DIY Dinghy Davit advise / ideas needed

Discussion in 'General Discussion' started by ArtWallach, Jan 11, 2017.

  1. ArtWallach

    ArtWallach New Member

    155
    Sep 12, 2011
    Lindenhurst NY
    2000 Sea Ray 310 Sundancer
    T300hp Mercruiser Inboards
    I drew up plans for a davit that will allow me to have the dink launch and retrieve from the swim platform
    https://scontent-lga3-1.xx.fbcdn.ne...=59e3b319e73510b52fead418f0d191a4&oe=58D5F91C
    https://scontent-lga3-1.xx.fbcdn.ne...=0463c30ee161f414b416d42279a6dea7&oe=591402C6
    https://scontent-lga3-1.xx.fbcdn.ne...=14398081b926a1a41c1ed95ae5daa1fb&oe=58DFAC56

    Im trying to figure out how best attach it to the underside of my swim platform.
    My goal is to attach two 2' x 1.5" SS square tubes to the underside of the swim platform (that a smaller tube slides into) without having any hardware or minimal hardware showing on the top of the swim platform. I'm afraid that just using a recessed screw or recessed bolt head will pull through the platform. I don't want a tripping hazard or anything that will interfere with the platform when the davit is not on the boat.
    Any ideas?
    Thanks
     
    Last edited: Jan 11, 2017
  2. hakunamatata

    hakunamatata Member

    155
    Aug 18, 2015
    Southport Marina - Kenosha WI - Lake Michigan
    410 Sundancer
    Caterpillar 3126
    There's been a few discussions on davits in the dinghy section, so may want to post there if you don't get many responses.
     
  3. TNT8808

    TNT8808 Member PLATINUM Sponsor

    109
    May 25, 2016
    Spring Lake, MI
    2001 Sea Ray 410 Sundancer, Raymarine E125 GPS
    CAT3126 TA's
    Looks nice. Your design reminded me of an earlier design I saw on a blog I was following a few years ago when Dale was working on his 340. Here's the blog address http://searay340restoration.blogspot.com Look at the July and October 2012 posts for more information and pics.
     
  4. ArtWallach

    ArtWallach New Member

    155
    Sep 12, 2011
    Lindenhurst NY
    2000 Sea Ray 310 Sundancer
    T300hp Mercruiser Inboards
    Thanks for the quick responses.
    @Tom,
    I saw Dale's post. I loved his davit concept, downloaded it, studied it and I've incorporated most of his ideas into my design. I just can't do them all since I can't machine and weld like he did. I had to adapt his and other concepts into something I can make with hand tools. I just don't have a great idea for the final attachment methodology.
     
  5. swaterhouse

    swaterhouse Member GOLD Sponsor

    232
    Jan 7, 2015
    Mattapoisett, MA
    2007 Sundancer 44
    Cummins QSC 8.3
    You'll need some type of backing plate, a very large washer or square plate would do fine. Then use a button head screw, put the nuts on the bottom side under the platform.

    https://www.boltdepot.com/Socket_button_head_Stainless_steel_18-8_3_8-16.aspx

    Will be about as minimal as you could possibly get unless you route out the top of the platform and "countersink" the backer plate and screw head.
     
  6. Ididntdoit

    Ididntdoit Active Member

    Dec 5, 2007
    East Coast Florida
    300 Sundancer
    5.0MPI Bravo III
    My platform has "stringers" under it for support running from the edge of he platform to the transom - they are glassed in and part of the platform. I know some older boats don't do this - and support the less ridged platform by using metal down bars......if your boat doesn't have the stringers....add them, perfect place to tie the mounts into
     
  7. magstang1

    magstang1 New Member

    May 30, 2010
    Lake St.Clair
    1998 31 Sedan Bridge
    Twin 350 Marine Power
    Your Davits are too far forward on the dinghy. All the weight is in the back. I would also question making the arms out of 1/2" starboard. That's pretty small. I used 1".
     
  8. MasterFab

    MasterFab Active Member TECHNICAL Contributor GOLD Sponsor

    Aug 17, 2010
    Wallkill, NY
    2002 340 Sundancer, Rescued, Restored, Modernized, and now Sold
    8.1L Horizons, ZF 63 V Drives
    You are within driving distance of my shop, so if you want to come up one day, I can machine any specialty parts you need to get this done. I'll need to know what size and thickness material, beforehand, so I can have it in stock.

