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Gelcoat cracks at Tower Mount.


rustie

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Ouch. The things we do when we get in a hurry. Whistling.gif

Like I said, that's not to say that the Illusion is a bad tower - it's not. It just takes a little more care with the installation to be sure. I'll be curious to see how the Illusion XS proves out. I'm not an engineer, but the little bit that I've been around them makes me suspect that the support design on it is better than on the X.

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I had the Illusion x tower on my old Bu, and I had put quite a bite of strain on it pulling out 5 wakeboarders at the same time. There was no sign of cracks thank god, so I know it would not have any problems under normal use. That boat was not designed to take that tower seeing it was an 2001 Sunsetter VLX and the tower had not come out yet. Mybe just dum luck. The new bu has the Illusion SX tower. It seems to be a little wider front to back. Hope for no problem.

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I talked to Don at SkySki about this a while back.... he's an engineer.... a guy with a real edumacation. He mentioned that the best way to reinforce the area for mounting a tower would be to add both top & bottom plates, sandwiching the fiberglass, then drilling mounting holes & chamfering them correctly. The top & bottom plates should be as large as possible, have rounded ends, no corners, and be bonded to the glass with a heavy duty epoxy or resin.

Yes indeed....that would definitely be the best possible method (high strength, aircraft epoxy bonding of both upper AND lower plates to the hull)...but, I would add one additional step that has served me quite well over the years working with many different types of aircraft repairs:

Consider using a substantially larger (longer) 3/8" plate...then if there is enough width for your specific hull, CNC machine the footprint of the Illusion tower into the plate approx .125"~.187" deep (for just the upper), and additionally machine multiple "dimples" under the bottom surface of the plate where it contacts the hull, and THEN epoxy the plate into place. Plus, additional roughing up of the rest of any remaining smooth mating surfaces as well (just short of knurling).

These additional steps would add a tremendous amount of "shear strength" to the plate, likely preventing any future dislodging and subsequent movement of the reinforcement plate during the life of the hull. The bottom place is not nearly as critical, but I would certainly roughen it's contact surface too.....

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I talked to Don at SkySki about this a while back.... he's an engineer.... a guy with a real edumacation. He mentioned that the best way to reinforce the area for mounting a tower would be to add both top & bottom plates, sandwiching the fiberglass, then drilling mounting holes & chamfering them correctly. The top & bottom plates should be as large as possible, have rounded ends, no corners, and be bonded to the glass with a heavy duty epoxy or resin.

Yes indeed....that would definitely be the best possible method (high strength, aircraft epoxy bonding of both upper AND lower plates to the hull)...but, I would add one additional step that has served me quite well over the years working with many different types of aircraft repairs:

Consider using a substantially larger (longer) 3/8" plate...then if there is enough width for your specific hull, CNC machine the footprint of the Illusion tower into the plate approx .125"~.187" deep (for just the upper), and additionally machine multiple "dimples" under the bottom surface of the plate where it contacts the hull, and THEN epoxy the plate into place. Plus, additional roughing up of the rest of any remaining smooth mating surfaces as well (just short of knurling).

These additional steps would add a tremendous amount of "shear strength" to the plate, likely preventing any future dislodging and subsequent movement of the reinforcement plate during the life of the hull. The bottom place is not nearly as critical, but I would certainly roughen it's contact surface too.....

I do not agree with the highlighted portion... Why would you create a divit to collect water??? I do not think shear is the problem. It's more of a pivot point issue. The tower is a large lever...

I do agree on sandwiching the fiberglass with an aluminum plate. The tower itself could have a longer base plate (hint-hint...) and then another piece below deck.

Patrick

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I do not agree with the highlighted portion... Why would you create a divit to collect water??? I do not think shear is the problem. It's more of a pivot point issue. The tower is a large lever...

No...you missed my point somewhat. The "divits" are machined on the bottom of the top plate (same place you'd roughen it up), and are filled with epoxy when compressed on top of the deck area. The whole point is indeed to add additional shear strength to prevent "peel". You would want this plate-to-epoxy-to-hull-joint to be as strong in shear as possible. The plate itself would never be torn off at an angle (pivot), but rather sheared off (or loosened) from shock and vibration over an extended period of time...which you would certainly want to be equal to the life limit of the hull.

Epoxy bonds well to cured vinyl ester resin (AME4000), but you always want the benefit of additional surface area with small "angular contact" grooves = the roughened/knurled smooth surfaces (including the deck contact patch area...which would certainly cover any gelcoat cracks!) Once filled with epoxy and cured, the "divits" would simply act as small additional anchoring "pegs" to prevent/decrease the chance of any possible shear failures.

The only items that will fail in a pivot mode (tension) would be the bolts themselves. Remember, the tower itself is not epoxied to the deck.....only the plate would be....and the epoxied reinforcement plate is there only to reduce the fore-and-aft slip component (shear) while the bolts are being stretched (tension) until eventual failure....should that ever happen while pulling 10 big guys up (as an extreme example).

