Leveling sagging deck BEFORE fiberglassing?

[bstruble]

Hello, I am restoring a 1968 nautaline houseboat. I am about to refiberglass the roof deck and had a question regarding leveling before refiberglassing. The fiberglass has sagged over the years between the studs and has a slight wavy character to it. Any tips on correcting this before refiberglassing? My plan is to do a layer of 1708 and then a second layer of 1.5oz Chopped Strand. Will I just be reinforcing the wavyness of the deck if I dont correct first? Should I level before relay the glass with bondo or something. Thanks!

 

[Scott Danforth]

first, you need to understand why it sagged. is the roof sound enough? why the need to add 1708 and CSM? did the underlying material start to be compromised by decades of use. you are dealing with a 53 year old boat

next, adding bondo to straighten it out will not only add hundreds of pounds 9if not thousands of pounds) of material up there, however bondo is made from talc. you want a true fairing compound.

if the material just sagged over time, and you re-enforce it as it, you will still have a wavy roof. depending on how critical it is I would go with 2-3 layers of 1708 and one layer of CSM over a new deck layer of 3/8" exterior ply.

 

[bstruble]

Hi Scott, The roof is sound, should have mentioned that. It has new support beams added from underneath. It's just a cosmetic issue. I have read bondo is a no-no for repairs but was curious if it was just supporting new glass then maybe I could get away with it ($$). Is true fairing compound that much lighter? It's only a slight sag, couldn't even get a good photo of it. Was also hoping that the 2 layers of glass would be enough. Adding the glass partly for strength but mostly to seal up the hairline cracks that have started to leak.