Reinforcing for tower

Will be installing an Aerial Airborne on my '00 MasterCraft Maristar 230 VRS. It seems like most say that the fiberglass in those areas of a MasterCraft will be at least 1/4" thick and won't require reinforcement. However, I don't see how it could hurt if I could reinforce a little bit with minimal effort.

I see that many use plywood and epoxy or fiberglass and resin between the metal backing plates and the hull. I was thinking about getting a plastic chopping board or two from Wal-Mart in place of the wood. I've seen plastic marine lumber but it's crazy expensive.

Also, I already have some automotive Bondo that I thought might be a good adhesive/filler behind the extra reinforcement plates. I figure butter the back with bondo then put them in place and torque the bolts lightly. Allow the bondo to cure completely and then finish torquing. The logic would be that the backing plate would come into contact with the high points of the fiberglass while the bondo would spread the load out to the low spots.

Any thoughts on these ideas? Any better ideas for an adhesive? Should I even bother?

Good idea on the plastic cutting boards. Maybe use a silicon marine adhesive instead of bondo.

Always wondered about doing a nice top plate too. Maybe out of carbon fiber or billet.

I thought about the silicone adhesive. I have some of that too. It would definitely be easier to deal with vs. a 2 part adhesive. I liked the idea of the material filling the gaps being rigid but flexibility could have its own set of benefits.

I installed the same tower on my Outback.. I highly advise using backing plates in ALL areas. Better safe than sorry..


We cut backing plates out of treated plywood.. 1/2"... We cut them shape wise to fit the underside of the gunnel - approximately a foot long by maybe 4-5 inches wide as allowed.. We covered the backside with liquid nails, pre-drilled a pilot hole and cinched them up.. Over 2 years and no cracking, creaking or noises..

Good luck.. It's a relatively easy tower to install. The only issue we had was actually with the packaging. Some of the plastic got stuck in the h-brace on the top piece and we could not seperate two of the pieces that we needed to. It took us about 2 hours to get the plastic out. Aside from that - pretty standard.

I had 3 guys helping me. I think you could do it with 2 guys total - but I certainly wouldn't try to install it alone. Lining up the H-brace, drilling some holes etc is a tough job alone..

Good luck Jeff. You'll be stoked about the tower. As I recommended in another thread - do yourself a huge favor and have the 4 bolts that you need to drop the tower down made with knobs. Will be WELL worth whatever price you have to pay.

I have a 'bu with a custom tower, but I went with more of a "suspension" approach. I used 1/4" aluminum backing plates, and sandwiched 1/4" solid rubber sheet above and below the deck. 8 seasons / ~500 hrs with no cracks, and my tower is pretty tall and very stiff.

Given that the gunnel cap is not flat you want to use treated or coated plywood blocks with radiused corners and face to better fit and mold to the underneath contour. Silicon and Bondo have zero structural integrity so use a body filler containing fiberglass strands. You want all gaps filled with something that will cure and be as strong as the blocks. Then you can add aluminum flatbar under the blocks. We've installed many towers this way with no spider cracks in the top cap gelcoat after years. I don't trust 1/4 inch.
David
Earmark Marine

Found some cutting boards at Wal-Mart for around $8-13 that were pretty rigid but 3/8" thick. They would probably be fine but I will hold out for something a little thicker. My wife has a Cutco board that's about 1/2" and stiffer than plywood but I won't be allowed to use that one.

I have some thick fiberglass mat and resin that I guess I should use to bond the supplemental backing plates to the hull.

You actually want a very small degree of flexibility in the block so that it somewhat conforms to the curved underside of the deckcap. This goes along with the suggestion to remove the corners and face edge of the blocks. Its better than four small points of contact with gaps between the deck cap and block. Then the idea is to completely fill the gaps with a material that bonds and has serious structural strength. You can make your own by cutting the fiberglass mat into very short strands. Mix a thick quantity of the strands in with equal parts of bondo and fiberglass resin with the hardeners of course. First give the blocks a good coating of figerglass resin for protection. Apply a good portion of the compound to the top side of the block. Tighten it all down, let the excess ooze out and let it cure. Its permanent, covers alot of surface area for good distribution and there are no gaps betwwen the blocks and deck cap. This is just one way.

David
Earmark Marine

The 3/8" material was stiff but will bend and conform under the clamping force of the bolts. I guess I will proceed with that instead of looking for thicker material.

After spending many hours laying things out (Measuring, looking at it from every angle, checking what's behind the feet, etc) I finally drilled my holes last night.

The fiberglass on the starboard side was 1/2" thick at each hole (Hooray for MasterCraft). The port side was 3/8" at the front hole and 7/16" at the rear hole.

So, I'm well over the 1/4" minimum but I still plan to cut some plastic reinforcements, bend them with a heat gun to conform to the inside of the hull and then fiberglass them in place.

I ended up having to grind the front to feet to conform to a ridge in the hull because there was no flat place to bolt it wide enough for the foot. That was scary at first but came out really well. I used a contour gauge like you'd use for crown molding to mirror the shape of the hull at that point then took it to the garage. I started with an angle grinder and a sanding disk and then moved to a 1" diameter sanding drum on the drill press for the final "tuning".

Defintely use reinforcements... I wonder if a thick sort of rubber would work. - like the type of material they make rubber flooring from.. Probably not strong enough to transfer the weight - wood and fiberglass is probably better.

Jeff DeV,
From your description it sounds very solid with no worries over gelcoat spider cracks several years down the road. A few extra steps initially are worth the peace of mind.
David
Earmark Marine

As I said above, I've got 1/4" thick black rubber "gaskets" on mine. It's about the same durometer as a tire. I got it from my old job, but you can order from www.mcmaster.com.

We actually have tons of scraps of 3/4" thick rubber workout room flooring at my office. I'm just wondering if fiberglass and plastic cutting board would be better because it will contour to the surface then dry solid.