small holes drilled in prop

[RodneyPierce]

..........................

 

[Tom Foley]

With whats been said here and abroad about props you can decide for yourself if only knowing the TE is important. For me in my "school of thought" a gauge that cannot effectively measure leading edge pitch is useless. You are of a different school, so I dont know if your wasting your time, but you are wasting mine, with questions you can answer for yourself as soon as you take some LE numbers with your gauge. Only takes a minute with the right gauge.

Or you could try the "heads up" approach .

Later

Hugh

You sure do know a lot about pitch gauges and their worthiness for a guy that has never even used one ? Maybe you ought to try one of the many available first before proclaiming yourself the all knowing critic on them !

I have used the Hughey and the Woods gauges, I own both , and continue to learn more about them every time I use them . there are lots of little tricks to using the tool quickly and wisely to see what's up with a prop . I still employ the two best prop guys I know to do some special props but you can document the progress of your mods on a prop with either of these tools .

As far as wasting peoples time ..well ..I think you have that covered bud !

 

[hugh hargett]

........remember all those steps of zeroing etc.. holding the prop and all that. :lol: Gotta unlock/lock and hold coz 45 degress aint quite enuf in one sweep HUH? Lord forbid if your hand moves while holding the prop.Could be a pain to do series of props this way but okay theres a method. Id rather have a gauge that just does it not requiring so much process.

 

[hugh hargett]

I have several different ones . And will be producing one for the masses. Tom thought you left all the prop work to experts did you decide to jump in the game? I decided not to leave it to them and learn it for myself.Tom youve had 6 pages of thread to leave a method of recording Leading Edge numbers your solution was to leave all prop work to experts so do just that but that is no solution for me.

Hugh

Andy Brown, John Beardslee, and Eric Canto do all my professional prop work "BUD" but I dont leave my understanding of props to them :blink: Its your responsibility to know what youre buying and so I do PERIOD!

I suggest you do the same and do some reading before asking alot of questions coz, If you dont know the importance of the leading edge in a propeller, a gauge of any type wont help you anyway -_- .

 

[Andy Brown]

Thanks David for posting that! And thanks Andy for sharing!

Nice calculation there! Do you not have to worry about slip then? I assume the props are always going to slip some?

Yes, you still have to look for SLIP or "PLOW". The LE pitch and RPM only give you the POTENTIAL OPTIMUM SPEED. Therefore if your LE/RPM says you should run 80mph, but you are only running 77 than there is SLIP and you need to add more cup. On the otherhand if you run 82mph then there is PLOW and you need to reduce the TE pitch. What happens with PLOW is that the TE pitch is pushing harder than the LE pitch and is forcing the LE into the dead water in front of the prop. This becomes WASTED horsepower. This PLOWING can actually be seen when running the boat. It is what causes that big trench in the water behind the boat.

 

[RodneyPierce]

Andy, awesome simple explanation! Thanks again!!!

 

[Marty Slater]

hugh

 

[Marty Slater]

ya Rodney what hugh said

 

[RodneyPierce]

ya Rodney what hugh said

:wub: :wub: :wub:

 

[hugh hargett]

Based on Andys post Rodney how would you know if you slipping or plowing? Since you never messed around with LE numbers??????

It "only" confirms the need to know your LE numbers.

or you could stay with your school of thinking and just not know them - your personal choice.

BTW have you suceeded at Davids method of taking LE numbers with your gauge sounds intense. Just curious?

Hugh

 

[Christian Lucas]

Hi Andy,

have you ever used a propeller from the tetherd line hydros ? They use in all motor size propeller with dia to pitch ratio of Pi ( 3,1415.. ) ,so a 60 mm Dia Prop for 60 size engine has 188,.. mm pitch 2,36"/7,42" .

 

[Andy Brown]

Hi Andy,

have you ever used a propeller from the tetherd line hydros ? They use in all motor size propeller with dia to pitch ratio of Pi ( 3,1415.. ) ,so a 60 mm Dia Prop for 60 size engine has 188,.. mm pitch 2,36"/7,42" .

No ,I have not. The tethered boats can get away with that much pitch to diameter ratio because they are always going in a circle. We have to hold a straight line and it takes a fairly large rudder and powerul servo to hold a 2.4 P/D ratio prop in a straight line. That prop is about a 3.0 P/D.

 

[Christian Lucas]

Thanks for your answer Andy,

i have some of this propellers as i do this in the 80tis .Best result was 200 km/h with 5ccm OPS 29 SPA . in my brain i have a cracy idea .The propeller is halv in the water ,thats wy we get this much propwalk. if we use a stearable strut we can counterakt the propwalk if we do so like to drive a left corner. Prowalk trust the boat in a right corner .If we take a stearable strut with no fin and it will have not so much effect to do this. Now we use also a ruder to set the boat in straight way .In this case the prop will now work with less pitch like a prop with change able pitch .Also the propwalk will now reakt not only to side walk the back it will also help to aclerate the boat like a paddelsteamboat. If the boat has enough speed the stearable strut can turnd in straight postion and act like ithas to do,best in a little offset position.

