Comparing Hulls

[Fisherman]

Soooo...I'm interested in some feedback as to what features you guys like/don't like about several hulls. Not interested in sheerline so much nor the cabins that are in the photos. I am interested in how the boats will perform offshore. I realize looking at a few photos does not replace a sea trial. But I would appreciate feedback as to how you presume they will function in offshore conditions. I'm looking for thoughts such as "Hull "A" will be more stable but probably pound more", or the deadrise in Hull "X" will probably make it unstable while drifting", etc.

A 28' Pacfic Hull


A Lee Shore Hull


A 28' JaxonCraft Hull


A Bayweld Hull

[welder]

The steeper the dead rise(24*) and the sharper the bow entry the better the ride at higher speeds offshore but to attain that smoother ride offshore the MORE fuel it takes.
The shallower the dead rise ( 18* ) the less fuel it takes to stay up on step or plane and the more stable one is at rest.
There is always that trade off of ride Vrs mpg kind of like the gears in the rear end of your truck , the 4:10s are the 24* DR and the 3:55s are the MPG BUT the 3:73s are the best of both worlds.

Your next question is ....
What do I want this Boat to do for ME , do I want it to go 70MPH in 3 to 4 footers or do I want 30 MPH with a huge load and a HAPPY wife and kids.
You will find that most guys will just get up on step [Plane] then find the HAPPY SPOT speed wise where to cruz to get the best MPG .
Most boats above 26' will start to take some serious Horse Power/KW to move around which means a serious fuel bill so what I'm trying to say is .....This hobby cost a buttload of money to play.

You answered your own question in your post ... Seatrial is what is really needed to compare hulls/rides, let your Butt and knees tell you what hull to get and how much you want to spend on power and fuel.

[welder]

By the way , now that I have the "Scorpion" off of my arm, NO JOKE, those are some VERY nice hull you posted.

Got to love the BUGS in Texas.

[dawgaholic]

That Jaxon Craft has some beautiful lines...

Don't expect any relief from fuel cost increases anytime soon....

[Fisherman]

Would you presume the Lee Shore hull would be the most stable, yet most probable to pound (less deadrise) whereas the JaxonCraft will be the highest deadrise out of the four? Would the Pacific and Bayweld fall inbetween?

[kmorin]

fisherman, welder has given some base lines for comparison but there's more to consider. Ride is a relative term, meaning that a very heavy boat with less dead rise will ride 'better' than a very light boat with more deadrise and the reason is the movement of the hull 'about' the pitch of the center of buoyancy- closely coupled with the rate of deceleration when entering a wave face (slam/pound).

Another factor is the speed factor regarding the bow's forefoot; the faster you go the less forefoot you want but the slower you travel the more forefoot you want. So... hull A and D have much more forefoot curve (keel in profile in the last 1/4 of the bow is more deeply curved=forefoot. ) and hulls B and C have a 'cutaway' forefoot. This means that hulls A & D will ride more smoothly below 25-30knts and lift to a swell (more pitch by the bow) in any seaway than hulls B&C as the hull has to be more deeply immersed farther aft along the waterline for any displacement to occur.

Therefore the first and last hulls will be 'drier' in a head sea but have more pitch so they will not go as ultimately fast without 'launching' as the middle two hulls. The more cutaway forefoot boats will tend to hit harder in short seas since they don't pierce them with the extended bottom curve in a 'slower' entry, especially if the wave shape and size is nearly the same as the forefoot curve; then the hull would wet all along this area and the transition from dried hull to wetted can create a drag change that is dramatic.

This is countered by the hull moving much faster than 25- then the hull more or less bridges smaller seas and does not pitch as much by the bow, and the means the impact area of the leading edge of the waterline is farther aft where the V is more pronounced in the deeper V hull's.

Roll, or side to side movement, of the hull around the fore-aft axis of buoyancy is less for hulls with less deadrise as welder has mentioned, but... the complication is not just top speed can be greater with more deadrise its the fatigue factor of deeply V'd hulls. The roll all day when not running is extremely fatiguing so unless you're planning a bikini freighter- welder's idea of a compromise bottom shape is great advice. Hull A and D look more similar in regard deadrise than B or C where C looks deepest and B looks the most flat angle? but I can't tell from the pics. I think you'd have to see the transoms to make a valid comparison?

