Robert Q. Riley Enterprises: Product Design & Development
Build it yourself FAQs


FAQs for build-it-yourself cars, EVs, hovercraft, boats, subs, and more.

Frequently Asked Questions

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Fiberglass Construction

Q Where can I get urethane foam sheets. Normally, you will not find it at a building supply or small retailer of fiberglass materials.   Look in your local Yellow Pages under Plastics-FoamFiber Glass Materials, or Insulation Materials.  We purchase it locally from McCarther Company, 202 N. 47th Ave, Phoenix, AZ 85043.  Phone: 602-272-6806.  Also, check our links page for on-line suppliers.  The foam is difficult and costly to ship.  Mostly, they are shipping air.  And since the foam is easily broken, it must be well packaged. 
Q My supplier asked what density of foam I wanted.  What should I tell him. A  Most rigid urethane foam sheets come in either 2- or 3-pound density.  Either density will work fine.
Can I use the urethane foam that has foil on one side. A  You can use it if you take the foil off, but we do not recommend it.  The urethane sheets that have a foil covering are about two to three times as expensive as the plain sheets, and the foil is sometimes difficult to remove.  It's best to use the right material.
What is the brand name of the urethane foam sheets. Do not shop for urethane on the basis of a brand name.  The foam is usually cast in large pillows by a local manufacturer.  The manufacturer or distributor slices it into sheets according to local needs.  In this area, rigid urethane sheets come from a company by the name of Atlas, which is located in Mesa, Arizona.   But Atlas does not sell to the end user, and there is no brand name for their product.  It's just generic urethane foam, which is the least expensive way to buy it.  If you buy it under a brand name, you could pay more, and you may not get the right material.
Q  Plans say that you can't   use a water-based contact cement to glue the foam together.  Why not. It just doesn't work very well on urethane foam.  Use the solvent-based contact cement made by Weldwood or Wilhold.  Coat both pieces with adhesive, let the adhesive tack off, then press the pieces together.  (Water-based cements are the non-flammable type.)
Q Can I use Styrofoam instead of urethane foam. A  Polyester fiberglassing resin will dissolve polystyrene foam (Styrofoam) on contact.   If you must use polystyrene foam, you'll have to switch to epoxy resin to avoid dissolving the foam when the resin is applied.   But epoxy is about three times as expensive as polyester, and polystyrene foam is much more difficult to work with than urethane.  If you switch to Styrofoam and epoxy, you'll hate the system.   If you stay with urethane foam and polyester resin, you'll love it.  
Q  My local supplier does not carry urethane foam, but he does carry polyisocyanurate foam.  Can I use it?  A   Yes.  The original urethane (technically, "polyurethane") foam is no longer carried by many suppliers.  Many of them are now supplying polyisocyanurate foam.  It's a slightly different compound within the polyurethane foam family.   Many salesmen still call it "urethane foam" and then supply you with polyisocyanurate foam.   Others will simply say that they do not have "urethane" foam, but they do have "polyisocyanurate" foam.  If you can locate it, the original polyurethane foam is better.   It has a tougher surface.  But polyisocyanurate foam will work.  The body for our latest vehicle, the XR3 Hybrid, was built of polyisocyanurate foam (which the company supplied when I ordered urethane foam).
What is the difference between laminating resin and finishing resin. A Finishing resin has wax in it.  When the resin cures, the wax comes to the surface and seals it off so the resin fully hardens on the surface.  Laminating resin has no wax, so the surface will remain slightly tacky because it is not fully hardened.  Use finishing resin only on the last lay-up.  BUT... be sure to wipe the surface with acetone (just lightly) and sand it to remove the wax prior to applying other coatings.  If the wax is not removed, any coating applied over it may not adhere well.
Where can I get more information on how to use fiberglass-over-urethane foam. A The manual that comes with  Tri-Magnum plans is very good for general how-to information on foam core construction.  The manual is very detailed, and includes over 130 photos and illustrations.   We also have a photo-illustrated document on line that gives a pretty good overview of how to use fiberglass over urethane foam.     But Tri-Magnum plans are far more detailed, and cover things like installing substructures, hinges, windows, lights, upholstery, and more.  The manual that comes with our recently released XR3 plan-set may actually surpass Tri-Magnum plans in terms of detail.  And either of the two XR3 plan-sets that include the discs have a one-hour video showing how the body is fiberglassed.  If you're interested in working with this material, the video itself is worth the price of the plans. 