Edited by rustie
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Honestly the illusion mount has a ton of surface area compared to other towers (even ones with four legs), I don't see why you would need a top plate. The fiberglass is already thicker and reinforced in that area.

A properly installed tower, ala chamfered holes in the gelcoat will be more than enough to prevent stress cracks. Malibu went through a "learning" curve of instaliation when these towers were introduced. And like all boats, the people putting them together will be lazy and not chamfer the holes - but in an application like a tower, the stress cracks show up pretty quickly.

-Chris

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martinarcher

Well I decided to go with the epoxy method. I figured a few pics would fit well in this thread. I guess I have a tendancy to over engineer everything. It's hard to be an engineer and leave my job at work. Whistling.gif

I ended up drilling the 5/16" tower holes to 3/8" and then chamfering the hole on the top and bottom. I taped the holes from the bottom and filled them with Loctite's Hysol 9462. If any of you are into adhesives you know this stuff is no joke. It bonds very well to fiberglass and is an awesome gap filling, impact resistant, non-sag adhesive that has an unbelievable bond strength. I filled all 16 holes with Hysol last night and it looked great this morning. Hopefully tonight it will be set up enough to drill my 5/16" holes. I figure the epoxy plugs will seal the fiberglass layers together as well as add a little extra gelcoat crush protection when reefing down on the bolts once I get the tower in place.

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.....I taped the holes from the bottom and filled them with Loctite's Hysol 9462. If any of you are into adhesives you know this stuff is no joke......

Yep...you are abo-lutely keeerect on thatun. Hysol is the best you can get (many different types too)....and several (including 9462) are used in aircraft repair. You definitely did the right thing there Martin..... Thumbup.gifThumbup.gifThumbup.gif

Edited by rustie
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I do not agree with the highlighted portion... Why would you create a divit to collect water??? I do not think shear is the problem. It's more of a pivot point issue. The tower is a large lever...

No...you missed my point somewhat. The "divits" are machined on the bottom of the top plate (same place you'd roughen it up), and are filled with epoxy when compressed on top of the deck area. The whole point is indeed to add additional shear strength to prevent "peel". You would want this plate-to-epoxy-to-hull-joint to be as strong in shear as possible. The plate itself would never be torn off at an angle (pivot), but rather sheared off (or loosened) from shock and vibration over an extended period of time...which you would certainly want to be equal to the life limit of the hull.

Epoxy bonds well to cured vinyl ester resin (AME4000), but you always want the benefit of additional surface area with small "angular contact" grooves = the roughened/knurled smooth surfaces (including the deck contact patch area...which would certainly cover any gelcoat cracks!) Once filled with epoxy and cured, the "divits" would simply act as small additional anchoring "pegs" to prevent/decrease the chance of any possible shear failures.

The only items that will fail in a pivot mode (tension) would be the bolts themselves. Remember, the tower itself is not epoxied to the deck.....only the plate would be....and the epoxied reinforcement plate is there only to reduce the fore-and-aft slip component (shear) while the bolts are being stretched (tension) until eventual failure....should that ever happen while pulling 10 big guys up (as an extreme example).

...well since you put it THAT way... I thought the machined area was for the tower base plate to sit in.... Sure, I getcha now.

P

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.....I thought the machined area was for the tower base plate to sit in....

Well, actually...you're right. The tower base will indeed sit in these "shoes". Their benefit would be to eliminate any "ovaling" of the tower mounting bolt holes from movement under load (specifically shear...fore and aft). Although, the oversize hole drilling, and subsequent epoxy filling/redrilling that Martin is doing may be far simpler....and also reduce the chance for any tower shear movement. It just won't hide any gelcoat cracks that the "shoe" would (kinda killing two birds with one stone).

I'm leaning more towards Martin's method each time I read this thread (it's FAR easier!).....and just have the gelcoat cracks repaired.

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martinarcher
.....I thought the machined area was for the tower base plate to sit in....

Well, actually...you're right. The tower base will indeed sit in these "shoes". Their benefit would be to eliminate any "ovaling" of the tower mounting bolt holes from movement under load (specifically shear...fore and aft). Although, the oversize hole drilling, and subsequent epoxy filling/redrilling that Martin is doing may be far simpler....and also reduce the chance for any tower shear movement. It just won't hide any gelcoat cracks that the "shoe" would (kinda killing two birds with one stone).

I'm leaning more towards Martin's method each time I read this thread (it's FAR easier!).....and just have the gelcoat cracks repaired.

Yep - it wasn't bad at all and makes me feel a little better about any risks to the hull from the tower stresses. Between the epoxy plugs and the Titan heim joints I should be good to go. Tonight I'll get some pics after I re-drill my 5/16" holes for the mounting plates and finish it up. It was probably set-up enough after 24 hours (last night), but I didn't want to take any chances since it was only in the mid 40s yesterday. It will be in the 50s all day today so I'll be good to go tonight. I'm excited to get that Titan mounted! Clap.gif It's supposed to be 84 Sat - time to get the boat on the water! Yahoo.gif

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martinarcher

Well here is the last couple steps. It turned out great. Clap.gif I'm pleased I went this route and would recommend it. Just be sure to have some rubbing alcohol to clean up any excess epoxy you get on the gelcoat. The tower almost clears the garage door - I need another three inches and the spindle would clear. Dontknow.gif Oh well - folding it down isn't too bad.

