Revolt motor height?

[TheJANG]

Hi all,

First time posting, though I've been all over the place trying to learn as much as possible. I'm a car/truck guy and the Revolt is my first proper boat, so please bear with my ignorance

In the car world the height of the center of gravity is always a big deal, and we always do stuff to get it as low as possible. With my Revolt in pieces for unnecessary upgrades & silly experimentation (can't help myself), I quickly noticed that the motor is up about 1/2" higher than it physically could be. Even considering room for a 40mm motor & its jacket, plus an air gap to aid cooling there still seems to be an excess of space under there.

A big part of my brain screams at me to chop that down to lower the CoG and reduce the cable/tube angle, but a couple neurons thankfully remind me that I don't know anything about boats, and shouldn't assume that I do. So, my questions to the community are, what is the reason for the Revolt motor (as an example) being up so high? What would be the detriments of lowering it & rebending the stuffing tube? Is there such a thing as a CoG that's... aaaagh my brain.... too low?

Thanks in advance for any advice!

[Make-a-Wake]

I wouldnt mess with it, the COG would barely be altered by moving it, and if you are running for sport/pleasure, then for sure dont move it.

[tlandauer]

COG in boat talk generally refers to the balance of the boat longitudinally. Sure, the lower the components sit in the hull , the more stability it will have.
I don't have the boat, but looking at pictures I think I can understand what you mean, keep in mind that this boat is designed by Grim, and from all the members' reports it is one of the best RTR boats out there. Therefore I think the settings are optimal for a mass-produced RTR. No telling what angle and height Grim would have made if it were a one of a kind boat. I don't know how much of a difference you will notice.
I keep reminding myself on these mass -produced boats one has to take into consideration the "EASE OF MANUFACTURING", in my opinion, if the motor mount were to be lowered to your level of desire, the tighter clearance ( margin) would mean longer assembly time, that price tag would be off the maker's goal.
This is just my opinion, could be complete B.S. !!
The reason I am writing this is that if I were you I would not attempt to rebend the stuffing tube, you would at the very least have to take that tube out, remeasure everything. Time could be well spent doing a build YOURSELF to you exact liking. I say this because if you have the know-how and desire to rebend the tube, you must have the ability to build a boat yourself.

[Grimracer]

dauer,

Good question and one that does not come up all that often.

Your cars do not lean in" in the corner.... a mono does...

Do this.. Think about the relation of the motor to mass/force as the boat leans into a corner. If you get the motor to low the boat will try to self-right.. if its to high it will badly over compensate. You want to spike the weight of the boat on the keel as the boat turns.

Its not a perfect science (none of boating is. lol) but you get the picture.

Grimracer

[ray schrauwen]

It's called COB (Center of Boyency) that grim talks about isn't it?

I've wondered about this for some time. Since the revolt handles great I personally would leave it alone.

I'd have to dig up my old books on fast electric setup or just mono COB setup.

[siberianhusky]

We have a Revolt running here now, first time I saw it I thought the same sort of thing but about the battery tray. That boat still needs a bit of trimming to see if the chine walk can be sorted out, It's only been run a couple times for 2 packs each time so it has very limited testing and tuning done. I have to say I'm pretty impressed with how it runs for a RTR boat, also looks much nicer in person than in pictures. Until I saw one I had my doubts about that canopy.
I wouldn't change the motor mount, it's a pretty good setup, I don't think you would see much if any gains moving the motor down that small amount, especially for the work/risk involved cutting the existing one out of a new boat!

[Mike Caruso]

We have a Revolt running here now, first time I saw it I thought the same sort of thing but about the battery tray. That boat still needs a bit of trimming to see if the chine walk can be sorted out, It's only been run a couple times for 2 packs each time so it has very limited testing and tuning done. I have to say I'm pretty impressed with how it runs for a RTR boat, also looks much nicer in person than in pictures. Until I saw one I had my doubts about that canopy.
I wouldn't change the motor mount, it's a pretty good setup, I don't think you would see much if any gains moving the motor down that small amount, especially for the work/risk involved cutting the existing one out of a new boat!

Look for an old book ISBN: 0-911295-21-6 which will help you learn about mono, cat and rigger hulls. They is another good oneISBN: 0-911295-26-7 again loaded with Boat info these books are dated but still apply except for most of the battery sections. Just do a search on line they are still out there great books my friend.
Mike

[Mike Caruso]

It's called COB (Center of Boyency) that grim talks about isn't it?

I've wondered about this for some time. Since the revolt handles great I personally would leave it alone.

I'd have to dig up my old books on fast electric setup or just mono COB setup.

Ray,

I am reading the old books right now LOL I listed them below.

Mike

[siberianhusky]

Thanks for the books but I don't know! Starting at 113$ used going up to 225$! for the Finch book.
The second is reasonable 13 to 30$ so I'll look into ordering that one.
If they are that valuable they should look at doing a reprint of the Finch book! Almost as bad as buying textbooks for school! WOW!

[TheJANG]

Thanks for all of the input, gentlemen. Reading these replies I was inspired to do some really informal force vector analysis on a turning mono. Holy crap is there a lot going on there The most interesting thing is how what my car-guy mind thinks of as the "ground" is such a relative thing with boats, with how much the water surface itself bends depending upon what the boat is doing. Such exciting stuff!

Mike Z. especially thanks for helping knock me out of my box to think differently. Also thanks for making this boat I had a miserable pile of factory assembly-related issues early on, but with that stuff sorted out I can finally really appreciate the boat with run after trouble-free run.

I'll leave the motor mount alone as it's a very, very expensive thing to experiment with, time-wise. My battery tray is out, though, so I'll go ahead & experiment with battery heights once I build my new one.

[mtbenjamin77]

I've found with my mono builds that the lower the vertical center of gravity the better it handles in the straights, less chine walk and handles rough water better. Although, going back to what grim posted earlier there is a trade off, better in the striaghts but not as good in the corners. It's definitley a give and take. It really depends on your driving style. And it's all a balance. Just like a gear ratio, benefits and drawbacks. Me personally, after running the revolt I would be inclined to lower the motor mainly becuase I've had good results in the past. But then again the revolt is the best cornering RTR boat I have ever seen. I can do a full turn at full speed in about a 12ft radius. I don't know of any boat that can do that as fast as the revolt can. Maybe there's some room to give in the corner to add some top speed. Most race courses don't have 12ft radius turns

[TheJANG]

Thanks for that input. Makes sense. I'm looking for less chine walking when running dry along with more straight line stability over "rough" water. I'm not going to race and you're right, the turning radius on this thing is bonkers, so I think I'm on the right track.

[Mike Caruso]

Thanks for that input. Makes sense. I'm looking for less chine walking when running dry along with more straight line stability over "rough" water. I'm not going to race and you're right, the turning radius on this thing is bonkers, so I think I'm on the right track.

The Re Volt will reverse direction @ 35 mph in less than 3ft. more like 2ft. It is just crazy goes where you what it to, Also my 4s Grim battery is spaced with three tongue depressors shoving the battery to the left or port side. Turns great with either Grim prop stock or 45x68. SEND SOME CHINE WALK OVER THIS WAY OK. It will look like it is going to flip but it just keeps going and when the water is rough, drive it like a real boat across the waves at an angle, not head on.