Q Can I make a two-place version of AquaSub. A  Making AquaSub into a two-place craft would require extensive redesign.  If you enlarge the cabin to fit two occupants, buoyancy will increase, which means the sub will have to be heavier in order to submerge.  If the sub is significantly heavier, then the substructure will have to be strengthened.  And you would have to consider the difference in the center of buoyancy between submerged and surfaced states with the new design.  So it's not just a simple matter of making the cabin a little larger.  There would be trickle-down effects throughout the design. 
Q Can I make AquaSub go deeper by lengthening the outriggers. A  Theoretically yes.   But lengthening the outriggers will increase the loads on the hinges and the frame inside AquaSub's hull.  The pontoons are subjected to the force of wave action on the surface, but the submerged passenger pod is not.  This can translate into significant loads on the supportive structure.  And lengthening the outriggers will increase these loads.   We recommend that you do not lengthen the outriggers unless you are qualified to do the necessary engineering.
Q Can AquaSub be powered by a generator instead of batteries. A   You could install a gasoline-powered generator to power the air-circulation fan and the propulsion motors.   The generator could also power an air compressor to provide compressed air for ballasting.  Ballast air should be contained in a separate tank, rather than supplied directly from the compressor.  The necessary hardware could be housed in the pontoons.  Naturally, the pontoons would have to be enlarged to provide the necessary room and greater buoyancy needed to account for the extra size and weight of the new hardware.  Pontoons should have enough buoyancy to prevent AquaSub from sinking (plus a good margin of safety), even if the cabin were filled with water.  Also, design the system so there is enough compressed air to bring AquaSub to the surface should the generator quit at any moment in the operating schedule.  And locate the generator's exhaust pipe so fumes cannot be drawn into the cabin.  A fair amount of engineering would be required to make such a system safe and reliable. 

Ground Hugger

Q What does it cost to build Ground Hugger. A  Ground Hugger plans give you lots of options in the selection of materials and components.  So you can build it to the level of sophistication that fits your riding needs and pocketbook.   The down side of this is that it's almost impossible to provide any meaningful estimation of the cost to build it.  It all depends on which components and materials you select.  If you use mild steel for the frame, and take parts from a used bike, then the cost to build will be on the order of $200.  But if you use aluminum or 4130 steel for the frame, and buy new, high-end bike components, then you'll end up spending much more, depending on what you pay for parts and materials. 
Q Where do I get the parts. A  Except for the steering tube, seat, and frame, Ground Hugger uses standard bike parts throughout.   So you'll find most of what you need at a local bicycle shop.  The universal joint at the front of the steering tube can be machined by a local shop, or you can make it from a tool universal joint. 
Q What size riders does Ground Hugger fit. A   Built to the size shown in the plans, Ground Hugger will adjust to fit riders of roughly 64 to 72 inches in height.   The seat and handlebars are adjustable.  If a rider is taller or shorter, then the frame should be lengthened or shortened accordingly. 

