fiberglass repair :-\

[gobeer net]

Homemade tower on a bayliner, already seeing cracks.

I talked to a guy today who said he would reinforce the inside of the hull to make sure the cracking wouldn't continue. He is quoting 300'ish to add a few layers on the inside, then some marine wood, then another layer or two over the wood to seal everything up.

I'm wondering how good/bad this price is. Its a younger kid who works at a boat hull repair place. I'm leaning towards trusting the kids work after talking to some mutual friends and hearing him describe my problems. He sounded educated and experienced since he described a few other boats with similiar problems.

I did some searching on wb.com and found alot of diy fixes, but not any prices of how much a professional would charge for something like this.

Any ideas on the price and if I need the layer of wood on the inside? Of course its important to get it done "right", but how hard/important is it to get it done perfect.

[joedirt00]

you are going to do this on the inside so it could look like total crap and nobody would know. I would get a fiberglass kit and some wood an do it my self. It shouldn't be too bad unless your a slob and drip resin everywhere its not supposed to be. is he going to fix the cracks on the exterior for that 300? if so might not be too bad but 300 bucks could buy some good gear.

[MrBlean]

Looking for the cause rather than necessarily a cure, looking at your tower design, it appears that the pin on the mounting plate to which you then attach the Heim joint is overly long. The amount of downward force and hence twisting moment on te mounting plate that is able to exert is very large. If you could shorten it and get it the attachment point closer to the boat that would help.

In terms of addressing the cracks, are you planning to have these made cosmetically good on the outside too? If so, that involves a fair bit of gel coat work taking several hours. I'm happy to mess around with glass fibre and resin myself where cosmetics aren't important but gel coat is hard work and labour intensive to get a professional finish.

If he's including the gel work for 300 dllrs I'd bite his arm off.

Hate to say this but your tower ain't looking so inexpensive now, is it?

[gobeer net]

the 300 is not doing anything to the outside. He even admited that a few more small cracks might come up, but none as big as the ones i have right now.

As for the mounts, I've made provisions to shorten the mounts, making them a shorter lever. This makes the tower not folding friendly :-\. Before it folded with minimal effort and would ride down the road like that. With the shorter mounts it hits the windshield when it folds so it will only be folding when I'm going in/out of garages.

As far as doing it myself.....I've never done any fiberglass......I'd say i'm just a wimp with anything thats not metal, but I might be game for trying if I could get it done for around $100.

[MrBlean]

[salmon_tacos]

Honestly, you probably don't even need any additional glass in there. What did you use as backing for the mounts? Doing a good job laminating some fiberglass cloth in a tight area will be MUCH more difficult than the possible alternative.

Here's what I would probably do:

1. Buy some epoxy resin, hardener, and some 404 high-density filler from West Marine along with the $3 how-to book.

2. Make either a marine plywood backing plate, a metal backing plate, or both (if you use aluminum, you can buy an aluminum etching kit so the resin will stick to it).

3. Mix up the resin and add filler until you get a peanut butter consistency.

4. Spread the resin mixture on the plates thick enough so that when you press it against the inside of the hull, it will fill all of the voids and squeeze out of the sides.

5. Put it in.

6. Clean up the edges.

7. Tape it in place and let it harden (how long depends on the hardener you chose).

8. Drill holes, if they aren't already there, and bolt it up. Allow at least 24 hours for a full cure.

The cracking is usually caused by pressure points at the edges of the washers, plates, or whatever you used. By using the process above, you're basically making a custom molded high-density plastic backing plate that will eliminate those pressure points.

I bought a mini-tower with less than perfect geometry (read: high-stress at the mounting points) and small feet. I used the above technique with the 3" circular aluminum backing plates and two bolts, and haven't gotten any cracking at all with hard use.

BTW, if the cracks are originating from the bolt holes, make sure you chamfered the edges of the holes (run the drill in reverse with a large drill bit to round off the edges then hit it with some fine-grit sandpaper on your fingertip).

[MrBlean]

salmon - if you go to gobeer's other post on thios subject (http://forums.wakeboarder.com/viewtopic.php?p=427793&highlight=#427793) and scroll down to the picture of the cracks you'll see that these:

1) Don't emanate from bolt holes

2) Lay roughly parallel to the edge of his mounting and backing plates

and that gobeer has used some pretty substantial backing plates.

