prop rake

bob lico · Post by **bob lico** » Jan 22nd, '09, 16:16

ok guys enough of e-mail and pm`s here you go the first picture is a stock prop and the second is a raked prop to level the boat without putting a oars (trim tab) in the water.will work at all speeds but you will need tabs if "haystacks calhoun" at 680 lbs. is standing on port gunnel.

bob lico · Post by **bob lico** » Jan 22nd, '09, 16:18

Rawleigh · Post by **Rawleigh** » Jan 22nd, '09, 16:33

Did you have to pay extra for the nick!! LOL.

Carl · Post by **Carl** » Jan 22nd, '09, 17:21

My last boat, a tunnel drive, ran like the dickens when a few degrees of rake was introduced. We are talking 13-14mph to 19-20mph, same rpm, same top end same burn.

Sr's Hatteras, when some rake was added it picked up the stern and really gave the boat better performance.

My 31, added rake...horrible. Lost several knots, same rpm, same top end, same burn. My prop guy wanted to play a bit more, but it was around the time of the ethanol issues and I just wanted something I knew worked. Maybe I'll give it a try again...

bob lico · Post by **bob lico** » Jan 22nd, '09, 17:32

sim you can go from a positive rake to a negative rake.i received so many e-mails and pm`s i just wanted to post a picture of what a rake does.actually in reallity this could only be used on a 31 bert if you had bermuda brother situation with a engines with a huge set of balls but no way to get horsepower to drive the boat without causing the bow to act as a rudder.hey sim people think i am crazy with the "the need for speed"you are my new hero---tunnel boat ---------wow 120mph with the chance of blowing over at any time now you be the man!!!!

bob lico · Post by **bob lico** » Jan 22nd, '09, 17:38

rawleigh that nick was cause by running over a bayliner at 100mph.they took him away in chains!!! i think he needs you in court. we have the boat
twin mercruser 750sc. some people have to know there limits!!!

CaptPatrick · Post by **CaptPatrick** » Jan 22nd, '09, 18:16

Bob,

I know what you're talkin' about; ie Rake, but it'll be hard for some to see the rake difference between your two images. This'll help you out...

Rake is always refered as: The percentage of the amount of degrees the propeller blades angle perpendicular to the propeller hub. A positive rake will angle back away from the transmission and a negative rake angles towards the transmission. The drawing below shows about 15Âº of positive rake.

While the drawing is of an OB or I/O wheel, the same holds true for full inboard wheels.

bob lico · Post by **bob lico** » Jan 22nd, '09, 19:47

capt patrick as usual your illustratration is better than my photographs.we have many raked props in the 3 marina`s but it is cold and most boats are cover up for winter.

bob lico · Post by **bob lico** » Jan 22nd, '09, 20:29

sometimes patients is impossible,people asking the same questions makes you look at them and ask yourself are you that dumb or are you just jerking me off to see my reaction." bob how come my boat at cruise increases speed as i let the trim tabs down"how can i be gracest,what to tell a person? can`t you figure that out-----you are plowing water and those reverse chines are acting like brakes on water!!! putting down the tabs is lifting the stern reducing the drag.however the drag of the tabs is less then the drag of a 11'6" hull plowing water.the best thing to do is have a prop made with rake that with take advantage of the strakes that ray hunt desigh to give maximum lift and minimum water drag(coefficient)WHEN THE 31 BERT IS RIDING ON THE EDGES OF THE INNER STAKES,with the boat dead level to the water.incidently the fuel efficiecy goes up dramaticly.of course if some unforseeable changes occur like your bringing home a 1500 pound marlin in the back of the cockpit or the top ten of the wwf is sitting on the stern gunnel you need tabs.the closest you can come to level the boat speed goes up exponently.this is perfect that is why he was the world champ in open class we can do this to a lessor degree of course just be open minded the b.s factor is o here.

JK · Post by JK » Jan 22nd, '09, 21:01

Bob,

Now if we could just get our Solo II's to get us full WOT then we could really talk speed!

--JK

bob lico · Post by **bob lico** » Jan 22nd, '09, 21:16

doesn`t that just piss you off.i love to strangle him for not getting back.i put so much work into that console i just don`t have the heart to take it apart.the marina gave me a complete glendening set up could not use it.like driving a zr-1 corvette with two plug wires off or a 3 tited women.

JK · Post by JK » Jan 22nd, '09, 21:24

I've emailed them about 10x and called several times and they have not returned any of my calls or emails. At this point I don't expect the them to fix this issue. I think it's all up to us to figure something out. Or, maybe we can present a solution to them and they can fabricate a part or something. If I would have known this issue would have come up I would have saved some $$$ and bought 210's or 250's if I wanted to cruise at 24knts.