Ground Hugger XR2

Q Where do I get the carbon fiber materials for the Ground Hugger XR2. A  The carbon fiber cloth and vinylester resin come from the same type of source that you'd buy conventional fiberglass resin and cloth.  Check your local Yellow Pages under "Fiber Glass Materials."  And there are a number of sources listed on the "Links" page.   The material for the prototype was purchased from Composites One in Phoenix.  They have 14 outlets around the U.S, and they'll ship to U.S. destinations. 
Q Are any special tools required. A  Tools are mostly ordinary shop tools.  You'll need paper buckets for the resin, several cheap paint brushes, a small Surform file, a sanding block and sandpaper, ordinary scissors for cutting the carbon fiber cloth, and a hand-held reciprocating portable saw (saber saw).  A Dremel tool will come in handy, and you'll need the wrenches used to assemble a bicycle.  A drill press is good to have, but you can use an ordinary hand drill.  Some machining is required (threading the steering tube, making the fork, etc), but you can farm that out.  The bottom bracket shells are purchased ready-made and already threaded.   The frame is built on a flat table. 
Q How difficult is it to build the XR2. A  Building the frame is pretty straightforward, and the carbon fiber and vinylester resin composite is as easy to use as conventional fiberglass.   If you're comfortable working with your hands and building things, then you shouldn't have a problem building the XR2.  In other words, there's nothing uniquely challenging about building the carbon fiber frame, provided you're comfortable with other types of construction projects. 
Q I'm very large.  Can the XR2 still fit me. A The XR2 can be made to fit someone of any height.  But since it fits like a sports car, it will not be a good candidate for someone who is significantly overweight.  A person of normal height who is 20 - 30 lbs overweight, for example, wouldn't have a problem.  But if you're 70-100 lbs overweight, you could have trouble fitting into the XR2, then it may be difficult to pedal and steer due to the position of the handlebars and seat. 
Q What does it cost to build. A The primary expenses of building the frame are listed on the XR2 information page.  Beyond that, it really depends on the components you select and how you purchase them.  For example, we paid $180 (new) for the combination speed-shifter and brake lever set.  And the carbon fiber wheels used on the prototype cost nearly $500.   So expenses can add up fast if you buy new top-of-the-line parts, individually.   But about five years ago, I purchased a practically-new Cannondale road bike from a private party for $275 (the whole bicycle).  Admittedly, that was a steal.  But those kinds of deals are out there if you shop around in the classified section of your local  newspaper.   And that $275 bike would have supplied lots of parts for the XR2.  So it truly depends on what you buy and how you buy it.

    Gluhareff Pressure Jet Engine

Q  Can the Gluhareff Jet run on a different fuel, or do I have to use propane. A The engine was designed around the fuel, and Mr. Gluhareff was emphatic about the use of propane.  But propane is readily available.  It's the same fuel used to fill barbecue tanks. 
Q   What size jet do I need to power an ultralight. A If you know your craft's L/D ratio, simply divide the gross weight (including your own) by the L/D ratio to obtain the jet thrust needed for level flight.
Can I get plans for the backpack helicopter or flying platform. A   We have access to Mr. Gluhareff's plans for these craft, but have shelved the idea of making them available.  These craft were experimental, and were never fully proven out in free flight.     
Q How much fuel does the jet use. A   The "Specifications" table on the info page for the jet provides specific fuel consumption in lbs/lb/hr.   This means that the jet will burn x pounds of fuel, per pound of thrust, per hour of operation.    A 130-pound engine with a round intake running at full throttle for one hour, for example, would burn about 100 pounds of fuel (0.77  x 130  x 1 = 100.10).   Propane weighs 4.23 pounds per gallon, which translates into 23.66 gallons of fuel.  
Q How fast can a BD-5 type plane go with two 130-pound engines. A    In order to calculate speed from thrust, you really need to have some sort of a drag curve for the aircraft.  The point at which drag equals maximum thrust determines the top speed of the craft.   Mr. Gluhareff worked up a drag/thrust curve for a hypothetical plane that he called the MEG-600, and came up with 400 mph on two G8-2-80 engines.   This info is included in the manual that comes with the plans.   But it must be stressed that the calculations are based on a hypothetical, not an actual, aircraft.   So the drag curve of your aircraft is likely to be different.
Q How much will it cost me to build a jet with 130 pounds of thrust. A   There are lots of variables that affect the cost to build the jet.  If you make it from sheet metal, there is roughly $350 to $450 worth of stainless steel and aluminum in a 130-pound thrust engine.  The jet is built mostly of 0.032-inch No. 321 stainless steel sheet.  If you farm out the welding, then the cost of welding would have to be added in.  Plans show how to spin the nose cone yourself.  But if you purchase a ready-made nose cone, then that cost would have to be considered.  So if you shop for the best price on materials and do all the fabrication yourself, $350 would be a rock-bottom estimation of the cost to build the jet.  But one could spend considerably more.
Q I bought the Standard Plans package and built the  20-pound engine, but now I want to build a 130-pound thrust  engine.   Do I have to buy another complete set of plans. A    The best way to go is to upgrade to the Deluxe package.  Purchasers of the Standard Plans package can upgrade to the Deluxe Plans by paying only the different in price between the two (plus the P&H charge).  When you upgrade, you'll get the other three sets of drawings and the CD-ROM.   So you'll end up with drawings for engines in all four thrust ratings.  There is no upgrade option to select on the order form.    So send your order by mail, or phone it in, and let us know which thrust-size you already have.


