interlake sailboat specs

Latitude 42° 24' 51.3936'' N, Longitude 83° 55' 5.2032'' W

+1 734 426 4155 [email protected]

Interlake 18′

Never before have comfort and performance been so successfully integrated into a one design sailboat. Not only is the Interlake an exciting and challenging boat to race, it is also the perfect boat for a leisurely sail with family or friends. Its efficiently designed cockpit allows you to daysail comfortably with 2 to 6 adults. The large, dry storage area under the front deck provides lots of storage space for racing gear or picnic supplies. The hard chine hull adds stability without adding weight, while the rocker keel allows quick turning, tacking and exceptional maneuverability in tight places.

Generous sail plan makes for a fun boat to sail in light to medium air. – MICHAEL

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Review of Interlake

Basic specs..

The hull is made of fibreglass. Generally, a hull made of fibreglass requires only a minimum of maintenance during the sailing season. And outside the sailing season, just bottom cleaning and perhaps anti-fouling painting once a year - a few hours of work, that's all.

The boat equipped with a fractional rig. A fractional rig has smaller headsails which make tacking easier, which is an advantage for cruisers and racers, of course. The downside is that having the wind from behind often requires a genaker or a spinnaker for optimal speed.

CentreBoard

The Interlake is equipped with a centreboard keel. A centreboard keel is a pivoting lifting keel, allowing to sail both coastal and inland waters.

The boat can sail close to the beach as the draft is just 0.20 - 0.30 meter (0.66 - 0.96 ft) dependent of the load. See immersion rate below.

Sailing characteristics

This section covers widely used rules of thumb to describe the sailing characteristics. Please note that even though the calculations are correct, the interpretation of the results might not be valid for extreme boats.

The immersion rate is defined as the weight required to sink the boat a certain level. The immersion rate for Interlake is about 69 kg/cm, alternatively 391 lbs/inch. Meaning: if you load 69 kg cargo on the boat then it will sink 1 cm. Alternatively, if you load 391 lbs cargo on the boat it will sink 1 inch.

Sailing statistics

This section is statistical comparison with similar boats of the same category. The basis of the following statistical computations is our unique database with more than 26,000 different boat types and 350,000 data points.

What is L/B (Length Beam Ratio)?

Maintenance

This section is reserved boat owner's modifications, improvements, etc. Here you might find (or contribute with) inspiration for your boat.

Do you have changes/improvements you would like to share? Upload a photo and describe what you have done.

We are always looking for new photos. If you can contribute with photos for Interlake it would be a great help.

If you have any comments to the review, improvement suggestions, or the like, feel free to contact us . Criticism helps us to improve.

Interlake Sailing Class Association

Class contact information.

Click below

Class Email

Class Website

One-Design Class Type: Dinghy

Was this boat built to be sailed by youth or adults? Both

Approximately how many class members do you have? 100

Photo Credit:Lisa Aspery

Photo Credit: Celtic Girl Travels

Photo Credit: Lisa Aspery

About Interlake Sailing Class Association

The Interlake Sailing Class has something for everyone, and has been providing the best of racing and fellowship for nearly 100 years! Our goal has always been to be a Midwest regional class and to promote high-level competition in a friendly atmosphere. Members not only value the feel and performance of the boat, as well as the competition, but also enjoy the festivities which surround the events. This philosophy has served the class well for over seventy years. “Extremely tactical” is the way multi-class champion George Fisher describes Interlake racing. “The stiff mast makes a great equalizer,” says George. This fact also allows the skipper to tune into the great feel and responsiveness of the boat and concentrate on wind and tactics . . . not tweaking the rig. Interlake racing is tight!

“Our mission is to create an environment that promotes keen and friendly competition with an emphasis on teaching and assisting the entry-level sailor. The ISCA is committed to growth through the managing of sales, distribution, and marketing of the Interlake boat.”

