Props and Chine Walking (My Specific Case)

[dasboata]

I recently did this to a big ole 45" Dumas hull. Too much epoxy to hold a stuffing tube. Also under Rx box. Box was easy to move and the epoxy I got out using a Dremal MultiMax. You know the ones with the oscillating flat blade. Use the metal blade on it and don't be afraid to bend the blade for easier angles. Rent one if you don't already have one
But if you buy one you may be surprised how many jams it helps you out of around the home.

If you hit the epoxy with a soft heat gun it will soften just fine for easier removal where as polyester will not do that you need a right angle dremal to remove the stringers I have some pics on here doing that to a 1990 scorpion

[Pennstater]

@T.S.Davis - You are right; I need to think about what I want to do. I'm not looking to break speed records, but I'd like to go a bit faster without the boat getting loose. While I am thinking about it, here's some more photos for your viewing pleasure...

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[Pennstater]

One more...

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[srislash]

And on that note, anything wrong with trying a smaller prop?probably a 40 mm. I mean if you are just 'trying to get it running'.

[Jamey]

And on that note, anything wrong with trying a smaller prop?probably a 40 mm. I mean if you are just 'trying to get it running'.

That is just what I was thinking. Being submerged it will run with a smaller prop then what is common for a boat that size. I personally would try both a m440 and x440/3 blade. Not to mention 10S on that motor isn't exactly a low RPM setup so you will still get some okay speed. Just depends how fast you are wanting to take it.

[Pennstater]

At half throttle now, the boat is faster than anything I have ever run before (glow or electric). It's that "splinter in my mind" knowing that I am in fact only running at half throttle that makes me want to try for a bit more.

It probably can't hurt to try the props first - easy to do. The builder/tinkerer in me wants to do the Stinger setup, but if props can help, then that seems like a prudent first step.

40mm seems like a big step down in size, but since the prop is completely submerged I guess it is a good place to start. What does a 3-bladed prop give you over a 2-bladed prop (more surface area)? And I haven't been able to find a definitive answer on the difference between an "m" prop and an "x" prop - what are the differences?

Do you think I can get away with an unfinished (stock) Octura prop to test before spending the mony on one that has been sharpened, balanced, etc.?

I want to thank everyone for their input - one thing I love of RC hobbies in general; so many disciplines (electrical, mechanical, aerodynamics, fluid dynamics, plain 'ole gut intuition, etc.) to keep the mind young and to keep learning new things.

[Jamey]

To me that is the whole thing with these boats, just so fun to build and modify. If you want this boat set up right don't bother wasting money on the smaller props and just move forward with the re-config. There is no doubt you will want surface drive for best results.

For a quicker and less expensive fix though, in theory a smaller prop should let it settle down in the water much better and allow you to get closer to full throttle but keep some good speed and stability. Believe it or not cruising around at half throttle for long periods of time can be bad for the speed controller. Keep that in mind. As far as how much smaller to go you are just going to have to test. I have never ran a raw prop. Sharpening and balancing is fairly straight forward just be cautious of the dust and not breath it in. Only wet sand, etc. I am no expert but I usually leave the general blade shape and simply remove and smooth the casting flaws. Put a good edge on each blade with a sharpening stone to the back side only. I like the orange balancer they sell here in the OSE store. You just remove a slight amount of metal from the back side of the heaviest blade until they seem about even. If wanted maybe polish a little with some fine sandpaper under running water. Common sizes you might think about would be x/m440, x442, x/m445 . In a nutshell the "m" series has the leading edge of the blade near the hub cut back, or what is termed de-tongued. The "tongue" has the lowest pitch of the blade area and does little work at high speeds. You can compare pictures in the OSE store of the x and m models. The m tend to be more efficient at high speeds and are a little easier to turn. Where the "x" bites better at lower speeds but can be a hindrance at high speeds. You can also de-tongue the x series with good results if you are into modifying blade shape, it is just that some of the work and thought has already been done for you if you buy an m up front.

Come to think of it though this "m" versus "x" theory really applies to surface running. Not sure how each may respond totally submerged.

[Pennstater]

@Jamey - TYVM for the great information!!! I have read too that running at half throttle for an extended period of time is not good for the ESC. Why is that? When I pull the boat out of the water, the ESC is barely warm to the touch. Does temperature mean anything in this case (I am using a Seaking HV130).

I think I will try giving the surface drive a go (why not, right???). I took a look through OSE and came up with the below (and you guessed it, more questions)...

Speedmaster Stinger Strut - 3/16" (.187) prop shafts - http://www.offshoreelectrics.com/pro...os-stinger-str

Speedmaster 1" Rudder Assembly - http://www.offshoreelectrics.com/pro...d=ros-spdr-013 (what setback - best place to mount (right or left of Stinger - I usually see them mounted to the right))???