Q How maneuverable is HydroRunner. A   It's very maneuverable, but it turns differently than a personal watercraft.    PWCs heel (bank) into turns.   HydroRunner turns flat like a hydroplane.  If you let off on the throttle, crank the handlebars to one side, then apply power again, HydroRunner will spin around practically in its own length.  But this is an extreme maneuver with lots of skidding, and it would not be considered normal operating practice. 
Q Can I jump wakes with HydroRunner. A    Naturally we're against the practice of jumping wakes.    But HydroRunner will operate much like a PWC in this regard.   It handles jumps and rough water very well.
Q What happens if I fall off the boat. A   Plans recommend that you install an emergency shut-off switch, then attach the lanyard to your life jacket while riding HydroRunner.  If you should ever fall off, the lanyard pulls the rubber cap off the shut-off switch and instantly kills the motor.   We had a test-rider get swept off during extreme maneuvers by diving through a wave, only to find HydroRunner sitting in the water about 10 feet away.   The rider heard the engine stop almost simultaneously with having been struck by the force of the water.
Q What kind of tools and skills do I need to build it. A   Ordinary woodworking skills and tools are all that you'll need to build HydroRunner.  It's made mostly of plywood, which is then sealed with a coating of fiberglass.   You'll need a vibrator sander, a portable circular saw, a reciprocating saw, a screwdriver, a long straightedge, and a belt sander.   A table saw is also helpful.   HydroRunner is built on a 3 x 8 foot table made from a sheet of plywood.   Imagine looking down on HydroRunner from above and tracing around the outside profile.   This silhouette is cut from a 4 by 8 foot sheet of plywood to provide a stable foundation to build on.   The top half of the boat is built on the top surface of the plywood, and the bottom half is built on the bottom surface. 
Q   How do I get a license. A    If you're in the U.S., you would take your finished boat to a local office of the Department of Fish and Game, and they'll give you a license.   It's a fairly straightforward process.  For more details, see the on-line document on licensing and insuring homebuilt vehicles.
Q   Where do I get a trailer. A    The least expensive route is to make your own from one of those inexpensive utility trailers sold at building supply stores like Home Depot.  Support HydroRunner on a carpet-covered length of 1 x 10 or  1 x 12 wood down the center.   Install a carpet-covered rail (2 x 4 or 2 x 6 wood on edge) on each side to fit snuggly under the wings - the connecting piece between each sponson and the center-hull.    The weight of the boat, however, should be supported by the bottom of the hull, not by the wings.   Purchase a winch and tie-down straps from a boat shop. 


