Prop Mod Basics: Class 101

[Doubledog]

As promised here are a few basic mods that I've done to a few props of my own with good results. Keep in mind, I'm not a racer, but do like to play with these things.

Here are two P275's. The one on the left is stock. Balanced, sharpened (razor sharp) and polished.

One on the right has the tounge removed.

[Doubledog]

Forgot to add that removing the tounge helped it to unload and accelerate noticeably.

[Doubledog]

Another photo from the side

(prop in the top left is an Octura X470-3 that I've removed the tounge and cut the blades straight. This also helps it to unload and accelerate better over the stock)

[Doubledog]

A better photo of the X470-3.

This shows the straight cut on the side of the blades (X470-3). Notice the tounge is removed also.

[Doubledog]

Backs

[Doubledog]

Side shot of Stock 275.


A back cut would be done along the hub (shaft area) tapered out to the tip... ie. 1/8" would be a good starting point before doing the tounge removal.

Test from there and try a 1/16' more totaling 3/16".

This would help it unload better also. Try one mod before starting with the next.

[Doubledog]

Back cut performed on another prop.

Notice how the cut is straight from the hub to the tip tapering out.

This one has about 3/16" removed.

[Doubledog]

This one has a BARR cut done.

Taking a little blade area from around the hub. Use a small round file and burry it till the hole is about 1/4" before testing. This will help it unload a little also.

You could try this mod first or the back cut.

[Doubledog]

Though not a gas prop, this is the same thing as the X470-3, just a smaller version. This shows what the blades look like stock before cutting.

[Doubledog]

I'd have to say that the Modded 275 is my favorite prop for my Super G' (WHH 48" sport hull) & Zen 230 combo for sport running.

Stock v/s the Modded prop (tounge removed), it seems to accelerate better and hold the rev's higher in the turns allowing the shot out of the corner.

I've tried a back cut on a stock 275 (no tounge removal) and didn't really care for it. Seemed to slip (rev to high) more in the turns not allowing it to hold as well.

The BARR cut is one that I'm playing with on other props but haven't got the nerve up to try it on a new prop just yet. Hate to say it, but it just doesn't look that good either. Sometimes the ugliest prop will perform the best. Go figure.

As far as the Octura X470-3: Humm, The first thing I did before ever mounting it to my rig was to remove the tounges. Still it was too much prop for the 230. It took a while to come up to speed and was 3 mph slower than a stock 275. It did hold like glue in the corners, but didn't accelerate away. Now that I've cut some of the sides off, I can't wait to try it. My guess is that it should work better on the same setup, but if it doesn't then my other boat with the 260 should spin it like no tomorrow.

We will see.

Hope this helps and keep in mind that I'm no racer, just passing along some information thats worked/hasn't in the past. Check out these sites to see the same mods.

http://rcboat.com/prop.htm

http://www.rcprops.com/rcprops/index.html

Btw, next mods I'm going to try to the 275 (tounge removed) is to put a little cup in the tips. Easy enough right? lol.

[BoatDoc]

just out of curiosity...i've seen some props with holes drilled up near the leading edge. what is that called and what is the purpose? i would think that it allows a little slippage. do you know anything about that?

[Ron Olson]

doc, that trick has been used on full-sized props as well as ours. You don't see it much any more. It was used to aerate the water to help the motor to get up to speed faster. On props on motors like Mercury's, they would drill holes on the hub as the exhaust would serve the same purpose.
BTW, DD, you have my attention. I haven't tried too many props tricks myself, the ones that I've done so far haven't turned out too well.

[Doubledog]

Just passing along info that others have been kind enough to share with me. lol. We cross paths on other forums and as you can see, what I'm learning there, I'm bringing back here...... (with a different approach).lol. Now I can't wait to start doing some cupping on a few and testing. This weekend isn't looking too bad.

Regards.

