Building Flareline 18, would like to extend by 2 frames...

Bert just my 2 cents

if you want a longer boat buy plans for a longer boat

the plans that you indicate are basically a very old design

http://www.bateau.com/products.php?cat=17

have a huge variety of modern designs that are much easier and faster to build AND LIGHTER

skin over frame is all fair and good, for traditionalists, but a lot of work

 

Thank you Tom,

But there are no plans for an electric boat which can go onto the sea. I have lots of books, boatbuilding with plywood by Glen Witt, Yavht Design Details by Roger Marshall, Yacht Design by Larsson and Eliasson, one by Peter Cook, etc etc. The problem is that our principle harbour engineer will want to know who the NA desinger is of the boat, for that reason I selected NA from NZ. At least he gives the thumb up.

Yes indeed , there are lighter boats, Manie pointed that out, but if the boat is loaded with all kind of stuff, both boats maybe having the same weight, where is then the advantage of having a lighter boat, other that one has more stuff on board or more passengers? Please, I am a foreigner and I write as of I speak. Sometimes it could come over as rude, but it is not intended. What my concern is that sofar nobody has told me why it is wrong to add 2 frames, although the NA did stated in a previous boatplan that one could add a frame and use the same distance. (Not 2, but 1).

My logic tells me that unless somebody points out
a) if you add 2 frames, the boat gets too long and will capsize.
or
b) if you add 2 frames, the boat will break in 2 if going in rough seas (which I am not planning to do)
c) if you add 2 frames, it weakens the construction to such an extend that you will flex too much or whatever, but Tom, I really mean it, I do not want to come over as rude, but because some books make such a statement, I am a different quy. I need facts and reasons why.

I love Rick's design, he is really on the correct road, but any design has advantages and diadvantages. His is sadly only in the begining phase.

Who else has plans for electric boats, apart of the Thames ones, with solarpanels and reflectors, not just one, but 1000 watt etc etc. There are no boatplans for sea going electric boats with dual motors and battery banks.

Flareline 18 has advantages, solid, well proven, I love woodworking, disadvantage: older design and heavier, but seaworthy. Maybe I have to stick to the original design and accept that I cannot add 1 or 2 frames. Pity
Bert

 

Oh, let me, a very uninformed amateur try to explain!
(This is the internet after all. )

Hey Bert,

You must treat a hull as one piece, where each chine, curve, and angle (all dimensions) are carefully calculated to produce a design to meet a set of performance specifications the designer wanted to achieve (in good designs that is). When modifying a design, even with the addition of a frame or two, you now enter the realm of unknown consequences. Depending on the modification, some or all of those thoughtful, carefully made decisions have been thrown out the window.

Right from the start, I can see where your hull extension could have an effect on the boat's pitching characteristics. It might even assume a bow down attitude at cruise speed. I don't know and you don't know. Which is what everyone is trying to tell you.

That's why it has been suggested to enlarge all the boat's dimensions by 10 - 15 percent to get a larger hull. It has been historically/empirically proven that using that method actually does give you the same boat, with its characteristics scaled by 10 - 15 percent. Enlarging it by a greater margin is not recommended as the scaling fails not far beyond that and again you enter a new realm.

Also, remember that although a boat must be designed for a given propulsion method, it doesn't matter if the propeller thrust comes from an electric motor or a gas one. You just want a power boat hull that fully and safely utilizes some number of kWs or horsepower, carrying a given load, within a user defined range of sea states (for a short list of requirements, anyway).

Finally, a lighter hull is always better because less weight allows you to either carry more stuff, use a smaller engine, or at the very least, add weight where it does the most good - as in improving pitch and roll or achieving a proper cruise trim (important as that can also effect power requirements).

That's my contribution to today's internet jungle!

 

Very close to exactly correct. In some cases making a boat heavier makes it less safe.

I think Bert was thinking that if the ribs are identical then adding some more would not have an effect. But I tend to agree with the consensus here.

Having been involved in the construction of a few boats here and there, I would say that you can add ribs to a skiff, but any boat that changes significantly from bow to stern; I would think twice about.

Plus out of curiosity, why do you want a boat with hard chines.
There are some real reasons to build a boat like that, but I would be interested to know yours.

One last thing, I have givin some more thought to the Quonset hut thing and I believe it would be better to make some trusses of 2x4s and plywood gussets. I will get around to drawing a little picture, hopefully before you start building your boat.

 

You cannot just add frames. The boat will not be fair. There will be a flat spot where the added frames are. To change the dimensions and shape of all the frames would be a lot of work. Just increasing the size of the boat 10% or so should work fair but some of the parts may not be available 10% larger in which case the balance of the design may be upset. In a constant deadrise design adding 10% at the transom should not upset any applecarts and I'm sure there are some on this site that can tell you specifically what you can do with this boat.

Easy

 

Thus we have concensus here. No adding of frames. What a pity. I wish, somebody had a simulation program and put the data into it and tell me what happens. (because nobody can really tell me what will happen if I add 2 frames, you all say, it is all wrong and I start agreeing with you.) Pity that I don't have friends at the Dutch test center, they would be able to tell me what would happen if I did so.