Running into a head sea is not all forefoot dependent, but ride in a short <4' sea at speed is also influenced by displacement where a 1959' Cadillac will ride at 70mph in the back roads almost like you were on the Interstate but a 2013 Volkswagen will feel rough and bouncy, by comparison, on the interstate and may not even stay on the road if driven at 70mph on the roads between corn fields?

So hull D is the smoothest ride in short head seas and is more 'full' in the plan view waterlines so it will the driest in that head sea as it will have the largest pitch vector due to the full 'shoulders' of the bow and especially the topsides above the chine. Next in the same conditions is A then C and finally B (edited) where the buttock lines and waterlines show descending 'fullness' forward.

So in mid range speed hull D is going to enter and run the smoothest then followed by A as both hulls have more forefoot. The cut away boats, C and B will not run as well at the lower speed compared, but since B has less deadrise than C it will impact them most at these speeds where the leading edge of the running waterline is the entry. So C is the ultimate higher speed craft of all shown, followed by B but with the smaller deadrise than A (as it appears) the performance of A and B may be similar depending on power and all up displacement? D is the most (final state) 'seaworthy' as it can take more by the bow than the others in a displacement mode or under 8 knots 'walking' when weather is so heavy nothing can 'plane'.

(so) when pushed to their top end C is the fastest, B next then A and finally D (this depends on the displacement and power). But.... steering becomes an issue with a deep forefoot as the wetted areas will be most imbalanced by an uneven wave entry, the most pronounced will be the most full bow hull D-therefore limiting top end speed in high and higher sea states. Hull D looks the biggest displacement also -therefore the power to push her to high speeds (>30mph) looks like it will be the most as well.

I hope you understand I'm just echoing and expanding on welder's comments; there's nothing for free in marine design, it's all interrelated. Displacement, hull lines, power/speed and sea state all contribute to 'ride' so deciding what you'll do with your boat is the best advice already given. Once you can define your 75%-90% use pattern you can then evaluate a hull for 'your' conditions- before that things are a bit theoretical.

But even with that, you can look at the hulls and make some generalizations about the form and it's outward shape. I hope the types of comparisons I've made were in the general spirit of your question(s)?

cheers,
Kevin Morin

[Fisherman]

Kevin, thank you, thank you. Exactly what I was looking for! I have read through your post 3 times now, will read through some more and probably have more questions later.

One area I'm a little sketchy....

So hull D is the smoothest ride in short head seas and is more 'full' in the plan view waterlines so it will the driest in that head sea as it will have the largest pitch vector due to the full 'shoulders' of the bow and especially the topsides above the chine. Next in the same conditions is B then A and finally D where the buttock lines and waterlines show descending 'fullness' forward. However, when pushed to their top end the reverse order will apply to steering as the wetted areas will be most imbalanced by an uneven wave entry, the most pronounced will be the most full bow hull-therefore limiting top end speed in high and higher sea states.

Where does hull C fit in?

[welder]

Kevin, thanks for bailing me out.

[kmorin]

fisherman, I got my letters confused but I edited that post- maybe read ist now for more (hopefully) clarity?

Welder, I was trying to expand on what you said so fisherman had more guidelines for his evaluation. I agree with your summary, just trying to tell 'the rest of the story'.

Anyone can make a few sketches of these hulls in profile/side view and compare them, then looking at the bow areas, we could also decide which if the four is more rounded when looking down on the hull. Once these two comparisons are made most of the observations I've made will make more sense (well hopefully they will?) as these are the two major differences in shape of these four hulls. D is most full, A is next, B and C are not as clear in the photos but I'd guess that C is the sharpest deadrise of all the hulls shown? So my remarks are based on the idea that the sharpest (with the least forefoot) will go the fastest with the least 'veering' of the helm, and the roundest will be the most difficult to steer in the same speed and wave form.

On the other hand.... the roundest will lift the bow the most in any given wave face so that means D is the most able open ocean boat, overall, and C the least as C needs to travel at highest speeds to take advantage of the cut away forefoot and high deadrise angle otherwise roll will be a huge movement. B will likely have the highest impact/slamming of all the hulls due to the limited forefoot combined with the modest deadrise.

This discussion does not address each hull in a following sea; just a head sea.

Cheers,
Kevin Morin

[welder]

Kevin, expand away , I was hoping you would come along .
We enjoy and look forward to your input, keep it coming.

