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Thread: Keel and strakes

  1. #1
    Join Date
    Jul 2022
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    Cape Coral, Florida,USA
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    5

    Default Keel and strakes

    I'm building a 20' ply on frame, flat bottom, flats boat based on the Spira Sabine plan. In addition, the transom is 20" Ht, 6' 4" wide. I will probably use it in the canals and flats in SWFL.

    My question is: should I install a keel? if so, dimensions, shape? The same questions re: strakes. any pros or cons, advice on materials, installation, would be greatly appreciated.

    Mark
    .

  2. #2
    Join Date
    Oct 2009
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    South Puget Sound/summer Eastern carib./winter
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    Default Re: Keel and strakes

    I think one needs to balance out pros and cons.
    Consider how a keel will affect the whole shebang. Trailering, beaching the boat, protecting the boat,handing.
    The boat may not need one , modern power trim helps that.

  3. #3
    Join Date
    Oct 2013
    Location
    dfw
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    Default Re: Keel and strakes

    on my skiff(14x4) i have a single shoe/keel that is 5/4"x5" SYP thru bolted(which i don't like) on a 1/2" bottom that is heavily glassed w/ 2 layers of mat set in epoxy

    IMG_2205.jpg served well for over 30 years

    on my current sailboat build (16x4) i have a keel 3/4"x2 1/2" w/ 2 strakes/skids 3/4"x1 1/2" all Doug Fir epoxied over 6oz glass cloth set in epoxy

    strake's/skid's spacing based on the width of the transom and run fwd to just short of the chine intersection

    IMG_4768.jpg IMG_4767.jpg

    since this boat has yet to be launched my choice is simply based on others of like size and kind that sail the waters i intend to sail

    in theory the 3-like thicknessed pieces on the little sailboat will balance her on a beach if i choose to sleep aboard as well as help protect her from oyster bed reefs on the Gulf Coast

    GOOD LUCK W/ YOUR BUILD

    sw
    "we are the people, our parents warned us about" (jb)

    steve

  4. #4
    Join Date
    Apr 2021
    Location
    Jonesport, Maine, USA
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    31

    Default Re: Keel and strakes

    I agree with what Steve did. On my 18 ft. flat-bottom skiff, I chose to install a centerline keel/shoe, and parallel runners/skids similar to what Steve shows in his pictures. My hull bottom is 3/4" MDO, encased in xynole/epoxy, then I'll paint the bottom with at least 2 coats of epoxy/graphite. In my picture below, you can see my keel almost ready to be installed, with one coat of the epoxy/graphite already applied. The keel is 1-1/2" x 5" CDF, and the runners are 1-1/2" x 1-3/4" CDF, all encased in 2 layers of xynole, faired, then the graphite/epoxy. I'll bring the bottom coating all the way up to 1" above the design water-line, before painting the topsides with Pettit Ez-Poxy. I chose to finish the coatings on the keel & runners off the boat hull, simply to avoid additional stick messes on my finally sanded & faired bottom. I'm glad I did, because I wasa able to do a much better job on the finish, and now can just glue & screw them onto the finished bottom.
    Attached Images Attached Images

  5. #5
    Join Date
    Apr 2021
    Location
    Jonesport, Maine, USA
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    31

    Default Re: Keel and strakes

    OK, Steve... you've got me. What the Heck is that little bell doing attached to your bow eye???

  6. #6
    Join Date
    Oct 2013
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    dfw
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    Default Re: Keel and strakes

    Quote Originally Posted by CaptChap View Post
    OK, Steve... you've got me. What the Heck is that little bell doing attached to your bow eye???
    that's the Termite's BELL OF HONOR

    for many years i have awarded bells to my motorcycles Jeeps and boats when they have performed wondrous feats by bringing me home safely from adventures not even attempted on similar conveyances

    kinda like completing a 150 mile motorcycle enduro on a showroom stock Honda 125SL

    going over Black Bear Pass in a stock 4-cyl Jeep Wrangler(so basic it didn't even come with an AM radio)

    and a little red 13'6" wooden skiff that took me offshore to catch a fish that when laid on the floor curled it's tail up on one side and it's head on the opposite side of the hull

    i think she earned her bell ;-)

    IMG_1485.JPG

    sw
    "we are the people, our parents warned us about" (jb)

    steve

  7. #7
    Join Date
    Apr 2021
    Location
    Jonesport, Maine, USA
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    Default Re: Keel and strakes

    I figured that there was a great story behind that bell! Can't wait until we see where the bell goes on your new sailboat, and especially hear about how she "Earned" it! BTW... Great pic of your skiff ar speed; looks like she flies!
    Well I finally finished installing my keel & side runners/rails/skids (whatever you want to call them)...I'm VERY glad that I decided to do all the xynole/epoxy/fairing & graphite coating on them off the boat, outside my tiny shop; it saved a ton up messy clean-up on my prepped hull bottom.
    Today I'm starting on the bottom coating with the graphite epoxy; 2 coats & I'll be done with the bottom, then I'll paint the topsides with Pettit EZPoxy. More pics to follow.
    Attached Images Attached Images