Boats Produced: 1450

Class boat builder(s):

Customflex Terry Kilpatrick (419) 349-6109 [email protected]

Approximately how many boats are in the USA/North America? 500

Where is your One-Design class typically sailed in the USA? List regions of the country:

Ohio, Michigan, Indiana

Does this class have a spinnaker or gennaker? Yes

How many people sail as a crew including the helm?  2-3

Ideal combined weight of range of crew:  400

Portsmouth Yardstick Rating:   90

Boat Designed in  1933

Length (feet/inches): 18′

Beam: 6′ 3″

Weight of rigged boat without sails: 650

Draft: Board Up: 8″ Board Down: 4′ 7″

Mast Height: 24′

Coaching or Clinic Resources

Back to One-Design Central

Copyright ©2018-2024 United States Sailing Association. All rights reserved. US Sailing is a 501(c)3 organization. Website designed & developed by Design Principles, Inc. -->

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Listen To Your Helm

For many years, I have been giving clinics and helping folks try to get more out of their Interlake sailing experience. We do this sailing thing for fun and the easier it is to sail your Interlake, the more enjoyment you’ll receive.

One particular facet of sailing Interlakes that is tough to master is managing the helm. Too often I’ll see a team that has excessive helm (myself included!), that is when the driver is driving/working against the boat’s natural course. I attribute this, partly, to the Interlake being relatively heavy-helmed. There are plenty of boats out there that have a light helm, so when you come to an Interlake, the relative tug on the tiller is so much more that sometimes you just don’t recognize what the boat is communicating.

Weather helm is what we generally experience when going upwind. Here’s a picture of 13-time National Champ George Fisher. Look closely at how far off centerline the tiller is. Granted, this could be a situation where George is footing to get through some waves, etc., but the point here is that he is fighting the boat a bit and therefore dragging the rudder through the water.

What contributes to excessive helm? There are generally three main factors: 1) Sail Trim, 2) Boat Balance/Heel, 3) Position of CB. For the Interlake we can zero in on each factor and try continue to use points of reference to reduce the amount of helm the boat has, and thus go faster in a straight line (and arguably higher with added hydrodynamic lift).

Sail Trim .

Generally speaking if you understand the concept of how the sails affect the way the boat goes through the water, you are already ahead of the game. For many, we do understand, but we don’t always use the sails to help us listen to the boat. In its basic form, the jib pulls the bow down away from the wind and the mainsail, when trimmed, lifts the bow up to the wind. On a perfectly balanced boat, you will be able to feel any change in helm by just a click or two of trim on either the main or jib. Because the Interlake is so “mainsail driven”, we need to focus more on the mainsail as it contributes to the helm. Constant adjustment will directly affect the helm of the boat. That is why some have considered taking off their mainsheet cleats, to force you to hold onto the mainsail and adjust the main as it relates to the tug of the helm. I have a mainsheet clean and always will…just my style. But for those that have sailed any of my boats, you’ll know that the cleat is set low enough that you have to work hard to place the mainsheet in the cleat, and conversely it is easy to uncleat…this is the same as not having a cleat, though my hands are grateful that I do!

So when you are on your close hauled course with the jib trimmed just with the battens in lined with the centerline of the hull and the top tell tail flowing, you are now working the mainsail as an extension of the helm. Trim the main harder and the helm will increase. Ease out and the helm goes more neutral. Find this range, mark your mainsheet, look at the spread between the pulleys @ the transom…do anything you can to gain better understanding of the range and create a point of reference that you can then quickly check when the boat seems slow. Take this knowledge and then plug in the depowering factors (vang sheeting &/or traveler adjustment) to fine tune the balance through main trim!

Boat Heel/Balance.

The Interlake is a stable dinghy. More so than many other smaller one design boats. For this reason you have to have good communication with your team about your fore/aft weight placement and, as it relates to the helm, the side to side balance. When I was a Jr. Sailor my coaches always preached sailing the boat flat and that the rudder was a brake if you didn’t.   Not for a number of years after did I “get” the concept. If you think about the amount of heel you are carrying upwind and then correlate that to the tug on the helm, you’ll quickly understand this concept. The question always asked is “how flat do I need to sail”? The answer, as we have witnessed in GPS tracks of sail testing and boathandling, is that the flatter the faster. I like to challenge Interlake Sailors to find the transition point of helm (the point where the helm goes from windward to leeward). That is as flat as you’ll want to sail. In some cases (especially lighter winds), you’ll want and need a little windward helm to gain hydrodynamic lift off the blades. When you gain a slight increase of helm, you should work on managing that with sailing flat and regaining neutral helm. This is an important range of balance that you need to work with your crew to perfect. It all translates into faster sailing!

