MiniMental

Aye but i cant really afford to buy new. We'll see.. ive got a CMB .21 Valvola in my sights atm.. i'll let ya know how that goes.

Aidan

MiniMental

I think i have a CMB .21 Valvola hehe. Just wondering, if i could make a ''ram air'' scoop for it so air is forced into the carb, and ran the engine a lil bit rich, would it make any difference?

black talon

My Feedback: (5)

on a nitro engine, the leaner you go the faster you go. (within reason)

MiniMental

yeah i know, but what i mean is, if i'm forcing the air into the engine via a scoop.. and richen it up a lil to make for the fact theres more air... will it make any difference.

Aidan

**update** Its confirmed. I now have a .21 CMB Valvola courtsey of Piper Chuck Wahooo finally... This boat is p[roving to be very expensive to make lol.

so far my estimates are

$180 for the hull
$120ish for Hardware
$400 for engine
$100 for other bits and bobs..

Better be fast for all this work and money lol

Aidan

MiniMental

I need some guidance on exactly what i need to order now..

So far i have

.21 Speedmaster Hull
CMB .21 Valvola
Speedmaster stinger/strut and SM rudder
2ch Radio.

I know i need to order an Octura X400/3 and a Sully SS-8 Fuel tank (will 8oz be enough for this engine/setup) and an 18" 3/16 flexcable welded to a 3/16 stub shaft.

What else do i need to order... :/ i have no idea..

Aidan

MiniMental

okay i have just ordered:

.187 flexi inner 18
Octura X440/3 bronze 3/16 dog drive propeller
Hexflex 1.4 unf 3 16 Coupling
.187 drive dog
.187 brass tube for 18 inch flex cable

Aidan

Ron Olson

My Feedback: (1)

If you ordered an Octura drive dog make sure that you get the one with the smaller outside diameter otherwise the 440/3 won't fit on the larger one as the third blade is in the way.
Use the small .21 hydro rudder from Speedmaster, it'll more than do the job.
The Sullivan 8 ounce should do the job. The only engine that needs a 10 oz. is the MAC as it's a fuel hog. If later on you think that you need a larger capacity then add a 2 oz. hopper tank. It's a squeeze but it will fit on the starboard side over the CG.
Got a pipe and header yet?

MiniMental

No, i havent got a pipe and header yet. Already got a Speedmaster .21 mono rudder. As for the drive dog, it was the only one on prestwich so i just ordered it.. i think the prestwich owner can put 2 and 2 together if the dog dont fit the porp, if not its only £4

Aidan

f16man

You won't have to worry about getting more power out of that valvoa as it's a screemer already, setting up the boat and keeping it from blowing over or flipping will be your challenge for sure.

MiniMental

Hahaha. I think im gonna get a macs 3.5 pipe but i have no idea whats going on with header i dont know where i need to look nor what i need to look for. Ron, Before i order my fuel tank do you think it would be wise to just fit a hopper tank with the rest of it rather than later. I can get a 2oz sully with my order for an xtra $1.

So, with the given setup and setup right.. what sort of speeds could i hope for from the beast?

Aidan

Ron Olson

My Feedback: (1)

You should be in the low 50 MPH range with the 440 prop. A buddy had a Green head CMB and it spun some good sized props so once you get it going you might find that it will spin something larger. On mine, we must have went through a good half-dozen props to find one the boat liked.

carlnoki

being as you are going to use the valvola,
start with a pipe length of 8 1/4 to 8 3/8 inches measured alng side the motor starting dead even with the glow plug to teh high point of the plug.

head clearance as per the instructions i wrote earlier in this thread.

you will need the 18 degree header from Ian Folkson www.iansboats.co.uk

start fat on the needle and let the motor slowly break in. put a small wheel collar on the water pipe just above the nipple on the rudder blade. adjust it so that you can just barely blow thru it. the 21's need HEAT to work properly.
if there is anything elsee i can help you with, please feel free to write.
[email protected]

carl

eengler

get CMB parts at http://www.hobbysupplies.com.au/

MiniMental

ryt i have my valvola and all the runnign hardware. now i need advice on installing it all. for starters whats the best way to cut a flex cable?, i'll use a lathe to turn the brass tube down and ive heard rumours that i should take 1/2" off the stinger aswell. Am i right in thinking the engine needs to be as low down as possible?

