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Hull design question

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  • Hull design question

    I wonder if some if you more experienced boaters can explain to me the benefits ad drawbacks of the general hull design if these older classic cruisers. I have a Skagit 20' but the hull shape is not that different from the many other small cruisers of that era. Why is it that the hull shape with the pointed front and wide flat keel is no longer the choice in modern boats? Is it because they ride too hard in rough seas? Are they more prone to flipping over or maybe they generate too much drag?

  • #2
    Because of pounding. The advantage of a relatively flat hull is that it runs at reasonable speed (say 12-25 knots) with modest propulsion. Back in the 50's and early 60's a 35 hp outboard was considered powerful, and 60 hp, when they became available, were huge. Then in the mid sixties Ray Hunt became famous with the deep V hull. If you have power to drive it, a deep v will run at 30, 40, 50, 60 knots or even faster. Instead of dropping off the back of each swell, it partially cuts through them. Try running a flattish hull like the Bellboy 21 I'm restoring at 30 knots in the open ocean. It will beat the fillings out of your teeth and possibly damage the hull. My last boat was a riveted aluminum Starcraft 21 with a shallow V hull. In moderate Southern California chop at anything over 12 or 15 knots, over every swell it sounded like somebody dropped a bucket of bolts and felt like I dropped two feet onto concrete. In say 1,000 or 2,o00 miles max of open ocean travel at 15-22 knots it literally beat the hull to death. With a modern welded 21 foot deep V hull in the same ocean I could have run 25-30 knots in relative comfort. Using twice the fuel.

    The designers of the day understood this, and tried various tricks to get a better ride while still planing with the modest outboards of the time. I am aware of the tradeoffs, and am willing to run slower to get the dramatically lower fuel consumption.
    Owner of a Bellboy 21- delusional enough to believe it will run some day.

    Comment


    • #3
      Yup, Ed nailed it.
      I my Skagit 20 offshore I have a early set of electric trim boards (looks like a heavy duty automotive heater motor and works the trim boards like a screw jack) and of she is riding a little too rough, I just slow her down or use the trims to poke her nose into the water.
      I see were some would add weight to the bow to help keep the bow down for a better ride. She has a B-18 with dual weber carbs and is said to produce about 105hp which will push her along at about 28mph if pushing it. She has too much extra added weight to her. I will cruse with her at 15mph all day and she just sips fuel.

      I used to refer these hulls to like a barn door with a motor on the back due to the pounding.
      I now have a Dorsett Catalina that once the boat is setting at rest in the water, the lowest point is just under the cabin bulkhead. These of course are California boats and were designed for the San Francisco Bay area and ride quite well because of keeping the Bow in the cut of the water all the time.

      Your question would also bring up Hull speeds. Most of them are lower speeds and I see most people over power the hull with big engines.
      I seen Marty Loken power Many of this 16 to 18 foot boats with a 50hp Honda which worked Perfect.
      Jack Dando has a 19ft Bell Boy, almost identical hull design and he has a 60 Yamaha engine on the rear of his boat, all the weight has been kept to a minimum as well as moved forward to the balance point of the boat.
      Once they load the personal gear aboard plus themselves, that boat will preform better than when first designed. All the structural work has been done on Jacks boat and now with his new location and new shop, I am looking forward to seeing pictures of her being finished.
      Helmar Joe Johanesen
      1959 Skagit 20ft Offshore, 1959 Skagit 16ft Skimaster,
      1961 17ft Dorsett Catalina.1958 Uniflite 17 ft
      Outboards: 2.5 Bearcats, 3 50hp White shadow Mercs
      2 40hp Johnsons, several smaller Old kickers for a total of 12

      Our Sister club
      http://www.goldenstateglassics.com

      Oh, and Where is Robin Hood when you need him??

      Comment


      • #4
        Hey guys,
        The smaller Arima and C-Dory owners still use the flatter type of hulls to keep their engine size down and thus raising the odds of a boater being able to get into the sport.You can still tow with the family car.
        The Deeper Vees of today use lift strakes,notched transoms and steps on the bottom to create the feel without the need for Hp.
        A heavier motor will change the Feel of a boat ,hopefully not so much as to change the Center of Balance.
        Coast Guard used to test their hulls dropping from 10 feet onto re-inforced concrete to simulate a drop from an ocean wave at speed.
        Usually your feet and back will let you know when a hull isn`t designed for the water you are on.....your ears will let you know as well. My Seafair would rattle over 30 but calmed right down and rode flatter if you kept it at 27 mph.Chuck Bauer taught me that one at Renton one rough day....
        TimM
        unk.year 10` Mahogeny "DragonFly"racer
        15` SAFE boat w/120 hp Johnson
        SeaRay 175BR
        Hi-Laker lapline
        14` Trailorboat

        Comment


        • #5
          Thanks for the in depth replies. It helps explain to me as well the challenge I'm having with balancing my Skagit 20. It came with an old Johnson 70 which amazed me because I couldn't believe that would move it. I currently have an older merc 90 2 stroke on there but with that on the back I have very little weight on the tongue of the trailer. As a matter of fAct on my first sea trial with that setup the whole thing popped off the hitch on the way to the boat ramp and gave me a scare of a lifetime (luckily I live closeby and was only doing about 15 mph at the time). Anyways I have a 90 four stroke Yamaha I want to use but am a bit worried about the weight. What do you guys power your boats with?

