Propellers have a habit of getting knocked out of pitch -- all it takes is skimming a reef or boating over a submerged log. Unfortunately, even a slight pitch misalignment results in reduced fuel efficiency and engine performance.
You can't easily determine improper pitch by eye, which is why boat mechanics use a pitch block, a cast that lines up with propeller blades to ascertain whether they are aligned properly. Repairing your own propeller is not recommended, but you can make your own pitch block to figure out whether it needs repairing. Measure the width of the bearing end of your propeller shaft. Measure the width of the bearing area on the shaft just ahead of the propeller.
Record these measurements. Seat the shaft in the first piece of plywood to become the base. Place the other piece of plywood over the top of it and hold it in place. Position the propeller on the shaft as far as possible. Raise the upper piece to lift the prop off the shaft's shoulder.
Place the supporting piece of wood into the corner, between the base and upper pieces of plywood. Screw it in place. Repeat this step for the other three supports. Draw an outline of one propeller blade on top of the plywood piece to position the three anchor screws that will secure the propeller form to the plywood. Drive two screws into the top plywood board, one on either side of a blade that is not being used to cast the mold.
This approach will work for propellers that do not have slots. For propellers that have slots, or notches, drive a screw into the board in a location that keeps the propeller from turning while you are making the mold. Hold the cardboard, smooth side in, and position it so one end hugs the hub of the prop. Drive a nail through the second last corrugation into the plywood at the hub end.
Drill another hole in the plywood next to the opposite, wide end of the cardboard. Untwist a coat hanger. Pass the hanger through the wide end of the cardboard and the hole in the plywood. Bend it to a right angle and wrap it around the propeller shaft. Mix the plaster. Tip the unit on its side with its opening on top.
Ladle the plaster into the opening with a spoon. Stir the plaster regularly while pouring it into the hole to avoid air pockets from forming. Once the hole is filled, hold the unit in this position until the plaster sets. As a freelance writer and editor sinceKiva Bottero's work has appeared in magazines such as "Healing Path," "Green Living" and "Synergy. Bottero holds a Bachelor of Arts in political science from the University of Western Ontario and studied magazine publishing at Ryerson University.Remember Me?Sciopero settore scuola 15 5 20
Forum Main Technical Discussion Prop repair User Tag List. Page 1 of 3 1 2 3 Last Jump to page: Results 1 to 15 of Thread: Prop repair Thread Tools Show Printable Version.
Prop repair You can see how the correct blades lay on the pitch block and how he lays the leather strap under the bent blade and corrects it.
Lots of hammering Excellent thanks for sharing Made my kids watch it. Great Video Knock on wood- but I've never messed up a prop that bad- so watching the fix was most interesting. I'm not impressed by his balancing rig, but then again its just a repair and not a fully blueprinted prop.
Thanks for posting this. That is the industry standard balancing rig. Believe it or not, some of the best, most expensive racing props in the world are balanced with the same type 4 wheel balancing rig. If its good enough for Craig Dewald, its good enough for me. F1 teams pay Craig to accompany them to Portugal, UAE, China, Finland, Russia and Qatar even if he doesn't have to do anything, he still gets an all expenses paid trip just to be there MAn, Thats alot of work That is close to the same set up we balanced tires on race bikes at the track, simple and it works.
Thanks for the video. Very interesting.
I wonder what he was using for the polish part. Best speed yet Cool vid! Wondered how they did the whole process. Very cool. Got any videos of adding cup? Thanks Jerry.Oxiclean and dawn
Appreciate the info.Salvador Mejia maneuvers a pound yacht propeller onto a stand using a hydraulic lift. He hoists a pound hammer over his head and strikes one of the blades. Lauderdale has decades of experience. He can see and feel the smallest of dents with his hands. Lauderdale last month.
Yacht captains understand that myriad things can whack a prop out of balance, said Brandon Cooney of Lauderdale Propeller Service. Electrolysis, cavitation, a bottom bump, even driving over a submerged log or coconut can cause vibrations, fuel inefficiency and mechanical issues.
