The overwhelming majority of engine-driven craft use propellers to convert the power of the engine to useful work. There are plenty of alternatives which may have advantages for specific applications, but propeller systems are good all-rounders that are reasonably cheap, simple, reliable, efficient and easy to use.
They suffer, however, from one potentially significant drawback, which is that a large slow turning propeller is generally more efficient than a small fast-spinning one. Even on small pleasure craft, where the maximum size of propeller is often limited by hull shape, the optimum shaft speed is usually in the order of 1000 rpm - only a half or a quarter of the speed of the engine. Running the engine more slowly isn't the answer, because you'd just lose most of the power you've paid for by buying it in the first place. What you need is something that will reduce the shaft speed but increase its torque (turning effort).
It's also very useful to be able to reverse the direction of rotation, to provide astern power to stop the boat or make it go backwards, or to fit counter-rotating propellers on a twin-screw boat. Again, there are alternatives such as variable-pitch propellers whose blades swivel on the hub, scoop-like deflectors, or even boat engines that can be stopped and restarted in the opposite direction, but by far the most popular arrangement is a reversing gearbox.
Reversing gearboxes
Two gearwheels, whose teeth mesh together so that as one turns, the other has to turn as well. The smaller gear has 9 teeth, so if it is turning at 1000 rpm, its teeth are moving at 9000 teeth per minute. The larger wheel is twice the size, and has 18 teeth, so although its teeth must also be moving at 9000 teeth per minute, that means only 500 rpm. Note, too, that if the smaller wheel is turning clockwise, the larger wheel must be turning anticlockwise.
Now imagine that you're using a spanner a foot long to turn the smaller wheel. If you apply an effort of 10 lb to the end of the spanner, you're applying a torque of 10 lb/ft (10 lb at a radius of 1 ft). The gear-wheel is much smaller - let's say it has an effective radius of 1 in. That means its teeth must be pushing on the teeth of the other wheel with a force equivalent to 120 lb (120 lb at a radius of 1/12 ft = 120 x 1/12 = 10 lb/ft). The larger wheel has an effective radius of 2 in, so a force of 1201b to its teeth corresponds to a torque of 20 lb/ft (120 x 2/12 = 20 lb/ft).
In other words, by using a 9-tooth wheel to drive an 18-tooth wheel, we've halved the speed doubled the torque, and reversed the direction of rotation.
Simple gearboxes
Real boat gearboxes look more complicated, but depend on exactly this principle. In fact, the main difference between the simple gear train and the Volvo MS2 is that the MS2 uses coneshaped bevel gears, so that although the input shaft is horizontal, the central driven shaft is vertical.
The motive for this is that it provides a simple way of achieving a choice of ahead or astern gear.
The bevel gear on the input shaft turns two slightly larger bevel gears that spin freely on the vertical shaft. One is driven by the top of the input gear and the other by the bottom of it, so they rotate in opposite directions, but they are the same size as each other so they turn at the same speed.
Between the two gears is a sliding clutch assembly, shaped like two shallow cones mounted base-to-base on the shaft. Ridges called splines on the shaft and matching grooves in the clutch ensure that it can easily slide up and down, but can't turn without turning the shaft as well. Moving the gear lever slides the clutch up or down so that one of the cones engages into a matching hollow in one of the spinning gears, which locks that gear on to the shaft.
At the bottom of the shaft, a relatively small bevel gear engages with a much larger gear on the output shaft, to give a horizontal output, at a much lower speed of rotation.
Layshaft gearboxes
Although the MS2 and its derivatives are common on Volvo engines up to about 200 hp, it's somewhat unusual in using a vertical shaft. A more widespread arrangement is the layshaft gearbox.
In this case, a small gear on the input shaft turns a larger gear on the layshaft. Like the gears on the vertical shaft of the MS2, this is free to spin around the layshaft, but can be locked on to it by a clutch. If the input shaft is turning clockwise and the clutch is engaged, the layshaft turns anticlockwise and more slowly. At the other end of the layshaft a smaller gear meshes with a large gear on the output shaft, driving the output shaft clockwise and even more slowly.
