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View Full Version : Cracked stringer-cross members. Problem?



zimm17
10-23-2006, 04:58 AM
I never paid attention to some minor cracks where the cross-stingers tie into the hull in the engine compartment. My dad was down in there and thought it might be a problem. Is it just cosmetic, or do I have a major problem?

MOP
10-23-2006, 06:21 AM
My 22 an 86 has the exact same thing, I when I cut/groud the transverses out I found the -0- hull damage. I did go back with two transverses and more glass, I think if more glass was laid near the tips there would not be any pull away from the hull. If you search through the old posts you will see this was a very common problem but a fairly easy fix, you can PM me for a few photos of what I did.

Phil

need for speed
10-23-2006, 08:21 AM
:bonk: my 93 22 did the same thing... never fixed it

Rootsy
10-23-2006, 09:10 AM
that's a very high stress point in the whole structure.... the rib is stiff the area between the end and the chine still moves around... especially so if the gusset (or transverse as MOP calls it) is not well bonded to the hull.

if i had to do it over again on the Red boat i'd begin by #1 sandign the contact area... pre-laminating the whole transverse in glass and resin... gluing it in place to both bottom and stringer with the transverse ending at the turn for the chine... the glue would be one of the high strength polyurethane adhesives minimum but honestly i'd prefer a methacrylate (ITW Plexus) due to some of it's flexibility.... the glass lamination will fail before the glue ever gives up it's hold...

one thing i did on the tip of my transverses is to spread the glass out onto the bottom... to help distribute the load

(attachment function seems to be having a hiccup so sorry bout the size)

here is an example of what i did to try to alleviate the issue we see... my transverses are also glued and bedded to stringer and bottom and filleted with a fiber reenforced polyester putty.. then covered in 45/45 biax stitchmat.

http://i108.photobucket.com/albums/n27/jaroot13/IMG_3784.jpg

zimm17
10-23-2006, 09:28 AM
Nothing wrong with the bottom of the hull.

I've worked with west marine fiberglass before- I installed the stringers in my 55" (yes inches) Dumas scarab radio controlled boat that runs a 4HP zenoah go-ped engine. (48mph on GPS).

Anyway, sounds like I can grind it down with a sanding wheel and lay some more mat w/ resin on all those transverse ends to reinforce it. Then what- paint it with grey bilge gelcoat?

BUIZILLA
10-23-2006, 09:53 AM
I've seen trailer bunk location issues causing the same scenario of damage.

JH

MOP
10-23-2006, 11:00 AM
Hey MOP, how about posting the pics for others to see?? Maybe even do a little tech writeup of the repair for us please?

I have some after shots in this post http://www.donzi.net/forums/showthread.php?t=39332

I am pretty sure I have a couple of before's will look tonight.

Phil

realbold
10-24-2006, 06:43 PM
Nice lookin work there Roots. Epoxy and non-woven glass? Thats what I'm usin, all bi and tri-ax with an extra layer or two in the corners.

zimm17
03-13-2007, 05:42 PM
I'm going to tear into this next week. Dad says to use a 4 1/2" angle grinder, get the broken up fiberglass out of there. Then lay down some woven mat and west marine resin. Any hints on what resin and cloth to use? I plan to lay down about 1/4 to 1/2 inch of mats- depends on how it looks as I build it up. Then grey gelcoat to top it off. Shouldn't be that hard.

gcarter
03-13-2007, 06:13 PM
Here's what I did back in '04.....
I glassed the transverse pieces before installation. Next I used thickened epoxy to glue the pieces and add a nice fillet. I finished it off w/ a substantial amount of glass over the joints. If you look at my avatar, you can see I don't baby the boat.
There have been no issues.
If you want it grey, can I suggest International Bilgekote (grey or white). Why? It's a paint and is very easy to repair and renew. Doesn't tend to absorb stains like gel does. It sticks to EVERYTHING!

http://www.donzi.net/forums/attachment.php?attachmentid=2398&d=1083022388

zimm17
03-15-2007, 05:35 PM
Well here's stage one of the repairs. Hit the cracks with an angle grinder. 2 layers of glass over 5 of the joints. The sixth one- shown in the pics as bare is getting filled with resin first, then it gets a cap. I'm now up to 3 layers, good enough for today. I'll let it all set up then get back to it another day. I plan to build up 1/4". Any ideas for the final coat? Grey pigment for the last layer, or just paint it?

justleft
03-15-2007, 06:30 PM
When you glass it don't use mat. Mat is just a filler. A good woven or even knitted (Rutan)
glass is much stronger and doesn't hold as much resin so it's also lighter.

Resin is not strong, it's the glass fabric.

http://www.aircraftspruce.com/catalog/cmpages/rutan.php

zimm17
03-15-2007, 06:33 PM
Crap, what does the woven glass look like? This is 6oz west marine stuff. It's not the random weave, but looks like woven stuff. Do you have a link with a picture?

justleft
03-15-2007, 06:39 PM
Mat just has swirls of glass. Woven looks like cloth.

I put a link to Rutan knitted glass in my last post. Very much over kill.

zimm17
03-15-2007, 06:44 PM
Okay, cool. I'm not using the swirls- what I call "random mat". It's the 6oz woven cloth. the curved parts in the photos are just a few stands that got stuck to my resin cup and fell back into the fiberglass patch. They'll sand right out.

I'm using the 6" wide west marine tape: http://www.westmarine.com/webapp/wcs/stores/servlet/producte/10001/-1/10001/264284/0/0/fiberglass%20tape/All_2/mode+matchallpartial/0/0