Basic Raft Construction

The six basic elements to join together when building a raft are floatation, a deck, propulsion, steerage, teamwork, and safety. The information that follows will explain each of these key principles in more detail. This knowledge should give you a good idea on how to build a raft. Rafts can be built from scrap wood, foam, plastic bottles, barrels, and recycled materials of every kind. With a little creativity you can take whatever is around you and recycle it into something that floats. Rafts are as varied as the imagination is capable of conceiving them.

Floatation Materials

First off rafts are not boats and therefore donít need watertight integrity. This is because theyíre almost always built from materials that are naturally buoyant. A typical raft can be made out of some combination of foam, plastic barrels or bottles, wood, and anything else that floats. These floating materials will continue to provide lift even when they are damaged. Since a raft doesnít require watertight integrity, it can be built out of anything that is available. The most common material used is foam.

Chunks and odd scraps of foam are often found floating up on riverbanks and beaches. These can be stuffed into a frame you construct out of wood. Expandable foam in a can (used for insulation jobs) quickly spreads out to fill in gaps and cracks. It can be used as glue to hold all your floating objects together inside your hull. The trick is to fill in as much airspace as possible before using the expandable foam. Consider adding things like packing peanuts, small soda bottles with lids, and anything else that is small and will float. If you use a wooden frame to hold everything together be sure to enclose it on all sides with wood to catch any loose pieces of foam.

Sometimes foam scraps can be found at construction sites, in dumpsters, or at the landfill. Always ask for permission before taking any surplus materials being thrown out. Sometimes you can find a marina that has lots of old dock foam pieces piled up. If you ask nicely or offer to do some work for the boatyard you may be able to get some second-hand foam pieces for free.

Foam can also be bought at Home Depot or Lowes if you canít find any for free. The foam there is usually available in sheets and can be cut to size and stacked to form your floats. If you want to glue your foam sheets together try the adhesive on a scrape piece first to make sure the glue wonít dissolve the foam. Remember, a raft is much more rewarding to build with free recycled materials and on a shoestring budget. A good example of this can be seen from a group of guys who built their raft out of a picnic table and some old foam scraps they found laying around. They named their raft $1.98 which reflected the amount they spent on the materials used to construct their raft. This clearly illustrates that it is not always necessary to spend lots of money in the construction of a raft. Using what you already have on hand can be a real time & money saver.

Plastic barrels of all types & sizes can also be used as floatation. These can take a lot of abuse without puncturing. These can usually be obtained at your local car wash, bulk juice distributor, or landfill. Be sure to also get the round bungs that are used to cap them and keep them watertight. Donít use a barrel which had toxic chemicals in it as these have the potential to leak harmful pollutants into the river. You could also get a good supply of plastic 5 gallon buckets & lids from a painter or sheetrock worker. Their bulk materials come in these large containers and are perfect for building rafts. Be sure to clean out any residual soap, juice, paint, or plaster before using plastic barrels and/or buckets.

The use of plastic buckets for floatation can be very convenient. To begin with they are easy to obtain and can be used as is. They are very durable and do not breach easily when abused or dragged over rocks, mud, or submerged sharp objects. They are also of a manageable size and can be easily adopted into many raft designs.

To illustrate how simple these are to use consider the group of girls who built a raft called the ďBucket Brigade.Ē It was constructed out of an old ladder which had a bunch of 5 gallon buckets duct taped to the rungs. The girls also attached some foam to the sides of the ladder using some more of their duct tape. Then they added an outrigger for stability at the suggestion of the raft inspectors. A plastic duck was added to the outrigger to add some much needed character to the extra raft appendage. This raft worked flawlessly and they ended up winning the Becky Thatcher Award for their efforts

If you want to use plastic soda bottles for floatation you can get them for 5Ę from people returning them at a recycling center. This is a good way to get a lot of plastic containers without having to buy the full container and drinking the contents before using them. Be sure to also get the lids so you can make the bottles watertight. Soda bottles can be configured in many ways and allow for a lot of design flexibility. Another good plastic container easily found in recycling boxes by curbside are plastic milk jugs. Be sure to glue and/or tape the caps on the milk jugs as they arenít as secure as the threaded soda lids are on bottles. The best scheme to employ when using lots of loose plastic soda bottles is to contain them in some sort of box or net. A length of rope can also be used to hold all the milk jugs together in a big mass; or they can be duct taped end to end onto a wooden frame. Whatever your configuration is please be sure to contain all the separate bottles maybe even taping a bunch of them together. You donít want to have to chase after lots of loose bottles around if they break free from your raft.

