Feedback on my first hull design

[Tim B]

I have encountered that problem with free software, John. However, it is usually ok for getting an idea, and since Vince is largely using his own formulae I don't think it's a huge problem. Buildability of twisted panels is a very different story. You might notice, that on my powerboat, whilst there is no flare there is a fair bit of twist on the hull panels. Twist is no problem, as long as the boat is laid up from thin panels. ie 3mm + 3mm rather than just 6mm. Generally, developing the bottom panels can pretty much be done on the boat when the bulkheads, frames and stringers are in on a hard-chine hull.

That's a problem for later, though,

Tim B.

 

[Lecter]

VinceS i'm sure your an expert compared to myself.
I like how you hull looks, you said something about instict (i think, i read that a while ago)
how did you learn what you know and can you recomend any resources?

Much thanks.

PS:-how have you gone about designing it?

 

[VinceS]

Lecter - I think you might be wrong, I know very very little. Anything I know I have learnt from this (and other) thread on this forum, and from examining pictures from the internet.

The main resource I can recomend is curiosity, persistance and the internet. A boring job helps too, but not required if the curiosity is strong enough.

As for designing - Draw on paper and see if I like it, then try to incorporate the rules others have suggested (like the 20 degree deadrise etc) It can be a little tricky to incorporate these two things (like when I tried to increase the deadrise from 20 degrees to 35 degrees at the bow) but if you draw one profile (side on, in my case) and then you can decide key points from the top view, like maximum width and location of maximum width, curves, etc and then some key points from the back, slowly these things start to come together into something. In my case I am confident this boat will go well because of the few rules I have followed, and the feel of it. it feels good.


-- In other news, my mother in laws 13 meter tourist boat hit the rocks and needs an almost complete rebuild - the hull is totaly wrecked. Her staff made an expensive mistake.

 

[Tim B]

rules? who said anything about rules? Obviously there are regulations which will work as guidelines.... You can basically make a boat any shape and put power into it until it goes at the design speed. Do this enough times with small changes, and you'll have a reasonably efficient powerboat... The suggestions for deadrise etc. (and looking at other boats) just enable you to start from where everyone else left off. And thus reduce the need for the 100 or so years of trial and error.

I'm sorry to hear about your mother-in-law's boat, vince. However, if you can get down to the yard fairly regularly and talk to them about how they're doing the repairs and watch what they're doing you'll get a very good idea of what goes into a boat (although bigger than yours) and it may give you some ideas.

How are the drawings and the model coming along?

Tim B.

 

[mackid068]

In other news, my mother in laws 13 meter tourist boat hit the rocks and needs an almost complete rebuild - the hull is totaly wrecked. Her staff made an expensive mistake.

And how do you do that? But remember, you can't fix stupid...(not your mother-in-law, regardless of how much you like her , but her staff)

 

[VinceS]

The story goes as such, the boat had just arrived from the ship yard and her staff had sailed it 100 miles to her place. They had parked it just out from the rocks so she would see it as she drove around the headland the next morning. During the night there was a storm and obviously wasn't anchored correctly, anyway, she ended up on the rocks with a total wrecked hull. The marinised 2.8l nissan engine is basically the only bit to survive without any problems.

Tim B. - Thanks for the interest, they are coming along quite nicely, I still haven't had a chance to bring the drawings in to work to scan them. The model is semi-built and I am making constant adjustments.

 

[DPetersen]

You dont see tumblehome like that because you cant pull it out of a one peice production mold for fiberglass building. They tried pulling the bow first and going straight forward out of the transom part of the mold but it destroys the mold finish after a few pulls. I have a seen al ot of sixties boats that have a chrome gunnel strip on the side where the seam for a two part mold was used, but that is also not practical. Two part molds for that type of transom require gel coat repair and detailing after pulling. PITA to patch and detail.

The hull has endless topics of discussion. If you cold mold it over a male mold, you have a shot at the deadrise progression forward, but .... why?

