Prop Placement?

[rc10gtisthebest]

I have decided to convert my Boat to an inboard.

And I don't know where to place the prop. How high or how low?

Here is a rough sketch of the stern of the boat:

NOTE: The hieght is 3 inches. Each red mark indicates an Inch..

Thanks for the Help!

[haljmac]

drill a 3/8" hole as low as you can get without going throught the bottom of the hull. 3/8" because it will give you room to make adjustments, and also will work as a drain while running.

[hydroracer]

something like this picture below. don't get to close to the bottom as you'll weaken the corner of the transom. the angle of the shaft will put the prop a little lower in the water. haljmac's right about leaving some room to move it up and down for adjustments. 1/16" to 3/32" above and below the stuffing tube is plenty. ultimately, you want the bottom of the strut just about even with the bottom of the keel right where the prop starts. have fun buddy

[hydroracer]

btw, the top half of the prop will be above the water while on plane. this is a surface drive setup.... the fastest way to go! an octura x440/ 3 blade should work for you if the hulls not to heavy. your center of gravity point should be about 30% of the total length-of-hull forward of the transom. this is important...

[rc10gtisthebest]

Originally posted by hydroracer
your center of gravity point should be about 30% of the total length-of-hull forward of the transom. this is important...

english please... LOL you lost me....

[hydroracer]

lol! ok, when you have EVERYTHING installed in the boat when you're ready to run it, the whole boat must be balanced correctly to run right. i.e.- all the necessary parts installed including radio components, engine, pipe, fuel tank, hardware, etc. i'm referring to the balance point from front to rear, not left to right.

use one finger on the left side and one finger on the right side evenly spaced front to rear to lift the boat up off the table. if you get the position correct, the boat will balance and not fall forward or back. an imaginary line between the point where your fingers are touching the boat is your "center-of-gravity" or "COG". that imaginary line should be about 30% of the boats length measured from the front tip to the very back part of the hull called the "transom". plain english- the balance point should be 1/3 of the total boat length when measured from the back of the boat towards the front. (the COG will always be closer to the rear of the boat on a monohull)

example- if a boat is 30 inches long, then the COG should be about 10 inches measured from the back edge of the boat.... the "transom". math formula is:

(length of boat) X .30 = (where your COG should be when measured from the transom forward)

you must do this before permanently installing the engine. move the engine and pipe forward or back to move the COG forward or back as necessary to get the right balance point. i just throw everything in approximately where i want it to be and adjust from there.

hope this helped...:cool:

[FlyerCAN]

Certainly helped me. Good info and I even understood it that time.:D

[rc10gtisthebest]

That's better I started getting lost about mid way but the end really helped...

[hydroracer]

fwiw rc10gt, it would no doubt be easier to just get a new hull. of course it will set you back about $150 or a little more. this amount is negligable when you've got to buy all new hardware anyway. then it's as simple as setting the boat up the way the instructions tell ya. i feel this is probably the way to go for you and you'll be happier.
on the other hand, what's the worse case scenario? if you're conversion to inboard doesn't work out "perfectly", then you can always upgrade to a new hull in the future and swap over the hardware, right?.

check out this speedmaster boat hull link below. this boat is one of the fastest .21 monohulls you can buy. not a bad price for a world class racer. (at the site, click on speedmaster boats on the left)

http://www.rossisales.com/boats4.html

[Doubledog]

:)

[Ron Olson]

Ask about the new version of the Speedmaster 21. I saw one at the IMPBA Internats. I own one of the first versions and love it! The new one has a shallower channel for MAC or other front carbed motors and the strakes are supposed to be different for even better handling. I run mine without trim tabs or a turn fin which saves you more money.

[rc10gtisthebest]

Originally posted by hydroracer
on the other hand, what's the worse case scenario? if you're conversion to inboard doesn't work out "perfectly", then you can always upgrade to a new hull in the future and swap over the hardware, right?.

check out this speedmaster boat hull link below. this boat is one of the fastest .21 monohulls you can buy. not a bad price for a world class racer. (at the site, click on speedmaster boats on the left)

http://www.rossisales.com/boats4.html

That really isn't a bad price for such a nice boat... But you see I'm on a VERY strict budget.. that's why I came up with the Idea of converting it in the first place.

I will just go ahead and do my hull and see what happens.

[hydroracer]

sounds great.... you'll get it! :cool:

[lovinnitro]

Patience, Then check and double check,. after that more patience then triple check!:D Honestly take your time think about what your going to do and it wil come out fine. I redid a deep vee (my 1st gas) and it it came out great and I filled and changed everything. If you have any questions we all will try to help you out the best we can.
Oh, and don't forget those pics!

Later
Steve

[rc10gtisthebest]

One quick question. Actually two,

How big (inches) is the Speedmaster .21 hull?

And also on my boat, the transom is at a slope. Instead of being flat (when placed in water, on the table, or anything) the transom is at like a 110º angle instead of a perfect 90º angle. ( when looking at it from the Port or starboard side of the boat)

Is this good, bad, ok, or does it really matter?

Thanks!
Todd

[Ron Olson]

29" long and about 8-3/4" wide. I just ran down and measured it. The transom is angled? Weird. The important part is getting the strut angle right. Start with the bottom of the strut level with the bottom of the hull then adjust from there if needed.

[laxmasta2039]

what engine are you using? what hull?
if you'll send me an email [mmlennarz@earthlink.net] ill send u some pics of my .21 mono, it should give you an idea of how a .21 mono should be set up with the correct CG. an easy way is to install a 10 or 12 oz tank right in front of the engine, the engine at about where you'll want the CG, the radio box right next to tha transom, and the hardware [duh] on the transom. then if the CG is a little off, you can install you're 2oz hopper tank anwhere you need to compensate.

oh yea, btw:
.21 monos kick a$$!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!111
yeeeeeeeeeeeeeeeeeeeehaaaaaawwwwwwwwwwwww!!!!!!

;)
Joe

[rc10gtisthebest]

Where can I find a complete line of CMB engines? I've been looking everywhere...



The transom is angled like this:

[hydroracer]

here's one place-

http://www.seaducerboats.com/motor.htm

i think you'll be able to compensate for the angled transom by adjusting the strut. even if you must modify the slot in the bracket a little or file the top front corner of the strut so it doesn't hit. it won't be a big deal, just use a file or dremel. you'll be alright, don't sweat it.

a more important issue is making sure the transom has enough strength to hold the strut well. hopefully it's got a sheet of plywood across the inside of the transom for support.