One quick note about fore/aft weight placement.   A common error I see is that when the boat is “loaded up” people tend to sit too far forward. If you are going to error, this is a good place to be, but just keep in mind that you’ll want to slide back and together as your feet slide into the hiking straps. If you are sailing 2-up, be sure that the forward crew is about one body-width aft of the shroud. If you are sailing 3-up, that should be ½ a body width.

Position of Centerboard.

Fortunately for us in the Interlake Class, the Centerboard down position is pretty standard (leading edge perpendicular to the hull). Most of the tuning guides talk about having relative marks on your CB pennant so that you know exactly where the board is set up for a given wind range. I like to mark mine so that I know exactly when it is perpendicular (for 0-5 knots), up a few inches (5-10 knots), up 6” (10-15 knots) and up 1’ (over 15 knots). I rarely set it and forget it…rather I see how the boat feels through the helm, check the relative position and adjust accordingly. Knowing where you have it set and then fine-tuning is really important in the Interlake.   An example is sailing in waves. You’ll need a little more board up to free up the helm to drive around the waves. The point here is that there are a number of One Design boats out there that have CB’s that are integral to the balance of the helm. Be sure to read the tuning guides and ask the experts if you have a question as to whether you could reduce the helm by moving the centerboard. In the Interlake Class you’ll find that some folks do and some don’t. That is why we practice and experiment at the club races!

In conclusion, the purpose of this article was to get you to think about helm. As I already mentioned, too often I’ll see a boat sailing upwind with too much helm. By easing the main (or depowering), balancing the boat or goofing around with the CB position, you will find the boat’s sweet spot and recognize better upwind performance.

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Interlake 18' for first sailboat?

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Want to learn to sail. Found a cheap interlake. Is this a good enough boat for the wife and I to learn to sail on?  

I have never sailed an Interlake myself. They have always struck me as a sensible design, and one that should be an excellent design to learn on. There is still an active Interlake One-design racing class and so used sails and hardware may be available. There is a webpage where you can turn for advice that is specific to the boat. On the down side, they are not self-rescuing, meaning that they can capsize and if they capsize, they do not have a self-bailing cockpit and so you will need a rescue boat to help get back to shore. The class rules require floatation bags or other methods of keeping the boat afloat, so it won't sink. Another show coming is that these boats typically do not have a way to mount on outboard and as a new sailor there may be times when you will want to simply motor home. Other than that, I don't have any useful information. Jeff  

I haven't sailed the Interlake, but I've sailed similar boats. They're a bit unique because they are neither self rescuing nor self righting. Which means it's up to you the operator to ensure they always stay upright, and bouyant (not full of water). Staying upright will probably be fairly straightforward most of the time, but I am not sure it would be the best choice for brand new sailors. Certainly not the worst, but you might want to be extra cautious with it. If you went a little smaller like a CL16 you would at least be able to right it if you dumped.  

Masthead float of some sort so it can't go mast down and stuff flotation in any void you can. Without those I wouldn't use it as a beginner boat because a beginner WILL lay it over on its side. This is one reason they use Sunfish, Lasers and such for beginners. The hulls are pretty well sealed, so its not going to sink without breaking the hull. Cockpits on these are self bailing and one person (appx 100 lbs or more) can get it back upright even if its fully inverted.  

They are good boats and the newer ones are self rescuing. An older boat would require a bow tank and under seat tanks to be self rescuing. There are very active fleets and help is just an e-mail away. Nationals are in Lorain Ohio this week, stop in if you are in the area.  

I know only what I see in the pictures. You may want to consider these: 1) It looks like some Interlake 18s are sit-on-top rather than sit-in boats. That configuration makes it difficult to relax. 2) It looks like some Interlake 18s do have benches, but they look narrow and the backrests look short. 3) It appears that Interlake 18s do not have ballasted keels. This will require hiking out, with your butts hanging outside the gunwale. This may or may not be the type of sailing experience you are looking for. Don't buy without talking to your wife. She might hate it. I know I would.  

I have owned an Interlake and loved it. They are stable and easy to handle. Mine had foam under the seats and self bailers. I would buy another (and may) but would also consider a Flying Scot or an O'Day DaySailer.  

