Option 1 Design Ideas (Trailerable, 300 mile range, Coastal hopping)

[Willallison]

ok, here it is. These are images of the design I have been working up. They started out as a result of my ideas for a ULDB, but have since evolved into something a bit more along the lines of the boat I suggested for option 4. Some aspects of it are probably just as applicable to option 1 - the winner of the poll

There are still some aspects of it which need fine tuning - any thoughts / suggestions / criticisms most welcome.....

[Willallison]

hmm
Don't know about all of you but I can't see any pics.......
I'll have another go at that when I have more time

[Jeff]

Were you trying to attach a DXF file? I just realized that I gave you some misinformation earlier. I have now added dxf and iges to the permitted attachments in case that was the issue, though gif and jpeg are still preferred since they will display inline rather than as a link.

Sorry about that.

These formats will display inline when attached:
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These formats will display as a link when attached:
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Also max file size is currently set at 400Kb. If anyone wants to provide a larger file than that for others to download or a format not listed, let me know or send via email to webmaster@boatdesign.net and I'll either change the settings or put it on the server for you.

[Willallison]

ok, here goes again.....
probably should really have posted this in the new thread about our project design but anyway......

[RobCEW]

I voted for option 1. As much as I like inboards, (I own one) the outboard (s) option seems more practical for trailering and launching. The cost of new outboard motors seems extravagent compared to conventional inboard engines, but the associated equipment required for inboards pretty much offsets this $ differential.

My suggested hull design would be a modified V with 13 degrees deadrise at the stern. LOA would be 28' allowing for scarfed sections of MDO plywood. Max beam - 8' 4". Transom beam at WL would be a hefty 90" and 88" at the chines. Being a sucker for tumblehome, the transom at sheer is a nice neat 7'.

If I figured right, the bouyancy would allow for a good 900 lbs. of engines hanging off a bracket (not including bracket wgt.)

In profile, the cabin lines would would start well forward to accomodate bunks and a standing head amidship. The forward placement of quarters also helps out with that pesky cg/cb as well as providing some cockpit room for dancing or laying about.

Hull/Cabin - 2200 lbs Disp - 6440 lbs.

Conventional hard chined, oak frames and stringers, conically developed hull (less slap and we can deal with the spray later) and lots of bright work!

I don't know about you coastal guys, but (and I bet Gary might agree on this) the ramps in the Land of 10,000 Lakes are not exactly inboard friendly.

Oh yeah, I just got my color chart in the mail from Kirby's!
I can hardly wait to get into That!

Rob

[duluthboats]

Wow! Will,
You have been busy. I like the looks very much. It has some thigs I didn't thik of, and I can see twin O/B hanging from the transom.

I wanted to make sure that all reading this post saw this.

www.rotarypowermarine.com

From this thread.

sterndrive for 16 ft powerboat


Gary

[Jeff]

Just a note that I've done a little bit of reorganizing and pulled some of the design ideas for Option 1, the winner of the last poll, into this new thread.

Option 1 - Trailerable, couple, home build $
1 Coastal hopping
2 Trailerable
3 Range 300 miles
4 Crew, 2 minimum
5 Price range, under 50K US, for home built.
6 Must be able to carry on a normal conversation at 3/4 throttle.

I'm glad to see that some great ideas are starting to emerge. Onward on upward from here...

Related Threads:
Paul's overview of the next steps:
May I have the envelope please...

Outboard vs. Inboard propulsion discussion:
outboard vs inboard

What Units - Metric?
What standard?

and 8knots initial design (because I like it )
the 1 hour sketch

[Willallison]

Gary,
I've been busier than you'd think - I'm only just learning how to use my surfacing program, so there's about 5 times as many points, lines surfaces etc as there probably needs to be !! - but I'm getting there....

As far as being suitable for option 1 - the model is currently as follows:

LOA 11m
LWL 10.75m
B - max 3.75m
BWL 3.75m
displacement approx 6000kg

so its not exactly trailerable. Scaling back to beam 2.5m would produce a length of about 7.3m - about as big a boat as one can comfortably tow.
Features such as the walk around decks might be a bit more difficult to accomodate in something that narrow. I'll have a bit more of a play......

Is it time we started thinking about some basic parameters?
Here's a few suggestions:

Loa 7.5m
Max beam 2.5m
displacement <2500kg

[Willallison]

Some alterations to above:
the displacement at 11m LOA os closer to 4500kg.
Scaling that back to beam 2.5m puts the displacement at around 1400kg.
Both I would suggest are lighter than it is possible to build?

[duluthboats]

Will,
I had your boat in my mind last night when I was trying to sleep.
I was thinking about the walk around deck. It took me some time to realize how small the cabin would be with a 2.5m beam.

Thanks to Jeff for getting this thread started. I asked him to do it, then tried myself. I made a mess of it. Jeff cleaned up my mess and didn't take away my password. This is a great forum and I'll be more patient in the future.
Gary

[tom28571]

I dissagree that it is diffcult to build a 7.5m x 2.5m boat at a displacement of 1400kg.

My boat is 7.32m x 2.44m and displaces 1270kg in full cruising dress including crew. Complete hull weight is 840kg and trailing weight is 998kg.

We need to agree on what is meant by displacement. I suggest the following:

Boat weight = weight of hull and all fixed gear except engine installation.

Trailing weight = boat weight plus engine installation plus some cruising gear and 1/3 load of water and fuel.

Displacement = full cruising weight including all cruising stores, gear, fuel, water and crew.

Unless we are willing to accept a speed "dead zone" between about 12.5km/hr and 25.5km/hr, the kg/hp and kg/sq m of bottom planing surface will have to be kept near and preferably below 30.4kg/kw (50lb/hp) and 240kg/sq m (50lb/sq ft).Most designers like the weight per hp to be less than this. Dave Gerr says it should be 25lb/hp. That is probably true of heavy boats but I know that a boat with light bottom loading will do much better than that.

Almost none of the planing boats on the market will cruise in the dead zone I mentioned. They have bottom loading far exceeding the limits I gave and therefore require power much greater than the above suggested limits. To me the optimum cruisingspeed is right in this dead zone. Having to run at a higher or lower speed in order to be comfortable or economical is not my idea of cruising fun.

This is my first go at metric units in quite a while and I hope I did not screw up too much.

[Willallison]

Tom,
I'd be delighted if we could keep the weight down to the sorts of figures you are talking about - I've spent years (and years and years...) as a "doodling" designer - drawing little more than profiles & arrangements, with the occaisional set of sections thrown in - so this "real" stuff is somewhat of a learning curve for me. You've already proven that it can be done, so I'm not about to argue....
Further, with an all up weight of under 1300kg, it makes towing a breeze.

[Willallison]

For those who have not seen Tom's lovely mini-cruiser before, it can be seen here
http://boatdesign.net/forums/showthr...=1250#post1250

[ErikG]

Just for your information...

The US might be reluctant to change to the metric system but even here in Sweden (where we've alays used metric) we use knots for speed and nautical miles for distance on water.
From a technical viewpoint calulations would be much easier to handle if they where all completly metric, ie. we'd use meter/second as our speed reference and meters for distance. I think there are/have been some discussions about this within the European union, but I don't think they ever dicided about anything.

I don't think any designer would use Km/h ever when it has anything to do with a boat. Well one exception then... Trailering speed limits, road speed is measured in Km/h over here.

I' dont want to put you off not using metric at all, just so that you know.

ErikG

[mitch]

The hull design reminds me of the GermanPatrol Boats used in ww2. I woud op for more of a rounder and more flair in the bow. It would make int a more plaining type hull.