surface drive vs subsurface drive

[FlyerCAN]

I've only ever had subsurface drive and would like to know the pro's and cons of each being that some hull makers offer both on a gas powered 50 some odd inch hull.

I've always wondered the benifit of having half the prop out of the water. I am assuming that it lets the engine get higher revs, but then only half of it is getting used no?

I know someone can tell me on here:D

Thanks for the help guys;)

[Doubledog]

Hey Bud,

Pretty much any one of the numerous brand name drives is going to be surface.

I'm talking the:

Enforcer XP (like I have)
& SPDIII (like Shannon SC, & BH have)
Ballentines (Lovinnitro has one from them)
Most all MHZ .........and on are going to be surface.

One blade being out of the water... yes, your're absolutly right. (thats why I like a three blade:D )

Serriously, I would stay with what the main # of boat manufact. & folks are using. They are using it because it works. Not a lot of maint., gives good speed, and is easy to replace. Oh, throws a nice ROOST too.;)

Now can I name the pros and cons of it? Not a whole lot to say off the top of my head besides whats stated above.

Hope it helps.
Check out these links. You'll be hard pressed to find a single sub drive there.
http://www.rocketcityracing.com/tek9.asp?pg=products&grp=43

http://www.whobbies.com/store/agora.cgi?product=Drive_Systems

http://www.ballantinehobbies.com/DRIVES.htm

[FlyerCAN]

Does the 3 blade prop change the speed any on the surface drive compared to the 2 blade of same pitch?

[haljmac]

if the 3 blade and the 2 blade prop, were the exact same in both pitch and diameter, the diferrence would be, the 3 blade would get up on step faster, would also have more water drag(more surface passing through the water) with a surface drive you will less prop in the water(about 1/2 or less) wich is a good thing. Pitch is the distance the prop will travel in one revolution.(so it realy does not change the boats speed if the prop is under the water or half above, thats if they are both turning the same rpm's) I guess the best way to state it is that if you a have a surface prop you can go with bigger pitched prop(less water drag) than the sub-surface. Remember that not all boats are the same, try different props and set ups.

[Doubledog]

Too technical for me to really debate over the sub or surface drive. lol

But I know I like the surface.

As far as the setup goes with it, I'm always looking to improve the performance and after you get used to how your boat acts, you'll notice a little different riding attitude, acceleration out of the corners, handling... is it loose at top end or steady etc... just by changing the prop from a 2 to 3 blade of the same design.

Before running yesterday, I cupped one of my fav props just 3/16" back from the tip and the slightest amount. Ran it, noticed it seemed to hold better. Brought it in, tweaked it just a hair more,,, and then I noticed the rooster was flying a bit lower and it really seemed to hook up better. Maybe its all in my head, and when I put the GPS in on the last run I forgot to reset it, so a top end # will have to wait. But handling was noticeably better.

Back to the sub..... I really wouldn't worry.

[lovinnitro]

I gotta find someone who has a selection that would be willing to let me check them out for a day. I'm told with all the torque the mac puts out vs rpm that a x482/3 would be best for my set up. will have to see. Going to post some results tomorrow. (got rained out today) but so far I'm somewhat disapointed. Did a few mods today and we'll see from there.

Double,
When your boat is sitting in the water. how far in is your prop?

[Baja-Destroyer]

i dont know about r/c but for real boats surface drives a good for calm water if its rough they will go completly out of the water and burn out ur transmission and ur done for a wile but everybody sez there good for r/c cuz u cant burn them out like a real boat
but i dont know?

[FlyerCAN]