[Fisherman]

Kevin, thanks again. It all makes sense. My next question was going to be about a following sea, but I realize there is a lot more involved than just the bow. There is a thread from several months where you explained the different factors that are involved with how a boat handles in a following sea. Boat balance is a major factor that enters my mind...probably hard to tell from a photo.

But....if you have any comments about how these hulls will handle in following seas based on what you see in the photo's, that would be great...I'm all ears.

[kmorin]

fisherman, the main question for these boats' handling in overtaking seas, if that's what you mean by following seas (?), would be the power versus displacement of each hull. Hull shape will be a big factor but if the power to plane is in a hull then it makes or breaks handling in following seas.

If you mean how would they run "overtaking seas" in the same course direction as the boat? then we'd have to know seas, displacement and power to have that discussion and that's a pretty wide set of variables!

With enough power to push the bows up, and therefore, out of a wave 'back' they'd all do fine, if any of the hulls had too little power then hull balance would become more important but to gauge that we'd have to see the lines and waterlines and a horsepower to weight ratio.

When waves overtake a hull that boat is generally at displacement speeds, <7-8 knots, but these are all planing hulls. Because they can plane, the power is assumed (my personal favorite form of [il]logic) to be enough to push the hull up a wave back even if the bow were buried. So if the hull were to slew or if one of these hulls were to have unequal drag tending to veer the bow to one side, adding power and opposite helm would be enough to correct course and remain full control.

if the hulls were to run overtaking the waves then again all up displacement would influence the 'ride'. Also where the hull 'landed' or laid down on the wave it was overtaking would be a matter of speed versus deadrise, slower speed the entry would be more and more forward, and faster speed the entry would be further aft. So at higher speed the C hull is again going to run well overtaking waves with its assumed higher deadrise, but the heavier displacement D hull may ride smoother yet?

we're really working with more variables than makes solid sense; welder's recommendation to test ride/drive the boats is best, not easily done if they're thousands of miles apart, but the final word.

Cheers,
Kevin Morin

[jrbaldwin]

One note on hull B in a following sea. My 22ft has a very round upper bow and I have to be careful not to go to fast and come of a wave and hit the next one to hard. If I do the round bow does not cut thru but can plow resulting in a rapid deceleration and sliding sideways. Was surprised once when I was not paying attention in a very short 5-6 sea.

Jim

[mojomizer]

Dialing this in a bit......... Albacore fishing...... 40 miles out.....Wind coming from the Northwest afternoon 20 to 30.
4 to 8 foot seas at 6 second intervals. Trolling 6-9 kts.???????

Channel Islands same weather????? but can duck behind an island.

Going out fairly calm...... coming back in following seas. Going out Northwest coming back Northeast otherwise fighting the afternoon snot???????

I know alot of assuming........ but details on sea conditions and how you plan on using her helps with hull performance questions. They all work great in glass like conditions.

My butts done writing carry on.

Jr. your Avatar makes me queeezzzy. Is that a true angle??????

[Fisherman]

Let's add another hull.

A Fishrite Seastorm (Hull E)


Kevin, where would you place this hull in the lineup? Seems as if it doesn't have as much forefoot as Hull D, but more than Hull C. Maybe a good compromise between the C and D??? Maybe closer to Hull A???

[Fisherman]

Dialing this in a bit......... Albacore fishing...... 40 miles out.....Wind coming from the Northwest afternoon 20 to 30.
4 to 8 foot seas at 6 second intervals. Trolling 6-9 kts.???????

Channel Islands same weather????? but can duck behind an island.

Going out fairly calm...... coming back in following seas. Going out Northwest coming back Northeast otherwise fighting the afternoon snot???????

I know alot of assuming........ but details on sea conditions and how you plan on using her helps with hull performance questions. They all work great in glass like conditions.

Mojo, right now I am wanting to learn the functions of design, not so much as pick out a hull for my use, although hopefully in a few years I can be in that position. I want to know the theory and mechanics behind designs and be able to predict(?) how hulls will react to different conditions.

[kmorin]

Fisherman, I'd put the new Hull E closest to C as the chine of A is much higher compared to the keel in A's forefoot; so that A is closer to D than C or E from what I can tell. Still like to have all three views or a lines plan set, to make any kind of 'true' statements.

But this surely confirms mojo's reading of calm water running being for 'free'.

In this picture we're looking at a hull that just left a wake crossover, or is porpoising, or is pretty light** displacement since it's running on the last few feet of the hull.