1.) Teflon tubing inside the stuffing tube (my current setup has it)?

2.) Reuse my current flex shaft (should be long enough - will measure to be sure - not sure about the actual prop shaft length needed for the Stinger (buying a new one is not an issue if required))?

If "no" to #1 and "yes" to #2, then...
> K&S Tubing = 1/4" brass for .187 Flex Cable per http://www.offshoreelectrics.com/pro...dh-ks-brass-tb

If "yes" to #1 and "yes" to #2, then...
> K&S Tubing = 9/32" brass for Octura .187 Teflon tubing per http://www.offshoreelectrics.com/pro...dh-ks-brass-tb
> Teflon Liner for .187 flex cable - http://www.offshoreelectrics.com/pro...=oct-oc187t-24

If "yes" or "no" to #1 and "no" to #2, then...
> OSE 3/16" (.187) Assembled Flex Cable for 3/16" Propellers : 3.125" Long Prop Shaft - http://www.offshoreelectrics.com/pro...?prod=ose-1190

3.) In a surface drive setup, keep my same prop (OSE CNC Machined Prop, number 4814)?

Thanks all!!!

[srislash]

Yes it is mostly a heat issue with partial throttle running. It can be more in the long run dependant on the switching of the ESC design but let's not get into that( I just had a good read on this). You look to be on the right track with your choices there. I run that Standard stinger on my 35" delta force mono with this rudder and it handles awesome
http://www.offshoreelectrics.com/pro...prod=ose-80050
I am thinking the rudder you chose with the 4" option

How heavy is that boat? 3/16" flex will take a lot but I am just checking.

[Pennstater]

I took the boat to a UPS store (I don't own a scale) and they read out 11.5 lbs, fully loaded (run weight).

I think I am ready to pull the surface drive trigger. I have the above-mentioned parts (and then some) in my OSE cart. Drive line parts are 3/16" as of right now... do I need to go to 1/4" (I noticed no issues with the current 3/16" cable)? If I should go to 1/4" is it okay to get the flex cable that is 1/4" but steps down to 3/16" at the prop shaft? If yes, then do I stick with the 3/16" Stinger or use the 1/4" Stinger? If no, then it's the 1/4" Stinger, new thrust bearings, drive dog, and prop.

Does the stuffing tube get cut flush with the transom or does it protrude just a bit and fit inside the Stinger?

I noticed that some of the flex cables have different length prop shafts (2.5" to 3.125"); what length prop shaft would work with the Stinger?

While I am waiting for answers/parts, I'll look to start dismantling the current drive line (remove strudder, stuffing tube) and remove the radio box (for easier access to the inside of the transom).

[Pennstater]

I took the plunge and converted over to a surface drive setup. See the maiden voyage here: https://youtu.be/2hSttM7sjfA (I'll apologize in advance; video was shot with my old Galaxy SIII bungee-corded to my forehead). Install was fairly straightforward; I just took my time.

I think it ran great. Much more stable and much better turning radius. I definitely got above half throttle but never hit full throttle. Boat remained stable; no chine walking. It was pretty breezy and I was a bit of a chicken. Note the 15 minute run-time/video length (and I had to chop off a couple of minutes). Temps were barely warm and battery cells had 3.78v remaining.

I think the hull is running a little "wet"; what do you guys think? Tempted to angle the Stinger up just a nudge.

Thanks for all of the advice. Very much appreciated.

[Jamey]

Very nice! What battery set up and mah are you running? 15 minutes is an incredible run time. Not going full throttle increases run time so it will drop when you start running it faster.

You should post up some pictures of how it turned out

[Pennstater]

10s (2x5s) 5000mah 25c (high voltage, low current). Motor is a Leopard 4092 930kv.

I'll try and post up some pics later tonight or tomorrow evening.

Any thoughts on if the boat was running too "wet"? Or is it too hard to tell in the video?

[Jamey]

I actually watched the entire video

Im not sure I would change anything though it was difficult to tell in the video. When the boat was close enough to see you were either in the middle of a turn or just barely on plane loafing by. Overall, at least at the speeds you ran, it look well tuned in my opinion. Kick up the throttle some and you might find it is actually a little loose. You have a very well disciplined throttle finger my friend!

[Pennstater]

I give you "props" for watching the whole thing!!!

Thanks for taking a look and weighing in; much appreciated. I first need to find a day where it's not so windy - what seems like a gentle breeze at the house turns into some pretty good wind down by the water. Also note that I am playing it a bit risky as I have no recovery vehicle (except for maybe the random paddle boarder that drifts by), hence the reason I kept my finger out of the trigger. The local West Florida club runs at a lake about 45 minutes south of me - I might have to make another trek down there to run it wide open.

I didn't get to taking any pics tonight, so I'll try tomorrow and get some posted.