Converting Standard hull into bowrider

Hi guys,

Im a new member here, this looks like a really great website. I have just put down a deposit on a used older speed boat with a closed front section and not many seats or accessories onboard. I have decided to convert it into a bowrider, but i have never taken on such a large fibreglass project. This is my basic plan.
1. construct a wooden frame for the back bench, place plywood sheets ontop of the bench and down sides. (Can I use screws to secure the wood? will they rust and cause issues in the future?) coat the wood with resin to seal it, fix the bench to the boat (Using fibreglass and resin). Paint
2. Cut out the frond covered area with a jigsaw/grinder, cut out the steering columb and dash board, move the (now two piece)colum back a few centremetres, fix to side of boat with resin/fibreglass.
3. Use the same construction method for the front benches with wood, fibreglass and resin. Paint

I have attached some pictures of the boat and a rough "paint" drawing of what i would like to do to it.

I would really appreciate any help with this project.

 

Maybe wrong project

Daveint,

First, you can use the search function (toolbar above, 3rd link from the right) to see if your topic was covered before. I checked, and here is a link to a similar request in 2005: http://www.boatdesign.net/forums/showthread.php?t=4052&highlight=converting bowrider

In addition to the cautions mentioned in that thread, I wonder how much hull strength you would be removing by cutting away the bow deck. I suspect enough to make it unsafe. The deck liner in a FRP boat is an integral part of the overall structure. Factory made bowriders use the same molded top deck structure as in conventional flushdeck bows, fastened securely along the perimeter of the hull. It's really a conventional deck with big recesses molded in for people to sit in. Engineered to be an integral part of the hull, reinforcing the bow, etc, etc, I think you get my point. Removing the deck will create a serious weakness. You can design and build reinforcements, but now you've converted a professionally designed boat into a homebuilt with no data to predict the hull's strength. Presumably, the very reason you want a bowrider is to carry people you care about in the boat with you, so safety will be a priority.

I'm not trying to discourage you for any reason other than safety. I've restored old boats and I admire those who are willing to invest time, money, and hard work into a project. For the sake of safety, my advice would be either to add the benches (use stainless steel or bronze screws) and retain the bow as is, or purchase a used bowrider. There are plenty on the market.

Welcome to the forum, and good luck, however you decide to proceed.

Charlie

 

After looking at the pics, I would advise against it. You have too many problems to deal with. Ingress and egress. structural reinforcement for the bow section. I have done a conversion and its a lot of work.

 

Thank you so much for the advise, I will definately take it into concideration, especially the safety aspect of removing the bow cover.
To me boating is not only taking the boat out on a lake and enjoying it on the water it is also fixing it, improving it, madifying it. I know i can easily get a inexpensive bowrider but i really enjoy customizing my boats, more than likely i will be going ahead with this project of course keeping safety in mind. So the big question is. How can I remove the existing bowcover and install benches and at the same time keeping the existing rigidity of the bow? If the benches are made strong enough surely the answer would be that? using the benches as a means of securing the front section? And if that is the answer, how do I go about making secure enough benches to secure the bows rigidity?
Thank you so much for your time.

Dave

 

Hello there,

I would suggest that you rethink your conversion plans, or buy a bowrider. There is more to making these boats than just cutting and glassing. You would have to re-engineer the whole structure, reinforcing the bow area. The work would be overwhelming. Try pricing out a new windshield that opens in the middle, they are not cheap. Enjoy the boat as it is, then buy a bowrider to keep you busy during the winter.

 

Time to re-think...

Hello Davient:

I must agree with the other guys about the advice against what you propose.

How long do you plan to work on this project ?
How much experience do you have with boats... woodworking... fiberglass ?
How much time on a daily, weekly, monthly basis do you have available ?
How much understanding do you believe you possess about the structural entegrity of a boat... wood... and/or fiberglass.
Last but, not least... How much money do you have to invest in this adventure ????? $$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$ :?:
If the answer to this last question is PLENTY ! then by all means... go buy a different boat.

Look up the word BOAT in the Boatmans Exclusive Encyclopedia and it will tell you .... Boat > a hole in any body of water in which a boat owner pours his/her money into without regard to logic or sanity.

Constructing some wooden seats is one thing but, cutting out the entire (closed) bow and making an open bow is a different story.