Astern gear is achieved by a second layshaft. Its very similar to the first, with two gearwheels, one of which has a clutch that can leave it free-spinning or lock it on to the shaft, while the other is constantly in mesh with the output shaft. The key feature about the second layshaft is that it is not driven directly by the input shaft, but
by the first layshaft. This means that it's turning in the opposite direction - so if one clutch is released and the other engaged, the direction of the output shaft will be reversed.
Epicyclic gearboxes
The third alternative, renowned for its smooth operation but now becoming less popular - is known as the epicyclic gearbox.
The central gearwheel - known as the sun gear - is mounted on the input shaft, driven by the engine. Around it are several smaller planet gears mounted in a rigid cage called the planet holder. while the whole assembly is surrounded by a cylindrical ring gear that looks rather like the hub of a trailer wheel but with teeth machined into its inner surface. The output shaft is coupled directly to the planet holder.
For ahead operation. a clutch is used to lock the planet gears so that they can't turn. In effect, this means that the input shaft, ring gear, planet holder and output shaft are all locked together so the whole assembly turns as though it were one piece.
For astern gear, the ring gear is locked to the casing, and the planet gears are left free to rotate. If the input shaft turns clockwise, this means that the inner planets have to turn anticlockwise, driving the outer planets clockwise. In order to do this, they have to run anticlockwise around the inside of the ring gear, taking the planet holder - and, of course, the output shaft - around with them.
One major snag with this is that although it provides an ahead/astern facility, it can't offer the reduction in shaft speed that is one of the main reasons for wanting a gearbox in the first place. To do that requires a second gearbox in tandem with the first - adding to the cost, weight, bulk and complexity of the whole unit. The second gearbox is usually another epicyclic unit, but with the important difference that there are no clutches involved, and the output shaft is connected to the ring gear instead of to the planet holder.
In this case, the spinning input shaft coming from the reversing gearbox drives the sun wheel, which makes the planet wheels turn, and they, in turn, drive the ring gear.
Marine Clutches
An important characteristic of all marine gearboxes is that the gears of both drive trains - ahead and astern - are in mesh all the time, and that selection of ahead, astern and neutral is achieved by using clutches to disconnect whichever drive train is not in use.
There are two main types of clutches: the cone clutch used in the MS2, and the plate clutch used in most of the others.
The plate clutch consists of a stack of flat friction plates. Some of the plates have internal splines which mesh with matching splines on the shaft, so they have to turn with it. Sandwiched between them are similar plates which are free to spin around the input shaft but have external splines that mesh with splines on the inner surface of the clutch casing - connected to the output shaft. So long as the stack is loose, the two shafts are free to rotate independently of each other. Compressing the stack forces the plates into contact with each other so that they grip and force the two shafts to turn together.
For relatively small engines - up to about 100 hp - a hand-operated lever may be enough to operate either sort of clutch, but bigger engines need more pressure to be applied. This calls for hydraulics, in which a pump built into the gearbox creates hydraulic pressure to force the plates together. All the gear lever has to do is operate a valve, diverting the hydraulic pressure to whichever clutch requires it.
Who can help with your boat gearbox? boatpartsdatabase.com has lots of resources for the boating trade and public alike.
The web is a vast source of information. Boatpartsdatabase collects the leisure marine industry into one huge database of contacts. Freedom Marine can.
Friday, October 30, 2009
Friday, October 23, 2009
Marine Propellers
It is a good idea to remove the propeller from time to time, to stop it seizing solid on the shaft. This is particularly important in the case of outboard and outdrive propellers, which usually have either shear pins or flexible hubs that are designed to protect the engine and transmission by slipping or breaking if the propeller hits something. Unfortunately, after a period of time, these protective devices break of their own accord, so it's important to make sure that the propeller can be taken off and replaced at sea.
Removing yacht propellers
Straighten out the legs of the split pin and remove it, or flatten the lugs of the tab washer that holds the propeller nut in place.
Use a block of wood to stop the propeller turning and undo the propeller nut.
It should be possible to pull an outboard or sterndrive's propeller off the shaft by hand. Make note of the order that any springs or washers come off, and which way round they go.
