Transom problems with Larson 186 SEI I/O Bowrider

[JASinIL2006]

Re: Transom problems with Larson 186 SEI I/O Bowrider

Thanks!

 

[JASinIL2006]

Re: Transom problems with Larson 186 SEI I/O Bowrider

Doing a bunch of little things on the boat this weekend while I wait for warm weather so I can Durabak the deck.

Installed Garboard Drain 2.0 (after I spilled resin in the bilge and ruined the other one...)



Gelcoated the ski locker. I ran out of gel doing the bilge, and I had to order more from US Composites. I ordered it Sunday night and it was shipping via UPS Monday! Pretty good service!



I drilled out the holes for the U-bolts for the transom straps and coated the holes with resin using a pipe cleaner.



I need to be more careful with resin. I spilled some and accidentally glued this piece of 2x4 to the floor!

 

[JASinIL2006]

Re: Transom problems with Larson 186 SEI I/O Bowrider

I also foamed the cavities behind the transom shield where the hull bulges out.



Then a nice coat of Rustoleum white to make things look pretty.



Jim

 

[JASinIL2006]

Re: Transom problems with Larson 186 SEI I/O Bowrider

UPS delivered the new ladder today, so I'm going to try to reinforce the rear deck and install the ladder before I drop the engine back in. I'm going to reinforce the underside with a decent layer of hairy peanut butter which will glue a backing plate of two layers of 3/4" plywood (about 20" wide by 9" deep).

I have a bit of a quandry, though, and I could really use some help.

If I install the ladder brackets so the ladder, when deployed, rests against the rubrail (see first and second picture below), the ladder does not lie flat when pulled up and stowed. It rests on the rear wall behind the platform.





If I install the ladder so it lies flat, the pivot points of the ladder brackets extend a bit more off the back of the platform, so the ladder is hanging without touching the rubrail.



I'd prefer if the ladder could lie flat when stowed, but I'm concerned that when the weight of a wet swimmer is on the ladder, there will be too much force concentrated on the very edge of the fiberglass platform. If the ladder is up against the rubrail, the weight of a swimmer would push the ladder into the rubrail and take some of the load. (The rubrail would act as a pivot point, changing some of the downward load to a lateral load, I think.)

Am I overthinking this? Do I need to be worried about the downward force on the edge of the rear platform if the ladder isn't right up against the rubrail? If you have an over-platform ladder, does yours hang freely off the back or does it rest against the boat when deployed?

Thanks,
Jim

 

[HalfFish5087]

Re: Transom problems with Larson 186 SEI I/O Bowrider

Jim,
In summary the bolts towards the bow are doing all the work as their in tension and the back two are in compression (back bolt is there to hold the braket in place, but really is not doing much at all).

If you want to tackle the math yourself, here is what you need.
1. Put the ladder in the position you like the best.
2. Measure the supported distance (bow bolt hole to free edge of bracket), X
3. Measure the distance from bow bolt hole to ladder hinge, Y
4. Determine what is going to be the max weight on the ladder, W

The tension (T) in the bow bolt: T= W(Y-(X-X/6)) / (X-X/6) I had some help from a structural engineer

Now put put the ladder where the brackets are as far towards the bow, but with the ladder falling straight down without hitting the rub rail (and maybe an additional few degrees for comfort) and again calculate the tension.

Here is my thought behind my madness; if the ladder is hitting the rub rail before going vertical the bolts are now in shear (force in the horz axis) in addtion to the back bolt being in compression and the front in tension. If the ladder is allowed to swing under loading and does not hit the rub rail, there is no shear on the bolts. Therefore, I would look at the tension being applied to the front bolt under both scenarios and likely put the ladder/bracket as far aft as I could to where the aft most bolt would still get good support from the backing plate (just in case the bow bolt broke or came lose, etc.).

Let me know what you think. This is probably over thinking it, but if its worth doing its....

 

[JASinIL2006]

Re: Transom problems with Larson 186 SEI I/O Bowrider

Wow! I can't wait to get home and make some measurements. I'm assuming this yields a T value measured in psi?

Assuming (and I'm making guesstimates from the photos I took) X=4, Y=6 and W=300, I get a T of 240, which I'm guessing is psi. If that's correct, even 1/4" stainless bolts should be plenty strong.

Would it be fair to say the compression figures on the aft edge of the platform (I think this is what's called the "free edge" in #2 above) would be in the same ballpark as the values for T? It seems like as much as the bolts are taking tension as weight is put on the ladder, the free edge will be taking compression... I think. (But then, I'm NOT an engineer!)

Thanks for the info and special thanks to your engineer friend!

Jim

 

[HalfFish5087]

Re: Transom problems with Larson 186 SEI I/O Bowrider

Jim,
Actually the T value is in pounds. To get to psi you would divide the surface area of the backing plate and additionally would then divide this by two since there are two bolts. As far as the free edge, the force here would be W-T or in your example 60 lbs. Again divide this by 2 since you have two bolts so really only 30 lbs of compression near the back two bolts.

Again, I think as long as the aft most bolts are able to get a good bite in the plywood backing plate I think you are good to go.

As usual looks like your making great progress and doing great work. For myself, I have had to take a break for a bit but hope to get back at it soon. Can't wait to see that Durabak!

