Steel frame keel support

[Joakim]

I have just bought a 28-feet sail boat (very rare boat from 1999) that has a galvanised steel frame, which makes the whole frame system inside the hull. This frame is about 2 m long and it has three "arms", which are about 1.5 m wide (side to side).

The steel frame seems to be just glued to the glassfiber hull (of course keel bolts goes through the frame). The shape of the hull is almost flat at the frame area and there are no glassfibre stringers or frames.

Is this normal way of using steel frames? Are the steel frames of e.g. X-Yachts also only glued or are they also over laminated in some parts? What happens in grounding (happens quite often around here)? Will the glue hold? Will the hull hold if the glue fails.

What kind of glue is used for this purpose? Can the frame be reglued without totally removing it and the keel?

Joakim

[yokebutt]

Sounds fishy, since the bond then includes a zinc surface. The ones I've seen have been either glassed over (Cal 36 & 40) or fastened in with lots of screws. (Synergy 33)

To repair that type of bond I think you'd have to run glass over the steel to hold it together, and if the steel is severely deformed, you'll have a nightmare fixing it.

Joakbutt.

[Joakim]

I called to a local epoxy adhesive supplier. They said, that adhesion to galvanised steel is problematic and it would be better to remove the zinc, but I should still get about 1/3 of the rated performance of the glue. They suggested Spabond 340 (http://www3.gurit.com/pdfs/adhesive/Spabond_340LV.pdf), which has shear strength of about 30 MPa and adhesion (pull) strength ~10 MPa. With galvanised steel the adhesion should still be several MPa according to the supplier.

The area of steel frame behind the keel bolts is atleast 0.1 m2. Thus this should be able to carry loads of several 0.1 MN which is several 10 tn. Is this enough?

Joakim