[Doubledog]

8 May ------ Adding a little more to the thread

Pardon me if there's a very similar post in the photos or if my writing sounds repetative.

[Doubledog]

This is the best way I've found to remove the tounge, keeping both blades very close in shape.

After researching several sites, it seems the professionals like to use a block or a mold. They'll make a blade certain shape then sculpt the wood to the shape of that blade. I'm still in the beginning stages of this craft so I'm yet to design one of my own. Its a bit more technical and time consuming but it allows much closer tollerance.

Instead what I've done is to shape a blade, then use Play Dough to mold it and then pop it in the oven for a few minutes to harden it up. Once its done, transfere it to the other blade. Works pretty good but you've got to be careful not to drop the mold like I did and bust it.

Here's what I used to shape the P275. A small peice of plastic shaped, and trace the blades, removing the outer edge.

[Doubledog]

You can use calipers.

Done this in the past to cut the blade area down. Needless to say, you're making a large prop into a smaller one. If a 275 is a little small, but a 280 is too big, this could possibly work good.

Trace the blades and remove the excess.

Start with 2mm or 1/8". Try and then test.

[Doubledog]

Calipers

[Doubledog]

Sounds funny, but I've used this in the past.

Busted up an expensive prop a while back... Prop Works 7016. This thing was fast on my boat. While running, I hit something and chewed it up along with a warped strut and busted rudder.

Didn't want to reshape it, so it got cut in half, and used the blades a template of sorts. Notice the blade size when compared to a stock 275. Much smaller. This prop didn't accelerate too good but in the mid to high speeds, it was fast.

[Doubledog]

Photo

[Doubledog]

For those of you running a V' hull, this might be a good prop to try.

ABC G20 & G25

The G20 worked good with my 230 and I tried the larger G25 out the other day with the 260. Hooks up good and seemed to carry the bow a little better than the stock 275.

Notice the shape of the blades. Rolled trailing edges and rake.

On left is the G25 / right 275 stock.

A back cut on the 275 would produce similar shape, but you'd have to cup / bend the tips. Don't have the nerve to go bending a new prop just yet so I'll switch to the G25...lol

[Doubledog]

Here's an ABC H-31 mod w/barr & back cut. Stock right.

[Doubledog]

Bought these props as a package deal and haven't touched them with the files as of yet.

Did try to run the stock H-31 on my Gator and it didn't like it. Cavitated terrible. Once on plane it took forever to hook up and get moving...... Can you say HYDRO or Cat prop? :)

[Doubledog]

New prop to the family

Octura P767-3

Its about 68 mm Dia. Pitch, I'm not sure of just yet for its not on my prop chart.

Was told by Bonzi Sprorts that this works awesome on a Hydro & Cat. Also that with a good back cut, its a good performer on a V'.

Here it is new out of the package. Look at the slag left on the edges from the mold. Terrible. Would you run this in the shape its in?

The fun begins soon. Hitting with the files to shape & sharpen the blades.

New prop is in the front. No that isn't the pixles from my camera on the edges, its the slag. Notice the blade shape when compared to the modded X470-3. Diameter on the 470 is 70mm and has been left alone.

[Doubledog]

Side shot.

[Doubledog]

Comparison between stock Octuras & Prathers.

These are very similar to each other as you can tell.

LEFT TO RIGHT:

Octura X472 (72mm dia) --- P275 (75mm dia) --- P280 (79mm dia.) --- Octura X670 (70mm Dia) with various pitches that we can get into further, but later.

Notice how they all look very similar from the top. The P280 is a HUGE prop too.

The Octuras are very similar to the P275. With the X470 having a tad more bend in the trailing edge over the the others.

[Doubledog]

Side shot

Very similar but you'd be surprised how much different they can be.

[Doubledog]

Like any good modeler, we're going to balance while doing all of this right? :D

[Doubledog]

Last one.

ABC S-30 four blade. Supposed to be real killer prop on hydro's.

Hope this helped shed a little light on things.