--JK

In Memory Walter K · Post by **In Memory Walter K** » Jan 22nd, '09, 21:28

Write Boat US and tell them about their lack of responsiveness. It worked for me on a Rule pump that almost sank my skiff. Boat US called them and boy did it shake them up. I got an apology AND a new pump. Walter

bob lico · Post by **bob lico** » Jan 22nd, '09, 21:29

brother i wish i had a solution. i have to settle for 32knt when those engines are just into there hp curve ready to rip but no thottle cable left!!

JK · Post by JK » Jan 22nd, '09, 21:44

They have a new website and new email address. I just emailed them again and will see if they respond. I will also call them tomorrow. If they have any ideas or real mechanical type solutions someone else (Pat, Bruce, Bob) may have to take the lead here.

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

--JK

bob lico · Post by **bob lico** » Jan 22nd, '09, 22:03

what i did just to because i had ti know.i idle out into the river warm the engines up to 190degree and shut down. my son slid back the linkage sleeve then removed off the ball.took the 5/16 nut and broke loose.put the lever on the console to wot. then screw in linkage until wot on levers was against thottle stop of cummins /bosch pump.fire them up idle was about 1100rpm.put her in forward with vulkan drives that means hold on!!!aim the bow for a point 4miles away and drop the hammers.WOW the boat leaped out of the water came down on plane and in a manor of seconds was at 38kns incrediable power first 6' of boat was out of the water.broke my heart to undo thottles to come into marina

CaptPatrick · Post by **CaptPatrick** » Jan 22nd, '09, 23:19

OK, I haven't done this but I see no reason it wouldn't work, at least on the pair of Yanmars I have on location...

This was sugested in the past, first by Rawleigh.

Increase the mechanical advantage at the engine by re-locating the cable connection on the throttle lever. I can't design for Cummins since I don't have a pair to look at, but if I needed to do it on the Yanmar 4LH this is where I'd be aiming...

Carl · Post by **Carl** » Jan 23rd, '09, 08:10

Capt Pat, thats exactly what I made for mine and works perfectly. However, it's with gassers using much less spring pressure.

Positive Rake is what is shown in the 2nd outdrive pic bob posted. Positve rake has the blades skewed aft, which concentrates the water flow inward towards the hub. At least that is how our prop guru describes it to us.

A negetive rake would have blades angle towards the bow, we see this on draggers and push boats as it's supposed to grab more water for push.

CaptPatrick · Post by **CaptPatrick** » Jan 23rd, '09, 08:26

Carl, thanks for the pos/neg rake clarification... I'll edit my post accordingly.

The spring tension should be somewhat of a non-issue as far as changing the mechanical advantage as I drew it. The load applied to the throttle lever is still in the original place & the added bracket only changes the throw length of the cable needed to achieve the same degree of angle change. At least as I see it in my mind....

Bruce · Post by **Bruce** » Jan 23rd, '09, 08:33

sometimes patients is impossible,people asking the same questions

Bob, you can't put out information to people and explain it like you do and expect everyone to get it.

You have to learn to express in simplistic terms, not because people are stupid, but because they don't have the mechanical advantage some of us do.

My dad who had 92 patents, numerous tecnical papers, member of IEEE and SAE and stacks of other awards from industry was probably one of the worst at explaining things. I used to wonder as a kid why people listening to him looked like a dog hearing a high pitched wistle. When I got old enough at 8 to slide along side the port engine on the 42 Chris Craft to do repairs where he couldn't fit, I realized what the look was about.

Pat is probably one of the best I've seen on passing on information.

If I could draw, I'd be much better.

Pat, becareful where you change the point of leverage on the throttle arm.

JK,
I wish I could remember what the hell I did on Buddy Boy to correct the problem but I don't. i know I didn't use one part that came with it. The heavy return spring on the 6LY engines in Buddy Boy required a cable clamp to keep the throttles in place.

I have to go to Stuart next week. Perhaps they would let me on the boat to look see.

Pete, where's the boat at again?

CaptPatrick · Post by **CaptPatrick** » Jan 23rd, '09, 08:56

Pat, becareful where you change the point of leverage on the throttle arm.

I wish I could remember what the hell I did on Buddy Boy to correct the problem but I don't. i know I didn't use one part that came with it. The heavy return spring on the 6LY engines in Buddy Boy required a cable clamp to keep the throttles in place.

Hopefully, I won't be making this modification at all.

As I recall on "Buddy Boy", there wasn't an issue with cable throw, but the two issues were helm control lever slippage on the shaft of the control head, which was remedied with the use of #609 green Loctite . The other issue was too much return spring tension, remedied by your installation of the cable brakes. The only adjustment to the control head was a slight tightening of the tension set screw.