The best way to remove a stubborn propeller is with a puller. Once the puller has been tightened, a few light taps with a hammer on the puller should make the propeller slide off.
As a last resort, try warming the propeller boss with a blow lamp.
Propeller repair
If necessary, use a file to smooth any burrs or nicks from the edges of the propeller, but be careful not to remove so much metal that there is a risk of the propeller becoming unbalanced. If it is badly damaged refer it to a propeller repair workshop.
Replacing propellers
Before replacing the propeller, grease the shaft with a non-graphite grease.
Slide the propeller back on, making sure that any keys, shear pins, springs or washers are replaced exactly as they were removed, but use a new tab washer (if there was one) to hold the propeller nut in place.
Tighten the propeller nut just sufficiently to grip the propeller, then insert the split pin (if there was one). Bend up one tab of the tab washer to hold the nut in place, or open the legs of the split pin and bend them round the nut.
Stern glands
Greasing stern glands
If your stern gland is fitted with a greaser, routine greasing involves either turning the handle or tightening the cap by one turn after every few hours' running: once every four hours is about right. Eventually, this will use up all the grease, which will have to be replaced. Don't use graphite grease: its carbon content causes extremely rapid corrosion in the presence of salt water.
Remove the top cap of the greaser. If yours is the type that uses a handle like that of a garden tap to operate a plunger, 'unscrew' the handle to return the plunger to its starting position.
Invert the grease can, so that the hole in the plastic disc is over the greaser.
Press the whole can downwards, so that the plastic disc slides into the can and forces grease out. You may have to stop a few times, especially when the greaser is nearly full, to allow trapped air to escape.
Replace the cap of the greaser.
Adjusting stern glands
With the engine stopped and out of gear, turn the shaft by hand to get a feel for how stiff it is.
Slacken off any lock-nuts holding the two parts of the stern gland together.
Tighten the clamping bolts that hold the two parts of the stern gland together, or screw the sleeve into the outer casing. Don't tighten them by more than half a turn at a time, and - if yours is the type that has two or three bolts - make sure that you tighten them evenly.
Turn the shaft by hand and check for drips: it should turn freely and leak between one and six drips per minute. If it is leaking too quickly, repeat.
Outdrives and saildrives
Outdrives and saildrives circumvent the need for a stern gland altogether by - in effect - extending the gearbox right into the water in the form of a drive leg. Of course, this doesn't make the problem go away altogether: it just changes it a bit, because instead of having to seal the gap around a small rotating shaft, there's a much bigger hole to plug between the hull and the drive leg. Outdrives achieve this by using flexible rubber bellows between the transom and the leg, while saildrives use a rubber diaphragm to seal the joint between the drive unit and the bottom of the boat. Servicing recommendations vary depending on the manufacturer and model, but the importance of following them to the letter is obvious.
Repair your propellers? boatpartsdatabase.com has lots of resources for the boating trade and public alike.
The web is a vast source of information. Boatpartsdatabase collects the leisure marine industry into one huge database of contacts. feathering and folding propellers and where to buy them is just one example.
Removing yacht propellers
Straighten out the legs of the split pin and remove it, or flatten the lugs of the tab washer that holds the propeller nut in place.
Use a block of wood to stop the propeller turning and undo the propeller nut.
It should be possible to pull an outboard or sterndrive's propeller off the shaft by hand. Make note of the order that any springs or washers come off, and which way round they go.
The best way to remove a stubborn propeller is with a puller. Once the puller has been tightened, a few light taps with a hammer on the puller should make the propeller slide off.
As a last resort, try warming the propeller boss with a blow lamp.
Propeller repair
If necessary, use a file to smooth any burrs or nicks from the edges of the propeller, but be careful not to remove so much metal that there is a risk of the propeller becoming unbalanced. If it is badly damaged refer it to a propeller repair workshop.
Replacing propellers
Before replacing the propeller, grease the shaft with a non-graphite grease.
Slide the propeller back on, making sure that any keys, shear pins, springs or washers are replaced exactly as they were removed, but use a new tab washer (if there was one) to hold the propeller nut in place.