However, the cracking isn't the usual kind and is more likely to be overstressing caused by the leverage of the mounting feet due to the relatively long connecting bars attached.

His problem may also be that the mounting and backing plates are flat and are in contact with a large surface area over which there is a significant curve (and hence are trying to flatten it when bolted together) so your conformal backing plate idea will help in that regard. However, he'll need to use something similar on the outside too.

[MrBlean]

salmon - if you go to gobeer's other post on thios subject (http://forums.wakeboarder.com/viewtopic.php?p=427793&highlight=#427793) and scroll down to the picture of the cracks you'll see that these:

1) Don't emanate from bolt holes

2) Lay roughly parallel to the edge of his mounting and backing plates

and that gobeer has used some pretty substantial backing plates.

However, the cracking isn't the usual kind and is more likely to be overstressing caused by the leverage of the mounting feet due to the relatively long connecting bars attached.

His problem may be that the mounting and backing plates are flat and are in contact with a surface with a significant curve (and hence are trying to flatten it when bolted together) so your conformal backing plate idea will help in that regard. However, he'll need to use something similar on the outside too.

[salmon_tacos]

If that's the case, I would recommend that he either use the same process on the outside feet or bend them into shape. I machined the outside curve of my hull in the aluminum feet and perfected it with some thickened epoxy resin. That way, you don't really see the resin but the contour is perfect. If he chose not to bend it, he'd have some thick epoxy at the edges of the plate.

gobeer net,

That reminds me of an important point though, which is optional on the inside but most likely mandatory on the outside. If you do not want to adhere the mount or backing plate to the hull, place some clear packing tape on the hull and coat it with mold release (you can get that at West Marine as well) before molding the epoxy to the hull. That way it will come off. I did this on both the inside and the outside of my considerably curved hull. Then, I stuck some rubber material on the mounts and backing plates before assembly to further isolate the stresses. I used peel-and-stick firm flat rubber "Sano pad" (www.sanosports.com), but any dense rubber material would do.

[MrBlean]

salmon_tacos - I don't think bending is a practical proposition. You simply couldn't make the plates follow that 3D curve accurately enough. Any resulting small high point would be bad karma when the plates were bolted together.

If the feet were ally and gobeer has access to templating and machining capabilities, that would be the way to go. But gobeer's tower is steel so you'd need a pretty hefty chunk of plate to start with, it would be more difficult to machine and the end result would be quite heavy.

The conformal layer is the best alternative and your suggestions re packing tape and release agent are excellent.

BTW, thanks for the tips on my own tower.

[Brit Rider]

Hmm. this is an interestnig one gobeer net, did you strengthen the deck at all originally? Those older bayliners are generally built very thin and always require backing up with more glass or some ply to at least 3/8ths of an inch when installing a tower.

The damage seems to have been done.. and those cracks will never leave.. but you can slow their growth by using salmon tacos and Mr Bleans ideas.

Maybe you could look into having the cracks proffesionally fixed.. thats not something anyone without training could do themselves. and that should solve your problem, if left they will over time grow

First thing is first - if you didn't already - take that tower off, it looks to me (as already mentioned) that the mounts are stressing the deck big time. I'd get it off before it does more damage.

My advice would be:
to thicken the glass around the mounting locations with a DIY kit, trying to cover as much area as possible and bringing it to a thickness of around 4-5th's of an inch; over a few sessions. then let it cure fully.

Then get hold of some 3-5mm high density rubber as salmon tacos said and lay it on the outside and inside of the deck matching the shape to your tower feet and backing plates. drill holes in it around 1-2 mm bigger than the bolts that will pass through it - this will reduce stress in those areas. then.. this may be a bit tricky but try to bend those mounts some. they are too big and too flat for the curved surface. try to match them as well as you can to the bend in the deck.. and lose 1/2 and inch from each end. the rubber should do the rest. Bolt it all back together and re-install the tower.

Just my 2 cents.

Mike
www.WakeboardTowers.co.uk

[MrBlean]

Mike - we'll make an engineer of you yet! Or do I sense one inside trying to break out?

[Brit Rider]

haha actually i was going to be a precision engineer.. even spent a few weeks in my spare time at a local shop. but decided it wasn't for me.. then the strange and perverse world of wakeboarding took over my life and i got the name "tower fairy".. it was all down hill from there!

Later

Mike