Skagit 20 - Alaskan Bulkhead

[bruceb]

Lance-
Way back in this chain, you asked where and how many inches the keel faired into the hull. So here's the pic and the measurements. It becomes flush 5' 2" from the stern and does the transition in 5.5" . As you can see in the pic, the roller is resting just forward from the transition. The boat's been on this trailer (she's not really a trailer queen !!!!) since 1961 ! Dad showed us kids the six 100's before we went to get the trailer.....
So, in cornering, this lack of a keel in the last 5 feet allows the stern to slide smoothly, banks nicely, allowing the outboard lower unit to be the dominant rudder.
At lower planeing speeds(14-20mph), a Skagit hull with an outboard weight of 250-300lbs and a "normal" load distribution will ride on the aft 7-8 feet of the hull. Hopefully the pic I choose can illustrate this. Great idea in placing the transducer towards aft, and near the keel. I'd think that being too close to the keel might interject some air from the keel. Placement between the 1st and second air-o-glide grooves might work best.
That document on weight and moments is a keeper, super great resource.
Happy constructing !
bruceb

[Skagit Hideaway]

This Skagit had one through the hull just North of midships, which is too far foreward IMO. I took that one out and patched the hole. The Airmar recommended location is somewhere aft of the beginning of your planing surface:

"Planing hull powerboat—Mount well aft, on or near the
centerline, and well inboard of the first set of lifting strakes
to ensure that the transducer is in contact with the water at high
speeds. The starboard side of the hull where the propeller
blades are moving downward is preferred."

I'm pretty much stuck with right next to the keel, unless I modify the trailer, which is why I found bruceb's account of the improved stability of the keel-less (aft), Skagit inboard hull so interesting.

[Lyle]

I would like to see where you mount those transducers. I am trying to figure out what way I want to go with my electronics.

[Skagit Hideaway]

I took Helmar's suggestion today and cut the pilot house dash back ca. 12". What an improvement. 6" of dash now will be just enough to hide the new wiper motors, with the plotter and other stuff recessed underneith. The cuddy bulkhead moves up 12-1/2 inches to just short of the back cuddy window. Now the 400+ lbs of pilot/navigator and those of multiple batteries can be located a foot closer to the bow to help balance the weight of offshore bracket and twin outboards on the back. I haven't performed the weight test yet, but estimations using the published weight and probable distribution (optimal with 285lb single on back) indicate that balancing the new gear will not be a problem. Further, I'm thinking that 1/2" marine ply sealed with 1708 on the floor (in place of the original 1/4") plus a couple of heafty through-hull CHIRP transducers (halibut finders) will go a long way towards compensating for the cabin weight. Picts once things are trimmed up a bit more.....

Thanks Helmar!

[Skagit Hideaway]

Well, I guess before I slap a 22" extension and 640lbs of twin outboard motors (+rigging) on the back, get further along with the new AB roof and doors/windows, and start installing everything else that is perhaps going to go into this wonder cruiser (radar, gps, radio, AIS, heading sensor, autopilot, XM weather.....would love a thermal nite vision camera for when the tide is at 3am at Cape Caution - great for spotting logs and deadheads), I should figure out where the boat's various centers of gravity are, so I can keep track of them. This looks helpful:

http://microship.com/resources/cg-weight-study.html

I'll pick up a rental, 1000lb scale in the next couple of days.

Anyone weigh their boat like this - at each end?

[Skagit Hideaway]

....some interesting discussion/info here on keel reduction - http://www.thehulltruth.com/sportfis...-not-keel.html.

[Skagit Hideaway]

Fascinating, Bruce. Good to learn that. How gradual was that keel depth reduction - over what distance?

Lance

[bruceb]

Lance and Brian-
Fantastic discussion about the hull shape, ratio for slope to engine location, Gar Wood restoration.
The grooves in the hull bottom of the 20, 17, 16 Skagit had a Skagit marketing name of the Air-o Glide bottom. They were said to inject air under the hull to provide a smoother ride. Obviously they tended to give some extra stability to the direction/tracking of the hull. The unique shape of the Skagit chine out at the corner of the hull bottom allows a bite for the boat in cornering attitudes.
On 55-57 outboard boats, we've seen the keel run all the length of the hull bottom. However, the inboard boats had the keel fair/taper to the hull bottom 5'-6, where the shaft exits, forward of the stern. In 1958 the inboard hull mold was used on some outboard boats. We haven't been able to get the info from former employees as to whether they did it to improve cornering or if it allowed production increase. The inboard boats were built maybe at a ratio of one to twenty, as we've seen so few and mostly outboards.
I've ridden in outboard and inboard hulls with outboard power and think the cornering is a little more
smooth on the inboard hulls with outboard power. It's pretty subtle.
Great to have Brian's industry experience !
bruceb

[Skagit Hideaway]

reg. Box keel. I don't know what I'm thinking. LOL. The original Skagit 20 keel is a 2" wide/deep box keel, right? The Obsession racing boat is keel-less, which has high speed advantages, provided other criteria are optimal. Capping the Skagit keel would make it more a variable deadrise hull.

[Skagit Hideaway]

There is always, SH, Skagit Hideaway*, or you can call me Lance.