          Comment


          • #6
            Addressing only the boat tongue weight should be a high priority, unless you have handled it already. A little shifting of the trailer axle position while using a bathroom scale should take care of that.

            Comment


            • #7
              Bruce Drake's Bellboy 21 ( or as I call it, The Most Beautiful BellBoy Ever) has a 140 for a 21' boat, and that's been clocked at almost 40. I got 2006 115 Ficht for mine. I expect to almost never give it full throttle except on flat water when testing prop pitch, but it's very efficient in the midrange where I expect to use it. I'm a big fan of good balance, so my tanks and batteries are well forward. I'm no expert, but I would put the 90 on your Skagit 20. But find out how to adjust your trailer to better fit the boat. For some trailers you move the axle(s), and for some you move the winch post. I'm not the expert on this, but my understanding is that you should have about 10% of the trailer+boat weight on the ball. If you can't adjust the trailer to get that, you need to replace the trailer.

              When new, that boat would likely have come with a pair of 35 hp outboards, so a 70 isn't ridiculous. But in those days it was not unusual to find a boat that wouldn't get up on plane if you added an ice chest to your normal load.
              Owner of a Bellboy 21- delusional enough to believe it will run some day.

              Comment


              • #8
                Like I said, my 20 offshore has a B-18 in it and I see were the 58 I had came with a B-16 with the Volvo Penta outdrive. Those would scoot right along and were 80 to 105hp.
                I know when you over power those hulls they start porpoising really bad.
                Helmar Joe Johanesen
                1959 Skagit 20ft Offshore, 1959 Skagit 16ft Skimaster,
                1961 17ft Dorsett Catalina.1958 Uniflite 17 ft
                Outboards: 2.5 Bearcats, 3 50hp White shadow Mercs
                2 40hp Johnsons, several smaller Old kickers for a total of 12

                Our Sister club
                http://www.goldenstateglassics.com

                Oh, and Where is Robin Hood when you need him??

                Comment


                • #9
                  My Skagit 20' has a 2004 115 four stroke Mercury ( Yamaha ) with a rebuilt 2 1/4 thick transom. Never have had any problems with it porpoising at any speed. I really like the T/T as far as leveling her out as you go along and lowering the speed down and still being able to stay on a plane.The Dorsett 21' Farallon i had before the Skagit 20' with a 150 hp 2 stroke was very hard to level out even with Bennett auto tab$ at around 24-28.The only way was wide open to get the bow down so you could see ahead. On the Skagit I do have 2 -12 gal tanks up at the cabin bulkhead and a 28 gal in the stern ( i use that fuel first and then switch to the two 12's as back up, I fill them up at this time of the year as gas is cheaper and add the gas treatment and that will take me thru Spring/Summer next year when prices are higher ) and runs fine at around 35 mph but i usually run 24-32mph depending on the water conditions. As far as the trailer goes,it does a great job the way it is set up with the dual axles set back towards the stern. Luv that trailer and great to back up !
                  Attached Files
                  1957 17' Skagit Express Cruiser
                  1959 20' Skagit Express Cruiser 120 HP I/O "Chippewa"

                  Comment


                  • #10
                    Thanks for the replies - its great to see the photos of your Skagit - what a looker! I'm curious about your windshield up top. It looks custom and a bit smaller than the original ones. Was this just a style choice or does it improve your ability to see? I do find that with my hardtop I feel like I'm flying blind at lower speeds. Sounds like trim tabs are one way to help counter that problem but I also wonder if removing the hardtop would help

                    Comment


                    • #11
                      You should be able to get to the Gallery...Please try this for me.
                      You should see were it says, Home, Become a Member, Resources, Boating Safety, Store, Forums, and Gallery, then Events and Members.
                      Do you see all those ??
                      If you see the Gallery, click on that. Once that comes up, then you can pick events we have had in the past, Users boats, not sure about that at the moment. Looks like I need to relearn the Gallery program again to turn things on and off.
                      Once I get the Users boats back on, then you will be able to upload images to the Gallery as well as on the Forum...
                      Enjoy

