First time boat-builder

[timplett]

Hi

I'm completely new at this, so any advice would be helpful.

My plan is to build a small boat, 10' long, roughly 5' beam. It will seat two people, and will have a 40 HP outboard (I can get one cheap) to begin, and possibly somethign larger later if needed. I have a rough design sketched out on paper that I would like to get drawn up and posted for advice at a later time (btw, is there a good free program for that, or should I just use Autocad, which I already have?). My plan was to frame the hull out of steel, probably roughly 3/8" steel rod or something comparable. The plan was to space these framing members every foot along the length of the hull. I will then cover the frame with a (roughly) 1" square chicken wire, or perhaps something a little heavier, to get closer to the actual shape of the boat. The plan is to then apply layers of fiberglass to either side of the chicken wire to form the final hull.

The main purpose of this boat is to be small, relatively easy to build (I'm very good with my hands, can weld, work with wood, etc.), and go fast as possible to be a heck of a lot of fun. What I want to know, is if my build method is good or if I should scrap the idea and do something different. If this method is functional, what kind of fiberglass will I need and how many layers? I am on a fairly tight budget, so I don't have the money to buy Kevlar or carbon, or 50 layers of FG or anything like that. The steel will be free, and engine will be cheap or free, so I would say roughly $250 would be the aim for fiberglass costs, but obviously cheaper is better. For calculation purposes, I think the hull surface are is roughly 5 sq. yds.

Thank you in advance for any help,

TIm Plett

[timplett]

Perhaps I am completely out to lunch when I say $250. My reasoning was 4 layers of FG alternating between 24 oz. woven roving and 1.5 oz matt (.: 2 layers of each) as I have read that alternating the woven roving and the matt makes for a strong laminate. I thought that a total of 4 layers would be strong enough, seeing as I figure the boat would weigh 800 lb. MAX w/ engine and passengers.

[frosh]

Tim, you are way off the track. Most of us would believe that you are not able to design any sort of boat, after reading your posting. Maybe you will get the idea if you read this thread. Please click on it and have a read. After that do some research on Google on fibreglass boat building methods. Maybe come back when you have a few mainstream ideas.
http://boatdesign.net/forums/showthread.php?t=13162

[lazeyjack]

your 40 is more than adaquate
your plan is way out of whack so far as to be nutty, I,m sorry but there is no easy way of explaining that what you propose is, in fact, nutty
go to careen, or a free programme, type in your parameters, and in a couple hours you will have a print out of the developed :chines" to cut from ply
you can get the sections also, make a temp frame from them and screw the ply to the temp frames, vee out the joints and then later glass over the lot
you will see free programmes here in software
best of luck !! really!

[lazeyjack]

oh and buy some very cheap ply and do a practice one first

[timplett]

...Most of us would believe that you are not able to design any sort of boat, after reading your posting...Maybe come back when you have a few mainstream ideas.
http://boatdesign.net/forums/showthread.php?t=13162

First of all, I would like to point out that you have no even seen the start of my design, which is still in progress, therefore you have absolutely no idea whether I can design a boat or not. Now perhaps you are a little skeptical, or downright condescending of the method I thought of to build it, skeptical is ok, but perhaps not being a jerk in your way of saying it would be nice.

Now as far as my rational argument for my idea, basically it would be a steel ribbed fiberglass hull. No, it is not mainstream. I never had any intention of making it mainstream. I have no intention of shelling out thousands and thousands of dollars to make fiberglass molds and start making $200 000 dollar yachts. The basic idea is 1) steel structural frame, 2) fiberglass shell. Details are to be worked out, but while this may not be conventional I don't think you can really claim that the idea is total crap.

Just for further reference, 1) I'm not way dumber than you, 2) Show respect and you'll get it.

Tim Plett

[lazeyjack]

i never said that i,m willing to help and even call you, with a life time of building, i actually can help, now please calm down, Stu

[timplett]

Sorry lazyjack, that was directed to frosh.

