Hey guys… I’ve learned a lot here and other similar sites (and been inspired to try stupid projects like this) so thought I’d share something I’m working on. Here goes…
** DISCLAIMER: I am not a professional, I know there are probably better ways to do many of these things! But for me, thats all part of the learning experience. This is also not a complete tutorial, but if you have any specific questions about techniques or equipment I’d be happy to share what I know.
I wanted a T-Top electronics box, but was absolutely disgusted by the price for even a very basic box. So, in my usual fashion, I decided I could do better and cheaper! (reality: probably not so much, but oh well)
Researched what was out there commercially, and then started with some mockups to figure out what I wanted. A box sized to hold a stereo and vhf, with room for an auxilliary switch panel and possibly an external/amplified speaker for vhf, but not so deep that it obstructed my view. (I’m pretty tall, so a very deep box would really annoy me)
I used a combination of 1" EPS insulation and foam presentation boards. Easy to work with, I used 3M spray adhesive to put everything together. Melts the foam some, but works great if you just use a light mist.
I then used the basic layout and dimensions to build an MDF plug of the exact size/shape box I wanted. I used a plug-mold-part method here, could have just built a simple box out of MDF and layed up the actual box inside of it, but I couldn’t think of how to include the speaker bump outs I wanted doing it that way. Plus, why simplify when you can complicate?
Again, I didn?t include all the cutting/gluing/nailing/routing involved here. I used 1/2" MDF, cut everything so the box had a 2 degree draft (taper) in all directions for mold releas
I say we put you in charge of building all the cool custom things we need for our boats but nobody actually sells them yet. Good looking project so far!!!
Nice work. A trick if you don’t already know it. In one or two places in the mold where you know you’re going to cut holes in your finished part (e.g. speaker cut-out or door cut-out), drill a 1/4" hole. When you get ready to start building your part, after the mold is completely waxed (10x or more), place a little masking tape or similar over the 1/4" hole - a 1/2" round tape dot. Then, gel coat right over it and build your part. Once the part is set and ready to be removed from the mold, use a little air pressure (e.g. 10 psi or less) and shoot a little air in the holes from the outside of the mold. Most of the surface of the part will let go of the mold surface before you start removing it. 'Makes things much easier on the mold and the part when it comes to getting them apart.
The way that mold is shaped, if you put an air port in each speaker cut-out and blow a little pressure in them, I wouldn’t be surprised if the part released completely and slid right out (provided you’ve waxed the bugebeeeeze out of the mold before spraying). Oh yeah, don’t skimp on waxing the mold. Wax the bugebeeeeeze out of it.
Then, when you cut out the speaker holes, you’ll cut out the making tape hole cover / blemish in the part.
17’ Henry O Hornet w/ Johnson 88 spl
26’ Palmer Scott project hull
14’ Bentz-Craft w/ Yamaha 25
Looks great. Can’t wait to see the finished box. Would it be possible to build the box and then tape it up and lay the glass on the outside? Then pop it off the box and finish it?
Pelican, could do it that way, but you would have a really nice finish inside the final product and an outside surface that would need a lot of filling, fairing, etc. Simplest way to get get the basic shape would be to just build the mold out of mdf, fillet corners, wax it, and lay up the box inside.
should have a finished product to show off tomorrow! Spent some time this week patching the pits from alligatored gel coat, got most but still couldn’t get the same finish I had on the plug. Oh well, rather than perfecting the mold I decided my time would be better spent sanding/polishing the finished product.
I filled the pits with a mix of Duratec and gelcoat - I tried straight gelcoat, but I could not get it to harden without being tacky. I didn’t have any wax, so I tried spraying over w/PVA, but just didnt ever work well. I smoothed over some areas with plastic, and they hardened fine. Added a little Duratec to next batch and it air hardened no problem.
Also got all my hardware - .25" medium gray plexiglass, hinges, and a Southco latch I got lucky and picked up super cheap ($20) from amazon warehouse deals.
Will probably shoot the gelcoat tonight and try to get first layer of mat down, but I’ve had a few Hurricanes in honor of Joaquin so it might be tommorow…
Many coats of wax and a few of PVA. Drilled some holes as suggested by PalmerScott. Great tip!
Was able to spray gelcoat on w/my marginal HVLP gun and compressor. Had to thin it 15%, which is more than recommended but it came out fine.
(full disclosure here - the first attempt at spraying the gel coat was a complete abortion. I didn’t get it on thick enough before it started to cure, and it all just wrinkled up. Had to peel it off and reprepare the mold, but at least I was able to get it out and try again. Second time I calculated how much gelcoat would be required for the 10-20 mils over the whole box - about 10 oz, more than twice what I put on the first time. Sprayed it all on and ended up at about 15 mils thick. Way thicker than I would have thought required until I measured it out. Sorry I didn’t get any pictures of this - failure teaches more than success but I was in panic mode and didn’t stop for pictures.)
Let gelcoat tack up, then started laminating. Layers went in this way: 3/4 oz mat, 1.5 oz mat with an extra strip layered in the corners and around the top edge for a little extra strength, 6 oz cloth, 1.5 mat, 6 oz cloth.
I found that dry fitting the layers of cloth onto the slightly sticky previous layer and smoothing the cloth out completely BEFORE wetting it with resin to be very effective.
by the way, the little throwaway touchup paint rollers are awesome for rolling out resin - tray and roller for like $2.50 (I actually found some at Dollar Tree for $1 later), toss it when it gets too sticky.
Finally, the moment of truth… a little scared it wasn’t going to release, but after enough prying around the top edge it popped right out! No sticking and no damage to part or mold. I did wish I had built
One more tip for next time. Once your mold is fully prepped, apply masking tape around the flange. Spray and lay up. That way, when you go to remove the part from the mold, the adhesion at the flange is only as strong as the masking tape. And, the blemish that the tape causes get cut off, anyway. Sorry. Should have mentioned that one earlier.
17’ Henry O Hornet w/ Johnson 88 spl
26’ Palmer Scott project hull
14’ Bentz-Craft w/ Yamaha 25
Ha - forgot I never updated this! I did get it instatlled but I guess I forgot to get a picture. I have a tendency to document these projects very carefully at first and then by the time it’s actually done I’m usually sick of messing with it…
I built an internal box out of star board for electronics, pre-wired and mounted everything, and dropped the whole thing in. Routed a big bundle of wires down T-top leg to console: power, GPS NMEA output to VHF, speaker wire, etc.
I actually just pulled it down to make a few modifications - the stereo shook loose after a while. Going to add some extra support to mounting sleeve, and finish wiring some LED lights in the bottom of the box. I’ll get some pics of the finished product and post.
