Saturday, October 25, 2008

Hull preparation - my best techniques summary

This post is mean't to be a notes to myself for that time 'hopefully' in the not to distant future, when I am preparing the main hull.  It's also a post for others with the following label.  'Every amatuer builder is different and the best techniques for one builder will not be a good fit for another.'  

1) Lay up the foam as fair as possible.  Use the polyurethane construction glue (the stuff that does not expand that much) so that the outer hull can be immediately sanded without any hard spots.
2) Always wet out the foam before laying any laminate.  I have found that this is absolutely required with the fine weave aerospace cloth that I am using.   
3) Always use peel ply when doing any hand lamination.  Using plastic sheet over the peel ply is a good way to ensure a good result.  When squeegeed the plastic creates a local vacuum (for good adhesion) and allows you to remove the excess resin.  I may be at the point of not bothering with vacuum bagging as I fail to see any major benefit for all the extra trouble and cost.
4) Apply fairing compound sparingly and sand most of it off.  Good results were obtained with Quickfair.  Sand, sand and sand with the long board (60 grit) until there are no low spots left.  Where possible make sure the bare laminate serves as the local high spot for the long board.  
5) Apply skim coats of epoxy resin to seal up the fairing compond and fill the pinholes.  Sand with the orbital sander (no more hand sanding, except for the hard to get at places), with 120 grit until the hull is smooth.  Smooth is when the surface is all smooth and dull with no shiny spots.  It's okay to apply more fairing compond at this point, this is the last chance.  The thin first primer coat will seal it.
6) Apply the bottom paint.  Thinking ahead, do a good job with a manometer or laser to get the designed waterline right on the main hull.  VC Performance Epoxy can be rolled on.   At least 3 coats.  The  surface can be wet sanded as smooth as required.
7) Apply the topcoat finishing primer with a foam roller.  With Endura EP-2C primer sealer thinned 15% air bubbles are not a huge problem.   I have been waiting till it is fully cured then sand with the orbital sander with 220 grit until the hull is smooth. 
8) Unless an excellent method for applying the topcoat is found, take the hull to a paint shop for topcoat spraying.  

Wednesday, October 15, 2008

No topcoat painting for now

The weather was recently quite nice, low humidity and pushing 20+ degrees C,  so I decided to apply a coat of Endura topcoat on the outer half of the starboard float.  I used a foam roller and tipped out the air bubbles with a brush.  Making a long story over a few days - well short, I was not happy with the result,  so I sanded this coat down to 220 grit.  It is now very smooth but dull.  So ...I have decided to leave the floats for the time being with the finishing primer on the hulls.   Maybe I will have a professional paint shop apply the final topcoat when I have all 3 hulls ready.  

Winter is fast approaching and I hope there is  time get the port float all sealed and primed as well. 

Update: We weighed the starboard float today, it looks to be ~ 125lbs as is.

Wednesday, October 01, 2008

Finishing primer on the starboard float hull

The skim coats of epoxy seemed to work really well at providing a very fair smooth surface after sanding.  Fair enough, and I decided to hang the hull once again and apply the finishing primer to the whole hull (excluding of course the bottom paint which I masked off).  I applied the two coats of  Endura EP-FD primer with the foam roller and found that with the doors open I was able to get by with the half face respirator.  I think flowing on the paint is far less dangerous than atomizing it with a spray gun.  Quality wise I think rolling on the paint when the hull is hung like this is not optimal, I do have some paint runs here and there.  However since I will be sanding this primer down to 320 grit, I thought that getting it all painted was more important.  However, when I get to the topside paint I think I will be painting the hull in sections (roll and tip) , ie on one side, the other side and then the deck.   If anyone is interested I found a very good tutorial (for Sterling paint) here.
Below are a few pics of the now white primer coloured float hull.