Trying to compare these hulls' performance as you want to do, is what mojo and welder are trying to do. What you need to give weight to, in this discussion, is the sea conditions, as mojo does. The hulls perform differently in different sea states, so they're stressing the idea that we'd have to state the conditions; then discuss the hulls.

I agree, we can make generalizations but it's more realistic to assign a sea state and weather condition, then pick our performance goals in that environment -THEN compare hull performance by hull form.

** hp to wt/displacement ratio

Cheers,
Kevin Morin

[mojomizer]

Kmorin I wish I was eloquent and precise as you in my writing. The passing of knowledge that you give so freely, is so much appreciated.

Fisherman...... ahhhh good topic. I would also like to learn about different hull designs and the reason why the designers choose the many different hull shapes and combinations. I do see a pattern in different classic designs that are used regionally.

Thank You for posting

[Fisherman]

Kevin, if you like, I can try to find photos and more info if I can have some time to do it. Perhaps add a few other hull designs too. I am very interested in learning about hull design and will be glad to exert some effort, especially if others would find it interesting/usefull. Would you like for me to start another thread with more complete info, or start over below in this thread? I think it would be best to try and keep all the info regarding each boat organized.

Robert

[kmorin]

mojo, thanks for the kind words, I'm always glad to be part of AAB.com's conversations about shape and building.

Fisherman, we can keep moving here, or move if you prefer, its always good to check with the welder to see if he's got any ideas about organizing posts. One thing I'd like to suggest is a quick review of the viewtopic.php?f=45&t=2558 Helpful Info>Lines of a Boat post will be helpful to allow us all to use similar terms and observe similar aspects due the real shape of these hulls.

I'm not saying you're not familiar with hull lines and I realize my example there is just a flat bottom dory, but I'm hopeful that future illustrations will be more effective if you've spent some time with a lines plan set to enhance your shape visualization.

I don't think we're going to get the builders to post their lines!! so we'll have to make some guesses but I think we can continue here by 'stealing' the lines of some of these hulls as examples for the discussion?

I'll try to get some sketches done to help by comparing some of the shapes.

Cheers,
Kevin Morin

[mojomizer]

I have alot of Catch up to do......Well did some basic research found this article. The heading caught my eye. A very wise man once gave me this sound advise...... It stuck with me.

http://transpeninsularoutfitters.com/ar ... esign.html

Found this freeware to play with also....... http://hullform.com/

A little bit over my head but found it interesting......... http://www.shipstructure.org/pdf/218.pdf

Hope it helps some

[goatram]

Mark some good reading there.

I do see where we need to know where the boat will be based and used at for the design factors. Another thread to watch as Kevin Schools us some more.

By the way I have learned so much from the Internet by lurking and participating in some forums. I lurk in a lot and always under the goatram name.

[Fisherman]

Kevin, I have found a few more photos of the hulls I previously selected. Unfortunately, I was not successful in finding photos showing all the sides of the boat as you would like. If I am able to find them, or if someone else can find them, I will add them to this post.

Here we go...

Hull A
A Pacific 28 Hull



Hull B
A Lee Shore Swiftsure 28 Hull






Hull C
A Jaxon Craft 28 Hull







Hull D
A Bayweld Hull






Hull E
A Fishrite SeaStorm 28 Hull

Deadrise 16-18* at the transom






Hull F
A Seawolf 28 Hull

Deadrise 12* at the transom, 40* at the bow






Hull G
A Wooldridge Hull





Hull H
A Cope Design - suggested by Sculpin

[kmorin]

We’re not really going to get into a full blown boat design post here, at least I don’t anticipate that because there’s lots of hours of study and working out problems and trying to design (draw and calculate) for yourself as you study the overall topic.

But…. (everyone likes a nicely rounded stern) we do need to get some of the basics shown at the beginning so we’re not all taking about different terms and shapes while making generalizations that defeat any resultant conclusion(s).

I don’t mean we’ll solve the question of what is a ‘perfect hull form’, however, I don’t want to type a bunch and end up with the membership more confused than when we started trying to discuss the hull shapes of various different welded Aluminum Alloy Boats.

So let’s get some terms out here first, and if you use these terms differently than I’m showing them, or if there are fundamental differences of understanding (?), why don’t we get them out here and solved before going too far?

