Building a small mold, looking for advise

[MarlinTini]

I am building a small mold to house my gps unit on my boat. I have a wood "plug" constructed that I am just now finishing to prepare to pull the mold from to create the negative part. I am currently painting the wood plug with automotive primer to fill and smooth the surface area. Once I have a perfectly smooth surface I plan to seal the primer with a laquer paint then wet sand with 600 grit paper until a super smooth surface is developed. I purchased a can of meguiars mold release wax to prep the surface for gelcoat. Planning to brush on the gelcoat then once it sets up begin the process of laying on polyester cloth and resin to build the mold. I tried this once already with the same plug and had a problem with the gelcoat really adhearing to the plug - even after 8 - 9 good coats of wax. The only difference is I did not seal the primer paint with a coat of laquer. Thinking this could have been a contributor to my problem. Not sure - thisis the first time I am attempting to build a mold to create a fiberglass part. <br /><br />Need some advise from someone who has done this before and can provide some guidence. Don't want to have to sand the heck out of my plug again to try over!! <br /><br />Thanks, Jeff.

 

[SCO]

Re: Building a small mold, looking for advise

I have done this, but always destroyed the plug while getting a smooth part. You could make a test plug and paint with a few coats of epoxy or polyester prior to applying the wax and see if it works. I bet your lacquer idea also works. When I have done this, I have worried about the epoxy heat melting and removing the wax. I would try and make the gelcoat a fast application, and wouldnt work it excessively with the brush.

 

[Kenbo]

Re: Building a small mold, looking for advise

When I was building boats, we used a mold release agent containing PVA (Polyvinylalcohol). Defenders marine, www.defender.com, sells it by the quart or gallon. A quart goes for $7.49. We would wax the mold two or three coats first and then spray the PVA. It usually worked well for us. Good luck!

 

[BillP]

Re: Building a small mold, looking for advise

I'll bet you exceeded the number of coats the wax mfg said, right? 8-9 coats is way too many. That means you are using too much wax...this will MAKE it stick. It doesn't matter that it is mold release wax. I know it sounds wrong but I am 100% right and anyone who has experience in the trade will tell you the same. Clean the wax off the plug with solvent and start over...use the mfgs suggested applications (likely 2-3 max) and try it. I'm talking hard wax, not liquid mold release.<br /><br />In a long ago life I worked in the R&D dept for Aquasport boats...plugs and molds.

 

[caldog101]

Re: Building a small mold, looking for advise

hi i live down here in miami and would like to askeveryone a question on the mold release i am planing on building a "stich and glue" boat 11 ft. long it calls for expensive wood to stich and glue i was wondering if it would be logical to by some laun plwood from home depot 8 bucks a sheet instead of 100 bucks buid the boat fill in all the cracks smooth paint add wax and fiberglass it in then remove the molded fiberglass any help would be appreciated on the steps i nedd to take

 

[MarlinTini]

Re: Building a small mold, looking for advise

OK guys, thanks for the advise. I have just started cleaning up the plug and have a few days of work to do to it to get it ready. I'll post an update once I get back to the stage where I have pulled the plug from the mold. <br /><br />I'll reduce the number of coats of wax, I think I recall the mfgr recommendation to be 4-5 coats and will prep. the plug with a laquer finish instead of waxing ontop of the primer finish. Should provide a slicker finish to work with or at least one that will not provide as much opportunity for the gelcoat to stick to... Jeff.