It measures the prop. The process of fixing an imperfect prop begins by taking it off, either in-water or during a haul-out. Commercial Diver Services in Ft. Surprisingly, it took three days to remove the damaged prop. The topic of removal and installation are extensive enough for another article.
Back to the prop shop for the repair: first anti-fouling coating is removed. Since megayacht props are usually made of bronze or nibral a nickel, bronze, aluminum alloy they weigh hundreds of pounds and take the repair crew some effort to move with hydraulics and forklifts.
Sledgehammers with a variety of covers, including rawhide, copper and aluminum are used to repair props. The real repair begins when the prop is placed on a computer stand for assessment. Using a variety of manual measuring tools, craftsmen like Mejia scribe each blade with lines at 50, 60, 70, 80, 90 and 95 degrees from the hub.
Mejia will guide a Prop Scan or Hale MRI Measurement Recording Instrument to take readings along his prescribed lines and several computer screens worth of data are computed.
With these numbers, Mejia isolates and marks raised and lowered spots along the scribe marks. Next, he moves the prop to pitch blocks, which support the blades, chooses the appropriate hammer — covered either with rawhide, copper or aluminum — and pounds out the damaged areas. Big dents will require big hammers and big swings. He continues the sequence until the prop is within ISO class tolerances. It is important for all the blades, whether there are three, five or more, to be nearly identical.
During the repair, if any chunks are missing from the prop, it is sent to the welding department to make them whole again.Propeller Basics.
Propeller Diameter Diameter is the distance from the center of the hub to the tip of one of the blades times two. Typically you want to use the same diameter size prop that your engine came with.
However, diameters between different propeller manufacturers may vary slightly.
Computer Propeller Repair Basics
This small variance does not affect your performance as much as the pitch and overall design of the blades. Diameter is the first number listed in the propeller description.
Propeller Pitch Pitch is defined as the theoretical forward movement of a propeller during one revolution assuming there is no "slippage" between the propeller blade and the water. For example, a 21 pitch propeller will theoretically move 21 inches forward with every revolution. Propeller slip occurs with every propeller, but the amount of slip varies depending on propeller design.
More aggressively and efficiently designed propellers will slip less. When selecting a propeller pitch for your boat, it is important that the propeller runs at the upper end of your engines wide-open-throttle RPM range.
If you want your RPM's to increase, go down in pitch. To decrease RPM's, go up in pitch.
For water sports or extra people on board, you should generally drop 2" of pitch to help compensate for the added weight and drag on your boat.
It makes a noticeable difference in your boat's hole shot, fuel efficiency, RPM's, and overall performance. You should ALWAYS carry a spare propeller on board, and if you're into water sports or occasionally load the boat with extra people, a spare prop with a lesser pitch is a good idea.
Propeller pitch can be compared to a gear on a car - lower gear, higher RPM's. Pitch is the second number listed in the propeller description. Aluminum vs. Stainless Steel Many people argue that stainless steel propellers perform better than aluminum propellers. Material Stainless vs. Well-designed aluminum propellers will outperform an average stainless steel propeller.
The advantage of a stainless steel propeller over aluminum is durability. Stainless props can withstand more of the damage caused by small rocks, sand, or other loose objects in the water. With aluminum props, the blades will most likely sacrifice themselves before any damage is caused to your lower unit.
But it is important to always carry a spare propeller on board, and a spare aluminum is an inexpensive choice.
Cavitation Cavitation, which is often confused with ventilationis a phenomena of water vaporizing or "boiling" due to the extreme reduction of pressure on the back of the propeller blade.
Many propellers partially cavitate during normal operation, but excessive cavitation can result in physical damage to the propeller's blade surface due to the collapse of microscopic bubbles on the blade. There may be numerous causes of cavitation such as incorrect matching of propeller style to application, incorrect pitch, physical damage to the blade edges, etc Order a spare prop today and stay on the water longer tomorrow.
