jkjones23

Thanks, appreciate the info. It can be very confusing, but I think I got it.

rageman

Great thread and content. Maybe/likely against the rules but listing of sources for presharpened props (and prices) (and quality rating/comment) would sure be useful for us newbes.

jetpack

My Feedback: (1)

Here is a link to J&L Tools a division of MSC. They carry single sticks, all about three dollars each. Get 180, 220 and 320 grits - 1/8" x 1/4" x 6". Use them full length or score them against the corner of the wheel on a bench grinder, and snap them to length. They are brittle so be carefull with your pressures while your polishing. Snapping them in half or a third gives you a nice working length for a prop.

http://www.jlindustrial.com/Abrasive...294956595.html

Use 180 grit sandpaper to get your tip shape going. In example a one-sided chisel point (like a pink desk eraser) is good for the corners up near the hub, while a spoon shape is good for the cup area. Lay the sandpaper sheet down flat face up and just scrub to get your tip radius going for polishing. It will shape itself a little as you go along too, so stay in one stroke area at a time and it will form itself as you go as it wears. Light quick strokes work better than heavy slow ones. Lightly sand any sharp edges you put on the stone or they will scar. Don't press hard or they will snag and load up and dig, then you have to pick out the copper out of the stone with a dull exacto or re-dress it on the sandpaper and get your working contour started again. Remember to soak your stones in oil (mineral oil or light machine oil) before you use them, and keep a little oil on your prop too as your working.

Let me know if you have any questions and I'll help out! Remember, this is a polishing step and does not need to be done to the faces of the blades...most people simply file the front of the prop to get it to balance and use it as that.

You can hurt the performance of the prop more than you can help very easily if you're not confident on keeping the factory "shape" when you polish. Use the grit blast finish as your judge, and remember to stop polishing when you reach the bottom of it - go no farther in that area. Save some of the pitting for the next grit size so you dont get lost. Move over to another area, then final blend your areas with broader, larger strokes and tip size.

Save all of your outside edges for last...don't polish over them of course. You could even tape over them to protect from stray strokes and also make it more comfortable to hold as you work. Only sharpen and balance after you are done with all of your polishing on the blade faces.

When you get better at this, you will even be able to add extra cup or kick-out without even bending your prop, you can build it in as you polish. Using reflections off of a window blind or wearing a striped shirt will help you spot distortion and where it should be shaped better, or matched to the other blade. Don't be afraid of going back after polishing to correct it. The idea is to get it right, not just shiney.

An addition to our moderator's thread start links, here is another website which is useful in understanding props
http://sites.mercurymarine.com/porta..._schema=PORTAL

The picture I added to the right is a current F1 Tunnelboat team's prop box. You can enlarge it and save it to your desktop and zoom in. Try to pick out the differences in leading edge shapes, kick-out lips and cupping at the tips of the blades.

Mepete

Awesome tips guys! usefull for first time boat builders like me...

tmaxx boy

hi

Justaddwata

My Feedback: (3)

Not sure if it is already mentioned but I use a scotch brite disk for medium material removal to pre polish finishing. There is a great disk available at Walmart for about $8 (Brown disk called a surface conditioning disk I believe). It includes a nonreusable arbor. I have one setup in a pedistal drill for control. Wear welding gloves (as prop is sharp and also gets hot) and always work at the trailing edge of what ever surface you are finishing (the leading edge will grab the disk and want to fly - same rule applies to buffing disks).

I use this disk with Berillium and stainless props. I can slightly thin and sharpen around 40 berillium gas props or 20 stainless props with one disk.

I will use a screwdriver as an arbor which gives you a much more secure way to hold the prop. I secure the prop to the 1/4" shaft with a pair of drive dogs (being sure to lock one dog into the slot of the prop to prevent it from turning).

ALWAYS ALWAYS ALWAYS work away from the edge of the prop. (see picture). It takes some time to maneuver the prop to be able to do this on all edges but it not only saves you from damaging the prop and/ro cutting yourself - but it also helps your disk last longer.

JERRYG.A.S.

