Boatbuilding news, building tips, and builder feedback

WebLetter 3

An Occasional Publication for the Home Boat Builder

Glen-L Marine Designs - 9152 Rosecrans Ave. - Bellflower, CA 90706

In this issue

Glen-L Update

Web site: Since our last Web Letter there have been a lot of changes to the GLEN-L web site. If you are on our Guest Book list, you should have received notices of major updates, however, minor updates are made every week.

Many builders are using the Boatbuilder Connection and report getting useful feedback from other builders. If you are working on a GLEN-L boat and want to communicate with others building the same design, give the Connection a try.

There are new builder photos on the Customer Photos page; some with letters attached. We appreciate the photos that are sent in but would like to see lots more. Pictures that are fuzzy or have confusing backgrounds, or backgrounds that are the same color as the boat, don't scan well. Keep the backgrounds simple or scenic and avoid shooting at high noon. If you have any pictures of GLEN-L boats you have built and would like to have them on the site, send them attention Web Master.

The plans are finished for the McDrift, an aluminum Drift boat in 14' and 16' lengths. See the NEW section, and Feature Boat in this Web Letter.

Web Letter

  • We would really like to have your input, especially your experiences building your own GLEN-L. And what happened to the nice lady who was going to write about her husband's project from the wife's point of view. The article on designing a boat is in response to an email request... what would you like to read about.
  • More study plans: Glen-L 19, Glen-l 21, Lucky Pierre, Monaco/Riviera, and Tango.
  • AMP EATER test model has been held up because of larger than normal demand for frame kits that has put the AE on the back burner. Hope to have finished photos by the end of April.
  • Lots of email... lots of email. Mondays... 1 1/2 to 2 hours to answer. We've been leaving out the "Dear Sirs", and giving bare bones answers in an effort to keep up.
  • More on the FIFE (discussed in Web Letter 2): We've been taking the Fife out in the evenings, after work 'til dark, using a Minkota 35T (27 lbs. thrust) electric trolling motor. With one 12 volt battery and two adults, we've had her out for 60 to 75 minutes, with the motor still going strong when we came in. This summer we'll take her out and run until the battery dies and report on time run in an upcoming Web Letter.

Barry Witt      

Who's on the Phone?


Gayle Brantuk was born in Compton, California. She answers phones and processes orders, handles advertising billing, types letters, and substitutes in mail room when Alfredo isn't here or is blueprinting, and is assisant webMASTER. Gayle was a cheerleader at Bellflower High School and is always upbeat. She is frequently described by callers as "that nice lady I talked to last time".

Gayle lives with her husband John, and has three children, John II, Jaclyn, and Ryan (deceased). She enjoys gardening, and ball room dancing with her husband. She is heavily involved in her church and Sunday school. She attends aerobics class three times a week and is a demonstrator for House of Lloyds/Christmas Around the World. Gayle has worked at GLEN-L for 10 years. Oh yes, Glen is Gayle's daddy.

Danae IV

Letter from Danae Cruises
Les Croisieres Danae
Polynesie Francaise


Dear Mr. Glen,

Thank you for your nice letter and catalog. As I promised, here is our new brochure showing the KLONDIKE at her best running speed, 12 knots at 1550 rpm. As you can see, she is perfectly in her lines. The picture on the right shows her salon, clear and spacious.

She is definitely a wonderful boat and has a very smooth ride even in rather heavy seas. We recently had to make a passage to the island of Bora-Bora in 10 to 12 feet of choppy seas with 25/30 knots of winds on the aft quarter of the boat, and also to go through a pass with the same seas, but right on the nose and in either case, we did not even wet the front deck.


Our charter guests are surprised and pleased with the smoothness of her ride. Although we can tell you that her maximum speed has been 15 knots at 2000 rpm, with our Volvo TAMD 70E 300 hp.

Thank you again for this nice design. If you ever think of coming down in this area, you will be very much welcomed on board DANAE IV.

Best regards,
Claude Goche

Boat Speak, Part 1 of 4

Terms we use to describe our designs.

The four parts of "Boat Speak" have been consolidated and transferred to Useful Information & Suppliers/Glossary

Do plywood boats last?

error-file:TidyOut.log Letter:

Re: Audeen
Back in 1954 when I was 20 years old, like most of my friends, I wanted a boat. Young, no money, earning about $32.50 per week, I thought, no chance, then I came across a book of GLEN-L plans. That was my start, I bought blueprints only. After that, each week I would buy a tool, a plane, a saw, a square, a drill, box of screws, etc. The boat was constructed of white oak frames. The bottom was 3/8" plywood. Sides were 1/4" mahogany plywood.