Q How fast does Pegasus go. A   Pegasus goes about walking speed.  The speed of a hovercraft is determined by the amount of thrust power it has.  Pegasus does not have a thrust system, which means that forward thrust comes from the lift air that spills out one side when you tilt in the opposite direction.  You can install a thrust system and get lots more speed.  But keep in mind the safety implications.   A little thrust can translate into lots of speed on a hovercraft.
Q  Can I install a larger engine and get more performance. A Increasing the power of the lift engine will not have a big effect on the performance of Pegasus.  Even though Pegasus is rated for a 125-pound payload, it will actually lift close to 200 pounds free of the ground.   So it already has fairly good lifting power for its size.  The biggest improvement in performance will come from installing a thrust system.   But if you're after lots of performance, it would be better to select a high-performance design like Tri-Flyer.   
Q Can Pegasus go over water. A   Pegasus isn't designed for over-water operation.  When a hovercraft is operating over water, it makes a depression in the water like a boat.  The thrust system has to overcome this depression, just as a boat does when it gets onto plane.  Pegasus has no thrust system to enable it to do this.  Plus, it has no flotation system and it will not stand up to the water spray that hovercraft create over water. 


Q   I want to build Tri-Magnum, but can it be licensed for driving on the street. A   All our build-it-yourself cars are street-legal, including Tri-Magnum.   Three-wheelers are classified as motorcycles in the U.S., and in most other parts of the world.  So they have to meet the local requirements for motorcycles.  In the U.S., homebuilt cars are licensed on a state level, and must meet requirements of your particular state.   For more information check the document entitled "Licensing and Insuring Homebuilt Vehicles."
Q   Since it uses a   motorcycle chassis, what do you do about a heater and defrosters. A    If you use a water-cooled motorcycle as a basis, installing a heater and defroster system is fairly straightforward.  You would use a heater core from a wrecked car, then tap into the motorcycle cooling system and route hot coolant through the heater core.  Controls and ductwork could come from a wrecked car, or you could fabricate your own.  An air-cooled bike is more challenging, but it's still possible.   You could fabricate a heat exchanger to fit around the exhaust header and use a fan to move air through it.  That's the way heaters in small aircraft work.    But take extra care to avoid the possibility of letting exhaust gases mix with the air that's ducted into the cabin.   Carbon monoxide poisoning can be fatal.  Just to play it safe, go to a pilot shop and pick up a CO detector.  It's an inexpensive device that hangs from your key ring and turns color when carbon monoxide is present. 
Q What about windshield wipers. A   You can use the wiper and motor assembly from the hatchback of a wrecked car.   In other words, just use a single blade to wipe the entire windshield.     But you'll have to use laminated safety plate instead of the polycarbonate windshield shown in the plans.  Windshield wipers will scratch the polycarbonate material.  We've also heard good reports from folks who have used a product called "Rain-X," which is a coating that keeps the windshield clear even when it's raining.
Q How does Tri-Magnum back up. A   The prototype Tri-Magnum did not have a reverse.    The best option for a reverse is to build Tri-Magnum around a Honda Gold Wing.  The  Special Edition and  Aspencade models are factory equipped with an electric reverse.    And the Honda Gold Wing is about the best choice possible for Tri-Magnum.     Another option is to install a friction wheel that can swing against the rear tire, then power it with a car starter motor.   We've used electric reverse systems on other vehicles, and they work quite well.