*The word "Skagit" means, "Hide from the enemy." Apparantly, the Indians on WhidbeyIsland (Lower Skagits) were in the habit of running off to hide in the river delta when things got tense with their neighbors.

Thanks for the info.

[Bflaherty]

George, (you've not posted a name, so I have dubbed you George until corrected)

The "1:12 rule" is a very broad generalization that Mercury made to cover almost any motor on just about any boat. If you are serious about getting the setup "perfect" then you would need to mount the more on the transom, make a few test runs with a water pressure gauge positioned roughly as far back as you intend to have the motor then measure its height when the pressure just starts to decrease... Obviously this is a lot of work and not really feasible with a boat in mid restoration. Also, your pressure points will change dramatically based on hull shape, HP, propellor shape/pitch, and even passenger load! Hence the invention of the jack plate...

At ACB we modeled our motor brackets to keep the cavitation plate on a 2:12 slope from the transom's bottom edge. The serious racing types will often follow more aggressive angles (like 4:12 or even as much as 4" up and only 2.5" back!) with a 20' Skagit I doubt you are going for speed records so I would stay in the 1-3" for every 12" setback.

[Skagit Hideaway]

Brian,

Thanks for the info/link. What a beautiful boat! Great story and pictures. I suppose the first experiment I would do, were I to do one, would be to put a laminated cap on the existing keel that extended to the edge of the first groove (what do you call those?) on either side, making it broader and more rounded - like the Obsession's keel - more box keel-like.

Brackets: Thanks for the offer. You have the experience! Is there anything to the 1" extension/12" LOA general rule?

[Bflaherty]

If you want to read a real "bottom mod" disaster, google "Gar Wood Obsession" the vintage raceboat shop has a several page history of this vintage gentlemen's racer that the owner tried, unsuccessfully, to modify the bottom to be a step hydro rather than traditional V-bow with flat stern... It's a good read!!

If you need any design assistence with the outboard bracket, let me know as I was the primary designer for all of Aluminum Chambered Boats brackets for 2007 and 2008 (fabricated from aluminum but I did everything from simple single outboards to twins with kicker and retractable dive ladder).

[Skagit Hideaway]

Thanks for your thoughts, Bruce. We purchased the boat in June, from a commercial fisherman in Sedro Wooley. It had been sitting there for a couple of years. We had no further info on where he got it. That is interesting about it's Tacoma history.

It does make sense to finish the project without making alterations to the keel/hull, in the absence of anyone elses successful experience in that regard. I'll keep researching the idea though, I'm sure.

The E-Tec 90's weigh 320lbs each. That would be a lot of weight on the back but I plan to build the offshore bracket with very light weight composite materials and enough area below the waterline, that it provides enough positive flotation to take care of that. With modern materials and good design, structural strength needn't be lacking. Then of course, weight distribution in the rest of the boat and trim have to be right.

Once the AB cabin framing/top are trimmed of all unnecessary mass (corners rounded, glass shell thinned, etc.) I don't expect it to add much more weight above the COG than a tall person standing up in the boat.....hopefully. We'll see Anyway, everything in boat building is a trade-off. Being able to stay warm and dry is worth something in this case.

[bruceb]

Hi, and welcome to the club/group !
Intrigued by the scope of your project, and love to see the life being breathed back into a 55/56
built boat. These are extremely solid in the build of the hull materials and stringers. Like the look of how the upper windshield is working with the rest of the boat. Compliments the package, overall. Have recently been doing research on the weight of the boats as stated by the factory and the 55/56/57 design is listed as 45 lbs (1025lbs) heavier than 58(980lbs). 1959 and later is another story, as the factory sought to lessen the weight even more, but my chart numbers show increases in 59, 60 and 61.
I first came across your boat 11 years ago in Renton, where the owners referred to it as a Bayliner Skagit.
So my guess was that they had named it because it had the Bayliner windshield mounted on top, but ,no, the family member assured me that it was a Skagit model, built by Bayliner in Arlington. Any attempts on my part to re-adjust history met a brick wall.... then it showed up in Tacoma ? for sale on CL and assume you were the lucky purchaser.
Have thought of the same idea of adding some V to the bottom, specifically a 14 Sportster I was restoring a few years back, and reality of time management came between me and the execution. Possible to do, and the materials available today, as well as some very detailed hull designs to view on the internet could make it a reality. I would defer to Brian's knowledge of "tried" projects as a starting/ending point. Very good to see other's projects outcome !!!!!
The act of riding in a 20' Skagit express of your year is the best experience to determine your course.
Also keeping in mind that the perception of your guests onboard is very much determined by your choice of speed and water conditions. I've seen some spend time and money to restore a boat only to find their
spouse doesn't like the boat, mainly because it's operated at excessive speeds for the riding qualities of the hull.
Adding weight at the bottom of your hull ( as in adding a V shape to the bottom) would be a welcome balance to the weight of the Alaskan bulkhead. The structure above adds a welcome fore/aft balance but brings the question of high center of gravity in relation to the basic weight of the hull and cabin. As you mentioned the twin etec 90s ( great choice), lots of weight, though, not because of transom structure as much as the reduction of freeboard at the stern.

Quite a bit to consider, she's looking very handsome !

Thanks , Bruceb