I bought a 1956 Ford Thunderbird 292 cu in V8 from the dealer for $400.00. This as a 250 hp out of a wrecked T-Bird with 6K miles. I used a Capital reverse gear box, out of St. Paul, MN, Glenwood conversion parts, and a 12"x16" Michigan wheel to push the boat at 57 mph. In 1958, when the boat was launched, that was fast. We would pull 4 skiers most of the time, 6 skiers a lot, 8 on skis only about 4 times.

We sold the boat in 1969 to a friend, they sold it after 1975 to another friend. Then in July, 1997, they gave the boat to my son, free, if we would rebuild it. When I built this boat, the workmanship was flawless, I wanted it to last. So in 1997, after 30 long days and nights, we had rebuilt the AUDEEN into another good looking ski boat. The boat started life on the Mississippi River, then to Lake Okoboji, Iowa, now it has gone to Scottsdale, AZ.

40 years so far, how long will it last?

Mark Prokes
LaCrosse, WI

Note: Mr. Prokes increased the depth of the sides in the aft of the hull for added safety for the children.

What's the difference between "drawing" and "designing" a boat?

Most anyone can draw a boat; designing one takes a lot more effort and ability.

Of primary importance in designing a small boat is knowledge gained by experience. At GLEN-L we design boats, build testing prototypes, and then test the in-water performance. Most designers don't have the luxury of being able to test their final product. We do and the experience gained is invaluable for designing future craft.

A new design is started by establishing the parameters. The length, beam, depth, and type of boat is decided on; power or sail and the material the boat is to be built from must be selected. Every boat is a compromise and practical experience dicatates the inevitable give and take features that are best for the particular craft being designed.

Designers use coefficients that provide comparative factors to determine the general shape of the midsection and other factors. The range of coefficients for a given type of boat have been gathered over the years and are given in books on boat design. But a designers experience of the performance of previous boats is used to temper the figures, as little information has been published on smaller boats.

The basic lines of the boat are developed showing three views; plan, profile, and sections. A designer must rough out a set of lines that hopefully match the desired coefficients. The term hopefully is used because accurate coefficients cannot be determined until the lines are finalized.

The displacement of the boat must be estimated; this is the total weight of the hull, motor, passengers, and everything on board when the boat is on the water. Then an estimated waterline is sketched on the lines.

A boat will displace a weight of water equal to its displacement. The underwater volume can be calculated by determining areas of equally spaced sections ("s") and entering them into Simpsons 1/3 Rule formula; boat design computer programs do it quicker. The calculated displacement should be very close to the one estimated. If not, back to the drawing board to raise or lower the waterline or adjust the lines and recalculate displacement.

A boat has a balance point called center of buoyancy (CB) that is comparable to the pivot point on a teeter totter. The CB can be determined by using figures obtained from Simpsons Rule; the volume on either side of the CB must be equal. But the CB must be located at the ideal position to carry the loadings. The approximate desireable location of the CB is obtained from published figures or percentages of the waterline length gained by experience. The CB is virtually always aft of the mid-points of the waterline length. If the calculated CB is not within the design parameter its back to square one and modification of the lines.

But the designer isn't finished. Weights have been estimated and must be finalized. The weight of every component of a boat must be calculated and it's distance from the CB noted. Consider what is involved. A wooden boat may have a 1 14" x 3 1/2" keel 18' long. The volume of the member times the weight of the wood for a given volume is calculated and the center of that weight in relationship to the CB determined. And this is done for everything that will be in the boat. If the total weight isn't equal or close to the displacement or the weights are not equally distributed about the CB, modifications will be necessary. An experienced designer gets an "eye" or "feel" for a set of lines and can usually finalize a set of lines with minimal revisions. A neophyte designer may spend days or weeks bringing all of the factors into balance.

A sailboat will need to be balanced so it will sail properly without lee or weather helm. Rudder area must be calculated to provide good steering and the keel or centerboard determined to provide directional stability If a boat is towed sideways through the water so the longitudinal centerline of the hull is perpendicular to the towing line that point on the waterline is called the center of lateral resistance or CLR. The combined area of the sails must be positioned about the CLR properly (called "lead") to assure balance. And of course the sail area forces must be balanced with adequate ballast so the boat will not capsize.

Powerboats will require calculations on the most desireable horsepower based on the hull characteristics. If the hull is a semi displacement type, with limited speed potential, it doesn't make sense to overpower the boat. Conversely underpowering a planing hull will make a boat a real dog.

Some of the information necessary to make the many calculations are given in design textbooks. Other factors are obtained through technical writings and papers collected by a designer over the years. And if you test boats as we do at GLEN-L, parameters that work can be applied to future designs.

Most creditable designers have a background of engineering or schooling on boat design through universities and specialized boat design courses. Schooling covering the design of smaller craft however is almost non-existant and the experience gained through testing prototypes is invaluable on this size craft.

