Cruisers & Sailing Forums - View Single Post

Richhh · 28-03-2007, 06:49

Depends on the 'span' of the repair, but usually the most important for filling, fairing and polishing will be 'long feathering boards' for wet-sanding. Sorry (but to pardon my expression) this is a 'hand job' to get a fair and dead-flat surface. Just like autobody shop work the next to final sanding and leveling is usually done 'wet' and by low pressure pneumatic power sanding; the final sanding is usually done solely by hand to achieve the necessary FLAT surface .... If possible consider to spray the final gelcoat on once you get a dead-flat under-surface, then final polish, etc. If you dont want to spray the final coat consider to have a gel 'artist' do this for you.

8ft x 8ft. although not entirely impossible to get 'flat' will require some extra long feathering boards .... long thin wooden boards/battens to which you 'glue' waterproof sandpaper (1300 - 2000 grit for the final 'wet-sanding'). If you 'rush' such a job at the end you will wind-up with a wavy surface; as the human eyeball can discern 'unevenness' almost down to the micrometers range-difference using strong light 'incident' to the surface. If you want a 'quality' flawless job that rebuilds the original to 'new - from the mold' quality ... take your time with the 'final' steps. The finer the grade of paper the faster the 'cut'; but, you have to change paper more often the 'finer' the grit you use. Can be done but think 'precision' not 'production-speed'. Go to an autobody shop supply for wet&dry paper on 'rolls' to apply to your feathering boards - they will also have the proper (but weak) contact adhesive.
Once you get a FLAT surface, then you can power buff (variable speed auto body shop polisher and 3M 'knobby' foam pads) with the final 'buffing compound .... for fiberglass gel the best is probably a 'Super-duty' (3M #05964) then 3M 'Finesse-iT' followed by 3M 'Perfect-it'. Obviously, you want moderate speed/rpm but not pressure to final flatten the gel with the polisher. Dont mix polishing pads and grits .... use a new/clean knobby pad with EACH grit; dont mix!!!!!!!
hope this helps.

28-03-2007, 06:49	#4
Richhh Registered User Join Date: May 2005 Location: Pennsylvania Boat: Tayana 37, M-20/I-20 Scow Posts: 250	Depends on the 'span' of the repair, but usually the most important for filling, fairing and polishing will be 'long feathering boards' for wet-sanding. Sorry (but to pardon my expression) this is a 'hand job' to get a fair and dead-flat surface. Just like autobody shop work the next to final sanding and leveling is usually done 'wet' and by low pressure pneumatic power sanding; the final sanding is usually done solely by hand to achieve the necessary FLAT surface .... If possible consider to spray the final gelcoat on once you get a dead-flat under-surface, then final polish, etc. If you dont want to spray the final coat consider to have a gel 'artist' do this for you. 8ft x 8ft. although not entirely impossible to get 'flat' will require some extra long feathering boards .... long thin wooden boards/battens to which you 'glue' waterproof sandpaper (1300 - 2000 grit for the final 'wet-sanding'). If you 'rush' such a job at the end you will wind-up with a wavy surface; as the human eyeball can discern 'unevenness' almost down to the micrometers range-difference using strong light 'incident' to the surface. If you want a 'quality' flawless job that rebuilds the original to 'new - from the mold' quality ... take your time with the 'final' steps. The finer the grade of paper the faster the 'cut'; but, you have to change paper more often the 'finer' the grit you use. Can be done but think 'precision' not 'production-speed'. Go to an autobody shop supply for wet&dry paper on 'rolls' to apply to your feathering boards - they will also have the proper (but weak) contact adhesive. Once you get a FLAT surface, then you can power buff (variable speed auto body shop polisher and 3M 'knobby' foam pads) with the final 'buffing compound .... for fiberglass gel the best is probably a 'Super-duty' (3M #05964) then 3M 'Finesse-iT' followed by 3M 'Perfect-it'. Obviously, you want moderate speed/rpm but not pressure to final flatten the gel with the polisher. Dont mix polishing pads and grits .... use a new/clean knobby pad with EACH grit; dont mix!!!!!!! hope this helps.