I'm putting a new bottom on wildcat. I am close to being ready to put on the barrier coat and trying to figure out how much material to buy. I calculated 160 sq ft of hull wetted surface area and another 28 sq ft. for the keel. Does anyone know the actual sq ft of witted area, and any recommendations Petit vs Interlux?

Russ - when I did Rhapsody in 2007 I ended up purchasing 4 gallons of Interprotect 2000e - 2 gal white and 2 gal grey. Overall I used about 3 gallons with a total of 4 coats rolled on alternating grey/white. Both the Petit and Interlux products are good. Good prep is the key. When it is done, let the barrier harden and if you have an inside place to work, elevated temperature is your friend to get this to harden sooner. A light hand sanding with 80 grit on a foam pad of the fully cured barrier coat will provide a nice surface to spray the desired bottom paint.

Thanks Bill. We will be spraying on the barrier coat and will probably do 4 coats of gray followed by 3 coats of white. I'll plan on 4 gallons and return one if it is not needed.

At the risk of being redundant to all the previous info on doing new bottoms,in case anyone is contemplating doing this, I will share our bill of materials, time line and a bit of trivial info on how we (I) went about it.
First the list of materials
1 elephant steak ( started with that. I figured if I was going to eat an elephant I would find out what I was in for)
1 large bottle of Advil
1 heating pad
1 loving wife willing to massage my hands, arms, shoulders and back

12 - 50 lb bags of ground corn cob (pretty aggressive blast material) $25/bag
1- 126 oz. container of West 105 resin
1 - 27 oz container of West 20? "slow" hardner
1 - tube West system 610
1- caulk gun
2- 5 oz (large) containers of 410 filler
4 - gals Interlux 2000 barrier coat (not yet purchased) and thinner
2 - disposable paint suits
1- 3/16" ball nose bone drill (used to drill holes to core)
1 - Dremel
3 - 6" plastic dry wall mud applicators
2 - 3" plastic dry wall mud applicators (used mostly for mixing West resin, hardner and filler
1 - 11" metal extremely flexible dry wall mud applicator
1- 14" plastic dry wall mud tray (used for mixing resin, hardner and filler)
1- 1-1/2" metal paint scraper (used to clear clogged sandpaper))
1- gal xylene
1 - pair of heavy duty chemical resistant rubber gloves
1 - box of 100 nitrate plastic gloves
4- rolls masking tape
3- 3 packs of 9' x 12' rolls of plastic paint drop cloths (used to shroud boat and contain some of the sanding dust)
assorted rags for cleanup

1 - large industrial sand blast unit
2 - Ingersoll Rand model 315 in-line sanders (do not buy the Harbor Freight knock off)
1 - water separator
1 - Porter Cable model 505 1/2 sheet sander (buy used on line)
1 - 5" random orbital sander
3 - 60' x 2-3/4" x 80 grit rolls of sand paper (may need a 4th when we get to sanding the barrier coat)
1 - 120' x 2-3/4" x 120 grit roll of sand paper - not yet used
1 - box 50 sheets of 80 grit sand paper
1 - box (sheets) of 400 grit sand paper
1 - container of 50 - 5" disks of 220 sandpaper
1 - container of 50- 5" disks of 400 grit sandpaper
1 - spray gun capable of spraying barrier coat (to be determined) + pressure regulator
1 - dehumidifier
1- shop vac
6 - carboard toilet paper rolls, cut to fit (used inside of through holes)

1 - big honkin air compressor
1 - 50 ft air hose
1- high intensity LED shop light
1 - heated building
1 - Frers 36 (bottom done 2 years ago) parked next to my boat to remind me how small of a job my j30 would be

Time line (based on one 70 year old guy working 5 days per week, every day 9:30 till 3:30)
Last week of November, sand blast boat (it took two days to sand blast the boat (could have been done in one)
Next day boat moved inside heated, dry building
day 1 inside
drill aprox 30 holes into core to determine moisture
Turn on dehumidifier
Clean and remove all moisture from inside boat
Go home, do nothing to boat for 60 days

Last week of January (first week of February) real work started. 5 days per week from then till now (4 weeks)
first week
Vacuum up corn cob particles that covered boat and trailer (what a mess)
Check for moisture in holes drilled to core - all dry, balsa white and firm (we dug some of it out)
Shroud boat
Sand entire boat to remove residual bottom paint, barrier goat, etc
Wash boat with xylene
fill holes and large gaps with 610

I won't bore you with the details of filling holes. We basically followed the West System manual
My wife says I underestimate things that said, I'm guessing we had to fill 1 million holes

I took the Elmer Fudd approach, "be vaweey, vaweey quiet and sneak up on it". I did three fills of west resin/filler
Time frame = 2 days to cover/fill entire bottom with one coat, 3 days to sand it off (one week per fill)
So... in one month I have sanded the entire bottom 4 times, one initial sand and 3 times after applying resin/filler

Left to do: I am estimating
one week to do final touch up (fill about a dozen holes that weren't filled completely and hit 4-5 low spots - final sand
two days to paint
3 days to final sand

Now that I'm almost done, for those interested in how to eat an elephant... One bite at a time!