The foregoing outlines the general procedure that must be gone through to design as opposed to drawing a boat. Computers can do many of the calculations. However, a computer can't design a boat. Someone must put in the figures to form the boat and use the knowlege to select the proper parameters. It's been stated that designing a good looking, well performing boat, is a combination of engineering and art and the best way to develop this combination is through experience. And with more than 40 years of designing boats GLEN-L has experience plus.

  • BOOKS:
    • YACHT DESIGNING AND PLANNING, by Howard Chapelle ($35.00)
    • Westlawn Institute of Marine Technology
      733 Summer St
      Stamford, CT 06901
  • Computer programs:
    • PLYBOATS 2.01
      Ray Clark Enterprises
      7071 Warner Ave., #F
      Huntington Beach, CA 92647

New design: McDrift

GLEN-L already has a line of drift boats for plywood construction, so why more? The answer is "aluminum". These drift boats, commonly known as McKenzie River drift boats in the Pacific Northwest, are very popular in aluminum construction, and in response to customer requests, we have added the 14' and 16' McDrift. Aluminum construction is very quick and maintenance is low, although they are not usually lighter. For those who feel more comfortable with plywood, we still have the Drifter.

See the NEW section for further information on McDrift, and the DESIGNS/Special Purpose, for Drifter.

POXY-SHIELD The boatbuilder epoxy

How can I increase the working time of POXY-SHIELD?

This is a commonly asked question... and a good one. The speed at which any particular epoxy sets up is determined by temperature. There are several ways to affect temperature, both directly and indirectly. Either by controlling physical temperatures or by controlling the resin volume.

There are obvious ways to control temperature. If the whether is warm, the resin and hardener can be stored in a cool place or can even be cooled by the simple expedient of setting the resin container in a bucket of ice. Do not work in the sun. Will a fan help? Not likely. Fans do not cool. They move warm air away from your body and heat generated by the resin, but this is neglegible once the resin is applied in a thin film.

Which leads to the second, and possibly most important way of extending "pot life". Once the resin is mixed with the hardener, it begins to react; the reaction generates heat. This heat will accelerate the process. Once you can feel the heat it is probably best to discard the resin, particularly if you are applying glass cloth. So what do you do? As soon as the resin and hardener are thoroughly mixed, transfer the mixture to a container with a large surface area (pie tin, paint roller pan, etc.). this allows the heat generated by the reaction to dissipate. Obviously if you get the mixture onto your boat quickly it will have the same effect.

How about adding less hardener? Don't do it. Visualize epoxy as a plastic material that has been disassembled. If you do not put all the pieces back in, you will not have the same product. Although there is some leeway in mixing, it is best to keep as close to the recommended mix as possible. In the case of POXY-SHIELD, the mix is 5 parts resin to 1 part hardener.


When you're around this stuff all the time, you forget "v-drive" is not a household word. Serveral boats in our catalog are v-drive boats.... meaning the have a rear-mounted inboard motor, with a standard prop shaft. Obviously, if you have the motor at the back and the shaft exiting the boat forward, there has to be something between. That something is a torque tube (drive line) and a gear box that changes the direction of the power. That gear box is a v-drive, so called, because there is an angle between the centerline of the input and output shafts. That angle is typically 10 or 12 degrees.

Since most ski or speed boats under 20' are hurting for room and perform better with less weight, they don't use a transmission. For this reason, v-drives are available with forward only; forward and neutral; or forward, neutral, and reverse; and with various gear ratios.

So why put the motor in the back, and have all this extra hardware? Performance! Our Tornado and Thunderbolt designs are being raced at speeds over 100 mph. Center mounted engine boats usually top out in the 60 to 70 mph range.

Hardware "what's-its" for inboard installations

If you are unfamiliar with inboard installations, the selection of the proper parts is often difficult. For the novice, we suggest our book, INBOARD MOTOR INSTALLATIONS.

The following is a description of the various parts and their function in an inboard boat. Refer to the "V-Drive Installation" sketch above to determine the location of the parts listed below. Although the sketch depicts a v-drive installation, a direct in-line drive would be similar from the v-drive aft.


#1. QUADRANT or CUSTOM TILLER. A quadrant is required when cable type steering is used. The custom tiller is required when single push-pull cable steering is used.


#2. RUDDER POST BRACKET. The rudder post bracket supports the upper portion of the rudder. To prevent the rudder from falling through the bottom of the boat, a safety collar is used on the rudder above the rudder post bracket.


#3 RUDDER STUFFING BOX. A rudder stuffing box prevents the water from entering the boat through the rudder shaft hole. Various types of seals or packing glands can be used. It is advisable to use the same type for the rudder as for the shaft log (#9). The packing-type gland may be repacked while the shaft is in the boat. The seal-type requires that the shaft be removed to replace the rubber Neoprene seal.