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Interlake - potential purchase

• Thread starter Apex
• Start date Jul 15, 2015
• Forums for All Owners
• Ask All Sailors

Mom (73 but gets around just fine) just bought a house on a lake. She would like to use the sunfish for sailing, but we have opportunity to purchase an Interlake that I believe would be more comfortable for her. Everything is there with exception of a spinnaker, but it does have floor delamination. The outside skin looks solid, the cockpit floor flexes quite a bit. Anyone have experience with this boat? Value and how serious the delam is for putzing around? How difficult is the fix? Thanks in advance for your input!  

Hello Apex, The 1968 edition of The Sailboat Classes of North America says the following about the Interlake: "The 18-foot Interlake sloop, designed by Francis Swiesguth in 1932, came before the planing class erabut has survived. Since being converted from wood to fiber glass in 1955, she has become one of the fast-growing classes. With a hard chine and no "freak characteristics", as someone has described her, she has good stability and is a good all-around boat." Vital Statistics: LOA 18' waterline 15' 3" beam 6' 3" draft without centerboard 8" with CB down 4' 8" sail area 175 sq ft (no spinnaker) weight 650 lb trailerable; racing crew two or three I have never sailed an Interlake, but it looks like a beautiful, dry boat that would be fun for anyone. We owned several Celebrity Class sailboats over the years and the Interlake seems similar although it is described as hard-chined whereas the Celebrity is not. Personally, I would rather see a person "in" a boat like that rather than "on" a board boat like the sunfish. Will the boat stay in the water? On a mooring or on a dock will put some stresses on the hull and the rigging. A frequent check of the rigging would be in order. We bought one of our Celebrity Class boats cheaply because the mast had fallen and damaged the foredeck while the boat was on a mooring. If the boat is hauled out after each use then Mom will probably need help to do that although 650 pounds isn't too much boat to move. That depends on trailer and launch ramp location. The Interlake will probably offer an opportunity for one or more people to accompany her. Best Wishes. RE: cockpit sole delamination. Depends on how it is built. If it is laminated with wood between the layers you will have a real project to remove the inner layer and remove/dry the filler. Not impossible, but a serious job. If you can remove the "floor" layer in large pieces you can epoxy those pieces back into their respective places. Final thoughts: (1) sail the Interlake as it is for a while assuming it does not become waterlogged due to the delamination. (2) Let Mom decide. If she wants to sail the Sunfish let her do it.  

http://sailboatdata.com/viewrecord.asp?class_id=3200 clearly a dryer boat than a sunfish. where is it going to be kept? in the water? (how is she going to get it in / out of water).  

The sunfish is dead simple to rig, easy to sail, weighs in at what 120 pounds, and is eminently suitable for someone who just wants to get out for a while on a nice day. It can be bought and maintained for next to nothing and with a simple rig pulled up out of the water when not in use. If the water is less than 75 degrees I would equip the user with a wetsuit, good life jacket and whistle cause you never know when a blow might happen.  

thanks for the replies so far: yes, kept in the water at the dock. the Interlake has locations for a tarp to cover the cockpit, which allows the mast to remain rigged, while the sails should come on/off. We will be doing a sea trial with mom this weekend, and will decide then. Trying to put the Interlake back on the trailer requires a proper launch, we tried (and I am STILL SORE) to beach retrieve....she has a personal access ramp at the house, so perhaps not a big deal, depending on bottom type of the lake.  

I sailed Interlakes for 3-4 years. Still popular in Midwest/Great Lakes. It is a double handed boat though. Designed for the Lake Erie chop but raced everywhere. Easy to service/fix. Mine had a small roller furler with the drum under the deck. That would be a nice feature to add.  

You said "the" sunfish, so is do you already own a sunfish? If so, why not sail it, if that's what she wants to do. I sailed on an Interlake just once a long time ago. Liked it. But I wouldn't care to have one that I have to fix. Rather than the either/or you've presented, why not try the Sunfish and you can always find a little 16 footer later...O'Day, etc..  

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Interlake Sailing Class

The interlake, about the interlake.

The Interlake is a fast, maneuverable one-design sailboat that is generally sailed with a 2 or 3 person crew. Interlakes have a mainsail, jib, and spinnaker and they are:

• Fast and powerful due to a large roach mainsail and powerful spinnaker
• Stable yet nimble with hard chines and a generous rudder
• Comfortable to sail and race with a wide deck and low centerboard trunk
• Easy to set up and sail with a durable and forgiving rig
• Just plain fun to sail!

