Fibreglassing 101?

Just checked out the R&G site. Looks like they have everything you need except the tooling primer. Prices seem a little high but not outrageous. That VAT really kills you guys.

Check out my post further down the thread for a SWAG on quantities. Always best to order a bit extra. You can always find a use for it later.

"Glenn Ashmore" skrev i en meddelelse news:5DsCe.171890$sy6.143080@lakeread04...

Nick Müller pointed me towards

and they seem to be willing to ship to Denmark, although the resin seems to be cheaper at the local home depot wannabe....

These are approx. 4 times the size... So if I order:

10 lb bucket of resin 4 lbs of gelcoat 50 meters of mat ( ) 10 meters of cloth ) 10 meters of cloth ( )

• an appropriate quantity of hardener and release for a pair

Incase you are curious ( you seem to know something about horns ):

The horn is a Tractrix type straight midrange horn for an 8" driver w. a cutoff freq. at 300 Hz..

The vacuum is to drive the airbubbles out of the cast ? I have a couple of vacuum pumps from scrapped vacuum bagging machines ( industrial models for food products ) I might be able to make something usable from those..

Thanks for the guidance so far..

/peter

They will raise it next year here in Germany. The year after, government will be bankrupt. :-(

Ni-pissedoff-ck

I wouldn't take that risk. You don't know how old the home dept's one is, and you also can't select between different "pot time".

Just checked, they say R&G is good for fiberglas stuff. ... and Wacken is good for music. :-)

Nick

You think its bad in Germany?..

Try 25% on everything, like here.. And no, its not lower on food like it is on your side of the Border..

The fuel prices are rediculous too.. Diesel fuel costs about 5 US$ per gallon here and the price keeps going up at a scary rate... I was thinking of converting the van to run on plant oil, but unlike Germany, the plant oil for automotive use is taxed like diesel here, so if you want the conversion to pay off in an economical sense you need to cheat the tax people ( this is relatively easy with the plant oil trick, but damned expensive if you get caught )

Maybe its time to become a religious organisation and see about getting a tax exempt like that amusement park in the US I heard about recently..

/peter

"Q" skrev i en meddelelse news:3UuCe.60662$ snipped-for-privacy@news000.worldonline.dk...

Here:

/peter

There are lots of things that will work, but you'd need to do more experimenting with them. The special purpose waxes aren't much more expensive than car wax, floor wax, etc. But for two parts, you could skip the wax altogether if you use a secure layer of PVA.

PolyVinyl Alcohol. A liter of it should be plenty for your project. If you can't find a local place to buy proper supplies, just take some empty bottles and a box of donuts to a local fiberglass shop. Hopefully one that's used to building and prepping their own molds.

I can't imagine how. I'm guessing that you'll be brushing gelcoat onto your prepped mold. Whatever's under your brush strokes can't be disturbed.

This might be a good time to mention that gelcoat isn't really necessary. You could brush on a layer of resin instead, let dry, then start laminating. You'd probably get a bit more print-through, and you'd have to paint the finished horns.

That could help a lot in the worst case, but shouldn't be necessary if you do the prep right. If the horn is going to have a long throat like the one in the photo, then put any extra time into making that area nice. As much taper as you can, straight and shiny surface, heavy PVA.

That might help a little, but you could be surprised how much a part that isn't fully cured will distort if it's unsupported and you add thick laminations. So long as the mold has been tested to make sure it will release cleanly, I'd finish laminating the part while still on the mold, and then let it cure for at least a day before releasing.

Glenn's advice was very good, it's obvious he has some experience. I only disagreed on a couple of minor points - vacuum bagging, not worth the trouble IMO for two relatively small parts. Ditto for roving. I'd get some heavy mat (random strands bonded with a resin-soluble binder). You can split it into thinner layers if you like. You can wet it in place, but if it were me I'd lay the mat onto a flat, clean and non-absorbent surface like Formica, wet it out fully and quickly, and then pick up the slab of gooey glass and apply to the mold. As the binder dissolves, the mat can be stretched to fit contours. So your minimum shopping list could be: PVA, resin (promoted), catalyst, mat, acetone, brushes and rollers. BTW, getting polyester resin on your skin isn't anything to worry about. If it was I'd be dead by now. :-) Washing your hands with acetone is *not* a good idea, although it's done all the time.