Tighten the propeller nut just sufficiently to grip the propeller, then insert the split pin (if there was one). Bend up one tab of the tab washer to hold the nut in place, or open the legs of the split pin and bend them round the nut.
Stern glands
Greasing stern glands
If your stern gland is fitted with a greaser, routine greasing involves either turning the handle or tightening the cap by one turn after every few hours' running: once every four hours is about right. Eventually, this will use up all the grease, which will have to be replaced. Don't use graphite grease: its carbon content causes extremely rapid corrosion in the presence of salt water.
Remove the top cap of the greaser. If yours is the type that uses a handle like that of a garden tap to operate a plunger, 'unscrew' the handle to return the plunger to its starting position.
Invert the grease can, so that the hole in the plastic disc is over the greaser.
Press the whole can downwards, so that the plastic disc slides into the can and forces grease out. You may have to stop a few times, especially when the greaser is nearly full, to allow trapped air to escape.
Replace the cap of the greaser.
Adjusting stern glands
With the engine stopped and out of gear, turn the shaft by hand to get a feel for how stiff it is.
Slacken off any lock-nuts holding the two parts of the stern gland together.
Tighten the clamping bolts that hold the two parts of the stern gland together, or screw the sleeve into the outer casing. Don't tighten them by more than half a turn at a time, and - if yours is the type that has two or three bolts - make sure that you tighten them evenly.
Turn the shaft by hand and check for drips: it should turn freely and leak between one and six drips per minute. If it is leaking too quickly, repeat.
Outdrives and saildrives
Outdrives and saildrives circumvent the need for a stern gland altogether by - in effect - extending the gearbox right into the water in the form of a drive leg. Of course, this doesn't make the problem go away altogether: it just changes it a bit, because instead of having to seal the gap around a small rotating shaft, there's a much bigger hole to plug between the hull and the drive leg. Outdrives achieve this by using flexible rubber bellows between the transom and the leg, while saildrives use a rubber diaphragm to seal the joint between the drive unit and the bottom of the boat. Servicing recommendations vary depending on the manufacturer and model, but the importance of following them to the letter is obvious.
Repair your propellers? boatpartsdatabase.com has lots of resources for the boating trade and public alike.
The web is a vast source of information. Boatpartsdatabase collects the leisure marine industry into one huge database of contacts. feathering and folding propellers and where to buy them is just one example.
Friday, October 16, 2009
Folding Boats - The Different Types of Foldable Boats
Folding boats are small, lightweight kayaks, canoes or boats that offer convenience in storage and transportation. These foldable boats are available in a variety of sizes with 8 to 14 feet being the most common sizes, and some able to fold down to as little as 4 inches in thickness.
The folderable boats come in a variety of innovative designs. Those that are constructed of one central piece that's hinged together in a polypropylene material and folds flat (surfboard size) after use. To those that are again made from the flexible polypropylene material but can be bent and folded into a compact storage bag or those that are build out of an aluminum frame that has several pieces with the hull coated in a tough and durable boatskin.
Often compared to the inflatable boats in relation to its size and store-ability, although each have their own plus and minus points. The inflatable's need the time and effort to inflate and deflate it, while the foldables need time to assemble and to be broken down again after use. An inflatable can puncture if it snags on a sharp rock. On the other hand the polypropylene material is a tough and impact resistant material, so no branch or rock will damage these boats.
If not keen on the flimsiness of an inflatable than opt for the hard and stiff construction of a folderable. The small size of these boats is a positive point for the traveler as some are packed into a bag as small as a backpack-style bag.
These folderable water-crafts are ideal for those wishing to get into boating but don't have adequate space to store or transport a full-sized craft. And that's one of the most important points to these folding boats that can be easily broken-down after use and stored away in a garage, apartment closet, or the boot of a vehicle - awaiting that next fishing trip.
If you're interested in getting a more detailed look at Folding Boats, including a variety of boating tips and ideas, take a look at http://www.RecreationalWatercraft.com.