Interlakes excel in open water or small lakes and are a very tactical boat in all conditions. 

Our one-design rules keep the boats virtually identical or similar in design ensuring that the sailors determine the outcome, not the boat. It also keeps Interlake racing affordable and older boats competitive.

“Extremely tactical” is the way multi-class champion George Fisher describes Interlake racing.  “The stiff mast makes a great equalizer,” says George.  This fact also allows the skipper to tune into the great feel and responsiveness of the boat and concentrate on wind and tactics . . . not tweaking the rig. Interlake racing is tight !

Buy a New Boat From Our Builder

Buy or Sell a Used Interlake

Buy or sell Interlake sailboats on our website today.   

We put together a buyer’s guide to aid in your boat search.

Tuning and Tips

Interlake video library, boat measurement.

• How to measure a boat  (Powerpoint) 
• How to measure sails  (Powerpoint)  
• Measurement Certificate Database (Google Sheets)

Thinking of making a change to your Interlake? Check the Interlake Specifications here and if you have any questions (or just want to be sure) contact our Chief Measurer .  You want to be sure that your Interlake meets the class rules to maintain its one-design status.

Interlake Sailing

Copyright © 2022-2024 Interlake Sailing class association

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• Sailboat Guide

1973 Customflex Interlake

• Description

Seller's Description

1973 18’ Interlake Hull #982 with Gator Trailer

Rebuilt in 1997 at Customflex factory in Ohio - Stainless steel centerboard with cut down trunk and teak trim - New flotation system - New Harken mainsheet cleat base and system - Jib furling system, rigging and turning blocks - Spinnaker rigging and pole - 2 Super-max bailers

Equipment: - Standard equipment including Murphy & Nye Jib and custom Grenier Spinnaker. Needs new main sail.

• New Sailors Tailor Trailer/Mooring cover in 2011

Rig and Sails

Auxilary power, accomodations, calculations.

The theoretical maximum speed that a displacement hull can move efficiently through the water is determined by it's waterline length and displacement. It may be unable to reach this speed if the boat is underpowered or heavily loaded, though it may exceed this speed given enough power. Read more.

Classic hull speed formula:

Hull Speed = 1.34 x √LWL

Max Speed/Length ratio = 8.26 ÷ Displacement/Length ratio .311 Hull Speed = Max Speed/Length ratio x √LWL

Sail Area / Displacement Ratio

A measure of the power of the sails relative to the weight of the boat. The higher the number, the higher the performance, but the harder the boat will be to handle. This ratio is a "non-dimensional" value that facilitates comparisons between boats of different types and sizes. Read more.

SA/D = SA ÷ (D ÷ 64) 2/3

• SA : Sail area in square feet, derived by adding the mainsail area to 100% of the foretriangle area (the lateral area above the deck between the mast and the forestay).
• D : Displacement in pounds.

Ballast / Displacement Ratio

A measure of the stability of a boat's hull that suggests how well a monohull will stand up to its sails. The ballast displacement ratio indicates how much of the weight of a boat is placed for maximum stability against capsizing and is an indicator of stiffness and resistance to capsize.

Ballast / Displacement * 100

Displacement / Length Ratio

A measure of the weight of the boat relative to it's length at the waterline. The higher a boat’s D/L ratio, the more easily it will carry a load and the more comfortable its motion will be. The lower a boat's ratio is, the less power it takes to drive the boat to its nominal hull speed or beyond. Read more.

D/L = (D ÷ 2240) ÷ (0.01 x LWL)³

• D: Displacement of the boat in pounds.
• LWL: Waterline length in feet

Comfort Ratio

This ratio assess how quickly and abruptly a boat’s hull reacts to waves in a significant seaway, these being the elements of a boat’s motion most likely to cause seasickness. Read more.

Comfort ratio = D ÷ (.65 x (.7 LWL + .3 LOA) x Beam 1.33 )

• D: Displacement of the boat in pounds
• LOA: Length overall in feet
• Beam: Width of boat at the widest point in feet

Capsize Screening Formula

This formula attempts to indicate whether a given boat might be too wide and light to readily right itself after being overturned in extreme conditions. Read more.

CSV = Beam ÷ ³√(D / 64)

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