Tim Plett

[lazeyjack]

pm me I,ll help you

[timplett]

Thank you.

[frosh]

[QUOTE=timplett]First of all, I would like to point out that you have no even seen the start of my design, which is still in progress, therefore you have absolutely no idea whether I can design a boat or not.

You are very much mistaken, I DO KNOW! :eek:

[SeaSpark]

Hoi Tim,

Just in case you did not contact Lazeyjack yet, there was a typo in the software name, it is Carene available for download here:

http://www.epoxy-resins.co.uk/Carene/caren.htm

I think the way you want to produce your boat will result in something that rusts very quickly. When the mesh starts to rust it will push apart the fibreglass layers this will minimize their strenght and couse leaks. You will be unable to paint the inner side of your frames if they start to rust. Producing a hull with a fair, smooth, surface this way seems highly unlikely to me.

For the beginning designer/boatbuilder the multy chine plans carene produces are very good. You can build your boat out of steel plate but using ply will make it much more light so faster and safer.

Jeroen

[timplett]

My idea was mainly based on the fact that I would have access to a bunch of free steel, so it seemed practical at the time, but I have seen that it probably was a bit of a foolish thought. I ended up using Free!Ship to make my design before any of these other programs were suggested. I found it fairly easy seeing as I have used AutoCad a fair bit, and it had its similarities. If there was someone willing to take a look at my design and tell me if it's good or bad I would really appreciate it. The design was an attempt at an equal balance of looks, my limited knowledge of boat design, and design cues taken from other designs and pictures of other boats, so it might not be that good, so I would appreciate a second opinion. I can export from Free!Ship in many different formats so whichever you need I will see if I can get it for you. The DXF file format I think would probably be the most common.

[SeaSpark]

Iges format can be imported by anyone seriously interested in boat design it is much better than DXF for exporting curved surfaces. You can also post the Freeship model as Freeship is free most designers have it if only next to their main design package.

[timplett]

Here's my boat design in Iges and Free!Ship format. The top "cover" is not necessarly going to be as shown, the design of the hull is the more important part. Any input would be great!

Thanks,

Tim Plett

[lazeyjack]

i tried assist you by pm, never got acknowledgement, so

[timplett]

Lazeyjack,

Sorry about that. I read your PMs and they were rather helpful, I just completely forgot to email back. I've been sick, not sleeping well, and busy with work so my mind isn't quite here. I am sorry I never thanked you.

Tim Plett

[lewisboats]

An observation I will make is that you are likely to trip on that chine and that would be ugly. I think you will be really nose up too, until you get to a S/L ratio of about 4:1 and you are on the planing pads properly. You have an awful lot of beam for the hull style and length...perhaps you should consider narrowing it a bit, if only to reduce friction.

Steve

[VKRUE]

Reguarding; (My idea was mainly based on the fact that I would have access to a bunch of free steel)

Not to be rude but...:rolleyes: so what ! I have access to all the FREE concrete that I want but do yu think that It is useful in building a boat!

Listen to what the MANY people around here are trying (nicely) to tell you...

Sometimes, I think that someone just sits around an dreams up this stuff to get everybody stirred up.
By the way, about that surplus of free concrete................

[timplett]

lewisboats,

The reason for the wide beam is to fit two people side by side abaft. The rest of the hull would then be covered. I had considered making it a one-seater, but what fun is a boat with no one to share it with? Why not make it longer then? More material, more work, more money. About being nose up, Free!Ship calculated the longitudinal centre of flotation at roughly 3.3 feet forward of the transom, so would that not make for a nose down stance (unloaded)? The larger flatter section at the rear should provide more bouyancy than the front should it not? The outboard would then tip the nose up, but I had planned for a fuel cell and battery in the bow, which would hopefully help balance this. I'm doing my best to figure this out, but a little guidance is needed and much appreciated.