The folderable boats come in a variety of innovative designs. Those that are constructed of one central piece that's hinged together in a polypropylene material and folds flat (surfboard size) after use. To those that are again made from the flexible polypropylene material but can be bent and folded into a compact storage bag or those that are build out of an aluminum frame that has several pieces with the hull coated in a tough and durable boatskin.
Often compared to the inflatable boats in relation to its size and store-ability, although each have their own plus and minus points. The inflatable's need the time and effort to inflate and deflate it, while the foldables need time to assemble and to be broken down again after use. An inflatable can puncture if it snags on a sharp rock. On the other hand the polypropylene material is a tough and impact resistant material, so no branch or rock will damage these boats.
If not keen on the flimsiness of an inflatable than opt for the hard and stiff construction of a folderable. The small size of these boats is a positive point for the traveler as some are packed into a bag as small as a backpack-style bag.
These folderable water-crafts are ideal for those wishing to get into boating but don't have adequate space to store or transport a full-sized craft. And that's one of the most important points to these folding boats that can be easily broken-down after use and stored away in a garage, apartment closet, or the boot of a vehicle - awaiting that next fishing trip.
If you're interested in getting a more detailed look at Folding Boats, including a variety of boating tips and ideas, take a look at http://www.RecreationalWatercraft.com.
Friday, October 9, 2009
What Better Way You Can Think of Safeguarding Your Boat on Water?
For those who love to experience the wild spirit of water sports, fishing right in the middle of water or simply going on for boating excursions, are all a sheer sense of adventure to spend hours on boat. But, there are certain points where you need to be cautious while boating. When on water or outside it, you're exposed to millions of dangers that you may not even be aware of. In order to safeguard from these dangers you need to have highly efficient boat covers.
If you do not want to spoil your sport while on boating excursion or in the middle of some water sport then ensure the safety and maintenance of your boat beforehand. Thus, comes in the role of these covers. Before investing your money on covers you need to have thorough knowledge of boat covers, their fabric and types of covers so that you may not purchase an ill-fitting cover that proves to be of little use to you. There is stiff competition amongst boat covers dealers during peak holiday season and this may lead you into cheap bargains so be equipped with right information prior.
Select the right boat cover
There are wide array of covers available as per the style and type of boat you own and some of the popular ones include pontoon cover Bayliner boat cover Sunbrella boat cover and custom boat covers. Every boat has its specific requirements. As it promises you immense leisure and good time, so it's your responsibility to maintain it properly and keep it in good working condition throughout the year. Rodents, wind, waves, dust, UV rays and some water bodies may harm your boat terribly. In order to keep all these harmful elements at bay from posing any threat, you must install a right kind of cover on your boat.
Custom boat covers for a perfect fit
Definitely brand name works a lot like that of Sunbrella or Bayliner. But another option available to provide ultimate protection to your dearest possession is the custom covers. These are designed specifically in accordance with the size and style of your boat and are tailor-made to meet your personal needs. You can get the alteration and modifications done right at the time of designing.
Readymade boat covers may not necessarily have the same fitting as desired by you. For instance, they may not be made as per your boat's design and once you have made the purchase you are not left with any other alternative but to use that ill-fitting cover somehow. However, in case of custom covers you are spared from such hurdles and hassles. You can choose the fiber, color and design as per your requirement which makes custom boat covers favorite amongst people who love spending long time on water.
Nonetheless, the quality and assurance provided by boat covers from big manufacturers can also not be superseded, if it fits your boat well. So, it all depends on you if you think customized boat covers are best for your boat or the branded ones.
If you are on look out for some more buying tips on boat covers then check out http://www.boatcoversadvice.com
If you do not want to spoil your sport while on boating excursion or in the middle of some water sport then ensure the safety and maintenance of your boat beforehand. Thus, comes in the role of these covers. Before investing your money on covers you need to have thorough knowledge of boat covers, their fabric and types of covers so that you may not purchase an ill-fitting cover that proves to be of little use to you. There is stiff competition amongst boat covers dealers during peak holiday season and this may lead you into cheap bargains so be equipped with right information prior.
