Author Topic: Hello from Istanbul  (Read 70 times)

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Dudley

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Hello from Istanbul
« on: April 26, 2018, 12:36:47 PM »
I have built couple of plywood sailboats till today (attached picture - Didi 26). Now I have decided to build a plywood motorboat since I am experienced at using plywood epoxy method. I actually searched for something around 34 feet, because the wave top distance varies around 29 - 32 feet where I will use the boat. But the longest I can find was the 28 feet Great Alaskan. So I bought the plans to start building it with double outboards. I will use it as family day boat during summer and will go to tuna fishing in winter at the Aegean Sea. During day cruising we will spend most of the time swimming at the bays. Opposite of the seas there, we have no sharks, no tornedos, no threats what so ever. So we need an easy way to enter and come out of sea. If any of the forum members have found a solution to this please send your photo and advices. Thank you all.

Brian.Dixon

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Re: Hello from Istanbul
« Reply #1 on: April 26, 2018, 01:11:56 PM »
Spectacular job on that Didi 26!  That is one beautiful boat!  Oh, and welcome aboard!

As for how to get back into a boat from the water, would a swim step on the transom work for you?  Even with 2 motors, which can be mounted pretty closely together, there is still room for a big-enough swim step on either side of the motors.  For example, you would use the minimum 59" (measured at bottom) transom cut-out for the twin motors that you want, and per the dry well drawing, use a dry well that is just wider than the cut out.  This would still leave around 15" on either side of the motors for a swim step.  You can build a 'gate' into the transom for easier access from the swim step into the boat as well.  As long as you don't cut or modify the motor boards, this is OK.  I would probably also add a transom knee that bridges the top of the top motor board to the side of the boat as well - just because (stiff is good in a boat this size).  As for boat length, Kent Cannon holds the record at 29' 4" for a Great Alaskan ... you can do the same .. and that's pretty close to what you were looking for.  Hopefully more will respond with even more ideas :)

Brian

« Last Edit: April 26, 2018, 01:15:40 PM by Brian.Dixon »
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Dudley

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Re: Hello from Istanbul
« Reply #2 on: April 26, 2018, 01:30:38 PM »
Dear Brian, thank you for your comment. I do not know how the motor boards look like as of today. At the moment I have started to the convert the bottom panel lofting numbers from imperial to metric. I have a multicam CNC router to cut the panels. The panel sizes and thicknesses are different in metric system. I have to redo the lofting according to panels. One problem is the thickness of the panels. On the plans the thickness you are using are roughly 9 and 19 mm respectively. Metric system has 3, 4, 6, 8, 10, 12, 14, 16, 18, 20 mm thickness. Should I use 8+10 at the bow side and 18 towards transom. OR 10+10 and 20. When I finish the drawing I will e-mail it to you for further discussion on the length.

Brian.Dixon

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Re: Hello from Istanbul
« Reply #3 on: April 27, 2018, 05:05:29 AM »
Dear Brian, thank you for your comment. I do not know how the motor boards look like as of today. At the moment I have started to the convert the bottom panel lofting numbers from imperial to metric. I have a multicam CNC router to cut the panels. The panel sizes and thicknesses are different in metric system. I have to redo the lofting according to panels. One problem is the thickness of the panels. On the plans the thickness you are using are roughly 9 and 19 mm respectively. Metric system has 3, 4, 6, 8, 10, 12, 14, 16, 18, 20 mm thickness. Should I use 8+10 at the bow side and 18 towards transom. OR 10+10 and 20. When I finish the drawing I will e-mail it to you for further discussion on the length.

18mm is just fine for the bottom panel thickness.  The original design used a 5/8" (about 16mm) bottom thickness and was plenty strong.  But some people had trouble finding 5/8" thick plywood, so I rounded up to 3/4".  I would say that any bottom panel thickness between 16mm and 20mm (total) will work just fine.  I'd go for the 18mm total thickness that you mention, and would use the 8mm as the second layer in the bow.

