|Topic Review (Newest First)|
|02-09-2011 01:10 PM|
Originally Posted by Beersmith View Post
The polyethylene trowel 'forces' the flow-out.
|02-09-2011 12:56 PM|
I don't see why it shouldn't.
Originally Posted by Beersmith View Post
|02-09-2011 12:50 PM|
West System describes applying the barrier coat using a roller, then tipping off with a piece of cut up roller to smooth out the application. Would this method work just as well with Interlux, Pettit, or whatever product I use? Or even tipping off with a brush to avoid the orange peel?
Such as described here: Barrier Coating
|02-09-2011 12:40 PM|
Could not be more true
Originally Posted by sailingfool View Post
|02-09-2011 11:01 AM|
No, the peaks and pimple-tops from the previous 'roll coat' set the depth, the trowel 'rides' on top of the previous peaks. Usually takes 2-3 trowel applications to get the barrier smooth. You dont want to knock-down the first/previous 'pimples' with a trowel as they set the height for the trowel to fill. If you find that youre not 'thick enough' add another 'roll coat' and let partly cure.
You can apply bottom paint in the same way ... and you get a smoothness equivalent to 'almost as smooth as a babies ass'. Smooth surfaces have less adhesion for 'growth' ... and 'release' faster and more completely when at speed - less 'roughness' for the crap to 'stick to'. With smooth applied ablatives you also get longer life as the 'total' surface area exposed is at a minimum - somewhat important if you seen the latest prices for ablatives.
|02-09-2011 10:42 AM|
Thanks for this information. I am curious about the trowelling method, it seems that trowelling on successive layers would be considerably thinner than if applied by roller. Am I just overthinking it?
Originally Posted by RichH View Post
|02-09-2011 10:36 AM|
No need to sand a 'new' barrier coat to make it smooth.
You can apply the first coat with a roller but successive coats with a large polyethylene trowel (not a roller) and 'fill' the previous hills and valleys from the roller application. Method: roll on and immediately 'wipe' with a trowel, the semi-hard 'peaks' from the first 'roller coat' will set the height for the trowel to 'glide' on --- thus quickly filling and fairing the 'valleys'. This 'troweling' is in the same manner as applying the final gelcoat to a MALE plug mold. For perfectly smooth and faired you can finish with a thinned out fairing coat using a BIG trowel.... and the WHOLE job should be continuous so that NO layer 'fully cures' so that there is continuous bonding throughout. This can include the first bottom paint coats (hot-coating) for much better 'adhesion'.
The MOST IMPORTANT characteristic or goal of ANY barrier coat system is the MIL-THICKNESS. Without the proper mil-thickness you are vulnerable to future water (principally water vapor) permeation through the barrier coat into the FRG. With a roller you have to apply MORE barrier so that the deepest 'valley' is at the proper thickness; with a smooth or troweled-on application that required thickness is more easily controlled.
How to know that you have the proper thickness --- go to an industrial paint/coating supply and get 'mil-thickness gages'. These are 'little comb-like or 'toothed' gages' that you 'push' into the fresh/wet paint or coating and if you get discontinuous dots or dashes in the fresh surface instead of lines the thickness is too small and you need to add more paint/coating. With solvent based coatings you need to calculate the % solids so that when the solvents 'flash off' and the coating 'shrinks' you ultimately arrive at the recommended 'dry' mil thickness not the 'wet' / 'as applied' mil thickness.
Each barrier coating mfg. lists the proper 'thickness' in their 'tech manuals'. If you dont apply to the recommended (dry) mil thickness, you can expect to not have sufficient barrier applied and you will/may/can after some time observe the 'return' of the blisters/pimples. I always apply more thickness than what the mfg. recommends as I dont want to do a job 'twice' ... and barrier coating manufacturers seem to always continually 'increase' their thickness recommendations over time.
hope this helps.
|02-09-2011 10:08 AM|
If you are going to sand the faired areas or the bottom in total for smoothness, be sure to use a long board, see 3m Longboard, as that's the only way to remove the high points. You also need to use a long board if you actually shape your foils, which is pretty unusual outside of one-design racing.
This is an ugly and painful job best done by teenagers.
|02-09-2011 09:07 AM|
|zz4gta||There will be a difference in performance between a smooth bottom and one w/ orange peel. Not a big difference, but there will be one. Just put on an extra coat of barrier, and then sand it with 80 or 120 before the bottom paint. Should knock down any lumpiness and make for a pretty smooth finish.|
|02-09-2011 08:55 AM|
Originally Posted by T37Chef View Post
|This thread has more than 10 replies. Click here to review the whole thread.|