VKRUE,

What I was saying is that the free steel is why I came up with the idea, but I changed my mind after some input. And during WWII there was a design for aircraft carriers built out of something called Pykrete, a concrete-like mix consisting largely of ice, but I digress... I think it would be possible to build a concrete ship, just extremely impracticle, but if you've ever got some of that free concrete and some free time, give it a whirl. :p

Tim Plett

[timplett]

lewisboats,

I have done some more follow up reading on the LCB and LCF. As far as I can tell, the LCB is similar to a fulcrum upon which the hull balances (to reduce this to simple terms). The LCF if the centre of all the weight. Whichever side of the fulcrum the centre of the weight is, that is the way it tips. The hydrostatic calculations in Free!Ship place the LCF just slightly forward of the LCB, promoting a downward tilt. The calculations from 0.1' - 1' draft show that as the boat sits deeper, the LCB moves forward some, but the LCF moves further, to roughly 6" forward of the LCB (as far as i can tell, fairly negligible). These calculations are all with 0 trim, but the LCB and LCF stay within roughly 8" with +/- 1' of trim. Once again, I'm new at this, and interpreting best I can, but as far as I can tell it seems fairly balanced. As I said though, help is greatly appreciated.

Tim Plett

[antonfourie]

I see from your design that your displacement would work out to 189kg, no chance of it ever being that light with steel and concrete.

Best to google "stitch and glue" for a small boat like this ....

[timplett]

Just for the record, I decided to make it a plywood-core fiberglass design. This might not have been made clear with all the bantering back and forth.

Also, Regarding my last post addressed to lewisboats, I realized that I confused the LCF with the LCG. I'm having a little trouble keeping track of all the new stuff I've been taking in. In correction to my previous post, using the LCB and LCF provided by Free!Ship, and calculations I found online, I found that I would have a trim of -6" at the stern, so yes, nose (bow) up. What I am wondering, is if it is best to try and correct this by changing the design, or just by changing the weight distribution in the final product? How would I have to modify the design to change the trim of the hull? I have also looked into the benefits of trim tabs but I think that might be a little overkill on a small boat like this.

Tim Plett

[lewisboats]

You wil have to move the LCG further forward. Move the cockpit a bit forward, put the fuel tank up front (don't forget all the venting and safety concerns). You will still probably need some kind of trim tab or trimable mount for the motor. You could also design some sponsons around the motor to shift the LCB aft as compared to the LCG.

Steve

[timplett]

So if I basically make an "indent" in the transom to move the outboard forward, say, a foot, that would help make the boat more level?

Tim Plett

[timplett]

Modified the transom to move the outboard forward a foot. The LCF is now abaft of the LCB, which should actually made the nose dip down a little (before load is added), right? New files are attached.

Tim Plett

[marshmat]

Hi Tim,
Firstly, I think you're starting to find an OK direction for this thing. What you have bears a vague resemblance to a Stock Outboard runabout, a fairly common teenager's racer.
The indent in the transom, I think, is not a particularly good idea. This will significantly reduce buoyancy and lift in the stern (not good) and be harder to build (also not good) compared to a flat transom. With little zippy boats, you have to accept that there will be a nose-up attitude at rest and the crew position will be what determines the hull trim. You're essentially turning it into an 8.5 foot boat by making that cutout, as the part protruding past the motor will not add much buoyancy at all.
I would be quite worried about tripping on those sharp chines at the stern. Most fast outboard boats this size have the hullsides flaring outwards as they rise above the waterline; tapering them inboard like that tends to encourage the chine to dig in and roll the boat in turns. Also, if you're going with a warped-V (deadrise not constant) as you have drawn, deadrise should reach its minimum at the transom, not at midships. As drawn, with the V sharpening aft of midships, the stern will tend to squat at speed because there's too much lift forward.
As to the choice of power. I can absolutely positively guarantee that there is no way the Coast Guard will give you a capacity plate for more than 20 hp on that boat; it simply doesn't have enough size to be stable with any more.

