Aluminum vs. Beryillium test.

[mickvk]

Thanks Shooter, I look forward to hearing your results - could you also note water conditions? I'm wondering if there are any setup recommendations for different conditions or if there's a general setting that's best for all. I'm a little new at this. Thanks.

[Shooter]

Unbelieveable! :huh: Apparently I had two problems. After close inspection, the clasp on the rudder pushed it's way downward (off the ball joint). I have no doubt this is why the rear end has been doing a little dance.

Geez... All these adjustments and I had this extra variable in there affecting my results!! Argghh!! No wonder why she can't sit straight.

I also found some pretty significant cracks in the hull. I pushed on them and my finger went right through!! Yipes! A little epoxy should do the trick. Probably due to all those flips, roles, aerobatics, etc...

She's all ready to go again. Hopefully tomorrow night I'll get a few runs in. Just have to convince the wife why I need to spend an hour at the lake playing with my toy boat:stupid:

I'll get back to the AL prop comparison as soon as I get this thing dialed in. Did I mention I lost the AL prop? Yup, it's spending some QUALITY alone time at the bottom of the lake. Well, that's not exactly true. It has some friends down there. The drive dog ($7), the flex shaft ($18), and the prop nut. Hopefully they're having a good time. (2) more AL props are on order.

I'm currently set-up @ 1" strut depth (table top method....bottom of hull to bottom of strut) and 0° angle. X440/3 Beryillium.

[Drag Boat Bob]

Also keep an eye on the little 'allen set screw' on the forward side of the rudder just above the lower arm of the rudder bracket. It WILL come loose without thread lock or similar.

[6S HYDRO]

the AL props dont bend easy?

[Ub Hauled]

yes they can, I have seen Berillium Copper props bend like they were paper, but they are more resilient then you'd think

[Shooter]

Sad day on the lake folks. She went into a spin and the hull detached from the deck. Never seen anything like this before without hitting anything. One of the sponsons smacked the lake sideways and it just tore the deck off. A little epoxy should do the trick, but this hull is Frrrrrragile!!!!

All back together. I took her back out and and then encountered another problem after about 2 minutes of running. Stopped dead in the water. Disconnected the batts, taped up again, and it went about 300ft and stopped. I repeated this several times before I ran out of tape!! I've narrowed it down to the SC. Judging from the info on the forum, it sounds like the cap. I ordered a few from Kintec this morning.

Geeeeezz...never had this much trouble with a boat before. I can't complain though because I've never had a boat out the box this FAST for the price! (I think my last FE after all said and done was around $600!)

Anyways, simply just trying to do a prop comparison. Still love the UL-1, but am quickly getting frustrated with the fragility.

[Shooter]

BTW - The Aluminum props only have 1/4 the mass of a Beryillium prop!! 2grams compared to 9grams!! These things are light....and as someone else mentioned suprisingly resiliant.

[Fluid]

The prop mass difference is completely insignificant compared to the rest of the rotating mass. It is such a small percentage of the total motor rotor and cable that there can be no noticeable difference in performance. But an aluminum prop has major disadvantages over a CuBe or SS prop - the most important being the inability to take a sharp edge. The aluminum alloy used in boat props is a coarse-grained metal that is too soft to take an edge. The result is a noticeable performance reduction compared to CuBe. Fool yourself if you want to, but the main advantage of an aluminum prop is the lack of the need to balance it.



.

[Shooter]

Fluid - I agree completely with the inability of holding a sharp edge. This is no doubt a bummer. Would plastic props suffer this same predicament??

I question however the significance of the rotating mass. At the RPM's we are running, ANYTHING would seem to help. The prop hub mass doesn't have much of an effect since it is closest to the centerline, but the blades are THE farthest rotating mass from the centerline in the entire system. I think your comment "no need to balance" indirectly supported this.

Probably a moot point if we can't hold a sharp edge though....

[Fluid]

Question all you want, but the only thing that a reduced rotating mass does is reduce the time needed for acceleration. It would have no effect on top speeds. But that percentage of mass difference is so tiny - far less that one percent - that any difference would never be noticed in a boat. It would be covered up by the increase in cavitation - in fact acceleration of the boat could be even slower if the prop speed becomes too fast to 'hook up' quickly.



.

[Eodman]

What kind speed do you lose with an aluminum prop? For fun running & ease of use I would think the aluminum one would be the way to go!

Are we talking 8 - 10 mph or just 2 or 3?

[6S HYDRO]

definitely not 8-10, and probably not 2-3.

[Jeff Wohlt]

I remember Chris Fine telling me about the benfits of Alum props...I could never agree on that one. Sounded like it was better.

I never saw any difference but I did remove a couple blades long ago when a Octura prop would have survived. With high rpms I have heard of people throwing blades of on alum props.

We all ran alum props on our bassboats years ago....we then went to SS.

When you are fishing a back end of a cove in 2 feet of water and don't trim your motor up and the alum blade hits the bottom you can bend a blade...then you run it and blow your lower unit seal out.....the SS it does not bother.

I see Alum as better than CF but not near as good as BU or SS.

[Shooter]

I haven't completed the testing yet, but so far I haven't measured any significant difference in top speed. Assuming a frictionless axis of rotation, there is no theoretical difference in max angular velocity between a lighter or heavier prop, so top speed should be the same. However, the prop theoretically will spin up to RPM faster (more angular acceleration!!) Perhaps too much acceleration as Fluid mentioned.

If you are looking at it just for convenience (no balancing, no cancer causing dust, etc....), I'd say Go For It!!