9
« on: August 24, 2023, 11:10:37 AM »
Please note that I have updated the Kodiak Addendum, Caveats section, to clarify and expand on what the Kodiak design is for ... and why. In a nutshell, it wasn't just designed to be longer, but also to carry more weight in the stern (rather than in the house), as you would expect for a "serious recreational or light commercial" boat to be used. The reason is for safety. The number ONE cause of capsize for a planing hull is the taking on of water over the stern when the boat is stern-low due to loading (gear, people, ice, live wells, etc). Once a wave is in the boat, noting that it can weigh a couple of thousand pounds, the free-surface effect and momentum can easily capsize a boat - and it happens quicker than you can say "what thuh!?". So ... I clarified the addendum to help people both achieve the boat that they want, and to keep them safe at the same time. Please read the following new Caveats section. Feel free to ask questions and/or to work with me to help keep your boat trim adequate and safe.
-------------------------------------------
Caveats (for the Kodiak Great Alaskan)
For the Great Alaskan boat design, the Kodiak model’s 30’ length and 9’4” width is about as far as the design can be pushed without serious redesign work for an even larger (and likely much heavier and less efficient) version of the boat – which would not be a Great Alaskan, but would be an entirely new design instead. Similarly, the Great Alaskan Kodiak model is not suited for open-deck or open-console designs and requires the aft cuddy and aft pilot house bulkheads (or similar) for strength, and at least the pilot house itself for proper displacement.
Please note: The Kodiak was designed for serious recreational or light commercial usage. This means “for more weight in the stern for proper trim”. Why? The number one reason for capsize in an open planing hull is the taking on of water over the stern – the weight and free-surface effect is tremendous. If you will be loading up the stern with extra weight, people or gear, the Kodiak is designed to prevent a dangerous stern-low condition. 4 adults, gear, a few hundred pounds of ice and/or live wells can add up to 1500+ pounds in the stern of a boat being used as a charter or commercial fishing boat. On the other end of the spectrum, the Kodiak is not the best boat for carrying the extra weight forward that would occur if you add accommodations for more of a live-aboard arrangement and did not consider adjustments to help balance out the forward weight. For a live-aboard or boat camping with extra accommodations, I recommend that you either build the 28-foot standard Great Alaskan (and even with that boat, take care to keep extra weight aft) or follow the suggestions listed below to keep the boat balanced as designed – If this is disappointing to you and you would prefer a refund for the Kodiak Addendum – just ask. We’ll take care of you. If you want to build a Kodiak with lots of live-aboard accommodations, then the following selection of adjustments and considerations will help keep the boat’s center of gravity towards the stern where it belongs at about 9-10 feet forward of the transom:
• Anchor windlass and bow-thrusters: Keep them as small and light as you can get away with
• Place batteries at or under the dry well in the stern
• Do not use taller stringers, thicker decks, or extra glass – recall that 2/3rds of this extra weight, evenly distributed in the boat, is going to be forward of the center of gravity
• Consider foam-core pilot house and cuddy sides and roof to reduce weight as compared to plywood (2 layers of 1/8” door skin laminated on a layer of foam)
• Fuel distribution – Raise the cockpit deck 2” near the transom, sloping upward to 4” or 5” where it meets the pilot house. Fill the under-deck area with the largest fuel tank that will fit. Limit the size and location of the forward belly tank to extend no more than a couple of feet into the pilot house. Consider box tanks inside a step or seat just outside the pilot house aft bulkhead, or saddle tanks under the sheer deck on either side (similar location) instead of a forward belly tank.
• Move the pilot house 1 foot, or more, aft from the location shown to shift the weight of the pilot house closer to the center of gravity
• Use a longer, not shorter, motor bracket to move the weight of the motor(s) further behind the center of gravity, say 12” of bracket offset or even more. OR another option is to use an Armstrong-style motor bracket to reduce aft flotation - For example, if you're building a 30-foot Kodiak, have a 2-foot swim platform, and a forward or 'false' transom at the equivalent spot where it would be for a 28-foot boat ... then why not build a 28-foot boat, use a 2-foot Armstrong bracket that provides less flotation under the stern than just running the bottom of the boat out another 2 feet and putting a motor on a short transom? This would also help with preventing bow-down trim for boats that are highly-outfitted in the pilot house.
• Consider twin outboards or a sterndrive rather than a single light outboard
• Round up a little on the size and weight of the kicker/trolling motor
And most important: Note that a little bow-down trim is OK – you will generally always have some bow-down (or bow-up) trim when your boat is actually being used. These boats are light for their size and therefore they will trim differently based on how the boat is loaded, how much fuel remains, whether you are sleeping in the cuddy, etcetera. 2” or 3” of bow-down trim can be considered normal on these and will have little to no impact on performance – in this case, you may consider just repainting the bootstripe or water line to match reality and then be off … go enjoy your boat!
Show Posts