How Much Floatation Is Needed

A typical raft must use enough floatation to hold up the raft in the water and support the weight of the crew and any stuff onboard. This will vary for each raft and is dependant on your crew size, the raftís construction, and the materials being used. For each gallon of water you displace with floatation materials you will gain a floating force of about 8 pounds. For example a 55 gallon drum can float and/or support up to 400 pounds of weight and a 5 gallon buckets will hold up to 40 pounds. By comparison 1 cubic foot of foam will provide approximately 60 pounds of floatation. Whatever materials you use to float your raft be sure to build in some margin for error.

For example, letís assume you plan to have three people on your raft and the crewís combined weight is 480 pounds. You might estimate that your raft will weigh another 200 pounds. The total weight would then be 680 pounds. Next, divide this total weight by 8. The answer reveals that 85 gallons of water must be displaced to float the combined weight of the raft & crew. If you were instead going to use five gallon buckets for floatation, 17 would be needed to provide enough buoyancy to float the crew and the raft. It you were going to use foam you would need approximately 12 cubic feet of foam.

It is good practice to have much more buoyancy than what is necessary to just float your raft & crew. This extra flotation allows for a larger margin of safety. This is crucial because it is difficult to estimate the weight of a raft and all the stuff people may decide to bring onboard on race day. You are much better off to have too much floatation than not enough.

The placement of buoyant materials should be equally distributed in order to provide good stability. Most rafts typically place their floatation materials on each side of the raft just like on a pontoon boat. This is your best approach as it will provide good stability. Avoid placing all your floatation materials in one centralized location as this orientation will make your raft very unsteady and tipsy. Another trick to make your raft more stable is to add an outrigger. This is especially effective on longer rafts that arenít very wide.

The Deck

The deck of your raft is where youíll be sitting as you go down the river. It should be strong and be able to support the weight of the crew and any gear youíll have on board. The most common deck material used on rafts is plywood that is attached to some sort of wood framing underneath. Donít use old pieces of wood full of splinters as this isnít too comfortable or safe to sit on. Use newer pieces of wood that are strong and robust. Placing a piece of old carpeting on top of the deck will provide a nice surface to sit on.

The deck should have attachment points on the underside of the framing to secure the flotation materials. By drilling small holes in the wood you will create spots where ropes can be passed thru. You can then tie the floatation materials to the bottom of the raft. A few eyebolts or cleats should also be attached to the deck or framing so that anchor ropes and tow lines can be secured someplace on the raft as well. Screws should be used to connect the deck and framework, donít use nails. Once the raft is wet and starts striking waves it will flex and nails will tend to pull out, get loose, and eventually fall out. Screws stay put much longer. A nice addition to a deck is some sort of canopy to provide shade. A large umbrella will work just fine as will a small tarp and some sort of framework to hang it on.

When designing your deck leave plenty of room for your crew to do their rowing or paddling. If the deck is too small paddlers may bang oars or not have enough room to kneel down or sit comfortably while rowing. You also want some spare room for a small cooler, your first aid kit, anchor, tow ropes, and any other supplies or tools that you will be carrying along on your raft.

Propulsion Options

Rafts will need some way to move through the water. Most participants will use paddles or oars. If you can build some oarlocks this makes the rowing much easier. Another popular choice is to also try using a sail made out of a plastic tarpaulin or bed sheet. Sails are great on windy days but can be unreliable. Sometimes the wind will be blowing the wrong way and other times the wind will blow fast and furious in the intended direction. There is no way to know for sure if youíll catch a favorable breeze. Be sure to support the mast holding up the sail on three sides with a sturdy rope. This triangulation is necessary to safely hold everything together in a strong breeze.

A few raft teams have attempted to build a homemade paddle wheel using an assortment of bicycle parts. These can work quite well if put together properly. A key design element is to have a height adjustment built into the paddlewheel assembly. This is necessary so that the depth of the paddleís engagement in the water can be fine-tuned for optimal performance. Weight distribution on a paddle wheeler must remain stabile to ensure good performance. The Lin Lee raft is an excellent example of a raft with a well designed paddlewheel.

Another propulsion device that can be built is a homemade propeller. These can be more complicated to design and may require more than just a few odds and ends from a bicycle. The easiest way to make one is to find an old stationary exercise bike and weld a pipe underneath the sprocket. This pipe should have a T pipe on the opposite end where a sprocket, shaft, bearings, and propeller can be mounted.