Some about me , i have designed lots of boating hardware for Graupner ,stearable drives ,surface propellers and some boats . Also i am the L of LRK motors the high torque outrunner motordesign most comon in airplanes today.in 1983 i sent my 60 Crapshoter with electric drive to 50 mph under IMPBA rules in Italy .Current record these days was 25 mph by Herb Stuart.Last 12 years i spent most time to force electric drives like the outrunner and help the guys in airplane and helicopter to go for records with they all capture in the lest 4 years. i want to intruduce all who like to share know how .Thats wy i come here in these forum as i gave a lot to the german record holder team ,but they want not to share there knowledg.No propellers ,no boat ,nothing .Most the do is to limit the rules that other have do not have the power to beat there record. This is only my sight of the things but i love them not very much. My way is to be open in mind and help and share ideas ,this is the best way and i life it. Thanks to all that person i have learnd so much like Jimi Gale , Mr. Octura and may other in Italy, Russia Genadi Kalistratov .

 

[Andy Brown]

Christian,

Congrat on your successes and many innovations.

I have also given steerable struts much thought for SAW. With the newly availible high powered servos and batteries, the system may have some potential. We have build a .12 nitro boat with this system some years ago, but have not taken the time to test it. For initial test we have a small skeg. Tommy Lee of Tunnel boat fame told me that he tried to run his SAW tunnel boat without a skeg and the boat would not track straight. That confirmed my hunch that prop thrust angle alone is not enough to over come prop walk, even with average P/D ratios.

 

[hugh hargett]

Guys do u mean a outdrive like you find on some of the larger scale gas monos with the skeg?

Christian, please come to the fe section and teach us some things you picked up along the way with outrunners and such.

Your experiences would be highly valued there.

Thanks a million,

Hugh

 

[Christian Lucas]

Andy,

Thanks , without a fin i think we need a lot of electronik to find a straight way . i want not to remove the ruder but it can be smallish than befor as the stearable strut help during accleration.so less drag when speed is enough on the ruder to it´s job with it´s smaller size and as the angel of attac of the high pitch prop is lower when it is going sideway the boat acclerates in shorter time. I run also outrunner with small skeg also the old K&B 3,5 lower unit had a small skeg that was ok for outrigger but with the lager skeg the tunnel go much better in corners .

 

[John Beardslee]

Christian,

Congrat on your successes and many innovations.

I have also given steerable struts much thought for SAW. With the newly availible high powered servos and batteries, the system may have some potential. We have build a .12 nitro boat with this system some years ago, but have not taken the time to test it. For initial test we have a small skeg. Tommy Lee of Tunnel boat fame told me that he tried to run his SAW tunnel boat without a skeg and the boat would not track straight. That confirmed my hunch that prop thrust angle alone is not enough to over come prop walk, even with average P/D ratios.

Hi Andy,

If you look at the boat in my avatar it has an rudder in addition to the outboad, that's a "Record" forged steel prop, with LH rotation and the big boats run counterclockwise so the only way to get it around the corner was to add a rudder. That was a 100 + mph setup.

Thanks, John

 

[Jim Allen]

Christian,

Congrat on your successes and many innovations.

I have also given steerable struts much thought for SAW. With the newly availible high powered servos and batteries, the system may have some potential. We have build a .12 nitro boat with this system some years ago, but have not taken the time to test it. For initial test we have a small skeg. Tommy Lee of Tunnel boat fame told me that he tried to run his SAW tunnel boat without a skeg and the boat would not track straight. That confirmed my hunch that prop thrust angle alone is not enough to over come prop walk, even with average P/D ratios.

Andy,

I still have, somewhere, a print of the steerable strut used by Ed Kalfus on his record setting, straight away, White Heat 4-60, .90 powered hydro. The strut was constructed of 3/32" steel with a small 3/64" wide wedge shapped skeg on the bottom of the 3/8' steel hexagon shaped strut housing. All the pieces were keyed & silver soldered together. Drawn cup needle bearings were used with a hardened steel prop shaft. Ed used an articulated drive with ball & pin universals. The propeller thrust was driven up the shaft into the engine universals. The pivot point of the ball & pin universals was set in line with the pivot point of the strut. He set up twin Digitrio servos with metal gears in an attempt to control this thing. The drive train also had a clutch that allowed him to position the boat for short straight away runs. Many problems with holding this thing with a two bladed prop & the low powered servos.

Jim

 

[RodneyPierce]

Andy, Jim, John, anyone. Here are the numbers I came up with when measuring LE pitch as David described a couple pages back. If any of you guys can confirm numbers or let me know if they are close or correct that would be awesome.

These are numbers from 3 props that I have here that I just pulled from my prop box.

ABC 1914 - 2.375 LE pitch

ABC 1816 - 2.74 LE pitch

Octura 1450 - 2.59 LE pitch

Just curious if these are even close to the advertised or actual??? Thanks in advance!!!

 

[hugh hargett]

youd have to get the accuracy reference from your propman remember all his cuts are custom not stock so......

Rodney it isnt that you cannot do it. Its that it requires alot of step including one that lends itself to user error (holding it with your hand) for the other type gauge that doesnt require all that. They need to go back to the 90 degree swing style but I guess it cheaper to make that little thing. Post a video of the lengthy process.