Then let’s discuss some shape issues from a common sense point of view. I will provide some sketches and some text and we’ll see if it makes sense? IF not??? Then; I propose we refine the ideas at that point because, again, we’d need to agree to some basics before moving to some sort of shape and performance discussion.

Then we could put some of the shapes used to illustrate the concepts and proportions into ‘waves’ and see if we can come up with any shape versus performance conclusions?

Most of the definitions can be looked up on Wiki or online and there are many texts on these subjects that provide far more insight than I’m going to attempt. These words may be used somewhat differently by different people in the business so please make sure any questions are posted so we can iron out misunderstandings?

Before computers made 3D hull’s so easy to display and view from infinite number of points; boats were designed by drawing the hull as though it were in a ‘glass’ box. Traditionally, the boat shape was viewed from the Top or Plan View; one End of the box or Section View sometimes called Body Plan View and; the last traditional view was from the side or Profile View.

Each View could show the widest curves or outline of the hull but that would not ‘tell’ the designer or builder what shape the boat was between the widest part shown and the viewer.

So a series of ‘hull intersections’ were ‘cut through’ the hull. Each traditional View has a series of planes cut through the hull parallel to the ‘view plane’. The Plan View has waterlines, the Body Plan has Stations (sometimes called sections) and the Profile View has Buttock Lines (most often called butt lines)

There is an article here at AAB.org that discusses these, planes and views and I expect anyone interested to give a quick look so future remarks aren’t confusing. There are great discussions of this same topic on the “CelluloseBoat” (people actually make boats from pieces of dead plants) and many authors have written extensively about this means of viewing a hull.

One more remark about "lines plans” as the sets of traditionally drafted views of hulls are called, they are exactly like looking at a terrain map with elevations drawn as odd shaped contours of peaks and valleys. In fact the Plan View showing the many waterline contours is just like looking down on a mountain on a contour map with cuts taken at each elevation (called waterlines instead of elevations contours). Further you just need to use that idea to 'view' each of the other two viewpoints' (Body & Profile) 'maps'.

Next we should introduce some other terms.

Cheers,
Kevin Morin

[kmorin]

Links to some definitions of terms

http://www.glen-l.com/resources/glossary.html
http://en.wikipedia.org/wiki/Hull_%28wa ... t%29#Terms
http://www.fish.state.pa.us/anglerboate ... athull.htm
http://www.boatsafe.com/kids/022298hulls.htm

After reading some of these links, you probably realize that there are some lines' names associated with hull shapes? Keel, stem, sheer, chine, or chines, flare, flam, tumblehome, forefoot, rake, hollow or powder horn, and many others are all terms used to describe a specific line or some characteristic of that line in one view or another.

Not all these lines can be seen in all Views, for example the Keel is simply a straight line in the Plan View but becomes more an L in the Profile View. And, not all characteristics of a line, in one View, can be seen in all Views.

Where can we find the ‘angle of deadrise’? Only in the Body Plan View (section, stations) as that is the only View where the boat’s hull is viewed so the angle between the horizontal (waterlines) and the bottom’s slope upward from keel to chine is shown.

Is the sheer hollow or powder horn? We can't see that in the Plan View but we can in Profile. Is the forefoot deep or shallow or even 'cut away'? We can't say at all from the Body Plan but we see very clearly from the Profile View.

If we’re going to discuss how the relationship of these lines or hull intersections relate to any boat’s performance; then we have to be able to ‘speak this language’ so we’re not mired in ‘lingo’ or terminology. If you don’t have a handle on these terms and understand what is being said in the various remarks or explanations: YOU have the obligation to post a question to clear up those questions.

Many readers of the site, and all the designers and builders, understand all of what’s being discussed and have made their own conclusions about these various ‘questions’ or correlations between shape and performance. I don’t expect the pro’s to be too interested in our back and forth, here, but welcome their correction if we get ‘off topic’.

What we all need to do is to begin to use our imaginations to 'see' in 3D because only in 3D can a boat's shape be fully understood. As we begin to train our eyes to collect information to accumulate a 3D model of one hull compared to another; we need to describe our information ( to one another) from a collection of terms that imply which line from which view we are discussing.

a non-trivial undertaking.

One reason we're not going directly to 3D imagery is because of the distortion that happens in 3D. Unless you're used to looking at 3D skeletal frames or hull intersections; 3D is more confusing that the three traditional views for most people.

Cheers,
Kevin Morin