First build, in progress...

[whatatrip]

Re: First build, in progress...

Volume is going to come in shorter than I had hoped actually, you are correct. I would guestimate it could come in at around 60 liters give or take. Im considering a few things now. I had not really given a whole lot of thought to just how I would do the stand for these. I'm thinking that to increase volume, I can use the stand as additional enclosure volume. It would be tricky, but I think its doable. I dont particularly like the stand look in the sketch anyway, so I had already planned to deviate from that.
Its either that, or I end up tuning higher or going sealed and then using a sub for low end support.

You could always add another sheet of foam to the flat side to increase volume or 2 sheets to make sure you have enough volume.

Normally, making fiberglass parts requires that the model be what you want the finished product to look like. It is as smooth as your finished product will be and will have the exact shape. Then you do what is called making a "splash" of the model which entails pouring something like plaster all over the model so that you have an exact mirror of what you will be building. You will have to make a box to hold the liquid plaster and your model in place while the plaster dries. This might be difficult with foam because it will want to float. You will also have to apply some mold "release agent to your model so the plaster doesn't stick.

Then you remove your model as soon as the plasterk, now called the mold, is set up enough so it doesn't collapse. Your model will have to taper from the front to the back at all times. This is called a "draft angle". Without it you would not be able to remove your model without breaking the mold.

Then you will have a mold that you lay your fiberglass into and it will have a finish as smooth as your model. Of course the plaster will need a release agent applied to it also. The liquid glass will be against the mold, it will permeate the glass cloth and you can add bracing to the interior as you make your mold. Any bracing material can be covered with fiberglass with the fiberglass being the basis of your structural strength and the bracing material basically a mold to be covered over.

This way you will get an exact replication every time and you only have to sand the exterior once. Volume can be adjusted by how much of the shell is cut off. The more you cut off, the less the volume. Best to make it plenty large to begin with. You can then fill your shell with water and measure the volume with bracing rather than trying to calculate it.

I actually have a pair of speakers that were made of fiberglass by Community Loudspeaker. If I get around to it I will pull them off the shelf and take some pictures. They are basically designed as you are doing with top, bottom and sides rounding and tapering to the back. The baffle is also made of fiberglass with built in mid range horns and mounting for compression driver and 15" woofers.

[JustinG]

Re: First build, in progress...

You could always add another sheet of foam to the flat side to increase volume or 2 sheets to make sure you have enough volume.

Normally, making fiberglass parts requires that the model be what you want the finished product to look like. It is as smooth as your finished product will be and will have the exact shape. Then you do what is called making a "splash" of the model which entails pouring something like plaster all over the model so that you have an exact mirror of what you will be building. You will have to make a box to hold the liquid plaster and your model in place while the plaster dries. This might be difficult with foam because it will want to float. You will also have to apply some mold "release agent to your model so the plaster doesn't stick.

Then you remove your model as soon as the plasterk, now called the mold, is set up enough so it doesn't collapse. Your model will have to taper from the front to the back at all times. This is called a "draft angle". Without it you would not be able to remove your model without breaking the mold.

Then you will have a mold that you lay your fiberglass into and it will have a finish as smooth as your model. Of course the plaster will need a release agent applied to it also. The liquid glass will be against the mold, it will permeate the glass cloth and you can add bracing to the interior as you make your mold. Any bracing material can be covered with fiberglass with the fiberglass being the basis of your structural strength and the bracing material basically a mold to be covered over.

This way you will get an exact replication every time and you only have to sand the exterior once. Volume can be adjusted by how much of the shell is cut off. The more you cut off, the less the volume. Best to make it plenty large to begin with. You can then fill your shell with water and measure the volume with bracing rather than trying to calculate it.

I actually have a pair of speakers that were made of fiberglass by Community Loudspeaker. If I get around to it I will pull them off the shelf and take some pictures. They are basically designed as you are doing with top, bottom and sides rounding and tapering to the back. The baffle is also made of fiberglass with built in mid range horns and mounting for compression driver and 15" woofers.

