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  #1  
Old 01-13-2005, 06:50 PM
68Budweiser
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Strut angle (Bandit Shovelnose)

Hi friends
I'm having a hard time finding the correct strut angle on my Bandit shovelnose. Fuller said to set the strut at 1/4" below the bottom of the hull with the prop angle down a hair for lift but all this does is make the boat hop like crazy. I took the turnfin off and set the boat on a table then re-adjusted the strut higher (its almost touches the hull) and leveled the strut out so its flat on the table. I ran it again and the hopping is all but gone and the speed came up a little but I'm wonding if the strut should be this high on the Bandit. The very best speed with this boat on 8 cells is 30.1

Does anyone have some good setup ideas for this boat?
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Old 01-13-2005, 07:21 PM
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??????

What motor? What Prop? That speed is a bit slow for that boat.
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  #3  
Old 01-13-2005, 08:08 PM
RvE RvE is offline
 
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Bob
Dick Crowe wrote a set up article for an 8 cell Maus shovelnose and in that article he said to keep the strut up high almost touching the bottom of the hull. The article used to be posted on a club website ...I think it was Pugent Sound Fast Electrics. Not sure if that article is still readily available on the web anymore.

I ran a Bandit SHovelnose in LSH and found it ran better with the strut high...about 1/8" space between top stuffing tube and bottom of hull. I did have an angle on the prop for LSH, but this would likely not be required for 8 cell brushless.

Cheers RvE
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Old 01-13-2005, 08:41 PM
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The article is on Electrics unlimited northwest(?)
There's a link on Fullers site.
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  #5  
Old 01-13-2005, 09:33 PM
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I though the maus had a more shallow angle of attach than the bandit so you really needed to move the strut up. Anyway it would be a help to know what motor/prop you are running. For hopping I'd change my strut angle first and strut height second. My bandit gets 33-34mph on a plet290/20/4 wX435 and corners like its on rails.
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  #6  
Old 01-14-2005, 12:58 AM
68Budweiser
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The motor is a brushless L8 and the props used so far are a plastic X40 & X45. I have a X645 that I have not tried yet and a X445 that is due in the mail any day now. I also have a 10 cell pack that I have not tried yet.
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Old 01-14-2005, 07:22 AM
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Jay Turner Jay Turner is offline
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An 8L should spin around 24,000 rpm or higher on 8 cells - what prop did the 31 mph? I think that an x645 is too much. I'd head toward an x637 or x640. The speed is a bit low; where is the boat's CG? Did you sharpen the sponson edges? Is the driveline free-running? How long are the power wires (to and from batts/ESC and to and from ESC/motor)? Is there a gap between the drive dog and the strut? We need more information to help.
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  #8  
Old 01-14-2005, 10:59 AM
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4 factors that you need to address for a successful hydroplane.

1. Correct CG. Many factors will come into play that will determine a boats CG. I know where I like to start as a ballpark and then a move things around until I get the ride I like. A good place to start with sport boats is around 1 1/2 inches behind the sponson. Riggers, more like 2 or 3.

2. A clean running boat. Sharp prop, sharp trailing edges of the sponsons, good turnfin, etc.

3. Strut Depth - On My Maus boat the angle of attack on the sponsons was very shallow and I had to run the strut right on the bottom of the boat to get the front loose enough. On My Aussie cabover I run the strut deeper. NEVER confuse depth with Angle. depth's job is the front of the boat!

4. Strut angle - Used to lift the back of the boat. If the back of the boat is hopping it is due to excesive strut angle. If you are dragging the tail of the boat then you don't have enough angle. Many people get this halfway correct. They get enough angle to keep the boat up in the straights, but not enough to hold it up through the corners. You'll know when you've got this one right when you don't scrub speed in the corner. Sometimes you need to compromise a little and let the boat hop a little in the straights to keep the tail up through the corners, but some CG adjustment can fix that issue. NEVER confuse angle with depth. Angles's job is the back of the boat!

BTW - Fuller was 100% correct in what he told you as a starting point. I would have said the same.

Do yourself a favor. Go get the current issue of RCBM and memorize Jay Turners article about strut adjustment.

Most people figure out 1 and 2 no problem, but get 3 and 4 all mixed up. The best thing you can do is go to the lake and play will all kinds of strut angles and depths to see first had what happens. If you can get 3 and 4 figured out you will be heads above your competition.

Good luck,
Dick
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  #9  
Old 01-14-2005, 12:24 PM
RvE RvE is offline
 
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Hi Dick - good info in your post
Could you clarify how strut depth affects the sport hydro's performace. This is a bit of a confusing area for me and I'd like to learn more.

Thanks RvE
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  #10  
Old 01-14-2005, 01:28 PM
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Dick Crowe Dick Crowe is offline
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There are a couple things depth will accomplish. The most obvious is sponson Angle of attack. See pics.



A secondary effect on sport hydros is the amount of air you will pack under the boat. A shallow strut will pack more air and may lead to blowovers. If you can pack enough air to keep it light and still keep it on the water.....

The problem is when you get a boat with a flat sponson AOA and have to run a very shallow strut to get enough AOA to loosen the front up correctly you can also grab too much air and it's blow over city. This was the Maus's biggest problem. You can try to fix this with air dams, etc. which is what I did with my Maus and it worked out great! Or get a boat with a good AOA that doesn't require a super shallow strut like the Aussie Cabover 24. That boat has all of the good charicteristics of the Maus and none of the bad. I'm sure there are plenty of other good ones out there but I can only speak to the ones that work for me.