 

[fat fanny]

Re: Transom problems with Larson 186 SEI I/O Bowrider

My Ray and my buddies 07 Larson have the same set up and the same issue with pull away so to say bosses in the swim deck. We solved this by using a 3/4"x8"x20" pc of aluminum with through holes to match the ladder mount pattern we also used button head stainless allen bolts with matching stainless nuts so far so good but you have it easy with noting in the way when mounting I had to work around my tank and so did he! Good luck!

 

[JASinIL2006]

Re: Transom problems with Larson 186 SEI I/O Bowrider

I installed the backing plate for the new ladder last night. It's two layers of Aurauco 3/4" plywood glued together with Titebond III. The whole thing is peanut buttered in place. I made some really hairy peanut butter and used it glue in the backing plate and to fill the area under the aft edge of the platform (near where the ladder hinges hang over the edge) so that area is now filled with an extra 1/2" of structural PB. Between the 1 1/2" of plywood and the extra fiberglass, I think that area will be plenty strong.

I'll post pics later.

HalfFish5087, if all goes according to plan, I'm going to sand the deck with 40 grit paper tonight, wash it, and rub it down with Xylene. Tomorrow, if all goes according to plan, I'm going to apply the Durabak. It's going to be a little cool, but the Durabak came with an accelerant to use when it's cool out. It also cuts curing time down by 75%. I'll let you know how it goes.

Jim

 

[HalfFish5087]

Re: Transom problems with Larson 186 SEI I/O Bowrider

I'm sure you have thought of this, but it may be wise to conduct a trial like under a seat or back by the motor area just to be on the safe side. Good luck!

 

[JASinIL2006]

Re: Transom problems with Larson 186 SEI I/O Bowrider

A trial to test the accelerant, or to see how the Durabak turns out? I actually hadn't thought about it... I'm planning to do the sides (under the gunwhales) first, and then the deck since it sounds like you can't walk on the stuff between coats. Due to cost, etc., I'm pretty much committed at this point...

Jim

 

[JASinIL2006]

Re: Transom problems with Larson 186 SEI I/O Bowrider

Washed the interior sides of the hull and the deck last night. Just wiped down the sides of the hull with Xylene and I'm going to Durabak them first. (I think I'll do the floor after the sides are done. Too messy to roll around on a Xylene-coated floor while I'm rolling the sides.)

I think the biggest challenge will figuring out how to roll the floor after the first coat is applied. The directions make it sound like I shouldn't be walking on it.

Durabak application beginning in 3....2....1....

 

[JASinIL2006]

Re: Transom problems with Larson 186 SEI I/O Bowrider

Durabak is going on pretty well. The roughened stuff starts setting up really fast. I tried to use less accelerant, but it still gets clumpy pretty quickly. Altogether, though, it's not too bad to work with. It does stink, though. I've been wearing my respirator while applying it.

Here's some pics. The sides of the boat are done. They have one coat of textured and one coat of smooth.



The deck has a coat of textured Durabak. (Actually, I did a second coat on the high traffic areas and in places that were too smooth.



I still need to do a coat or two of smooth over the deck. The smooth stuff, even with the accelerant, seems to take much longer to set up.

Overall, I like how it looks. The real test will be to see how it feels in bare feet.

 

[jbcurt00]

Re: Transom problems with Larson 186 SEI I/O Bowrider

Well from your pix it looks GREAT. Seat bases look like they belong there & have always been there

Outstanding

What's the recoat window for Duraback?

 

[JASinIL2006]

Re: Transom problems with Larson 186 SEI I/O Bowrider

Thanks! The seat bases turned out OK.

Earliest you can recoat is about an hour (when it's dry to touch). It supposedly can handle foot traffic in 6-12 hours. The accelerant is supposed to reduce the cure time by up to 75%. I don't think the accelerant has quite that much effect, although it does seem to move things along.

The deck coating was done several hours ago and it's still too soft to walk on. I was on it after the first coat (when I was touching up the textured spots) and my shoes were leaving marks. My garage is just barely warm enough - 60 degrees - so I think it's taking longer. Between the smell from the Durabak and the fumes from the Xylene used to wash the deck and clean the tools, I don't dare fire up my propane heater.

I don't know what the outside part of the window is for recoating. The instructions says it will bond to itself, so as long as I get the next coat on before it's fully cured, I think I'll be OK.

 

[HalfFish5087]

Re: Transom problems with Larson 186 SEI I/O Bowrider

Looks great man. How'd the texture come out? Could we get an upclose photo showing the texture on the floor?

 

[JASinIL2006]

Re: Transom problems with Larson 186 SEI I/O Bowrider

I have one layer of smooth over the textured, and it's still pretty rough. I'll take a picture from down low next time I go out to check on it. I'm pretty sure it's going to need another coat of smooth before I'm done, at least over the traffic areas.

It looks pretty good up close. I'm pretty happy with it.

 

[JASinIL2006]

Re: Transom problems with Larson 186 SEI I/O Bowrider

I also got the ladder ready to mount.

Here's a side view of the test-fitting:



This is the ladder stowed. I plan to install a strap to hold it down:



This is the backing board I put in to support the ladder:



It's really sturdy. It held me (230 lbs) with no problem; didn't budge a bit.

 

[fat fanny]

Re: Transom problems with Larson 186 SEI I/O Bowrider

Man that deck looks really good and the color makes it pop! The more I look at it the more I wanna tear up my carpet and lay that down Nice work!

 

[JASinIL2006]

Re: Transom problems with Larson 186 SEI I/O Bowrider

Thanks, all the fairing and sanding made the difference. I'm glad that is over!

This isn't the best picture in the world, but you can get a bit of an idea of the texture.