Look up "vacuum bagging" I think this is close to what the above poster is talking about it. I was on a human powered vehicles team for a while and this is how we made our carbon fiber/kevlar fairings

[whatatrip]

Re: First build, in progress...

Look up "vacuum bagging" I think this is close to what the above poster is talking about it. I was on a human powered vehicles team for a while and this is how we made our carbon fiber/kevlar fairings

Well, vaccum bagging is used with glass impregnated fibre cloth. When using those materials, the bag has to be used to suck the air out during the heating time. The glass and mold are heated to activate the impregnated glass and allow it to flow and the vacuum sucks out any air. When you lay up using "wet" resin, careful application is needed to avoid air pockets. A vaccum bag wouldn't work with liquid resins.

[robwest]

Re: First build, in progress...

What I'm about to say will be similar to 'whatatrip's post above but different in a few areas.

What you have cut and shaped would be called a 'plug' in the boating community. (Yours looks nice, too!) There are a couple ways to go from here, depending on budget and time and final plans -ie do you want to make a bunch?-.

If budget isn't too tight, you could cover the plug with marine epoxy (WestSystem) and cloth and really sand and shape to perfection. WestSystem/ epoxy won't melt your foam. This would give you a finished plug which you can then use to make your outer mold. Carnuba wax and mold release will let you use poly and glass right on it. (Gelcoat if you care to.)

Once you have your mold, you can glass out as many copies of the shell as you want and not have to spend all that time sanding/shaping each one. Another advantage to having an outer mold will be that you could then use it to make an inner/baffle plug (and then mold), if you later decided to make the baffles out of fg.

Its looking good! Can't wait to see how it turns out.

[robwest]

Re: First build, in progress...

I made a thread with pics to illustrate what I was talking about so as to not fill yous up with a bunch more pics.

http://techtalk.parts-express.com/showthread.php?t=216343

[JustinG]

Re: First build, in progress...

What I'm about to say will be similar to 'whatatrip's post above but different in a few areas.

What you have cut and shaped would be called a 'plug' in the boating community. (Yours looks nice, too!) There are a couple ways to go from here, depending on budget and time and final plans -ie do you want to make a bunch?-.

If budget isn't too tight, you could cover the plug with marine epoxy (WestSystem) and cloth and really sand and shape to perfection. WestSystem/ epoxy won't melt your foam. This would give you a finished plug which you can then use to make your outer mold. Carnuba wax and mold release will let you use poly and glass right on it. (Gelcoat if you care to.)

Once you have your mold, you can glass out as many copies of the shell as you want and not have to spend all that time sanding/shaping each one. Another advantage to having an outer mold will be that you could then use it to make an inner/baffle plug (and then mold), if you later decided to make the baffles out of fg.

Its looking good! Can't wait to see how it turns out.

Hear is a gallery of what I was talking look at any of the "construction" photos there is usually a "plug" or male mold that they create that is what the end product should be and then they coat it and make a female mold out of that then cast the carbon fiber/kevlar fairing from the female mold:

http://www.rose-hulman.edu/hpv/gallery.html

[captainobvious99]

Re: First build, in progress...

Well, I dont have vaccum bagging tools or experience, so my methods will be a bit more rudimentary, but I do appreciate the links. Certainly a better way to attack it if resources are available. Looks like it was a fun project!

[Gristenn]

Re: First build, in progress...

How exactly do you attach the wood to the fiberglass? Is the baffle going to be seperate so you can install the componets and then screwed/glued into place or fiberglassed over? Just curious becasue i'm considering making my own computer speakers out of fiberglass and have never worked with it before. Any advice would be greatly appriciated.

Thanks,
Curtis

[captainobvious99]

Re: First build, in progress...