Your going to change the boats CG (center of gravity) just by removing and reconstructing the seating in the back alone. Not much but, it will. (You'll be changing the total weight & placement of this weight by doing so). To do what you propose to the front of the boat is going to add additional weight (not intended by the designer) to the front of the boat...again, a change in the boats center of gravity (where the boat would balance from if you positioned a fulcrum point under it.) Does this make any sense ?

In otherwords... your boat is designed to plain out (The way it rides on top of the water at cruising speed) according to how it is balanced fore and aft.
You want to add a bunch of extra weight to the bow now, pushing it (the bow) down into the water harder than before... this alone can cause the boat to "spin out"... at the very least it WILL change the way it will handle and steer. I've experienced a "spin out" before... have you ? It can throw you and everyone in the boat right out into the water at a very high rate of splash... or crash.

SOMEBODY CORRECT ME IF I'M WRONG... !

What you "want" to do "may" or "maynot" be doable... but, if it is... is it doable by you ? SAFELY ! This is the real question. The boat was designed a certian way and to change it more than just a little bit will surely be costly also.

I've had my boat for 3 years now... and it's never seen the water since I bought it. It will be another year or two yet still before it does too.

 

Daveint,

2 years ago when someone raised the same question, the response was overwhelmingly against the conversion. Now, again, a similar response. You'll note that several of us have brought up safety concerns. Your desire to work on a boat with your own hands is admirable. I agree with you; I was always modifying my boats, and one full scale restoration of a classic wood boat was source of great satisfaction. Vic has undertaken the restoration of a wood boat. The people who come to this forum do so because they, like you, want to learn more, want to work on their boats, want to make them better. Far more important than any sense of personal satisfaction, however, is the ultimate consideration: safety. You have asked for help in how to do this conversion safely, and the answers that mention safety all say you'll be creating a safety hazard. There is a reason for this. A bowrider is more than a boat with the bow cut open. It is a completely different design. The proper way to do what you want is to go to a qualified designer or naval architect and pay him/her to evaluate your boat and redesign it as a bowrider. Then do everything the redesign calls for, no matter how costly.

Too costly? Don't want to pay a professional to tell you how to do the modification? Remember the theme that comes up again and again: safety. Ripping out the old seats and replacing them with reclining lounges, changing the thwartship seats to fore and aft benches, adding a storage locker, these are all good projects that can give great satisfaction and make a stock boat more personal. They don't affect hull integrity or change the center of gravity drastically. Your project idea would do both, thereby creating a major safety hazard unless designed by a qualified professional.

People who like to do their own work or start their own business are strong, often stubborn, overcoming obstacles. Don't confuse warnings about safety with being negative. Safety is an obligation. I do not have the right to take anyone as a passenger in my boat unless I have taken all legal and reasonable precautions to be sure they are safe. There are civil and criminal penalties for failing to do so. Safety is that important.

 

a different approach to the same problem

Hi guys, I would like to thank you all for your generous input on my project and have decided to take your reccomendations to heart. I have atached a picture of the new design. Hope this one can be concidered more viable.
My plan is to basically remove the front cover and make a full covered seating area, keeping the structure and at the same time creating more space. so my question to all you guys is, will that work? and how can i attach that section correctly to the hull? I'll be making it out of plywood reinforced with fibreglass. Thanks Guys

 

Dude... this is still MAKING A BOWRIDER / OPENBOW boat out of what you already have. Don't you understand what we are trying to point out...

The "Front Cover" as you call it, IS what gives your boat it's structural integrety... it's what holds the hulls ( the sides of your boat ) apart in their specific shape... remove this cover and you could see your boat collapse unless it has frames or bulkheads to hold the hulls apart.

AM I OFF TRACK HERE ??? ANYBODY ???

 

determination

Hi,

All I plan to do is reposition the structure. It will still be there holding up the bow, stopping it from caving in on itself. Before I could understand that the side benches would not be enough.. I have attached a picture of my understanding.... this can be done, I just need someone to give me a small push in the right direction. I will be documenting my project on the net soon as i start at the end of the month, ill ask my mate to video me on my first tryout and if the boat crumble up soon as i give it power...... then we will have to find a different way to do the same thing. At least help me so you can say to me I told you so IF all goes assend up.

Thank you guys again for your input

 

Daveint,

Still the same problem: significant modification of the hull's integrity, unsafe unless done by a professional in the marine business. The point is: I won't help you do what I know is unsafe. I'm not qualified to help you, nor is Vic, because we're not professional designers. It's not a question of wanting to see you fail, it's a question of wanting to see you and your family safe.