Select the right boat cover
There are wide array of covers available as per the style and type of boat you own and some of the popular ones include pontoon cover Bayliner boat cover Sunbrella boat cover and custom boat covers. Every boat has its specific requirements. As it promises you immense leisure and good time, so it's your responsibility to maintain it properly and keep it in good working condition throughout the year. Rodents, wind, waves, dust, UV rays and some water bodies may harm your boat terribly. In order to keep all these harmful elements at bay from posing any threat, you must install a right kind of cover on your boat.
Custom boat covers for a perfect fit
Definitely brand name works a lot like that of Sunbrella or Bayliner. But another option available to provide ultimate protection to your dearest possession is the custom covers. These are designed specifically in accordance with the size and style of your boat and are tailor-made to meet your personal needs. You can get the alteration and modifications done right at the time of designing.
Readymade boat covers may not necessarily have the same fitting as desired by you. For instance, they may not be made as per your boat's design and once you have made the purchase you are not left with any other alternative but to use that ill-fitting cover somehow. However, in case of custom covers you are spared from such hurdles and hassles. You can choose the fiber, color and design as per your requirement which makes custom boat covers favorite amongst people who love spending long time on water.
Nonetheless, the quality and assurance provided by boat covers from big manufacturers can also not be superseded, if it fits your boat well. So, it all depends on you if you think customized boat covers are best for your boat or the branded ones.
If you are on look out for some more buying tips on boat covers then check out http://www.boatcoversadvice.com
Friday, October 2, 2009
Simple Do-It-Yourself Gel Coat Repairs
Got a scrape, crack, or soft deck on your power boat or sailboat? Here's a quick, easy fix that will save you money. There are many different ways to go about the repair, but my method works and is not too difficult to master.
Let's get started fixing that crack.
Did your jib pole come loose? Did the anchor swing too wildly or did your landlubber friend forget to tell you he had on his golf shoes? Don't laugh...it happens. I used to get all upset when I saw the slightest damage to my gel coat and thought it would never be the same. You will always see it even after a mint fix. But no one else will, even if the fix is not perfect. Power boats get cracks here and there from the pounding as they cut through waves. Sailboats get it the same way, plus all the heeling over they do.
I have read all the books and articles and found they all do a great repair. Some more complicated than others. I took the best from each and now do this procedure for a great fix.
What you'll need:
1. Get a Bondo can (auto/marine body filler), that is short and wide, with a plastic top. This comes with the catalyst you will need.
2. Sandpaper/wet & dry (emery cloth), 1 sheet of each: #220, #320, #400, #600
3. Gel Coat color from the manufacturer - it's worth the wait to get it. If not, you can use white gel coat with the tints you need to get it right. Most stores have a chart.
You can mix the gel coat over the winter. Get the right color card from Home Depot, and you can play with the color over the winter, until you get a match, and save it in a jar for the spring.
4. Acetone
5. Masking Tape
6. Spray bottle, sold in marine supply or hardware stores.
7. Screwdriver or metal pick
8. Newspaper
As you can see from the materials list, there need not be a great expense in performing your own repair. These materials can last through 10 repairs. Each time you take care of the crack yourself, you can save yourself hundreds of dollars.
1. In order to repair a crack, clear the area. Take a good look at it and then take some acetone on a rag and clean in and around the crack. A little goes a long way. Too much is no good. This cleans the wax, dirt, and stains off so you now can see clearly how far the crack really goes and what color you should mix, too. The factory gel coat that was sent is the original color of the boat's gel coat. By sanding lightly with 300 grit wet you will bring this color out, but it will not match the rest of the boat. You may have to add a touch of yellow or gray/black to get that faded color. Look from the sun. If you plan to compound to the original color, then go with the factory color, otherwise, tint it down.
2. Now that the gel coat is ready, let's get back to the crack. After using some acetone and sanding right around and in the crack, use a flat hand screwdriver or metal pick to loosen any material in the crack. Make good, fat edges at either side of the crack. Chip away at it until you get to good, un-cracked gel coat. Sand the area, blow out and acetone again.