#4. RUDDER STUFFING BOX PLATE. The rudder stuffing box plate goes on the outside of the boat. It is optional and often not used on the faster boats. It does provide a solid bolting and bearing for the bottom portion of the rudder stuffing box.


#5. RUDDER. Rudders of varying size and shape are listed to suit almost any small boat. Rudder Shafts (1" or 1 1/8") must be matched to the rudder stuffing box, collar, and rudder post bracket.


#6. STRUT. Struts are available in varying angles and drops to match your installation. Drop is the distance vertically from the base of the strut to the centerline of the strut bearing on the aft end of the strut. Two types of bearings can be obtained for most struts. The Aqua-Lube is a fabric type bearing. The BJ is a rubber-type bearing and is recommended when the boat is to be used in silty waters. Strut bearings are replaceable.


#7. WHIP STRUT. Whip struts are used to prevent deflection or whipping of the shaft in high speed boats with flatter shaft angles.


#8. FIN. The CUSTOM "V" FIN has a "vee" in the base to fit the "vee" in the bottom of most boats. The STREAMLINE FIN has a flat base and is usually intended for smaller boats. The two larger fins are used with the highest speed inboard boats.


#9. SHAFT LOG. The shaft log prevents water from coming into the boat through the shaft hole in the bottom of the boat. Shaft logs are available in varying angles to match the shaft or strut angularity. Refer to #3 (RUDDER STUFFING BOX) for information as to the types of packing gland.


#10. PROP SHAFT. Shafts come in standard lengths as noted. Shafts can be cut to any disired length and keyed on the driving end without additional cost. As an example, we can cut a shaft 63" and you pay for a 5'6" length.


#11. PROPELLERS. For all around use, the three-blade conventional-type propeller is generally used. Direction of rotation must be specified. Direction of rotation of the prop is as viewed from the back of the boat looking forward - left hand counterclockwise; right hand clockwise. All propellers are intended to fit our propeller shafts and have standard 1" tapers.


#12. PROP NUT KIT. A prop nut kit furnishes the parts necessary to securely hold the propeller on to the shaft.


#14. V-DRIVE MOUNT AND V-DRIVE. V-drives can be obtained that include integral forward, neutral and reverse gears. Others contain forward and neutral, while there are those that have no reversing or neutral position. With the latter, a marine transmission should be used on the motor. The exception to the latter statement would be for full race purposes. Ratios of the v-drives will vary. If in doubt, specify the type of boat, its purpose-pleasure or race-the size of motor, and preferably the diameter of the propeller to be turned or the space available for the propeller. We can then estimate the ratio required.


#15. V-DRIVE TAKE-OFF. A vee drive flange take-off is used to couple the upper shaft of the v-drive to the torque tube. This flange take-off can be obtained with a vee pulley to drive generators, alternators or other appendages. Refer to TORQUE TUBES (#16) for information regarding series #1310 or #1350.


#16. TORQUE TUBE. Torque tubes are used to couple the motor to the v-drive or a jet pump. Two series are available, a #1310 and a #1350. For ordinary use with the conventional pleasure boat and motors to approximately 400 cubic inches and a torque tube 24" or shorter, the #1310 series is satisfactory. For larger engines and for high speed use, the heavy duty #1350 series is desirable. Note that the motor power take-off and the v-drive take-off must be of the correct series to match the torque tube. The torque tube does have "play" in the spline that will make the torque tube approximately 1" shorter or longer than the noted dimensions. If a length other than those listed is needed, the torque tube can be cut and sized to your specifications. Check the price list for cost of this service.


#17. TORQUE TUBE GUARD. A torque tube guard protects the boat and occupants if a failure should occur anywhere along the torque tube assembly. Ordinarily, these are desirable on any of the higher speed boats with torque tubes 24" or longer. Note that these are made to accommodate both the #1310 and #1350 torque tube series. (See #16.)


#18. SAFETY COLLARS. Safety collars are used on top of the RUDDER POST BRACKET (#2) and in high speed craft just aft of the strut or forward of the shaft log as a safety device. Either split or conventional collars are available.


#19. POWER TAKE-OFF. A power take-off connects the motor to the torque tube. The Series #1350 or #1310 must match the torque tube. Drives are available for taking the power from the front end, the flywheel end or from a marine transmission. In most cases, the drive will be from the flywheel end. In many cases, driving from the front end is impractical with motors equipped with harmonic balancers or those with small diameter crank shafts at the driving end.

We also have 303 ss prop shafts with standard taper, cut to size, with keyway.
Prices: $75.00/48" + $9.00 per each additional 6" or fraction.
Order our $2.00 Inboard Hardware catalog for information on our hardware. Free with inboard plans and patterns.

Web Resources: Magazines devoted to boatbuilding

BoatBuilder Magazine: e-mail:
Messing About In Boats: website:
WoodenBoat: web site:

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