  8. #8
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    Default Re: Keel and strakes

    CaptChap, i clocked the Termite @ 29.8 on the GPS w/o the dog ;-)

    i might suggest filleting the corners where the strakes meet the bottom for a bit of insurance

    knot sure it'z kneeded butt i did ... just in case

    IMG_4675.jpg

    it'z easy and wont take long or cost much

    sw
    "we are the people, our parents warned us about" (jb)

    steve

  9. #9
    Join Date
    Apr 2021
    Location
    Jonesport, Maine, USA
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    Default Re: Keel and strakes

    Quote Originally Posted by swoody126 View Post
    CaptChap, i clocked the Termite @ 29.8 on the GPS w/o the dog ;-)

    i might suggest filleting the corners where the strakes meet the bottom for a bit of insurance

    knot sure it'z kneeded butt i did ... just in case


    IMG_4675.jpg

    it'z easy and wont take long or cost much

    sw
    Yes, you are right; today I'm going back and re-doing most of the seams with a little more epoxy/cabosil fillet. I'm not worried about the glue bond though, it oozed out all around. it was a long day and I'm a one-man show, so I didn't do a very good job finishing it up. I'm doing a tighter radius than you did, probably only a 1/4" or so, to make it pretty to the fish & the trailer.
    As for your skiff top speed, it might even be faster if your dog is a Greygound!

  10. #10
    Join Date
    Apr 2021
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    Jonesport, Maine, USA
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    31

    Default Re: Keel and strakes

    Finally finished the bottom. 2 coats of epoxy/graphite, sanded to 220 between coats. Next is to re-mask the WL and prime/high-build the topsides for the final EZ-Poxy.
    Attached Images Attached Images

  11. #11
    Join Date
    Apr 2021
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    Jonesport, Maine, USA
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    Default Re: Keel and strakes

    Better angle shot. Finish looks OK if you aren't too close (it will mostly be underwater anyway!)
    Attached Images Attached Images

  12. #12
    Join Date
    Sep 2022
    Location
    Biloxi, MS
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    3

    Default Re: Keel and strakes

    Hey guys,

    I have a couple questions. I am building a 16' flat bottom skiff - bottom is covered with 1/2 marine plywood and 2 layers of fiberglass. I am thinking of putting a keel and strakes/runners on the bottom. I understand that these will protect the bottom of the boat but do they provide much help in preventing the boat from sliding at higher speeds - being that they are about 1 1/2 inches in height? I originally, was going to put the keel down the middle and be done with it.

    If I do put them on the boat, are the screwed and epoxy. I have read some post where the screws are removed later, as they only act a clamps?

    Any help is much appreciated.

    Chris


    boat.jpg

  13. #13
    Join Date
    Oct 2009
    Location
    South Puget Sound/summer Eastern carib./winter
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    22,234

    Default Re: Keel and strakes

    Do you want the boat to slide?
    Do you want to plane easier and faster?
    You can finish the boat, and add or subtrack skeggy things later or not. They do not need to be sandwiched into the FG sheathing. In fact , that is a bad idea
    Modern power trim eliminates a lot of the need for skeg/keels for handling.They keep the prop biting so well.
    Use skegs for beaching, minimize them for handling.

  14. #14
    Join Date
    Sep 2022
    Location
    Biloxi, MS
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    3

    Default Re: Keel and strakes

    My plan is to make the boat a center console. Do not mind some slide, just want the boat to be safe in turns. So if 1 1/2" strakes reduce (sliding) noticeably then I will do them. If not, then I guess the main purpose is bottom protection?

    As to your comment concerning prop biting issues, I thought 1 1/2" would not affect the prop. But if I stopped the keel 18' from the stern then biting issues would be resolved?

    I understand sandwiching into the FG maybe bad, what would you recommend? 4200?

  15. #15
    Join Date
    Oct 2009
    Location
    South Puget Sound/summer Eastern carib./winter
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    Default Re: Keel and strakes

    I'm not saying the skeg will get in the way of the water in front of the prop.
    I'm saying that with modern power trim, the boat may not need any "handling" skeg.
    When a boat slides, it prevents tripping.
    This boat has no "anti trip" accomodation designed or built in.Start whippin around at 30plus mph...you may come home with some bruises
    Tripping is mo danger than sliding !

  16. #16
    Join Date
    Sep 2022
    Location
    Biloxi, MS
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    3

    Default Re: Keel and strakes

    thank you for the clarification

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