FWIW, my shop once made an assortment of horns (a few dozen of each size) much like the one in your photo. The largest was about 4 feet tall. We used heavy gelcoat, one layer of chopped glass strand (from a big machine), fitted Divinicell foam bonded over the flat areas, and then more chopped glass over the whole thing.

Wayne

"> Maybe its time to become a religious organization and see about getting a

Just register as a boatbuilder. That is a non-profit organization if ever there was one. :-)

I found a source for it, so it wont be a problem..

Hmmmm... Donuts?... I am in Denmark.. The only place to get donuts is Mc Donalds, but I get your point.... Over here stuff like that is usually solved with a sixpack of beer :-)

Gelcoat is available in smaller quantities, so that wont be a problem.. I think the Gelcoat I can get locally is white though..

It seems that my plan is to pain the mold with a couple layers of regular turpentine based paint, wax it and coat with PVA...

I like the idea of less things to go wrong or stick to the resin :-)

Sounds what we used to do with wallpaperglue, chickenwire and old newspapers in kindergarten :-)

Hmmm.... I work in the food processing industry and the cleaning products and desinfectants are hard on my hands as is.. Good thing about it is that I can get "free" rubber gloves..

I decided to try this.. I usually make horns etc. from wood, but theres a lot of work involved when you have to do everything by hand... Seeing that I may end up having to make 40 more of these things the fibreglass seems like a good solution..

/peter

I think you will need more resin than that. While a circular horn will not resonate as much as a flat sided one you will still need a fair amount of mass when your low end is around 300hz.. Look at product # 1901541 on page

7 of the fabrics. That is the roving I was talking about to build up the mass and strength. You probably won't need as much of the woven cloth because that only goes on the inner and outer layers.

You only need a little MEK-P catalyst as you use only 5 -10 ml per liter of resin.

What the vacuum does is uniformly press the laminations against the mold producing the densest possible layup. If you have the pump you can jerry rig almost everything else but the process takes a bit of practice. You may not want to risk it for your first time. Polyester sets up in 15 -30 minutes depending on the temperature, amount of MEK-P and the mass of the layup so you don't have a lot of time to get the bag on. You can read some basics of it on my web site in the Hull section.

If you want to try it get some 4 to 6 mil clear poly builders film for the bag and seal it with vacuum tape. prod # 3901701 on page 2 of the vacuum technology page. You will also need a breather mat prod# 3901801 on page.3 and a peel ply like 3901851. Alternately you can use nylon flag bunting or taffeta for the peel ply. You can usually find that on the remnant counter at a fabric store.

"Glenn Ashmore" skrev i en meddelelse news:oCvCe.171910$sy6.164164@lakeread04...

Yup... Seems that this project is going to cost a few boatbucks already :-)

Btw: I looked at your boat project page and I must say: DAMN, thats a big project ! Wouldnt mind seeing some pics of the finished boat once you get that far... Looks impressive..

Maybe you could enter the Tall Ships Race ( Formerly known as the Cutty Sark Tall Ships Race ) and stop by here.. I took some pictures of some of the ships that were racing here last year.. The most interesting ship was probably the russian ship Sedov, built in 1921. The ship is made from steel plates that are riveted, not welded. Theres a few pics of it here:

pics of some of the larger vessels here Thanks again for your help... I will report back when I get my hands on the resin etc.

/peter

"Nick Müller" skrev i en meddelelse news:1gzur05.rslk711m11ce7N% snipped-for-privacy@gmx.de...

True...

Excellent..

I doubt it would be considered good for Schlager fans :-)

/peter

Bloody 'ell. When will the insanity stop?

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"RoyJ" skrev i en meddelelse news:nKxCe.9238$ snipped-for-privacy@newsread1.news.pas.earthlink.net...

Hmmmm... Interesting idea.. Latex coated hands... Sounds kinky :-)

/peter