Building a Sea Chest

[Blue_Heron]

Originally Posted by mbmcdermott18

If anything looks out of place or anyone has any tips let me know...

Your mold doesn't have any taper. You will have to destroy the mold to free it from your part. Male molds that are intended to be re-used always taper from the opening to the inside. In other words, the closed end is smaller than the open end so it will slide out easily once you break the bond with the new part. I'm not saying it won't work, just that you need to think about how you're going to get the mold out without damaging your part.

Second thing is to make sure you seal your MDF with something to make it waterproof before you go any further. PVA is water based, and the MDF will soak up the water and the PVA won't want to dry. It will also probably raise the grain and make the surface rough.

I use clear lacquer on my molds, but I use masonite as the mold material, and that's smoother than MDF. Strick uses Duratech primer. I'm sure there are other coatings that would work, but Duratech is proven for MDF mold surfaces.

Your work looks good, though. Nice tight joints and good fillets and outside corner radius.

Dave

[mbmcdermott18]

Hey Blue Heron I assume since you are thinning the gel coat you are using a tip around the 1.5 size? Have you had any luck spraying unthinned gel coat out of a larger tip gravity gun like 2.3 size? I have a few other mold projects I would like to tackle if I can get this one to come out right so the money on the gun wouldn't be a loss but if a $30 gun works as good as the $120 cup gun I would rather save the extra cash.

I plan on ordering my supplies from us composites seems like they have good prices. I am going to use vinylester for the layup if that matters.

[mbmcdermott18]

http://www.harborfreight.com/air-too...gun-66103.html

Has anyone used the above gun for spraying unthinned gel coat? It comes with a 3/16" tip which is what the cup gun uses for gel coat.

[hermco]

2 degrees is standard minimum draft angle. A small part like that might blow off. I found Honey Wax works well on that material. I did some tests and PVA was the least effective on MDF. Since it is already made I would give it a try what the hell. Stuff is easy to bust out, just add water! Just do your layup then drill a hole in the top to accept your air blower tip. Be sure to only drill thru the glass and not the plug. Then tap with a rubber mallet.

[mbmcdermott18]

Well I decided to put a couple coats of polyeurethane to try and seal it up. We will see how it goes. Ringleader over on classic mako seems to have good success just waxing the mdf.

I am interested in removing these parts. How much force is usually required to separate the mold from the part?

After thinking about it I believe my plan of attack will be to drill a hole in the bottom of the mold through the mdf that will allow the air to get into the mold which will have holes drilled in it to allow the air to get in between the outside of the mold and the part.

Then I am going to thread a quick connect into the hole and hook up an air hose into it. Starting at 75 psi I will work the wedge around the flange and see how it goes. If she doesn't pop at 75 I will increase @ 25 psi increments.

If it becomes obvious that the part won't pop I will just unscrew the sheet of mdf from the mold and take it apart from the inside.

Thanks to everyone who has offered their opinions and advice.

Hope everyone has a Merry Christmas

Mike

[strick]

I would not worry too much about saving that male one off mdf mold as it will likely warp or break before you ever use it again (mdf loves to absorb water)...plus it is not tapered like Dave already mentioned. They are cheap and easy to make anyways..... If you want a super smooth surface then you should coat it something before you wax....the wax alone will leave some streaks in your part...I dont know that it really matters anyways....how smooth your surface is....I was thinking it may have been easier to make a female one off mold but then your smooth surface would be on the out side. It would have been easier to free the part....be careful with compressed air and molds! If you did not seal/join the area where the base connects to the box it may leak air....then start a hacking away!

strick

[mbmcdermott18]

Mold has 4 coats of partal #2 and three coats of #10 going to begin laying glass this morning we will see how it goes

[77SceptreOB]

Good luck, keep us posted...

[heynow2203]

Looks good

[SBD]

You might want to bed that in something more pliable and less permanent than cabosil thickened resin. Its going to be a prototype. You never know if you might need to make some changes, and thickened resin is brittle and will crack over time if there is any flexing.

Part looks good. Nothing more rewarding than an idea go from your mind to your hands.