Self forming fillets

The idea of a 1.5" radius would not make any sense in a place where noone sees it. Not sure the intent there.

 

They do it partly to spread the load of a structure against the hull and partly so a 1.5 inch roller fits the radius (ie if you were pressing 1708 or CSM against that radius, a popsicle stick sized radius doesn't allow the roller to bottom out well)..

Certainly there are other rollers, other ways, not arguing its the right way just saying out there in the industry 1.25 isn't always considered all that big.

 

Commercial production has different priorities from amateur building. Time is more expensive then materials. Epoxy they buy by the barrel, saving a tiny amount but increasing fabrication time because the worker has to swap rollers or fiddle around in a tiny crevice is not acceptable. Even having to order, stock and distribute different sizes of rollers might not be acceptable. It can go so far that mixing thickened epoxy by hand can be more expensive then using premix cartridges.

 

Not to beat a dead horse, but I am still bewildered by a standardized fillet that large. (This from a guy who has to use two rollers to paint for the very reasons spoken).

The cross sectional area of a fillet formed from a 1.5" radius tool vs a 3/4" tongue depresser which is a 3/8" radius is 16.6 times greater.

Based on my example above, I estimated 1000 feet of fillet weighs 55 pounds.. Now, I haven't had any coffee, yet, this morning, but a 16.6 times larger fillet weighs 16.6 times as much and it costs 16.6 times as much. I can't fathom justifying 913 pounds of fillet material vs 55. Nor can I justify the cost of a fillet at $1 per inch roughly versus a dollar per 17 inches. So, now way would a company be making epoxy fillets that large as a standard wisely.

There are certainly times where a large cove might be aesthetically pleasing.

However, another problem arises with massive fillets that I understand from pulling a couple thousand feet of small ones. A 3 layer tape job on top of a fillet that size would smoke and perhaps damage core and even catch fire because the thickness of the fillet is 5/8" thick at its max. The 3/4" with a 3/8" diameter is 0.155" thick. Most people get worried about exotherm of epoxy around that 1/2" thick mark..least I do

Of course, my main reason isn't chest beating here, but to point out the horrible diseconomy and even potential hazard of the idea. I suppose if you apply fillets and then sand them prior to tabbing; the fire hazard is gone, but then you also lose primary bonding. I still can't imagine throwing away 16 times the money; especially on hidden fillets.

Anyhow, if I am guilty of polemics, I apologize. But I'd rather correct people than they run for the fire extinguisher.

 

Doesn't an 1.5" roller have a 3/4" radius?
I don't think 3/4" radius fillets are excessive.
You guys are comparing apples and oranges.

 

Talking of the shop that uses a 1.5 inch PVC pipe for fillets, most of the work those guys do is not with epoxy, however they have also done entire boats with epoxy. Could be all polyester, could be epoxy, could be vinylester, is up to the customer (and their budget - $$$$). They are letting the fillets cure at least partly, ie you put a panel or part up against a hull and need to hold it in place temporarily, so you run a bit of a fillet, when that cures you remove the tape, hot glue, screws, brackets, clamps, whatever, finish the fillet, tab it into the hull.

I'm talking about a downeast boat builder who owns a few hull & top molds, and take jobs from shipping bare hulls for finishing elsewhere, to finishing hulls they didn't layup, to fully molding & finishing, to re-fit & repair, to widening/lengthening existing boats, to laying up custom hulls, basically they take a whole lot of different types of work and it's nearly all custom. An owner and a couple employees, though some similar businesses may have from 1 to 50+ mold sets, different scales, and some variation of what work they will take, but most operate kinda like that.

Watching those operations "go" is something else - some will literally sometimes build an entire interior space of say a 38 X 13 with plywood, cut & fit perfectly as if it was going to be glassed over, then they take it apart & use the patterns to cut panels of some sandwich composition, and in the end throw out what may have been a pallet of perfectly good plywood (sure if it's something they may do again those can become patterns too but the odds are the next customer won't want that design). The labor cost is really most of it, epoxy adds labor so often it is poo-poo'd but they use it.

I think the difference is usually those fillets are allowed to cure, heat isn't an issue.

 

A 1.5" diameter is indeed a 3/4" radius!

I did the calc on 3/8 versus 1.5".

I was talkin radius all the while, so when he said 1.5", thought he meant radius!

 

I attempted to build a carbon fiber bicycle a while ago where i shaped the frame out of cheap insulation foam, then wrapped it with carbon and epoxy and vacuum bagged it. when it cured I poured acetone into the open ends where it melted out all the foam leaving me with a nice hollow carbon fiber frame.

you could do something similar where you shape your filets with cheap foam, glass over them, then dump acetone into the channel and then fill it with whatever fillet compound you're using.

 

If you want to save the time of sanding fillets there is an easier option. Do the fillet and lay the glass on it before it is cured.

 

That's what I try to do. I'm just exploring options.

 

DCs only downside is the fillets can rot. Otherwise, he is saving quite a lot of epoxy with the wood fillet.

 

They certainly can. To the same extent that the strip planking underneath also can. I really hope it's all saturated well enough.
I'm making some very large fillets, for pennies.