I'm fitting patrick's boat with modified Morse SL/DC heads and Release Marine control handles...

Bruce · Post by **Bruce** » Jan 23rd, '09, 09:09

Pat,

It was a throw problem. I couldn't get full throttle when setting things up.
I fixed it before the boat ever hit the water.

It took like two to three days to figure it out and ended up eliminating a bracket in the back that came with it. And adjusting every part in the system and just got full throttle. Didn't think I could another mm out of it.

The other problem was friction and handle grip. The grip was solved with loctite, friction with a cable brake.

CaptPatrick · Post by **CaptPatrick** » Jan 23rd, '09, 09:29

You might call Jim and get him to authorize access to the boat, otherwise talk to John Spencer at the Hinkley yard and he can override any lessor minion who might say no go...

Jim's marina number is: (252) 726-4423

JK · Post by JK » Jan 23rd, '09, 09:37

CaptPatrick wrote:

I've had the slippage problem on several occasions. It is a pain to fix, thought about drilling a small indent for the set screw on the lever to fit into to get a better bite.

--JK

CaptPatrick · Post by **CaptPatrick** » Jan 23rd, '09, 10:00

JK wrote:I've had the slippage problem on several occasions. It is a pain to fix, thought about drilling a small indent for the set screw on the lever to fit into to get a better bite.

That'd work too...

bob lico · Post by **bob lico** » Jan 23rd, '09, 10:01

bruce part of that explaination problem comes from both car and marine competition for one it creates gross arrogants.one time in your neck of the woods ac marine a p-boat (production) had won some 20 races in a row.honest to god could not be beat.they would back off the thottle after taking the lead have you ever heard of that before? every race the winners go to victory row with checker flag drinking up a storm except ac marine --protest-protest every damn race the florida boys put up the money only problem was the only person alowed in the engine compartment was the protest judge.think about this for a minute 30' boat with two stock 350 cubic inch "mercruser" -350 chevy rated 280 hp.the boat would do 85mph all day.ridiculous that would take 700hp or more.they judges would say you guys built a sloppy engine because of the gasket material in the intake manifold to cylinder head.you could hear the boat tuning 7000 rpm but you just could not put your finger on it.then it got real bad every race p class,m class, offshore 1, florida engine builders hated the whole ny gang and the smart ass attitude when others ask a question.the ac marine boat went to PR. and they burn the boat to the trailer along with get out of town by sundown or we will kill you! alot of dirty money behind the seen.i took time out to explain as best i could i am sorry for the lack of patients but that is why i go out of my way to help people today.

bruce i have the new cummins storm block the bosch punp allready comes with 3 holes in the thottle lever as oppose to the older nippondenso 1 hole lever.i can`t change the fulcrum point or lower it.thank you for the time and patients to find a solution.

Carl · Post by **Carl** » Jan 23rd, '09, 10:19

Capt Pat, when you choke up on the pivot point you reduce the required cable throw but lose the mechanical advantage.

Kind of like when I was the fat kid that needed to sit closer to the middle, I didn't go for such a long ride, but at least I didn't send the twiggies flying off into the sunset.

On my setup I used a spring to counter the lost mecahnical advantge.

bob lico · Post by **bob lico** » Jan 23rd, '09, 10:21

bruce one more thing tell me your reaction.you are the winning car at daytona and you are engine buider/mechanic.the driver is doing backflips off the car after a series of " donuts" in victory lane.what do tell one of the other competitors or so call spectators if he ask what is the specs. on the cam and are you running it advance due to the fast track conditions.i know your one of the good old boys but are you a winner or are you polking fun,sticking it to them if you celebrate in front of them and ignore the questions!

CaptPatrick · Post by **CaptPatrick** » Jan 23rd, '09, 12:02

sim wrote:Capt Pat, when you choke up on the pivot point you reduce the required cable throw but lose the mechanical advantage.

Kind of like when I was the fat kid that needed to sit closer to the middle, I didn't go for such a long ride, but at least I didn't send the twiggies flying off into the sunset.

On my setup I used a spring to counter the lost mecahnical advantge.

Gotcha'... Adding a counter balance spring would be a good simple solution.

Carl · Post by **Carl** » Jan 23rd, '09, 15:44

Bob, you and my dad would have one helluva conversation...

bruce one more thing tell me your reaction.you are the winning car at daytona and you are engine buider/mechanic.the driver is doing backflips off the car after a series of " donuts" in victory lane.what do tell one of the other competitors or so call spectators if he ask what is the specs. on the cam and are you running it advance due to the fast track conditions.i know your one of the good old boys but are you a winner or are you polking fun,sticking it to them if you celebrate in front of them and ignore the questions!

Put me on your payroll and I'll let ya know...

bertram31.com

prop rake

prop rake

Who is online