Chris,
This may be a little difficult to understand, but it is purely fact. The prop is in essence a screw, like a wood screw being turned into a piece of wood. With each revolution, (the water being the wood) the prop moves forward. In a perfect situation the forward movement is equal to the pitch, but since water is in no way the same density of wood there is what is know as a slippage factor. In boating it is believed to be between 15-20 %.
In essence if the prop has 4 inches of pitch it should travel the equal distance forward per revolution, again that is in the perfect situation. The larger the blade (s) the more "bite" (power) per RPM. However, the larger the blades the more horsepower it takes to turn the prop under load. The most logical prop would be one of a single blade as there would be less water disturbance created, however it is quite obvious that balance would be not possible. In reality the more blades you add you gain better stability and less vibration, but less speed. That is the reason in full size boating we tend to produce 3-4 blade props. Since we are not in the boat and vibration is not as much an issue as ultimate speed, we tend to go for performance.
By placing the prop hub on the surface we are able to utilize the single blade theory as well as turn a larger diameter prop, thus traveling further per revolution with greater push potential with the lesser horsepower that the gas engines produce.
In comparison, a 60 size nitro engine can produce twice the horsepower and RPM's as a gas engine, and weighs 1/2 as much as well, therefore we can gain some hull stability and get extremely high speeds with a smaller prop submerged when coupled to a nitro engine.
If you look at some of the fast off-shore full size V's you will notice that they also run extended surface drive systems very similar to that done by us. I took the theory from them in the early 80's and applied it to gasoline. We picked up over 10 mph by just increasing prop size and running it on top of the water. There are other factors to consider though, like additional torque, so the hull has to be designed to overcome this. Cavitation at initial throttle-up is also a bit greater, but the overall performance is worth it's weight in gold.
Thanks,
Tony C.

[Doubledog]

All that stuff Tony was telling you is true, but its a lot of razz to me. In laymans terms, a surface drive will be the easiest to maintain and possibly give better speed. Besides, it looks cool also.

Came across this photo today while surfing ebay and had to share. Its a prime example of a submerged/subsurface running gear. Better put, its an antique.

I'll take that same boat with the same motor and put a few $'s that says a surface application will work better than whats on it; meaning she's going to give better #'s, handling and ease of maint.

[Doubledog]

Compare what you see sticking outside & under the boats.

If you look closely at the shaft exit of my boat, you'll see that its a bit high from the bottom. It came this way from the factory and I feel that it'd give a little better performane if it was an extra 1/8" down... at least far enough for me to put the gps on it and find out for myself.

[FlyerCAN]

I'm sold! lol

Definately getting surfacedrive. I like a good roost too:D
Guess now I will learn a lot more about them.

[FlyerCAN]

:cool:

[lovinnitro]

Double has one pretty drive don't he?:D

[Doubledog]

Sorry for beign so pushy. :(

I have a lot to learn myself especially when it comes to dealing with folks. But when I heard the part about considering a sub' drive, it shook me up man!:p :D :D :)

[FlyerCAN]

I didn't want to make you think you were pushy. You just finally made me decide what i wanted.:D

[Doubledog]

Ahh, Kinda put my foot in my mouth messing around on another thread so I'm just being a little cautious.

So whats the status on your homework? In other words what ideas are you juggling around with hull & hdwr.?

[hydroracer]

Originally posted by lovinnitro
I'm told with all the torque the mac puts out vs rpm that a x482/3 would be best for my set up. will have to see.


lovinnitro, you've got it backwards about the mac's power output. all mac motors generally put out LESS torque than, say piccos or cmb's. they love to rev high rpm though!, and therein lies their advantage. with a mac motor, you want to size DOWN a little bit from what props you'd use on other engines. then sit back and listen....the .21 sounds like a dremel on crack! hehe :D mac engines are awesome!!!

[lovinnitro]

Sorry Hydro but a 32cc gas powered McColloch (sp?) is NOT a high reving engine. Maybe a mac nitro but not gas. I know this for a fact my friend. I will get blown away by a high reving Zen. The most I can prolly get out of my air cooled mac is 10,000 rpm. Maybe. That would even be with a few mods.

Steve

[hydroracer]

lol, sorry bud! i thought you were referring to the mac nitro motors. disregard my babbling above :rolleyes:

[lovinnitro]

You know what hydro after I posted I went. duhhhhhh, He's talking about nitro motors.:D

I'm assuming from your name your into hydros. Got any pics?

[hydroracer]

sure! check these out-

6-cell blizzard

[hydroracer]

20 Daytona rigger- picco .21 power

[hydroracer]

45 Eagle SG- Mac .45 powered

[hydroracer]

i'm currently building this one below. it's called a firefighter and l've got a novarossi .12 for it.

http://www.firefighterboats.com/images/ff12whiteoutsmall.jpg

[lovinnitro]

Man Nice boats!:D You gotta be proud of those.

[hydroracer]

hehe, you can say i like outriggers. i have a 20 mono too, lotsa fun. the 45 eagle does between 65 and 85 mph depending on the prop/pipe length/fuel used. heat races around 65 to 70 mph on 60% nitro. long ass roostertail :D

[Doubledog]

I'm up for adoption:D

[lovinnitro]

I'm with Double :) :)