outboard props?

[synthon]

Bill,

Great info. Now we're talking. IMHO tunnels should be run with little to no angle in the prop shaft. I have always run less than 1 degree negative, and I balance with weight. On windy heats I add weight directly to the CG, this helps in two ways, one in the obvious way, keeps the hull from going over backwards, but more importantly lowers the CG to prevent rollover, especially when the wind blows offshore.

So what are your thoughts on prop angle and height?!?

Rick

 

[TimD]

I tried the X640 cut down to 37mm diameter. Wasn't too happy with the handling, but to be fair I didn't try different prop heights with it. Cavitated a lot on launch. I have also used the Hopper 1440 and thought the handling of the boat totally unsuitable for oval racing consistently ( I hate DNF's and would prefer to be down a few MPH and finish races)

Synthon, I agree with your comments about adding weight to the CG in windy conditions. I've been doing this for a while and it works well. I found your comment "I have always run less than 1 degree negative, and I balance with weight." a little interesting. Do you set the CG "statically" on the bench and then add weight to the CG until it is trimmed right?

Can you please clarify this for me?

Tim.

P.S. I think all these posts would justify a prop forum - & we've only been talking outboards here

 

[TomMoorehouse]

prop forum.... well.... i'm not totally sold yet, but it is looking better

 

[billr]

Hey TimD, what props do you find a little speed and stability with. I have been tempted to cut off the tongues of Hopper 1440, but it has been my fastest recorded prop. I am going to test my new x 440 this weekend on my stock boat. It has been cut on the tongue and back cut. Wish me luck. Results will be posted here and on our club page board (www.intlwaters.com/mmba ). Anyone tried a 438 prop? A guy from Baton Rouge told me that the 438 has been his best overall prop. Let me know

Bill R.

8)

 

[Martin Lovsund]

Bill R. I tried the x438, 437 , 440 and prather 215 on my Dunlap 27 last year. I live at an altitude of 2200' and found the 438 with tongue removed to be the fastest for me. The boat also handled great with that prop. When you guys are talking about rounding the tips off a prop is this just with the prather props or are you doing it with the x series octura's also. I was under the impression the x series was already a non lifting prop. Am I wrong?

 

[billr]

Well, in my opinion, if the tips are sharp at all, they have lifting components. I have the 215 that way with good results. I am experimenting with some X series now. So I will be posting results as we go. I am going to try out one or two this weekend if they rain will let up.

If anyone has a prop they want to show, I have added a Prop Pics page to the our club page. This way we can see what we are talking about. If you want to submit one, email me at [email protected] Include what it is, what mods you have done, and a speed if you have it. Make the pics clear.

Bill R.

MMBA ;D

 

[duc]

Tim

I use a Mega W21 Turbo on my 3,5 ob. Works great so far. and is pretty quite.

 

[TomMoorehouse]

ok.... ill ask whats a Mega W21 Turbo? is this a nova rossi made engine???

 

[ggillman]

Its a car pipe that Oscar adapted to work on his 3.5 K@B outboard, he also has a OS carb on it ;D

The 1400 and 1600 series Octura's handle different than the others because they have fixed pitch, whereas the Prather's, Octura X series, and ABC H series have tapered or progressive pitch. Fixed pitch is faster, but the tapered pitch handles better. ;D

Gene

 

[TimD]

I have tried the X438 and it is a nice prop for the NovaRossi. The boat handles very nicely with this prop and launching is a snap too! I use this prop as my "pipe tuner" - in other words if I try a prop and want to make sure it is not limiting the RPM I give it a run listening to the motor's rev range. I then change back to the X438 and listen to the RPM's again. I know it is crude but it is effective.

The X438 is 5MPH slower than a stock 215 on my current setup (measured with a GPS in the boat). I have to stress that I put maximum effort into getting the boat to finish races with setup. There are faster props in the straight line ( hopper 1440 for example) but if it does not handle then for me it is not worth using. I only do oval racing - no straight line stuff.

Oh yeah - the X440 with a slight back cut is a nice prop too - unfortunately I have lost mine and need to do another one.

Tim.

 

[TimD]

getting back to the rounded tips info, do you think the reduced lift makes the prop faster, or is it the reduction of surface area of the prop, or something else? ???

Billr, I have heard in the past that cutting the ears of the 1400 series props causes a lot of cavitation as it is a constant pitch prop. I have not tried this myself. Has anyone else tried this mod to these type of props?

Tim.

 

[osracer]

Wow! Being a new guy I have been working on consistency and getting a good needle. Now I want to work on a better set up and play with some props. The $64,000 question is this. If you order a prop from Hopper or Brown or somebody else how do you do it to get something that will work for your engine and boat combination. I know it's probably a crap shoot but it would be nice to be assured that you would get something that would add a little speed over a stock balanced and sharpened prop. ??? Bill

 

[ggillman]

Hi Bill,

Sorry to make ya wait so long I have been in build up

mode, If ya order a prop with specific mods for your application from Andy Brown, I believe he offers one free tweek if its not to your liking, Add cup, take out cup so forth, other than that just Test, Test, Test ;D

Gene

 

[synthon]

Gene,

Check you instant messages.

Got it Dude, Thank you

Gene ;D

 

[XtremeRcBoats]

I got a 1440 prop modified by mark anderson on my xtr21. What are the main differences between the other 1440 versions you can buy from hopper and brown?

Paul Wijnstra

[email protected]

ICQ: 23081916

Xtreme Rc Boats

R/C Powerboats, driven by Adrenalin!

 

[GRand]

anybody ever cut the tongues off of a 640? thinking of trying this with a slight back cut. i have trouble getting on the pipe with one stock, but when it does the boat drives and handles great. just dont ever slow down!!!! ;D

 

[ggillman]

Jerry D. runs a octura X640 with the dia. reduced to 37mm

with great results.

I might have to try one of the X640's, I am not a big fan of the 1440 series reguardless of mods, While they are fast, the turns are a different story, I do have a 1440 with totally different mods comming to test. Exception to this is Mike Z., he has very good results running a Anderson 1440.

Gene ;D

 

[GRand]

do you know if he rounds the tips to reduce the diameter or taper it back to a point?

 

[ggillman]

Not real sure, Jerry checks in from time to time,

maybe he can comment as to exactly what the mod is,

Gene ;D

 

[billr]

I called Jim Irwin about htis a while back. He said the same thing, use an x640with clipped tips.

I took a shft that would fit the hub, put an x637 on it then an x640 stacked on top. I clipped the 640 with the same angle and blade length as the 637. There is a special angle that each prop has that is not on the 1400 series. I tried a new version of that same 640 mod today. I slightly back cut the prop at slightly different angle for about 1/2 the backs radius. Then I slightly cut the front of the blade near the hub to help break free.

Well the results are still out on the mod tunnel, BUT that prop on the stock boat(DUMAS Hot Shot Sprint with a stock OS 21) MAN what a difference!!!! I turns great (keeps the boat up) and really hauls down the straights. Try it. If I can take pics, I will try to send them to those who ask for them.

Hope this helps.

Billy R.

MMBA

www.intlwaters.com/mmbe