Q   Trimuter plans specify a Briggs & Stratton 16 hp twin, but the same engine comes in higher power ratings.  Can I use a more powerful engine. A   Briggs & Stratton makes this aluminum-case opposed twin-cylinder engine in higher horsepower ratings, and any engine in this series may be used.   In fact, other manufacturers make similar engines.  So you do not have to stay with Briggs & Stratton.   But avoid any engine that has a cast iron block because of the increased weight.   Trimuter's engine sits on top of the final drive housing.   So a significantly heavier engine would increase the height of the vehicle's center of gravity, which would affect it's stability in high-speed turns.   For more information on the importance of center of gravity location, go to our on-line document on three-wheeler handling stability.
Q  Can I used a VW engine and transaxle and give Trimuter lots more performance. A   We've seen it done, but do not recommend it.   Trimuter was designed around the idea of a sort of in-town commuter car, and speeds above 60 mph were not considered when it was designed.   Trimuter's top speed on 16 hp is about 63 mph.  We installed a 30-hp rotary engine in the prototype and drove it up to 80 mph, where it began to feel light in the front end.   Notice that Trimuter's front end is angled slightly upward on the bottom.  This creates aerodynamic lift at higher speeds.   Since there isn't much weight on the front wheel, aerodynamic lift could cause control problems at very high speeds.   So if you're making a high-speed version of Trimuter, the body should be angled downward at the front to get downward pressure from aerodynamic effects.   And the cg should be lowered for a greater margin of safety against rollover.   For a really high-performance three-wheeler, take a look at Tri-Magnum.
Q What kind of transmission does Trimuter use and where do I get it. A Trimuter uses a Salsbury CVT, like the type used in snowmobiles.  You do not have to shift gears.  It's done automatically by the transmission.   Salsbury sold off rights to their CVTs to Hoffco/Comet Industries.   The  Salsbury transmission used in Trimuter is available from them. 


Q   What skills and tools are needed to build Tri-Flyer. A   Tri-Flyer is made much like a wooden boat.   It has station formers that are made mainly of 1 x 3-inch wood.   Wood stringer are then placed to run lengthwise across the station formers, then this framework is covered with 1/8-inch plywood.   Seams are sealed with a single lay-up of fiberglass.   The duct for the thrust prop is made of foam and fiberglass.  But basically, building Tri-Flyer is a woodworking project.   So you'll need basic woodworking skills, and ordinary shop tools like a circular saw, belt sander, hammer, straightedge, square, and similar kinds of tools.  
Q What happens if the lift engine quits while you're going fast over the water. A   When I was taking flying lessons, I asked my flight instructor what happens if the engine quits.   He said: "We land!"   That's what happens when Tri-Flyer's lift engine quits.   You settle to the surface.  But the bottom of Tri-Flyer's hull is sealed, and it's angled upward around the edges so it will not dive into the water.   Instead, it would plane across the surface then quickly settle into the water and float like a boat.    
Q Where do I get the parts. A   Plans provide a source for the lift fan and thrust prop.   You can also get skirt material from the same source.    The wood can be purchased from a local supplier.  But sometimes you'll have to shop a bit to locate the 1/8-inch plywood used for the skin.   Not every lumberyard will carry it.  And it's best to use Marine grade plywood for the skin.  
Q How do you stop Tri-Flyer.  There aren't any brakes. A To reduce speed, you just back off on thrust power.  Aerodynamic drag and the drag of the skirt occasionally contacting the surface will bleed off speed fairly quickly - especially over water.   But to stop a hovercraft quickly while going fast, use the rudders in the propwash to spin the craft around on its axis so it is traveling backwards.   You then apply thrust power to slow it down.    A hovercraft can yaw, or spin around on its axis, without changing its direction of travel.    So as far as the hovercraft is concerned, there is nothing unusual about traveling backwards. 
Q What does it cost to build Tri-Flyer. A The cost of the materials is not very high - about $700 - maybe a little more.   The biggest expense variable will be the amount you pay for engines.   Tri-Flyer uses an aluminum-case, two-cycle engine for thrust, and it takes engines of 40 hp to 80 hp.   If you buy a brand new engine in one of the higher power ratings, the cost can be quit high - perhaps as much as $5,000.   But if you locate a used one, or even a run-out snowmobile from which the engine can be salvaged, then you could end up with a thrust engine for as little as $1,000, or maybe even less.  For lift power, Tri-Flyer uses a single-cylinder, aluminum-case, vertical-shaft engine of the type used on riding lawnmowers and other lawn and garden equipment.  If you can find a used engine, expect to pay $200 or so.   New, they cost about twice that amount.   So with prudent shopping, the minimum estimated total cost to build Tri-Flyer would be on the order of   $3,000 - $3,500.   But much depends on the engines you purchase and what you pay for them.