3. Tape around the area you are working on, close to the crack. Then tape newspaper around it to catch any over-spray.
4. If the crack is deep, you need to add some plastic filler (bondo). You can use the type that has fiberglass strands. A white colored filler is preferable. Mix the proper amount of catalyst into the filler and squeeze it into the crack. If the crack is small, use a flathead screwdriver. Keep it just in the crack. Use masking tape along the edges, if you need. You can keep it level with the surrounding gel coat, because when it dries, you will sand it lightly with the 220 or 300 grit and make a slight depression in the plastic. Drying time will vary according to the temperature and amount of catalyst used. Pull the excess masking tape away. Use acetone to wash away the masking tape glue and any impurities.
5. Get the sprayer, read the instructions. Pour the gel coat (factory or mixed) into the jar. Add some acetone to cut the thickness of the gel coat so it can spray out. Add the proper amount of catalyst, stir and screw the jar back on and you're ready to go.
6. Find a piece of cardboard to spray on. Feel the force and the amount that comes out of the sprayer. Press the nozzle to move it to the right. Release nozzle. Press the nozzle again, move to the left and so on to get a smooth coat. Now, spray the repair area with the same motion. See how it looks before you repeat the process. Don't try to complete it in one or two shots. Slow and easy. It will cover. You can put extra coats on because you will do sanding next. Don't put too much on. Let it dry. It's good to do this in 70 - 80 degree weather. If it is cooler out, point a utility light at it. It should harden it in anywhere from 15 minutes to an hour, varying according to the outside temperature. If you want, you can leave it overnight. If it still doesn't set, use the acetone to get it off and try again with a better combo of catalyst. You will get good at this one you do it several times, just like riding a bike.
7. After the gel coat hardens, take that plastic cup top and put some water in it. Rip a 1" x 4" piece of emery cloth off the 220 or 300 grit. Soak it a bit and also put some water over the repair. Wipe it around. Now, with the emery cloth pliable, lightly sand over the repair. Feel the coarseness of the area you are sanding. Add more water if it feels pretty flush with the surrounding area. Move to 400 grit, then to 600 grit. Get it nice and wet. Watch not to take too much gel coat off. Do a little checking as you're sanding.
8. The final step is using a little white compound. Add a touch of water. Compound out lightly. Wash off thoroughly and wax. You're done. Is it perfect? Maybe, but if not, no will see it unless you put blue gel coat where white should belong. In the meantime, you will forget about where it actually is as it fades in. A scrape is basically the same, just a large area. Sometimes a light sanding with 300 or 400 grit, nice and wet, will remove most and sometimes, surprisingly, all of the scrape without a gel coat repair. It just depends how deep it is.
With a little practice, you can save yourself a boat-load of money otherwise spent on having the gel coat refinished professionally. If doing it yourself is not your thing, you may find understanding the process helpful when consulting with a repair center.
Douglas Malat is a licensed captain, freelance writer and co-author of http://www.YachtAuthority.com, where you will find gel coat repair services in your area.
Let's get started fixing that crack.
Did your jib pole come loose? Did the anchor swing too wildly or did your landlubber friend forget to tell you he had on his golf shoes? Don't laugh...it happens. I used to get all upset when I saw the slightest damage to my gel coat and thought it would never be the same. You will always see it even after a mint fix. But no one else will, even if the fix is not perfect. Power boats get cracks here and there from the pounding as they cut through waves. Sailboats get it the same way, plus all the heeling over they do.
I have read all the books and articles and found they all do a great repair. Some more complicated than others. I took the best from each and now do this procedure for a great fix.
What you'll need:
1. Get a Bondo can (auto/marine body filler), that is short and wide, with a plastic top. This comes with the catalyst you will need.
2. Sandpaper/wet & dry (emery cloth), 1 sheet of each: #220, #320, #400, #600
3. Gel Coat color from the manufacturer - it's worth the wait to get it. If not, you can use white gel coat with the tints you need to get it right. Most stores have a chart.
You can mix the gel coat over the winter. Get the right color card from Home Depot, and you can play with the color over the winter, until you get a match, and save it in a jar for the spring.