    Dale
     
  9. ArtWallach

    ArtWallach New Member

    155
    Sep 12, 2011
    Lindenhurst NY
    2000 Sea Ray 310 Sundancer
    T300hp Mercruiser Inboards
    I would prefer the port davit arm being more to the stern of the dink, but the model Zodiac I have purchased has two rudder strakes that are depicted with the dark rectangles. I basically have two choices.
    https://scontent-lga3-1.xx.fbcdn.ne...=65fa28fda94d8f84f34deb201225ef6f&oe=591B3E96
    Sliding the dink on either fore or aft of the rudder strakes. If I put the davit arm aft of the strakes I have only a 2" margin of missing the dink transom when pulling it onto the swim platform.
    If the davit arm is forward of the rudder strakes it is only 14" to the transom. The dink tubes going to the points are the vast majority of the overhang.
    Since I'm using rubber wheels I think (hope) I'll be fine with the 1/2" HDPE. I used 1" on a rocket launcher table I made (replaces cockpit table when fishing).
    https://scontent-lga3-1.xx.fbcdn.ne...=2ba8d0412b4bfbc3b46ca5c5b7a00ae2&oe=5914BEA3
    https://scontent-lga3-1.xx.fbcdn.ne...=3b496a3ea9dc96ca24888c425fcb7ee4&oe=591CAA47
    It is very heavy for its size.
     
    Last edited: Jan 11, 2017
  10. ArtWallach

    ArtWallach New Member

    155
    Sep 12, 2011
    Lindenhurst NY
    2000 Sea Ray 310 Sundancer
    T300hp Mercruiser Inboards
    Dale,
    Thank you for your incredibly generous offer. We are about 120 miles (2-3) hours apart.
    If it comes down to having to fabricate it would be worth the trip.
    Thank you.
     
  11. Creekwood

    Creekwood Active Member GOLD Sponsor

    Apr 26, 2009
    Oakville and Georgian Bay, Ontario
    '97 330 Sundancer
    2X 454 w/ vDrives
    Off topic, but that rocket launcher table for fishing is a great idea that I will be using, with some modification, on my 330DA for somewhat similar purposes.
     
  12. ArtWallach

    ArtWallach New Member

    155
    Sep 12, 2011
    Lindenhurst NY
    2000 Sea Ray 310 Sundancer
    T300hp Mercruiser Inboards
    What you can't see from those pics is that the redesign now has a slot for a fishing pliers, a knife and a a small cheap cutting board in the center (that is replaceable), but I don't like to cut any messy bait on it. I have no cockpit carpeting or transom bench when fishing. I tie down a cooler on the swim platform as a live well. for a SeaRay Sundancer, it makes for a decent fishing platform.
     
  13. magstang1

    magstang1 New Member

    May 30, 2010
    Lake St.Clair
    1998 31 Sedan Bridge
    Twin 350 Marine Power
    How far down do the strakes extend? Do you have a picture? I would consider putting the rear support right in the middle of that area. Are you planning to leave the motor on?
     
  14. magstang1

    magstang1 New Member

    May 30, 2010
    Lake St.Clair
    1998 31 Sedan Bridge
    Twin 350 Marine Power
    I would question the need for rollers as well. Starboard on wet fiberglass is plenty slick. I would thing the rollers would actually make it harder to haul out from catching on the ribs on the bottom of the dink.

    Not trying to tear your design apart. I'm just speaking from what worked for me. I had a 1998 290DA with a 10' RIB.
     
    Last edited: Jan 12, 2017
  15. ArtWallach

    ArtWallach New Member

    155
    Sep 12, 2011
    Lindenhurst NY
    2000 Sea Ray 310 Sundancer
    T300hp Mercruiser Inboards
  16. magstang1

    magstang1 New Member

    May 30, 2010
    Lake St.Clair
    1998 31 Sedan Bridge
    Twin 350 Marine Power
    My rear davit arm was only a few inches from the back end of the dinghy hull. Just far enough to give me a little wiggle room when hauling the dinghy up on the davit. The last thing you want is the dinghy sliding too far forward and the hull slipping off the front of the rear arm. Now the tubes are caught in the arms of the davit and it's a pain to straighten out.

    If your dinghy has a fiberglass hull I would omit the wheels. Fiberglass slides across starboard like ice. I would also consider moving that rear arm toward the back of your dinghy especially if you plan to leave the motor attached. You have to consider weight distribution, not length. All the weight is in the back. Make a cutout in the rear support that can go around the strakes and support on the hull.

    Good luck and keep us updated. I hope I've given you some points to consider. Search through my old posts and there are plenty of pictures of how I made mine.
     
    Last edited: Jan 13, 2017
  17. JVM225

    JVM225 Active Member

    Apr 8, 2008
    Farmingdale, NY
    2002 410 Sundancer, Monaco Edition.
    3126 Cats.
    This is what came with the boat I just bought last month. They are pretty pricey to buy, but after looking at them in person they seem pretty basic and should be easy to use as a guideline for a DIY project. They slide in to Weaver Davit brackets that are mounted on the edge of the swim platform:

    http://www.dinghyramp.com/dinghyramp-hd-slide-on-boat-lift/
     
  18. wingatesl

    wingatesl New Member

    86
    Jan 31, 2010
    Eastern Shore of MD
    2000 3672
    7.4 horizons
  19. ArtWallach

    ArtWallach New Member

    155
    Sep 12, 2011
    Lindenhurst NY
    2000 Sea Ray 310 Sundancer
    T300hp Mercruiser Inboards
    My dinghy is not fiberglass.Its 100% inflatable. I may rethink the placement of the portside davit arm.
     

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