The front baffle will be a seperate piece that will be joined to the shell. Inside the lip of the shell will be a wood ring bonded to the shell. Picture something like the pic below with the PVC being the "shell", but on a much larger scale. This will allow me to screw/bolt the front baffle to the shell (into the wood ring) for a very secure fit. Wood and fiberglass bond together very well. That said, I'll probably drill holes through the ring and the shell and apply resin to ensure an extremely good bond. I'll likely also use a slim gasket between the baffle and the shell where they mount together for an airtight seal. Some thin closed cell foam (probably volara or neoprene) should work great.

[Gristenn]

Re: First build, in progress...

So will you bond that ring after the outer shell is complete? Or will you incorporate the wood into the shell structure and bond it with fiberglass? I'm new to fiberglass and how to use it correctly so any advice is great. Or does placing wood into the shell and just hitting it with resin do enough to hold it in place?

Curtis

[captainobvious99]

Re: First build, in progress...

So will you bond that ring after the outer shell is complete? Or will you incorporate the wood into the shell structure and bond it with fiberglass? I'm new to fiberglass and how to use it correctly so any advice is great. Or does placing wood into the shell and just hitting it with resin do enough to hold it in place?

Curtis

Ill cut and insert the ring after the shell is formed. Ill then rubber mallet it into the shell and then resin it on the (backside) lip where the ring meets the shell. Once that cures, I'll drill right through the ring AND through the outside of the shell in many locations. THEN, I'll resin into the holes. That should make a very solid bond. :D

[captainobvious99]

Re: First build, in progress...

Thinking about enclosure volume now...

Assuming I dont try to fiddle with gaining extra enclosure volume by utilizing the stand as additional airspace (this probably wouldnt work well anyway), I am looking at somewhere in the neighborhood of 60 liters of volume for the pair of 8955a woofers. Stuffing heavily might give slightly more wiggle room. I have a couple of choices- I can either -

1: Go vented with a smaller airspace, and tune 60L, 30hz
2: Go sealed with a 60L airspace, Qtc 0.61
3: Go sealed with a 40L airspace (add mass), Qtc 0.71
4: Switch to Dayton RS225-8 drivers (sealed, 61.2L - 0.71 Qtc)

Recommendations?

Im not opposed to adding a sub for low end if needed, but I'd obviously prefer to avoid it if I can.

[captainobvious99]

Re: First build, in progress...

Applying painters tape




Fabric stretching. Yup, almost the same color as the painters tape...purely coincidence. Picked it cause the color shows flaws well







And in my walkout from the basement awaiting glassing. I figured since theres a doorway between here and my basement, and the walkup leads to fresh air, I shouldnt be smelling fumes in the house. Of course I was wrong :(

[captainobvious99]

Re: First build, in progress...

Disaster strikes ! :eek:

Well, I did say Id post my failures as well :o

BUMMER! Inspected the work after setting overnight...Looks like there was a bad reaction with the foam. I dont know if resin seeped through the painters tape in sections, or if the colder weather played a role, but its lumpy... Not good. Looks like this one may be a scratch. Didnt even cure all the way yet because of the cold air. I could probably salvage these to make one shell with alot more elbow grease, but It wouldnt make a great mold at this point, so Im probably going to scrap it.
Thinking about it, it may not be such a terrible thing...The enclosure volume wasnt going to add up to the result I wanted anyway. It would have required a higher tuning with just 60L or so of estimated volume, OR it would have had to have been a sealed enclosure. At least now I can plan it out a bit better on the mulligan.

I'm seriously considering just doing a wood enclosure now. Curved back utilizing either bent ply construction or kerf. Rounded back using these techniques will still give a not so boxy look, but they will end up still having the flat tops...decisions decisions...


Pics, of course below

[robwest]

Re: First build, in progress...

What a shame! That was a beautiful form.:(

I'd love to see that finished! Free-hand shaping is a remarkable talent, looks like you had it spot on.

I think the concept is valid, just lacked proper execution. Try again using proper materials. I'd love to see that completed!