Pick up ted brewers book on understanding boat design and go to the boat show to take a look at planing boats. Not the Regals etc but the fish boats. Youll notice flat sections aft until about 35 percent of the waterline length going fwd from the transom. Youll see a sharp edge where the transom meets the bottom aft to prevent back vortices and spray. Notice flat chines and how they allow the boat to widen for static stability even at the higher transom deadrises.

Also, as a bonus, notice how even the top makers use wedges at the keel transom intersection. Its a dig int he mold that means they thought the boat porpoised too much at normal trim and drive height. They wedge the heck out of them and people dont notice. Bayliner (believe it or not) has one of the only decent testing programs. Also see how the fancy hull features are all basically running dry when the hull is planing and runnign along at 4 degrees. All the fancy notches and especially steps (OMG) are bogus, made for you to look at while its in your garage. Anyway, study and have fun and keep modeling. Cool start.

Dave

 

[VinceS]

I found someone to build it for me, out of mahogany and fibreglass. going into some more meetings this week or next.

 

[TomE]

Hi Vince, I'm also new to boat designing and building and found this thread very interesting! I've been toying with some ideas in my mind for some time, and looking at various designs found around the internet. I started to get my tears wet when discovering the "Babyface Nelson", and then I found the "Alpha Z", wich really took my breath away. Very different boats in deed, but man are they beauties...

I'd like to quote Corky Bell; "Don't be afraid to copy, just make soure you are copying the best". I think this is a very good way to start any design process, no matter what you are making. I'm not telling anyone to rip off somone elses design entirely, but look thorougly trough other boats that are of similar size and purpose as yours. Pay attention to the differences between the cheaper/sipler design vs. the proven performers.
I strongly belive that this will keep one out of very many fall mines, and give one a very good head start.

As to the variable deadrise forward; there is a connection (in lack of better word) between keel line, and chine line and the deadrise. You cannot change one without altering one or both of the others. I found a couple of boats that have the performace I'm after, and used as guiding for my drawings - making lines that appeal to my eyes, and resembeles those that are proven to work.

Any chance we could be let in on a updated with pictures of your project? Or have they becomed classified industrial secrets by now?

Also, and this is what interest me in particular: How are your somone going to build you boat? In respects of maretials, thiknesses etc? Is it going to be stripplanked and then epoxyglassed inside out and skinned with mahogany? Or just stripplanked with mahog. directly? Thiknesses of layers? Frames? Stinges?

 

[TomE]

I don't have the ability to make a proper 3d wire image right now, but here is a side view showing the spring (?) chine and keel lines.
The boat is planned to be 25' and have a concave V-bottom, 24 deg aft of step, 28 porward, but increasing from where the chine line goes upward. It also have concave panels from chine to spring forward of midship and some tumblehome/barrelback aft.
I really like the lines I have found so far, and I'm relatively confident that the boat will be able to stand more chopping than what would make up my "wet-pants-limit".

My main boats for inspiration are:
Alpha Z - www.vandamwoodcraft.com
Hydrolift S-24R - www.hydrolift.com
if anyone takes interst? Input would be appreciated! (sorry for trying to steal you thread Vince!

 

[Tim B]

This thread has suddenly gone a bit quiet... anyway... TomE it seems that you really want to do something a bit smaller than my design, and a bit faster than Vince's. That's quite a sound idea. I wasn't worried about length etc. when I drew mine, I liked it and it was for me, so that's what mattered.

Seakeeping-wise, it's always hard to know what a boat will do in waves, but follow everyone else and it shouldn't be too bad. You'd be well advised to work out what sort of areas of the design you're interested in, then go around a few yards and take photos, sketches, sightings etc. to get an idea of how it's been done before. Interiors are a bit different, I usually go to a magazine in that case.

Vince, I hope the boat's coming on ok, you've obviously been working on it a lot,

Tim B.

 

[alex fletcher]

looks like a very wet boat in any sort of chop as it has very little bow flair