Plans on CD-ROM

Q    Suppose I buy printed plans now, then want the CD-ROM when it becomes available. A    If you buy the printed plans and then later decide you want the  CD-ROM, you can upgrade and get the CD by paying only the difference in price between the two plans packages.   
Q    I don't have a CAD system.   Can I still view the CAD files. A  You don't need a CAD or 3D modeling program to view the electronic drawings and 3D models.   The CD-ROM provides a link where you can download a free viewer.  
Q    With printed plans, why do I need the 2D CAD drawings that come on the CD-ROM. A   The 2D CAD files let you print out extra copies of the plan sheets and  close-up views of individual parts and work from them so the original plans stay clean.  Also, a local plotting service can make new prints from the CAD files, should the originals become damaged or lost.  And if a part was shown in scale on the original prints, you have the option of printing full-size templates if you need them.  Also, lots of people like to modify the original design.  So if you have a CAD system, you can import the CAD files and make changes to see how it works out on "paper" before going ahead.  You can then produce working drawings of your new design and have a personalized set of plans. 
Q    What are the advantages of having the 3D electronic models that comes on the CD-ROM. A   There are lots of advantages in having a 3D model.  One of the biggest benefits to the average person is the ability to see how something is built from any angle, and see what's inside and how it fits together.  Remember, the 3D models are full-size, fully-detailed electronic representations of the actual item.  You can strip off the skin, individually hide or display the parts, and take measurements in three-dimensional space to an accuracy of one-thousandth of an inch (or one hundredth of a millimeter).  If machining is needed, you can use the 3D files for CNC work (computerized machining).  This saves time (money), and it produces a much more accurate part. 
Q    What are the advantages of having the construction manual in electronic format. A    First of all, your kids can't use it for a coloring book.  But even if that would never happen in your household, there are plenty of other advantages.   The electronic manual is in color, and the printed manual is in black & white.  And the electronic format makes it possible to provide much larger images.  We've formatted the electronic manual to look like the printed one, but when you click on an image, a high-resolution version of the picture pops up and fills your entire screen.   So you can see things in much greater detail.  And if you're connected to the Internet, links on the CD provide seamless access to on-line updates, revisions, addenda, and technical support.   And if your printed manual does get used as a coloring book, you can print out a new one.  The electronic format makes it possible to provide features that are impossible to provide in a printed manual.
Q  Considering the benefits of the electronic format and CAD systems, why are you still offering printed plans. Like the issue of American versus SI units (see below), this is a tough issue because there is no way to generalize an answer that applies universally to DIY hobbyists.  Many hobbyists still prefer hard copies, and there are still consumers that do not have ready access to a computer.  But we are  migrating to electronic format in all our projects.  Looking to the future, the practice of shipping electronic files on CD-ROM will likely become outmoded too.  Technology is moving rapidly, people are adapting to it, and we are continuously re-evaluating the alternatives. 

Plans Format/Units of Measurement

Q    Why don't you make plans available in SI or metric units. A    This is a tough one.   Over 80 percent of our sales are to U.S. residents, and the U.S. has been slow to convert to SI units - at least on a consumer level.    In the U.S., common sizes for steel tubing and other ordinary building materials are still mostly in inches and feet.  And metric tubing, for example, is much more costly than similar tubing in inch-sizes.  So we design to common material sizes and use the units that the majority of our customers are familiar with.   Once a product has been designed , it's impractical to simply switch dimensions over to SI units.   Specifications for bearings, fasteners and other components do not match up, and dimensions end up looking nonsensical.  In order to use SI units, the product has to be designed in SI. 

NOTE:  As of July, 2011 our new solar-assist recumbent bicycle, the XR2 HP, is in SI units.  We will continue to reconsider the issue of units with new and/or updated plan-sets. 

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