IF U WANT THE BEST PROPS IN THE COUNTRY GO SEE MARK AT PROPS 4 U .COM HE'S THE BEST THERE IS...

brc51

Hey guys im not exactly new to boats just one with an ABS hull,all my others are glass,how do you get rid of discoloration in an ABS hull other than a total repaint,as i took this one in a trade and its discolored in a lot of places. It would be a very nice boat other than that fact, Thanks

Ron Olson

My Feedback: (1)

Without painting it, I really don't know of a way. Age and fuel/oil stains will yellow ABS over time. Using a solvent can do more harm than good.

brc51

Thanks Ron I figured it would take me repainting it,hate to but am going to have to to make it look good, so much for a like new boat as the add stated, so far ive airbrushed the cockpit insert and cleaned enough fuel residue and soldered and shrink tubed wiring problems,sometimes i cant believe how much people pay to get something and dont take care of it after they have it. my wife says im too particular about my boats as i clean and polish after running them and if they get scratched i repair the scratches. but i like the boats and condition to me is a reflection of how you do things in life. Thanks Ron

danman aus

im pretty drunk after reading 3/4 of the super vee 27 thread but a quesstion still raises in my head. other than the amount of blades what is he difference in lamens term between a 3 blade and a 2 blade prop? id like to know benefits/pitfalls of the two. does 3 blade accelerate faster etc etc. cant seem to find any physical answers anywhere. does 2 blade take longer to spool up and give greater top speed etc? im totally new to rc boats but want to learn so i can make educated choices in the future.
all help apprweciated,cheers,dan

jetpack

My Feedback: (1)

Generally speaking, the difference is prop slip. Three blades will have more traction than two bladed, but add more engine drag and prop walk.

Three blade will accelerate better in rougher water.

The ideal prop should only have one blade, eliminating drag of the other blades that are not producing useful work. Two bladed props are standard with most hulls, on other type hulls, 3 or even 4 blades may be required for additional acceleration and lift.

Outriggers and Hydros are the best examples of boats that demand lift at the transom, to ride properly on a 3 point stance.

To know where to start with your type of engine and hull, you would have to digest everything that is contained in this webpage. Props are one of the hardest things about a boat to get right due to it being the only "gear" in the system. Most every variable in the system is processed through the prop. Any tweek in the system has an effect in what the prop should be. It sometimes proves itself to be always a moving target to try and hit.

[link=http://www.rcprops.com/TechNotes/rcprop_tech_info.htm]Prop Tech Notes[/link]

jetpack

My Feedback: (1)

Here's a few full-scale prop shapes for the imagination and for those that want to experiment shaping their blades....

CC Racing Engines

Chuck,
This is a great post. I wish I would have had a post like this to read when I started boating, Great Job Man.

Carlo C.
CC Racing Engines
Home of the worlds fastest Zenoah @ 102.7 mph
1-504-305-5005

jetpack

My Feedback: (1)

I noticed there are a lot of prop charts around, but none of them point where to start with sizes so I thought this would be good to add.

piper_chuck

My Feedback: (12)

Thanks Carlo

jetpack

My Feedback: (1)

Here's most (not all) of the different prop shapes by Octura, and if you compare the look of the prop blades to the prop characteristics chart you can get an idea of how each different blade shape does its work.

jetpack

My Feedback: (1)

Here is a good question from Spetz in Nitro Boats forum that hasn't been discussed on our boards, but post number 59 further up will have a Prop Tech Notes link which goes into the subject in more detail:


Prop Diameter is a function of Load. An example would be as the Total Load or Weight increases, the Prop Diameter should increase with a goal of minimizing Slip for best efficiency.

Increased Prop Diameter reduces Slip at the expense of Thrust.

After the minimum Prop Diameter is determined, the Pitch is adjusted to the maximum. What you will then get is optimim Thrust and RPM.

By decreasing the Prop Diameter and increasing Slip, Speed will be decreased if RPM's remains the same.

By decreasing the Prop Diameter it will increase RPM, increasing Speed more than what was lost due to Slip.

Pitch will give you your top Speed, while your Prop Diameter determines you your RPM load and efficiency.

The effect of too much pitch will be cavitation and loss of thrust at lower speeds.

The effect of too much diamter will be excessive load on the engine and loss of RPM's.