And don't forget the tools If you have a Mercruiser drive, a combination prop wrench will do the trick. A 10 inch block of 2X4 makes a great block between the prop blade and ventilation plate will make it easy to loosen and tighten the prop nut.
Be sure to tighten the prop nut really tight. Return To DockSide. Propeller Basics Propeller Diameter Diameter is the distance from the center of the hub to the tip of one of the blades times two.Unfortunately due to a lack of suitable blade stock, I am currently not cutting any more prop blocks.
Either Fiberglass molds of my existing blocks or Fiberglass molds with camber for forming sheet props, available in any pitch and a choice of cambers. I am taking a break from producing FliteTork digital Torque meters. Please contact Bill Gowen for them. You will need to contact me with your specifications in order to get it set up. These may take a couple of weeks to make and send.
I accept PayPal at propblocks gmail. After choosing a blade size, I selected a bit of light A-grain balsa that bent easily around the form. Choosing the right piece of balsa makes life easier. I cut this piece in a rough rectangle larger than what the blades would be then sanded an arc into the blank.
The blank was then soaked in water for around 10 or 20 minutes. A center reference line was drawn on the block and marked at each inch. Once heated, I turn it off and let it dry overnight. Some use washed out tips, others stick with the helical distribution. Diameters can vary from HLS seem to be similar to F1D, maybe average a little higher in pitch. Instead I have switched to making fiberglass forms to build off of or form props from. I am no longer selling custom cut prop blocks.
F1D Template sets have arrived and are shipping. See the Misc stuff tab for information. E-mail me at propblocks gmail. I do ship Internationally and charge only what the post office charges me.4devs cep
Camber form being tied to block. F1L blades do not reach the washed out portion.Hitman 2 not launching steam
Our propellers are tough, durable, and exceptionally smooth. With our patented pitch block system, blade angles are precise and with the injection molding process, weights are held to a six-gram range for perfect balance. Replacement of a blade requires no balancing.
The original 2,3, and 4-blade Ultra-Props were limited to 59 inches and 50HP. We added 5 and 6-blade props to cover high HP applications. Over five years ago we started design of a new propeller to expand our offerings. We retained our pitch block and hub concept and Craig Catto designed a longer and more efficient blade. We evaluated several blades and resins and ended up with a long carbon fiber reinforced engineering thermoplastic.
Our manufacturing process requires expensive tooling and much testing. The propeller hub, pitch block and blade retention system have been successfully subjected to the required 2X loads. We have run over speed tests without failure; a test that is not required if you run a hour dynamic test and submit the formal documents to qualify for LSA. We did not run this test on the original Ultra-Prop and are confident that our extensive testing to date shows we will meet that requirement.
Prices for the Ultra-Prop II are significantly lower than our composite prop competition and in most cases even lower than wood propellers. Our low cost Spinner Kit adds even more appeal to our props. Competition Aircraft, Inc. Competition Aircraft. Ultra-Prop II. Introducing the Ultra-Prop II.Inboard Catalog Fixed Pitch Propellers. Email: johnnyspropeller yahoo. The right propeller can have a dramatic effect on peak performance, acceleration, handling, and fuel economy.
Whether you ski, fish, race or just like to cruise, Johnny's Boat Propeller Services in Detroit, MI, is your source for the right propeller and the way you use it.
We have a team of technicians that can handle all your propeller needs including repairs, installation, fabrication, and more. We use the latest technology in properly diagnosing your boat propeller.
We have the Hale MRI system to ensure your propeller performs to its maximum capacity.Star wars rpg specializations
The MRI system allows us to determine repairs where needed and help with your propulsion issues. Marine Propeller Repair Shop Johnny's offers the most reliable and hassle-free repair service in the country.
Our staff is experienced in using Michigan Wheel pitch block systems and manual pitch gauge and sweep gauge. We are also the only repair shop in Michigan using Hale MRI Propeller Inspection to obtain absolute recognition of propeller condition. We can have your propeller repaired and shipped back to you anywhere in the U. Call to schedule your service today! Johnny's Boat Propeller Service. Address: E. Warren Ave. Detroit, MI
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