[timplett]

Well I must laugh at my ignorance. When someone else suggested that I would trip on the chines, not knowing what they meant, I assumed they must mean when I was boarding the boat or something like that... I see the logic in that now. I am going to be honest and say I incorporated those chines because I like the looks, and that eventuality never occured to me. Flaring the hullsides outwards may also allow me to narrow the beam (as someone else suggested) and still fit two people side by side.

As for the deadrise, I checked my drawings again and the minimum deadrise is at the stern, or more specifically the whole section between the stern and two feet forward of the stern. Maybe I am calculating something wrong. By looking at it looked as if you were right, but calculating the angles showed that the transom had the least deadrise. I calculated by dividing the difference in height from the keel to the chine (at the transom) by the horizontal difference between them (simply, rise over run) and multiplying by 45 to get the degree value. I repeated this every six inches or so forwards.

About the power. Is the number on the capacity plate a law with penalties for breaking it, or is it basically a suggestion to cover all parties involved when some idiot puts a 200 HP outboard on his 8' dinghy? Not asking because I want to joint he ranks of the idiot that would really overpower his boat, but just in the eventuality that it does get rated at 20 HP and say I find a good deal on a 25 HP motor or something like that, can I legally put it on? My other concern is whether it will be fast enough to be fun. I don't mean stupid, death-defying fast, but 10 HP, no matter what it's on is only exciting for the fact that you don't have to row.

Concerning the crew positioning, any position forward of the LCF will help hold the bow down right? Obviously further forward will have more effect, but I am wanting to have the seat fairly low down, requiring a little more leg room, so I don't want the crew too far forward. Once again, I am a little concerned about looks too, I like the looks of the crew further back, but not so concerned that I will sacrifice other design elements like performance and stability just to get the looks I want (example: I'm changing the chines, which were basically for looks, to avoid tripping).

Have you ever registered a home-built boat in Canada? I have been doing a lot of research, and the matter of the HIN has got me stumped. I can't find where to I will have to (eventually) apply for one. Transport Canada refers me to Service Canada, which directs me to the Office of Boating Safety which refers me back to Transport Canada.

Thanks for all your input,

Tim Plett

[marshmat]

Class A stock outboards routinely top 40 mph with a 15hp, and they're not much smaller or lighter than your plan. A 40hp on that thing will flip it nose-over-tail quite easily; a 20 would be enough to get most passengers decently white-knuckled. The deciding factors of the calculation are, simply put, the boat's ability to safely handle the weight of the motor, and its ability to maintain a straight and level course with the motor at WOT. Overpower at your own risk. (In my case, I was young and inexperiened when I got the plate for my first boat, and so measured it wrong on the forms, thus giving a plate rating 30% lower than it actually should be. The current motor is sized for the correctly done calculation but I haven't bothered getting the plate fixed... don't tell Ike :rolleyes: )

Straightening out your hull model seems to indicate that my comment on the transom deadrise was due to the weird cutout and not due to the actual hullform... although the statement holds true your model isn't actually at fault on this count. Do fair the chines and keel though; weird curvature inflections in the chines will cause weird handling quirks. For reference, deadrise = arctan ( delta Z / delta Y ) but keep the lines fair and smooth and you'll only need to worry about deadrise at a couple of points (transom, midships, bow, that's about it for a boat like that).

As far as I know the procedure for getting the government paperwork hasn't changed since I launched Sunset Chaser in 2001. Read the small vessel construction standards (request document TP1332: 1999 from Transport Canada, I'm pretty sure it's free), fill out a form from the back of that book, send it in with a cheque and photos. You then get a plate in the mail that gives a HIN and weight, passenger and power ratings for the boat; you stick it beside the motor mount. Then you will get a letter from the Ministry of Finance asking you to pay the PST on the boat; you write back saying "I built it myself and bought all the supplies legally, so piss off now" and you're good to go. If you want more than 10 hp you also need to get a registration number to paint on the bow (free, takes 10 minutes).