4. Acetone
5. Masking Tape
6. Spray bottle, sold in marine supply or hardware stores.
7. Screwdriver or metal pick
8. Newspaper
As you can see from the materials list, there need not be a great expense in performing your own repair. These materials can last through 10 repairs. Each time you take care of the crack yourself, you can save yourself hundreds of dollars.
1. In order to repair a crack, clear the area. Take a good look at it and then take some acetone on a rag and clean in and around the crack. A little goes a long way. Too much is no good. This cleans the wax, dirt, and stains off so you now can see clearly how far the crack really goes and what color you should mix, too. The factory gel coat that was sent is the original color of the boat's gel coat. By sanding lightly with 300 grit wet you will bring this color out, but it will not match the rest of the boat. You may have to add a touch of yellow or gray/black to get that faded color. Look from the sun. If you plan to compound to the original color, then go with the factory color, otherwise, tint it down.
2. Now that the gel coat is ready, let's get back to the crack. After using some acetone and sanding right around and in the crack, use a flat hand screwdriver or metal pick to loosen any material in the crack. Make good, fat edges at either side of the crack. Chip away at it until you get to good, un-cracked gel coat. Sand the area, blow out and acetone again.
3. Tape around the area you are working on, close to the crack. Then tape newspaper around it to catch any over-spray.
4. If the crack is deep, you need to add some plastic filler (bondo). You can use the type that has fiberglass strands. A white colored filler is preferable. Mix the proper amount of catalyst into the filler and squeeze it into the crack. If the crack is small, use a flathead screwdriver. Keep it just in the crack. Use masking tape along the edges, if you need. You can keep it level with the surrounding gel coat, because when it dries, you will sand it lightly with the 220 or 300 grit and make a slight depression in the plastic. Drying time will vary according to the temperature and amount of catalyst used. Pull the excess masking tape away. Use acetone to wash away the masking tape glue and any impurities.
5. Get the sprayer, read the instructions. Pour the gel coat (factory or mixed) into the jar. Add some acetone to cut the thickness of the gel coat so it can spray out. Add the proper amount of catalyst, stir and screw the jar back on and you're ready to go.
6. Find a piece of cardboard to spray on. Feel the force and the amount that comes out of the sprayer. Press the nozzle to move it to the right. Release nozzle. Press the nozzle again, move to the left and so on to get a smooth coat. Now, spray the repair area with the same motion. See how it looks before you repeat the process. Don't try to complete it in one or two shots. Slow and easy. It will cover. You can put extra coats on because you will do sanding next. Don't put too much on. Let it dry. It's good to do this in 70 - 80 degree weather. If it is cooler out, point a utility light at it. It should harden it in anywhere from 15 minutes to an hour, varying according to the outside temperature. If you want, you can leave it overnight. If it still doesn't set, use the acetone to get it off and try again with a better combo of catalyst. You will get good at this one you do it several times, just like riding a bike.
7. After the gel coat hardens, take that plastic cup top and put some water in it. Rip a 1" x 4" piece of emery cloth off the 220 or 300 grit. Soak it a bit and also put some water over the repair. Wipe it around. Now, with the emery cloth pliable, lightly sand over the repair. Feel the coarseness of the area you are sanding. Add more water if it feels pretty flush with the surrounding area. Move to 400 grit, then to 600 grit. Get it nice and wet. Watch not to take too much gel coat off. Do a little checking as you're sanding.
8. The final step is using a little white compound. Add a touch of water. Compound out lightly. Wash off thoroughly and wax. You're done. Is it perfect? Maybe, but if not, no will see it unless you put blue gel coat where white should belong. In the meantime, you will forget about where it actually is as it fades in. A scrape is basically the same, just a large area. Sometimes a light sanding with 300 or 400 grit, nice and wet, will remove most and sometimes, surprisingly, all of the scrape without a gel coat repair. It just depends how deep it is.
With a little practice, you can save yourself a boat-load of money otherwise spent on having the gel coat refinished professionally. If doing it yourself is not your thing, you may find understanding the process helpful when consulting with a repair center.
Douglas Malat is a licensed captain, freelance writer and co-author of http://www.YachtAuthority.com, where you will find gel coat repair services in your area.
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