                      On the Hard Top, mine has the same hard top. I used to ride Harleys year around (yeah, I grew up and grew old) and to be totally honest with you, Do not like the Rain or getting caught in it. I realize I am in the Pacific Northwest were if you don't like the weather, just wait a few minutes.
                      I like the idea that I can Zip her up if I happen to be out or if crabbing and the weather is crap, I am still able to get under something to help stay dry. My cabin is also heated which is a plus. Got to pamper the old guy
                      Attached Files
                      Helmar Joe Johanesen
                      1959 Skagit 20ft Offshore, 1959 Skagit 16ft Skimaster,
                      1961 17ft Dorsett Catalina.1958 Uniflite 17 ft
                      Outboards: 2.5 Bearcats, 3 50hp White shadow Mercs
                      2 40hp Johnsons, several smaller Old kickers for a total of 12

                      Our Sister club
                      http://www.goldenstateglassics.com

                      Oh, and Where is Robin Hood when you need him??

                      Comment


                      • #12
                        Chris, When i got this boat it had a windshield somewhat like it has now , but just a little bit different. I replace it with this one. Back in 2003 a friend ask me if i wanted to buy his low styled windshield for my 1957 17' Skagit that he had on his 17' Skagit. Well the price was real right compare to buying another aftermarket one for $350.00 ! Save your money on tabs ! With that 90 four stroke Yamaha you have T/T that should be enough. I have heard that your motor is about the same basic motor i have so that should be fine ,but i would beef up the transom something like 2 1/4 inches thick or whatever you call it in Canada. LOL

                        Here's the "Pro & Con's"

                        Pro's....I like the looks of this so-called sporty looking windshield ( that's just me " ) If it had come with the original i would have left it on as that can be a whole another story about the orginal being mess with like trying to put new glass in them at the tune of about $1300.00 plus. That in itself can be a nightmare ! Towing the boat down the freeway there is less draft on the windshield that the original one by far.If you want canvas over your head get a bimini like i did on my 17' Skagit. With the Bimini there is not a major problem with the rain.I like to see the wide open sky. I see you have a hardtop , so that should take care of any problems.


                        Con's..... With this style windshield you do give up a few things...You cannot snap canvas to the low windshield.If you want to inclose the cockpit with canvas more or less as you are out of luck.Once in a while you can get a lap or face full of water when the waves are about 4 ft plus high. I hope this helps. Do you have any pictures? Chuck
                        Attached Files
                        1957 17' Skagit Express Cruiser
                        1959 20' Skagit Express Cruiser 120 HP I/O "Chippewa"

                        Comment


                        • #13
                          Love the photos. Helmar your side seating is a pretty cool layout and Chuck I am amazed at the paint on your boat (I'm assuming its paint anyway). I did build up the transom to 2 1/4" when I redid it this past winter so it should be plenty strong. Have a funny story about it though. The original splashwell is pretty narrow and I found I couldn't trim my motor all the way up so I thought I'd just raise it up a bit while I was redoing the transom. I never thought too much about what this would do to the prop because it still hung below the keel and I figured that would be enough. This summer when I took it out for its first run after that work it drove out of the Harbour just fine but as soon as I tried to build any speed the prop would come thrashing out of the water! Talk about a bonehead move. I had to go back and cut into my beautiful sanded and finished transom and notch it out to lower the motor back down. Also had to fill and drill new holes for the motor. Net result is that I rode my boat for one day this past summer and now it's back under cover. I also need to figure out how to cure the splashwell problem. Chuck it looks like yours might be a little deeper - what did you do to solve that problem?

                          Comment


                          • #14
                            Chris , First of all, i can't take credit for the structural rebuilding of this Skagit. Marty Loken at Island Boat Shop up by Port Townsend did the work for the former owner Bruce Drake. The first time i saw this boat was back in 2003, In later years ( about 2008 ? ) Marty put in new bulkheads,cabin, etc. What i did was paint ( Interlux brand with a 7 " felt roller ) ,new hardware,carpeting the complete boat , cabin door that Marty made, etc. Bruce did a lot of the wiring.The transom is 20" high. They did slant the splashwell up some i think to make it possible to fit the 28 gal gas tank under the bench seat / splashwell. Never have had any problems in tilting the motor up or down while under way or transporting on trailer. The only thing i have to look out for is when i tilt the motor up after putting back on the trailer is to stop before it gets to the flag holder bracket. Chuck
                            Attached Files
                            1957 17' Skagit Express Cruiser
                            1959 20' Skagit Express Cruiser 120 HP I/O "Chippewa"

                            Comment


                            • #15
                              Thanks for the photos chuck - I'm going to go and measure up mine to see how it differs and will report back

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