Any help on these or other things you know which may be useful would be greatly appreciated. Normally ide go straight in and do it hoping for the best, but ive invested around $700 in this boat so far so i dont wanna screw it up...

Aidan

Dan S

Aidan,

I don't know if you have used your brass stuffing tube yet, I just want to specify that for your 3/16 flex
you want a 1/4" OD brass stuffing tube, that tube will have an ID of 7/32 which will give you the correct clearance for the 3/16 flex shaft.

That stuffing tube will go in nice and snug inside the strut than after that the strut bushing will be a perfect fit (since it has an OD of 7/32) than your stub shaft will sit nicely in the bushing.

if you make a stuffing box use the next size up to make the stuffing box which is 1/4" ID and 9/32" OD, than your stuffing tube will fit nicely in it.

Dan.

MiniMental

Yo dan,

Got the correct stuffing tube for the shaft, shaft fits in with about 1mm-1.5mm of clearance. looks like i need to cut about 4" off the tube to get it 1" in front of the engine collett. And i need to cut about 6" off the flexi. I dont know the best way to cut it though? Grind it? saw it? chew through it ?

I want to mount the engine now. if i get a straight rod and line the engine up with the rod from the transom hole to the collet (straight) and mount the engine there at the lowest point, would this be correct?

Aidan

Dan S

I use a dremel with a cutting disc to cut the flex shaft, I also put a piece of tape where I will make the cut, this will prevent any frailing.

I normally mount the engine first than align the stuffing box and glass it in, but if its too late for you and you already have your stuffing box in, yes, make yourself an alignment tool and install your engine.

are you using a stinger drive or a strut?
if using a strut, did you make a stuffing box?

Dan.

MiniMental

i have nothing mounted, im just about to mount the engine now. will 1/2" clearance between the engine and stuffing box be ok or should i have more/less?? how far forward should i mount the engine? Should i mount it so the carb is underneath the deck or further forward.

As for the shaft, i'll probarbly use an angle grinder.

only thing i need to know now is clearance between engine and tube and how far forward the carb should be.

Aidan

Dan S

Aidan,

did you have plans/blue prints with your speedmaster hull?
those plans will tell you roughly where the engine should be mounted.

your stuffing box would come out about 1/2" more or less inside the hull and about the same outside (under the boat). Than your stuffing tube will slide inside the box and be approx 3/4" from your collet. enough room so you can easily remove the collet without having to take the engine out.

if you didn't get any plans I believe the best way to find out where to put the engine is to have everything mounted first, Strut, Rudder, trim tabs, fins, radio box complete and fuel tank (empty).
Than you can drop the engine in and move it forward or back to find your CG.

Dan.

MiniMental

whats this stuffing box thing? ive never been told about this. i though you just use a brass tube filled with grease :S. I thought the tube went straight into the machined part on the stinger aswell.. dont have any plans, i have pictures and it looks about in the right place...

Aidan

Dan S

Aiden,

your ok, the info I gave you regarding the stuffing box was if you were using a strut not a stinger drive, which you are.

Dan.

MiniMental

This is about where im plannin on mounting it.

Dan S

Aiden,
what is holding your stuffing tube inside the hull?

is it glassed in?

Dan.

MiniMental

nah, it was sticking through the transom, still needs cuttin down

Aidan

Ron Olson

My Feedback: (1)

OK, hopefully you haven't gotten the stuffing tube glued/glassed/whatever in there yet. You only need about 13mm at the most of a gap between the tubing and the collet, enough to replace the starting belt.