3rd toon question

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Mrtoler
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3rd toon question

#1 Post by Mrtoler » Tue Aug 09, 2011 4:50 pm

I'm wondering if I will need to add cross members to my boat if I add a 3rd toon with built in transom Jack plate and strakes? My existing ones are 24"s apart and the last 5 are 12"s apart. My boat is rated for a 120 but I'm going to use a 150-175 depending on what they are offering!The question is my boat strong enough now or dos it need to be beefed up?
Ryan, Martha, Ana and Nathan Toler.
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GregF
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Re: 3rd toon question

#2 Post by GregF » Tue Aug 09, 2011 6:40 pm

You really can't go wrong adding a stringer and they come 3 at a time (standard length of the material is 24 feet)
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Mrtoler
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Re: 3rd toon question

#3 Post by Mrtoler » Tue Aug 09, 2011 6:49 pm

What about the existing tubes? I understand they will be under a lot more pressure than before! They are round 22" logs should I have my welder add a few extra welds where the mounting brackets meet the log, or should I add more material behind them also???? I don't want to be doing 40mph across the lake and hit a wave at a angle and have a log crack on the mounting bracket or worse just break off!!
Ryan, Martha, Ana and Nathan Toler.
(SOLD)1992 24' monark sun spa 240 1996 (rebuilt) Johnson 112
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GregF
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Re: 3rd toon question

#4 Post by GregF » Tue Aug 09, 2011 6:56 pm

I have never really tried to analyze the stresses in a tri toon but I would think they might be less. Instead of a small motor bracket in back transferring the load to the toons on stringers the center toon takes the motor load and transfers it along a longer base. The toons are essentially just outriggers.
I would certainly want a pretty good amount of welded surface on the center toon but you are buying that one. Get what you need. I would think a U shape with a continuous flange on each side would be strongest. You night want an extra angle welded up there on each side to beef that up.
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Mrtoler
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Re: 3rd toon question

#5 Post by Mrtoler » Tue Aug 09, 2011 7:05 pm

I seems to me if I add strakes which I am, the logs will be under less stress since the boat will be on plain! But on the other hand it is a 1992 model and it's only rated for a 120 but I really wonder about that? It looks very strong the way it is the transom is all aluminum and there is the extra stringers back there!!!!! The center log is bolted from back all the way to the front so seems like the force will be spread more vs just on the back few feet of the boat!
Ryan, Martha, Ana and Nathan Toler.
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Bamaman
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Re: 3rd toon question

#6 Post by Bamaman » Tue Aug 09, 2011 7:56 pm

Cost of 3rd toon--$2500, $1500 if scratched/dented. Cost of materials for strakes--$1000? Cost of underskinning boat--$700-800? That's not including labor, if needed.

This is what a fabricator at one of the big 4 pontoon manufacturers says about strakes:

We add strakes to tubes all the time so yes it can be done but be very careful who you have do it as they are below the water line most of the time.
Does your manufacturer offer strakes, if so it would be best to use what they originally put on the boat, they can also provided dimensions.

Hydrodynamics are kinda funny, if the chine is just a little too long or short it will really affect how they work, we have run R&D boat that didn't do very well, you take off or add 2' of chine and they are perfect.

Too long and you lift the transom too much and cause the bow to plow too short and you don't get enough lift. No you don't need to weld them full length, we go 3'' of weld top and bottom every 2' of chine.

So get with your manufacturer and see if you can get chines from them
.

In your case, they were probably not offering strakes on your boat 19 years ago. Manufacturers have spent a bunch of time and effort designing and testing their strakes, and there are many, many different designs. It's not as easy as welding some aluminum angles on your toons.