The long length of chain needed to run between the two sprockets can be pieced together from two or three separate bike chains. A garage door opener chain can also be used as it is much longer than a bike chain and continuous in length. A chain guide made out of an old cutting board or wood will help keep the chain on the sprockets. This long length of chain will get pushed off the sprockets by the water if it is not supported in some way. You will not need to oil the chain as water is a pretty good lubricant, plus you donít want to be putting oil in the water. Cut a hole in the deck so the propeller can be put in the water while the frame tubes will rest firmly on the deck.

A homemade propeller blade can be made by attaching a strong piece of metal to a pulley. The pulley can then be mounted on a shaft. Boat & trolling motor props will work but are not optimal for pedal power speeds. A better choice is a larger diameter blade with lots of surface area. You will have to experiment with different shapes to get something that works. A bicycle driven propulsion system will take a while to refine. The key is to test them out, see how they work, and then make changes until they work right. The extra work can yield a very competitive raft. To see a first class propeller system have a look at the one used on the Little Willie. It has four pedal stations that run two separate submerged propellers. Whatever you end up using for propulsion it is good practice to carry extra paddles with you. They are handy to have if something breaks and/or stops working properly.

Steering

Paddles allow for propulsion and steerage around obstructions. But, if you use a paddlewheel, a propeller, or a sail, you will need some other means to steer your raft. In these cases a rudder is absolutely essential. One can be made by simply tying an oar, at its midpoint, to the back of the raft. Some folks use a door hinge and attach a piece of plywood to it. A handle can then be attached to turn the rudder. Being able to navigate straight on the racecourse and steer clear of obstacles makes rafts safer and easier to control.

Teamwork

Teamwork is one of the key ingredients to raft racing. You want to join forces and ideas with as many people as you can. The benefits of this joint effort become evident when looking for building materials, coming up with ideas, and constructing your raft. One of the best parts of the race is the preparation stage. Youíll all have fun together and get excited and really make great efforts to get everything done. Each person will have some special talent to contribute. All these different aspects coming together are what make the entire raft race team work.

Safety

Safety must be maintained at all times while procuring materials and building the raft. Itís no fun to get hurt, so wear safety glasses whenever handling power and/or hand tools. Also wear gloves when handling your materials and use caution whenever cutting materials. Your teammates may be working nearby on something while youíre busy doing something else. Always look out for each other and help one another whenever necessary. A good practice is to use sandpaper or a file to smooth out and remove sharp edges whenever you cut something. Chances are youíll be wearing shorts out on the raft on race day so you donít want to pick up a splinter or get cut on anything sharp. Bend over exposed sharp metal edges and cut off protruding bolts. Then apply duct tape to these sharp edges. Have a first aid kit available during your build sessions and whenever youíre out on the water.

Testing Your Raft

Once youíve finished building your raft, test it out to see how it works. This is important because you donít want any surprises on race day. Take your raft it a pond and see if it floats with your crew aboard and everything else you will be carrying. In some cases you may find that you need a little more buoyancy. In other cases you might need to reposition some of the floatation materials to help stabilize the raft. Next, find out if your propulsion works as expected. Your crew should try out their rowing stations to see if oarlocks are working right and positioned correctly. Try putting up your sail to verify it is in working order. Be sure to also try out the rudder. Since paddlewheels only need to be submerged slightly they may need to be adjusted up or down to run smoothly. There is a whole list of items that contribute to your raft being a stable platform out on the water. You wonít know how well it will work until you try it out. Make any adjustments beforehand and then retest your raft until you get it right. This ensures you will be ready to kick some fanny on race day. Make sure all crew members testing out the raft has on a Coast Guard approved life jacket. Never go out on the water without one and look out for each other at all times.

Emergency Repairs

Be sure to always carry emergency tools, duct tape, bungee cords, rope, fasteners, and anything else you can think of just in case you need to make an emergency repair out on the water. Things can break, come loose, or jam up. You want to be able to mend anything that needs fixing, tightening, or re-attachment. Sometimes periodic adjustments are going to be necessary, especially if you have a paddlewheel. All tools should have a safety landyard attaching it to the raft or enough foam attached so it wonít sink if dropped overboard accidently. Having the ability to recover from a mechanical problem can be a key factor in winning a raft race. You donít have to succumb to a simple mechanical problem if you bring emergency gear along to save the day.