As I said before, go to a professional and pay him/her to design the mod. Then do it exactly as the design says.

 

I don't think you can go wrong once you're familiar with bonding plywood bulkheads at right angles to a fiberglass hull, including proper filleting and taping schedules.
By designing your seating around say, three evenly-spaced transverse 3/4" plywood bukheads, well bonded with epoxy and several layers of cloth tape on each side of each joint, from keel to the top of the bulkheads, you can cut into those bulkheads to allow for seating so long as you leave at least 8" of plywood remaining along the outside side margins, and at least twice that (16") atop the keel. space the bulkheads no more than 24" apart.
This all works well if you learn how to bond the joints properly. The seatbacks and seat surfaces should be screwed and/or epoxied onto the bulkheads, but you'll need to add solid wood frames along the tops and sides of your seat cutouts to allow screwing where you can't get in to bond with fillet and tape joints. I would imagine that when you're done, you will have a stronger boat than when you started. The areas sealed between and ahead of the forward bulkhead will give you some added flotation too.
Overdo everything, and be meticulous. There are many articles and books showing how to fillet and tape. The existing bow deck should be cut to match the inner bulkhead tops, so an 8" horseshoe shaped deck will surround the seating. The underside of that narrow "shelf" should have a good strong frame on edge under it notched into the bulkheads (along the top of the seatbacks), and another piece of attractive wood on the flat above it, sandwiching the fiberglass deck edge between. That too should be glued with epoxy, and then screwed all the way through the sandwich.
You could probably buy a used bowrider with what you'd spend having a design done up for you, let alone having it done, so I figure you won't be doing that. Nor can anyone keep you safe from your mistakes. Read books to verify what you've heard, trust no sigle opinion including mine, and have fun, sir.

Alan

 

Yea... what Allen said.

It looks like your going to have a bulkhead after all.
This is good.

I'm in a bit of a hurry this morning... got to go to work.
Will read more later.

Listen to Allen.

 

Daveint, it sounds like you're committed to going ahead with this.
Your second plan, with bulkheads, would be somewhat better than your first, although still not something I'd be willing to go to sea in.
That part of the deck that's right under the windshield, what you might think of as a dashboard- that is probably structural and so you cannot cut it. So any sort of walk-through is probably out.
Now another issue is how safe this bow seating area will be. Factory-built bowriders are designed to lift the bow when they accelerate, and the seating areas are sunken with lots of solid handrails. Your boat was not meant to have weight up there at all, and so it will ride very much bow-down. This could lead to stuffing the bow into waves, or spinning out. Neither is a good thing especially when the people up there aren't well secured. If you sink that forward seating area deeper, you're further compromising the structure; if you don't sink it, your people will fall overboard.
The current cockpit layout of your boat is really quite inefficient. I think you could achieve the seating and socializing space you want with a wraparound bench layout much like MariStar http://www.mastercraftboats.com/index.php?znfAction=boatGallery&series=m&boat=ms215.07 uses. I suspect if you go ahead with the bowrider conversion, you'll find yourself putting a lot of money and time into a project that has a very good chance of turning a decent boat into a dog. Focus your efforts on creative use of the space you have.

 

Hi guys,

What a great response, thank you all again for your input. I'll make 100% sure that my project is safe before offering anyone a ride by thoroughly testing it myself, I only intend to operate this boat in dams with very little current/waves, no sea use. Charmc, you seem like a very Knowledgeable gentleman who I give my utmost respect but I am a determened young adult who does not usually go against the word of his elders but in this case with respect I will be proceeding with this project. I used to own a 18Ft Tremlett with a 40HP Johnson motor which had a very similar design in the bow to what I want to do here. I noticed it was a very secure structure upfront with many cross beams approx 50cm apart creating a chess board effect and a pillar supporting the structure in the centre. I now know that this was not just to support the people sitting ontop of it but to also keep the bow structure secure. At the moment my boat has a 60 HP 2 Cylinder Yamaha motor which I have sold (I have had bad experiences with the two cylinder motors) And will be replacing with an 85HP 3 Cylinder motor which should create the necessary weight at the back of the boat to compensate for the additional weight of one person sitting on the bow? I hope.... 85 Is apparently the max HP the boat can take. Sorry I gotta go, customers are calling. Once again thank you for all your input. It should be an interesting project, I cant wait to get started.

Dave