My question is whether it would be wise to sink in so much time, effort and money into a 19 year old pontoon boat? Would it be easier to just put aluminum skin to your underside, and accept your boat for what it is?
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GregF
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Re: 3rd toon question

#7 Post by GregF » Tue Aug 09, 2011 9:25 pm

The boat doesn't weigh any more up on strakes than it does dead in the water. The reality is a little bump into the dock probably puts more stress on the welds than anything you do under way.
What would you rather have? Gently set a 10 pound sledge hammer on your foot or drop a one pound hammer from a foot up? (about 4 MPH)
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badmoonrising
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Re: 3rd toon question

#8 Post by badmoonrising » Wed Aug 10, 2011 10:50 am

Mrtoler wrote:My boat is rated for a 120 but I'm going to use a 150-175 depending on what they are offering!The question is my boat strong enough now or dos it need to be beefed up?
It's never a good idea to overpower a boat, lots of discussion on this here and I wouldn't recommend it.
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GregF
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Re: 3rd toon question

#9 Post by GregF » Wed Aug 10, 2011 11:24 am

If he adds a 3d toon, any original ratings go out the window.
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Mrtoler
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Re: 3rd toon question

#10 Post by Mrtoler » Wed Aug 10, 2011 12:05 pm

I agree with Greg on the max hp sticker
Ryan, Martha, Ana and Nathan Toler.
(SOLD)1992 24' monark sun spa 240 1996 (rebuilt) Johnson 112
2014 South Bay chassis (IN THE WORKS)
2006 dodge ram quad cab
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Mrtoler
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Re: 3rd toon question

#11 Post by Mrtoler » Wed Aug 17, 2011 2:20 pm

Just got off the phone with parks and wildlife about overpowering, they sent me to the coast guard and they said since my boat is under 5 metric tons they pretty much don't care and it's parks and wildlifes decision. I got back with parks and wildlife and told them what the coast guard said and they said since the cg dosent care we don't either, all they are concerned with is overloading and making sure the vessel is registered
Ryan, Martha, Ana and Nathan Toler.
(SOLD)1992 24' monark sun spa 240 1996 (rebuilt) Johnson 112
2014 South Bay chassis (IN THE WORKS)
2006 dodge ram quad cab
Crosby Texas

dockholiday
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Re: 3rd toon question

#12 Post by dockholiday » Wed Aug 17, 2011 9:33 pm

Mrtoler wrote:Just got off the phone with parks and wildlife about overpowering, they sent me to the coast guard and they said since my boat is under 5 metric tons they pretty much don't care and it's parks and wildlifes decision. I got back with parks and wildlife and told them what the coast guard said and they said since the cg dosent care we don't either, all they are concerned with is overloading and making sure the vessel is registered


If that's what the said to heck with the strakes and 3rd toon, put a jet engine on it. That is good to know, I didn't realize they were that flexiable.
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Mrtoler
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Re: 3rd toon question

#13 Post by Mrtoler » Wed Aug 17, 2011 11:04 pm

I'm not set on what they said yet, I'm going to do some more research and ask every officer I see on the water!!! I'd like to have something in wrighting!
Ryan, Martha, Ana and Nathan Toler.
(SOLD)1992 24' monark sun spa 240 1996 (rebuilt) Johnson 112
2014 South Bay chassis (IN THE WORKS)
2006 dodge ram quad cab
Crosby Texas

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scfishnman
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Re: 3rd toon question

#14 Post by scfishnman » Thu Aug 18, 2011 5:29 am

I think the only reliable answer to your question can come from an engineer. The comments from a manufacturer quoted earlier in this thread by Bamaman are very revealing -- getting the desired performance from a boat requires experimentation and knowledge of hydro dynamics and marine engineering.

I would be very concerned about the additional stresses you might place upon the boat. It is not uncommon for older pontoon boats to develop cracks where the mounting brackets attach to the logs. I had a pontoon built about the same time as yours which developed cracks in the top of one tube at the aft most mounting bracket. It only had an 88 hp motor and was never abused.

Also, I would question that you will get 40 MPH out of the boat after you spend the money for the mods and the 150-175 hp motor. My boat only runs 40 MPH with a 225 hp and it was designed for that size motor. It has three 24" diam. logs, lifting strakes, and full underskin.

Your project and goal sounds exciting, but I would hate to see someone spend that much money and effort to be disappointed in the outcome.
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badmoonrising
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Re: 3rd toon question

#15 Post by badmoonrising » Thu Aug 18, 2011 8:35 am

Also if you plan to insure this boat, the insurance company will have problems writing a policy for a boat not designed to handle the bigger motor...unless it's certified after the improvements.
Ed, Cheryl, Ethan and Aspen.
2013 Sun Tracker Party Barge 22 w/90 HP Mercury, "Hellrhighwater 2"
2014 E-350 Extended XLT.
Chesapeake City ,MD

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