There's a few variables to have to think about here, and it is not easy sometimes to picture at first but if you study each example you can see it is a delicate balance on finding the perfect prop.

It is best to determine where to start by using a chart, and working either side of what they suggest and as you try different props and you actually see for yourself how your boat acts, helps complete the picture.

munro1656

hi all i finally have my boat in the water its a 60" mono with a 260zen now i am going to play around with props i have access to a balacing machine for automotive turbo's as you could imagine it balances all the way to near perfect. I just need to find out how fussy do i need to be on these props keeping in mind this machine balances turbines designed to spin at 200,000rpm

Justaddwata

My Feedback: (3)

You dont need to be that fussy theres so much more in that driveline thats out of balance than the prop. Use a regular balancer and get it close - beyond that and it is for your own satisfaction alone. Further - the props are not that precicely cast and sometimes blades are not always perfectly spaced around the prop hub. The guys going for electro records turning 60,000rpm may benifit from such precision but a 17000rpm zen wont.

munro1656

Any idea where i might be able to get a design for building a balancer or a contact to buy one remember i'm in aussieland (where the water never freezes LOL)

Ron Olson

My Feedback: (1)

I've been using the Top-Flite prop balancer that's used for airplane props. It's very sensitive and maybe too sensitive for most boaters but it's cheap at just under $20.00 US. This has had everyting from small nitro and electric props to big gas props.

Justaddwata

My Feedback: (3)

It does freeze - just not in January and not in the north

You could make your own balancer. A basic balancer has two parallel (Horizontal) edges and a tube of 1/4" (or 3/16" depending on your prop) brass with the prop mounted on it. Place the tube on the parallel edges and allow the prop to rotate between the parallel edges the heaviest blade will rotate to the bottom. There are some that use razor blades for the parallel edges but I think that is a little dangerous personally. The parallel edge balancer is not as low a friction as a magnet balancer but will get you pretty close.

To make a magnet balancer - you will need a steel shaft (straight) with a pointed taper on each end. This is your mandrel on which you will mount your prop (again use a 3/16" shaft for smaller prop). The shaft is then suspended by the magnetic field of two strong magnets contacting the magnet at one end with the point of the mandrel and about 1/2 mm from the magnet at the other end. This will allow the mandrel to rotate very freely and again allow the heavier blade to fall to the bottom (though it will take a long time to find the bottom as the rotating friction is reduced. This is the concept used by many commercially produced balancers and is very inexpensive and easy to reproduce. I will try to take some pics of mine later

sushi2me

I myself have been using a Prather prop balancer for years - really simple and cheap and a good investment if you're going to try SBP'ing (Sharpen, Balance, Polish) your own props - a LOT cheaper than paying to have it done.

You can find this balancer for between $6 and $14 at a number of online sources (do some shopping around for the best price):

1. High Performance Models at [link=http://www.highperformancemodels.com/Prather%20props.htm]Prather #3002 balancer[/link] for $14.50
(See picture below)

2. Offshore Electrics at [link=http://offshoreelectrics.com/proddetail.php?prod=oct-oc468pb]Prather Balancer (not 3002)[/link]. This one costs more at $29.95 but has a lot of features - This prop balancer has an extruded aluminum base and two parallel steel rods for the prop shaft to roll on. It comes complete with a leveling screw and three prop shafts (1/4", 3/16" & 1/8") which store within the unit. Basic instructions are included - more complex than the Octura #3002 but has more features.
(See picture below)

================================================== ==================================

The other choice is an Octura prop balancer (Note: see picture below!)

1. Pigs Airlines (French Hobby Shop) - at $14.70 - I'm sure you can find American at other locations, but here is this one: [link=http://shop.pigs-airlines.be/catalog/product_info.php?manufacturers_id=64&products_id=8867&osCsid=3f7074a65c05]Octura #3002 Prop Balancer[/link] for

2. [u]FunRCBoats at $36.95 at [link=http://www.funrcboats.com/ProductInfo.aspx?productid=OC468PB]Octura Prop Balancer[/link]

sushi2me

Oops, I forgot the promised pictures and am also adding an Octura Prop Chart that is relative to mostly the boats that we need them for in this and other FE forums for SV27, etc.

sushi