In anyway the battery technology is not yet there for me to take the boat on the choppy sea. I will have enough electric motor power, but not enough energy to last for long. No harbour Captain will allow me to go out in anyway, thus I am stuck for the time being to the local rivers and lakes.

My real problem is, I have to add solarpanels, wind generators and have to change the total upper part in anyway. Thus the carefull calculated design from the NA is in anyway violated. Find me an affordable boatplan for a seagoing boat at choppy seas with 2 x 6 Kw electric motors.

There are none avialable. The concept from Rick is the first one I feel will meet that criteria, whatever critisism he has received from you all.

The Flaireline 18 is a seaworthy going boat. I have to stick thus to the original hulldesign. What a pity. Sorry Fanie, I am not allowed to make it longer. Sure I can spent more money for another 20 designs, but then there is no money or little left over for the boat itself. All designs will have to be modified in anyway.

I am off to Cape Town. Will be back on Thursday.

Have a nice drive, thank you.

 

Interestingly, I have a set of Flareline 18 plans in my posession. The designer says it is possible and allowable to extend by one frame to lengthen the boat, and my boat had exactly that done to it.
Also interesting is that I used to own a Flareline 18 and they are a very well designed hull, quite light and very, very strong. Yes, they are an older design, but a very good one, and many people will attest to that.
My boat was well over 25 years old when I bought it, had all original documentation and receipts for engines, sterndrives etc. It was rock solid, all glue lines still solid etc, even with a 5 litre V8 and Volvo sterndrive on the transom.
They are a great boat and will plane off with fairly low horsepower (mine would plane at half throttle), and are quite good in nasty water. I had a customer in Sydney who built a Flareline 18 at 18ft, with twin 70hp Tohatsus, she'd hit 25kts fully loaded for a weekend...
He was an ex pat Sarth Effrikan too.

Regards, Andrew.

 

Well there you are, add a rib and it's still a good boat.

Experience will beat theory any day.

The tradition of being ultraconservative goes back many centuries in boat design. It came from so many people losing their lives to Davy Jones.

But in the early part of the nineteenth century, the United States took the old British frigate designs, and made them better.

The rest is Navy history.

 

My original comment was: do not add frames...Instead stretch the spacing. Let me hasten to add that you can install as many intermediate frames as you choose. In fact you will need intermediates if you stretch the spacing by 31% as you intend.

Your drawing shows a planing boat design. A seven meter boat of that type will need a 10KW of power at the very least if you ever hope to make it plane. 15 to 20KW is more realistic. You intend to use electric power, right? That is going to take one hell of a lot of battery power. For example: 15KW= 48v x 312 amperes. All those batteries will add so much weight that you will need the extra power to cause the boat to achieve even a mushy plane.

The problem here is that you have the wrong kind of boat plans. You will be far more successful if you trade the planing boat plans for a suitable dispacement type. With a displacement hull of seven meters, you could do nicely with 3 or 4KW of power. 4KW = 48v x 83 amperes.....Big difference, fewer batteries, less weight, lower cost, reduced charging power input and /or charging time. Begin anew before you do, in fact, shoot yourself in the foot.

 

Typhoon,
A light 18' boat that requires 140hp to make 25 is not something I'd brag about.
Bert,
I think we're all fine on the extension now but I still think (along w others) that a planing hull for electric power is not a good idea at all. Take a look at Russell R, an Atkin design of 22'. Very easy to build and most are powered w 25hp and are good for 15 to 18 mph. This is a boat that could expand your speed horizons as more electric power becomes available and be driven at respectable speeds w electric power now.
Mess,
Thanks. We were posting at the same time. I agree w you completely but have presented a bit of a compromise for Bert thinking he was going to be too stubborn to go for full displacement. That's exactly where he needs to be but there are a lot more good FD boats than semi types. The Atkin boat would only be a comprise but a good one (I think). < www.atkinboatplans.com>. See Russell R.

Easy

 

If you just space your frames aft of the stem equally then enlarge your bottom and side framing members slightly and add 1 or 2 stringers on each side of the bottom and sides. You might go up by an 1/8" in plywood thickness. If after that, you feel it is not strong enough you can scribe in extra bottom and side frames. That is the way I do it though I also add extra frames often and I almost always go thicker on the Ply by 1/8".

 

I won't comment on the issue of adding frames and stretching hulls, but I will say that a displacement hull is what currently makes sense for electric power.

This site: Electric and Solar Boat History has a lot of neat info. This section might be of special interest: SUN 21 - first trans-Atlantic solar crossing

Best of luck with your project... I can't wait to follow along via this thread.

 

Hence my question on hard chines.

 

A friend of mine built a boat with hard chines because curves intimidated him. He was going to use it in a lake with a small motor.

Two things besides planing, are a positive factor of hard chines (a sharp corner between the sides and the bottom)
1. Hard chines tend to have more initial stability, and are more forgiving of changes in weight distribution.
2. They also draw less water for the same displacement (load)


The down side is, and I know from paddling those flat bottomed skiffs all over the bayous of Texas, they have a considerable amount of drag.

I was shocked the first time I got into a kayak.

 

Hey Sleepy,
What if you had a one chine boat, a 2 chine boat , a 4 chine boat and an 8 chine boat. Which one would have the least drag?

Easy