[timplett]

Well it sounds like 20 HP will be plenty enough to keep me happy. The other benefit is that the 20 HP will be a fair bit lighter than a 40 HP, hopefully helping with the nose not sticking up too high. Also would it make sense to slope the top of the bow down slightly, I believe it is called downward sheer (I was just reading about that in another forum), or is the boat too small to bother?

About the paperwork, what you are saying is that when I apply for the compliance label I also get a HIN number?

Thanks,

Tim Plett

[marshmat]

A Canadian single vessel plate has the boat's HIN printed on it. If the boat has no HIN, one is automatically assigned when the plate is printed. Request the plate and you get the HIN too. In Canada at least, the legalities are really quite easy and simple.

[timplett]

That's good to know, thanks.

Tim Plett

[lewisboats]

Thanks for the comments Matt. I actually suggested adding the sponsons to the existing hull, not shortening it with a cutout. I figured a few extra cubic feet of bouyancy back there couldn't hurt. Putting a bit of a hook in the bottom of the sponsons might act a bit like a trim tab, forcing the nose down a bit at speed.

Steve

[timplett]

I made the indent in the transom mostly because it was easier, and I didn't see the difference at the time, I know do. Good thing I saved the original file. What size would be good for the sponsons, and roughly what angle to get the trim tab effect?

[lewisboats]

I was thinking just long enough to extend to where the back of the motor would be. I was also thinking of a 'hook', but on second consideration, it wouldn't work with a vee bottom. You would be better off with some external tabs to help deflect the flow downward a bit.

Steve

[timplett]

So are you saying to completely scrap the sponson idea and use tabs instead of to use a combination of the two?

[marshmat]

I agree with Steve on the hook... hook is great at slow planing speeds but for a zippy sportster you'd be better off with a plain V, a hook would force the bow too low at speed and make control difficult.

[lewisboats]

I think your best bet would be adjustable trim tabs. These would allow you to add tab to work the nose at slower speeds and reduce tab as speeds increase and you get more hydro-dynamic lift on the aft end of the boat. You will not get rid of the nose lift, as this is inherent in the short length of the boat, but you might attenuate it a bit as you progress from displacement speeds thru slow planning speed to high planning speed.

[timplett]

Tweaked the design, lost the sharp chines, narrowed the beam 6", moved the cockpit (or whatever you want to call it) forward 1.5' to offset the trim some. Thoughts, comments, criticisms please.

[marshmat]

Some good progress, Tim.
Pull up the curvature graph for the chine (select the chine, then Curve->new, f10 to increase scale). At the 3rd point from the stern, the chine curvature changes direction. I'd pay close attention to making the chine and keel as smooth and fair as you can; abrupt changes in curvature are hard to build and make control at speed difficult.

[timplett]

I smoothed all the curves as you suggested marshmat. The keel was the hardest, and still isn't perfect by any standards but I think it is much better. I started just numbering the files because I keep saving so many different versions as I go to make sure I can easily go back to before I made the changes. .: This is file 4.

Thanks for the help.

[SamSam]

There is a bunch of older plans at this site. Maybe looking them over will give you some ideas on what might work for you. Sam
http://www.svensons.com/boat/

[lewisboats]

Looking much better. Just a little point here...I would smooth the bow/chine intersection. Simply removing the checkmark in corner box of the point properties does a nice job of rounding over. Oh, and there are .bak files to rename also if something goes squirrely.

Steve

[timplett]

I unchechecked the corner checkbox but it keeps rechecking itself. :confused:

[antonfourie]

Tim, something else to be aware of is that outboard manufacturers tend to have two HP models that weigh the same i.e Yamaha 9hp & 15 hp is the same weight so check that you are getting the higher HP for the weight, you may even be able to get a lighter outboard by dropping 5hp

[lewisboats]

Open it fresh, uncheck it then save and close, reopen and see. Or, just take mine (attached).

Steve

[timplett]

Thank you, I got it to work now.