Another person already converted the plans to metric and sent me a link ... I'll see if I can dig that info up and get it to you.  As for stretching the boat, read about building to different lengths in the Construction Manual, part 1 of 2, for background info and then let's figure out how to do what you'd like with YOUR boat :)

Brian

The Great Alaskan - Professional grade offshore performance - Designed to be built by greenhorns -
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Dudley

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Re: Hello from Istanbul
« Reply #4 on: April 27, 2018, 08:03:17 AM »
Thank you for the offer of the link. Today I have finished the bottom panels and did lofting. With the optimum usage of the total panel length including the scarf joints, the total bottom panel length came to 8430mm (331,9 inch). I plan to go ahead with this size. I do not know what the total length will come at. Attached is the PDF output. 
« Last Edit: April 27, 2018, 08:06:27 AM by Dudley »

Brian.Dixon

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Re: Hello from Istanbul
« Reply #5 on: April 27, 2018, 02:12:35 PM »
Thank you for the offer of the link. Today I have finished the bottom panels and did lofting. With the optimum usage of the total panel length including the scarf joints, the total bottom panel length came to 8430mm (331,9 inch). I plan to go ahead with this size. I do not know what the total length will come at. Attached is the PDF output.

Since I'm not sure how you went about spacing out the stations as you show them, I'll go ahead and explain what I do for changing the length of the Great Alaskan:

When the boat is made longer, it is done by spacing out the lofting (and molds) from admidships aftward to the stern.  It has to be done this way because the boat narrows in width from amidships to the stern.  If you just continue the lines on things like bottom panels further to make them longer, then you'll find that the assembly is narrower than the transom - but you want it to fit the transom.  One builder found out the hard way that this will happen - he had to modify his transom to fit, and he lost buoyancy in the stern because of it.  Another way to look at it is that the very end of the bottom panels should have exactly the same width as the very end of the bottom panels on an un-stretched boat.  Clear?  Ask if not....

For more info, look in the construction manual to compare station spacing for bottom panels (and chines, shelves) between, say, the 26' and 28' versions of the boat.

Note that we do NOT change station spacing in the forward half of the boat ... all versions, no matter what length, have exactly the same bow (for reason).

Brian

« Last Edit: April 27, 2018, 02:13:33 PM by Brian.Dixon »
The Great Alaskan - Professional grade offshore performance - Designed to be built by greenhorns -
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Dudley

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Re: Hello from Istanbul
« Reply #6 on: April 28, 2018, 10:20:54 AM »
Dear Brian,
First of all thank you for the information. Actually I was wondering if the boat buyoncy will change and balancing will be disturbed by extending the length. So, it is good to learn this important point at early stage. So, I will redraw the bottom panels according to your recomendation. I will first first find the maximum applicable length for bottom panels by utilizing the full length of panels with the scarfing. So, to my understanding whatever the bottom panel length finishes the final width for port or starboard must be 32-11/16. That is clear. But how will I find the vertical station points spacing after 132.

Brian.Dixon

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Re: Hello from Istanbul
« Reply #7 on: April 28, 2018, 11:58:42 AM »

Don't jump ahead too fast!  Make sure you understand everything in the original drawings and the applicable section(s) in the manual.

If you want to calculate exactly how long your boat will turn out after maximizing the bottom panel length, just take a tape measure along the edge of the wood to where the last station goes for the 28 foot boat and make a mark.  That's where the end of a 28-foot boat bottom panels would've been.  Now measure from that mark to your new last station, and add that distance to 28'.  For example, if the last station for a 28-footer is 1.5 feet short of your new last station, then your boat will be 29-1/2 feet long ... Just make sure that you spot which stations get re-spaced out if making the boat longer and which don't (the bow half of the stations).  Studying the changes between the 26-foot and 28-foot loftings in the drawings and manual will indicate to you which ones you will want to space out to make the aft half of the boat longer.  Piece of cake!  :).  Think three times, measure twice, cut once....

Brian

The Great Alaskan - Professional grade offshore performance - Designed to be built by greenhorns -
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Dudley

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Re: Hello from Istanbul
« Reply #8 on: April 28, 2018, 03:14:33 PM »
I have done the placing of the available local plywood panels to find out what would be the optimum length for the bottom panels. I have made provisions for 1 to 8 scarfing ratio depending on the thickness. I have also shifted the scarf joints of the above layer from the below layer to have a stronger bond. According to CAD drawing attached, the 132 vertical station width will be 34-7/8 and the final vertical station will be where the plywood panel ends with 32-11/16 width. Where will be the 6 vertical station points between 132 and 330-9/16 (8396mm)
P.S. Did not accept the CAD file for uploading. Please send me an e-mail adress to send you the CAD file directly.