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martinarcher
I LIKE your work Martin! (and I'm very critical)..... Thumbup.gifThumbup.gifThumbup.gif

Thanks rustie. I'm a bit picky when it comes do doing things right too. Whistling.gif It figure if a job is worth doing, it is worth doing right! Thumbup.gif

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Thanks rustie. I'm a bit picky when it comes do doing things right too. It figure if a job is worth doing, it is worth doing right!

My sentiments exactly. Your stuff looks very clean...with aircraft precision. I like to work the exact same way on all projects. Only wish some of these shop mechanics felt the same way.... :) :) :)

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martinarcher
Thanks rustie. I'm a bit picky when it comes do doing things right too. It figure if a job is worth doing, it is worth doing right!

My sentiments exactly. Your stuff looks very clean...with aircraft precision. I like to work the exact same way on all projects. Only wish some of these shop mechanics felt the same way.... :) :) :)

I hear ya. I don't know how many times I've had work done on my cars or other things by mechanics (even dealers) and have been disappointed by their work. I guess that's why I do as much as I can myself - I know it will be done right by someone who cares! Thumbup.gif

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Whenever an illusion tower causes gel cracks they always seem to "round the corner" on the gunnel.

What do you mean by this?

Edited by spherren
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Whenever an illusion tower causes gel cracks they always seem to "round the corner" on the gunnel.
What do you mean by this?

Pretty sure he means that the cracks will eventually extend over the edge of the top rail flat section (where the tower is mounted), and down the sides of the top rail.... Cry.gifCry.gifCry.gif

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  • 2 months later...

I have an 08 LSV with an XS and noticed some stress cracks this weekend. The sad part is that I only carry one board on my tower and do not wakeboard very much behind it. There is a lot more surfing that goes on behind the boat. Is this going to be a major problem if I do start pulling more wakeboarders? I am not very happy to have this problem with only 1/4 of the second season with this boat underway. Also, my boat has never had any kind of tube even on it. I called my dealer and they said they could take care of it in the off season. Do ya'll think it will continue to crack and get worse. One side had 6 or 7 cracks at the base of the tower that are about 2 in. long. The other side had 2 or 3 in the same position. Also, my boat is stored about a mile from the water, so it is not being drug all over the creation every week. Thanks for any advice.

Edited by Andrew
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  • 1 month later...

UPDATE.....

Got my boat back last week, and although it took a little extra time to finish (a lot of work was put into this), Jay at Tilly's did one FANTASTIC JOB on matching my BU's Blue accent colored gelcoat. Valerie had a hand in eyeing the color match too....and the end result was the complete elimination of the pencil eraser sized chip. Of course it required a LOT bigger repair section to get the blend correct....but it's completely back to normal now! (with brand new side decals too). Thumbup.gifThumbup.gifThumbup.gif

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  • 1 year later...

I have a 2005 LXI with stress cracks at the side mounts (gunels) and they appear to be getting worse.  I think it's the Titan tower, has supports with two folding arms on the sides and 4 threaded knobs that secure the tower.  One side needs to be pushed out to line up and the other is 1.5" gap so maybe there is some shifting of the mounts that causes stress?  Bought used three years ago and not even sure if I transfered the hull warranty?

 

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I have a 2005 LXI with stress cracks at the side mounts (gunels) and they appear to be getting worse.  I think it's the Titan tower, has supports with two folding arms on the sides and 4 threaded knobs that secure the tower.  One side needs to be pushed out to line up and the other is 1.5" gap so maybe there is some shifting of the mounts that causes stress?  Bought used three years ago and not even sure if I transfered the hull warranty?

:no:

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I have a 2005 LXI with stress cracks at the side mounts (gunels) and they appear to be getting worse.  I think it's the Titan tower, has supports with two folding arms on the sides and 4 threaded knobs that secure the tower.  One side needs to be pushed out to line up and the other is 1.5" gap so maybe there is some shifting of the mounts that causes stress?  Bought used three years ago and not even sure if I transfered the hull warranty?

I was confused by this too. Folding arms on a Titan? Not one I'm familiar with.

Maybe a picture would help. Sounds like the tower has been bent or shifted to the side somehow. :crazy:

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I was confused by this too. Folding arms on a Titan? Not one I'm familiar with.

Maybe a picture would help. Sounds like the tower has been bent or shifted to the side somehow. :crazy:

Its one of those xtp xtreem towers (I had on on my lxi in my gallery) , which have rigid mounts to the gunnels and do cause stress cracking pretty easily.

-Chris

Edited by 99response
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