However, none of this matters until you get the correct angle on your strut. You are wasting your time until you can get your boat to run like a hydro with the correct strut angle. Once you know what this angle is stick with it! Change your depth but keep the same angle. (remember, the deeper you have to go, the more the angle will increase on it's own as the tail lifts higher out of the water. Need a picture for this one too?

Good luck,
Dick
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  #11  
Old 01-14-2005, 02:31 PM
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More great info!!! Thanks Dick

On the cabover. Did you ad ride pads or fill in the steps?

Where is your motor mounted?

Thanks
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  #12  
Old 01-14-2005, 03:05 PM
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I didn't do anything to the bottom of the sponson other then make sure the trailing edge was razor sharp.

Motor mount (where the motor bolts up) is 7 1/4 inches from the transom
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  #13  
Old 01-14-2005, 03:48 PM
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Thanks Dick!!!
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  #14  
Old 01-14-2005, 05:03 PM
68Budweiser
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I'm back from the lake and saw some excellent speed this time. My strut was set 1/8th" below the hull bottom on a "flat" angle. I used my new X645 prop and the CG was about 2" behind the sponson. On my first run she hit 37.9 and on my second run with a fully peaked 8 cell she hit 40.2, verifyed by GPS.

Looks like I'm starting to get very close.
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  #15  
Old 01-14-2005, 05:26 PM
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How were you motor/ESC/cell temperatures after two minutes? That is close to 20,000 rpm - with good cells you should be able to run the motor a bit faster. If you can get one, try an x640 or x642. They will let the motor unwind and may give higher speeds with less stress on the components. The plastic props are okay for sport running but don't expect too much with them. 40 mph is much more in line with what that boat should do!
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  #16  
Old 01-14-2005, 08:48 PM
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great thread

thank you Crowe and Turner... you make it all more clear and easy to understand!

i'll be tweaking on my hydro's all night for Sundays "Fun Run" based on this thread...

Capt Ron
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  #17  
Old 01-15-2005, 08:54 AM
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I have raced a Bandit Shovel nose a lot. With different setups.
I started with a brushed Plettenberg, and then I got me a Lehner 1940/8 brushless motor and raced with 14-16 cells.
The bandit shovel nose is scary fast!!!

On the photo below you can see air under the transom. Strut height is rather high as I went around 50+ mph on this occasion, and did not need that much lift. One can almost see air under the left sponson

Prop was X642, X640, and V937/3.

To reduce drag I made me a new hatch out of a balsa sheet.

More photos of my shovel nose at http://www.vasterortsrc.nu/Sigurds%2...ds%20boats.htm




Best
SIgge
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  #18  
Old 01-22-2005, 03:58 AM
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Newbie FAQ's!

Hi Guys,

As we don't have an "FAQ" section for newbies wanting to go fast, I thought I'd start one- perhaps this can be sticky'd at the top (will help until the search is back up and running).

What makes a boat go FAST? A combination of aspects are involved, and many factors are interrelated.

* Proper COG or Center of Gravity - As a ball park, for Mono hulls, this is typically 30% of total hull length from the transom. For Hydros, this is typically 1" to 2" behind the sponsons (longer for riggers). Start there, and see what works best for YOU. The topic of COG goes further, torque roll, high or low COG, centralization of weight, etc, etc.

* Sharp trailing edges (trailing edges being where water leaves contact with the hull, etc). A rounded edge will draw water around it, a sharp edge will let water "break" cleanly from the hull. ABS hulls, Fiberglass hulls, etc, all can be sharpened (though, some fiberglass hulls may not need it, you decide). Some use CA (Cyanoacrylate or crazy glue), some use "squadron putty". Run a piece of tape along the trailing edge, fillet, and sand sharp.

* LIGHT! Keep your hull as lightweight as possible. With every bit of weight you add, ask yourself, "is this extra weight going to offset the advantage of this piece?". Lighter weight means faster acceleration, and less "lift" needed from your prop to get your boat "on plane" (which means more power to go forward instead of up and forward).

* Batteries! Run the best cells you can afford. They DO make a HUGE difference. IR (internal resistance) is much more important in FE's than it is in RC Cars (NiMh and NiCd cells). Boats typically draw much more current than cars do. You need batteries that can deliver the required current as efficiently as possible. "Cheap" packs are just that- they'll heat up and won't deliver decent voltages at the high amp loads found in fast boats.

I could write a book, but many others have their answers, too!

Dick Crowe wrote an especially informative post about strut tuning. Perhaps a moderator can splice it into this and sticky to the top of the board...

If this gets sticky'd, please add your input to answer those newbie questions.

Thanks,
Paul
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  #19  
Old 01-22-2005, 09:38 AM
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ok for awhile.....

paul I'll put a sticky on it but I think it should be in the set up forum.. cept it get losT ...LOL ...
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  #20  
Old 01-23-2005, 06:35 PM
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another nice site for fe boat info for newbies

another good resource....

I recently revisited this site, and it has some good newbie/faq info, as well as some great tips/techniques/how-tos for seasoned racers:

http://www.rcboataholic.com/

(hope the owner does not mind the publicity...I have no connection)
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