How hard is it to add more fiberglass to a boat for a Tower

mnwakeboarder

I have a Monster Tower and I 'm goin gto install it on my Glastron GX185 and need to add more fiberglass underneath for strength. Is this a hard process that should be done by a professional shop or can I do this myself and get it correct? Anybody else re-inforce a Glastron boat for a Tower?

89comp · Posted: Jun 16, 2003 9:43 am Post subject:

I just put a monster tower on my 89 Supra Comp and the fiberglass was a little thin, so I just added a nice oversize block of wood beneath where the tower was going to mount. By using an oversized piece of wood, you increase your tear-out by distributing the forces over a larger area.

AC505 · Newbie Joined: 14 Feb 2003 Posts: 30

Most yachts have strengthening plates bonded on using a polyeurethane adhesive (sikaflex or similar). Yes adding more glass is going to give you the strongest mount however a reasonable sized alloy plate bonded using sikaflex is more than adequate. You'll delaminate the glass before you'll get the sikaflex off. That's what I've done on my '90 Mastercraft and the glass on the deck is thin.

MrBlean · Posted: Jun 17, 2003 12:08 am Post subject:

I largely agree with the other guys. I wouldn't use/rely on fibreglass or a block of wood alone but would use glassfibre resin to bond some shaped ply, a block of wood or other stiffening material to the underside of the deck at the attachment points. You simply need to increase the area over which the load is spread. Glassfibre resin cures real quick (sometimes too quick!) so you could use the boat the day after, no problem.

TSHutch · Posted: Jun 17, 2003 8:57 am Post subject:

I recently helped my Bro-in-law and riding buddy put a monster tower on his glastron 195. Firstly its fiberglassing upside down is a pain in the arse. We used a paint stirer stick to hold the mat with resin flat so we could get it to stick easier to the underside of the hull. This made getting the mat to stick evenly go from almost impossible to almost easy. Make sure to cover anything in the boat you dont want fiberglass on. After we got it on I noticed the outside of the hull got hot from the reaction in the resin. We just put a wet rag over the spot to keep it from getting too hot.

mnwakeboarder · Posted: Jun 17, 2003 9:23 am Post subject:

how much fiberglass did you add? do you feel it is required or will the stock fiberglass thickness work? Did you run into any problems?

MrBlean · Posted: Jun 17, 2003 9:46 am Post subject: Heat from Resin

TSHutch. Interesting to hear your tale. The heat is produced when you have a large volume of resin curing as a lump. Resin has a low thermal conductivity so the heat generated from the curing reaction can't pass thro' the material and escape so it gets hot (especially in the middle of the gloop of resin). To check, fill a plastic cup half full and see what happens to the cup as the resin cures! Exactly the same thing happens with concrete - thats why they can't cast huge blocks of the stuff and there are cooling pipes thro' which iced water was pumped all thro' the wall of the Hoover dam to take the heat out when the concrete was going off.

So, this suggests you had too much resin. The secret would be to make a shaped re-inforcer that is a snug fit to the underside of the deck. Not that easy, I know, but if it's real snug then you only need a small amount of resin which acts more like glue than anything else. Remember, resin itself isn't very strong, that's why boats are made out of Glass Fibre Reinforced Resin not pure resin!

Alternatively, you could add layers of glass fibre but remember the glass only needs to be "wetted" with resin not absolutely soaked in the stuff. If you get more than a few drops of resin falling off from the oidd sharp point or corner, you've got too much resin around. Resin should be squeegee'd off leaving the glass matt only damp with the stuff and self-adhering to the surface to which it has been resined. Excess resin adds no strength but simply cures into a brittle lump - just what you don't need.

Leggester · Posted: Jun 17, 2003 9:54 am Post subject:

While I agree with all that's been said, especially about the shaped re-inforcement, there are alternatives.

I used Liquid Nails to hold the reinforcement plate to the boat, then glassed over it with about 5 layers of cloth.

Basically, you do want a bonded reinforcement. Now, whether you glass it, epoxy ( same as glass ) or a permanent glue I think is up to you. If you do go with glue, you want to find one with the same flex capabilities as fiber glass.

There's many ways to skin/spank this monkey. But I'll tell ya, it's a real pain to glass upside down. Wink

TSHutch · Posted: Jun 17, 2003 12:38 pm Post subject:

My bro-in-law talked to bill from monster tower. Who also lurkes around this forum from time to time and usually replys on most topics about towers. He was tons of help. There was a minimum thickness (3/8 in but dont hold me to it) in the install manual for the tower. (go to monstertower.com and download or look at your book) Bill from monster tower says he does not install on less than 1/2 in. We added glass to get to the one he uses. If your gonna do it do it right. You can email him from their website also.

The only problem we ran into with the installation is the glassing upside down.

The only problem weve had with the tower is make sure to tighten it up everywhere after you break it down. Moving it around tends to losen some of the bolts. And I nosed dived a ollie 180 and smacked the water hard. The line tension I generated in a very short amount of time tweaked the tower to the left abit No problem though Just bump it back and retighten.

MrBlean · Posted: Jun 17, 2003 3:06 pm Post subject: Epoxy versus glass

Leggester - you probably know this but there's a big difference between epoxy resin and polyester resin, mainly in the cure time. Provided you don't mix too much hardener with epoxy and it doesn't get too hot, the cure time is typically a couple of hours. With polyester resin, it's typically a few minutes. So, for an intricate job where you may need to move things around to get exactly the right position, epoxy may be a better option. Still drips when upside down though, especially if you're over-generous with the resin!

blacter · Newbie Joined: 28 Apr 2003 Posts: 22 City: Bend, Oregon

OK...will this work (please say yes because it's what I did). Suppose one was to take a generous rectangle of half-inch plywood and sandwich it between the inside of the hull and the metal backing plate. Bolt the whole package together, then coat it all with that "Kitty Hair" fiberglass product.

blacter · Newbie Joined: 28 Apr 2003 Posts: 22 City: Bend, Oregon

OK...will this work (please say yes because it's what I did). Suppose one was to take a generous rectangle of half-inch plywood and sandwich it between the inside of the hull and the metal backing plate. Bolt the whole package together, then coat it all with that "Kitty Hair" fiberglass product.

MrBlean · Posted: Jun 17, 2003 11:48 pm Post subject: This is what I did....

If the piece of ply was significantly larger than the backing plate and was a reasonable fit up against the contours of the inside of the deck, then I reckon it should be OK. If, however, the ply is up against a concave surface (one which bows in) such that only the four corners of the ply are in contact with the underside of the deck, you haven't gained a lot. All you've done in that situation is move the stress points further apart which is better but it will still be point loaded. What you are trying to achieve here is to spread the stresses uniformly over a much wider area of the deck and hence reduce the loading at the relatively small area where the tower attaches.

Leggester · Posted: Jun 18, 2003 4:55 am Post subject:

yep MRBlean. I was just using that as an example.

There are many good adhesives on the market today that were not available ten years ago.