Cone question

[washboardchris]

I recently bought a NRP Estralita Delux from my local Gumtree for very little money & it's a monster(much louder and with more tone than any other wooden NRP I have tried)the guitar itself is in great condition but all the metal work has a lot of pitting and there is the start of corrosion on the cover plate.It seems that the guitar has lived by the coast and has been played by the sea shore a fair bit(hense the salt reacting with the metal work) I was wondering if the salt may have done something to the cone. The guitar dates from 2003 aned has a number in the low 300's & as far as I can find out was played by the sea for at least 8 years.

[snakehips]

Hi there !

What wooden NRP guitars have you played before - specifically what year were they made ?
The Estraluta you talk about may well be old enough to have a non hot-rod cone in it.

As for corrosion - looks like you purchase must have been a fair one, in hindsight.
If you could remember enough chemistry from school days you might remember aluminium is highly reactive to oxygen and forms a thin aluminium oxide layer on exposed surface almost instantly. The oxide layer is very unreactive and unlikely to corrode.

[gaucho]

If you like the tone and volume, I'd leave it be. I have a NRP Radiotone from '92 (does that make it vintage?) that definitely has an original cone in it and it sounds awesome! I have a Hot Rod cone sitting on a shelf (it was in my vintage Duolian when I got it and I replaced it with a vintage cone) and I've often thought about putting it in the Radiotone. The thing just sounds so good as it is that I'm afraid to make the switch....

[washboardchris]

Hi, I have had two more estralitas and two M2's and a green painted wooden Duolian pass through my hands, the green painted one and one of the Estralitas had hot rod cones in them.one of the M2's had a standard NRP cone (pre hot rod)& one had what was rfered to by friends a the super cone which was different in hight to all the rest and sounded very very good.This one seems to have the edge on it.

[preacherman]

Hello, my first comment here, Snakehips is right, the cone should be fine.  There are several different coverplates by NRP I have an early Estralita and an Estralita deluxe, plus an M2 from 2003 which has a coverplate which looks like a sand blasted steel and is very pitted.  The first generation Estralita has a painted on and laquered silver finish, which I think will eventually crack and craze and the Deluxe has in the 6 months I've owned it got quite tainted by me not wiping it down before popping it back in it's case.
I have a friend who is a bit of a reso fan compare them all and the Deluxe is a loud B*****d, I know the M2 has a Hot rod as I have the original cone too, but the sound seems to mostly come out of the front of the body compared to the Deluxe. It makes me more confident to play if I have a sense of the volume if you know what I mean?
I recommend getting some Autosol metal polish (as did NRP as a European alternative to Flitz.... I got a document here from them about this) and with care do what you can (don't get it on the finish of the guitar though) you really need very little. Then keep a clean micropore cloth to give it a wipe down after use.
Be grateful you have a guitar at a good price that has been broken in, and enjoy it more without fear of small wear and tear marks

keep cool

[bod]

Sept 7, 2013 10:31:16 GMT snakehips said:

...As for corrosion... aluminium is highly reactive to oxygen and forms a thin aluminium oxide layer on exposed surface almost instantly. The oxide layer is very unreactive and unlikely to corrode.

This is true enough, however one notable exception is the salt air found in seaside locations:

How surface reactions alter a metal’s corrosion resistance can be seen in the example of four common construction metals - aluminum, lead, copper and iron. Aluminum ranks as a very active, or corrosion-prone, element in both the AMF Series and the Galvanic Series for seawater, yet it is prized for its low maintenance and slow corrosion rate. This is because aluminum forms a tightly adhering surface film of aluminum oxide when exposed to the air. Under most atmospheric conditions, the oxide protects the aluminum from further corrosion. An exception is found in seashore locations.

When exposed to damp, salty air, most aluminum alloys behave very actively. Sea salt (mostly sodium chloride) destabilizes the normally protective oxide film, leading the localized attack, or "pitting." The reaction is so strong that a thin-gauge aluminum sheet will show perforation after being immersed in warm salty water for only a short period of exposure. However, not all aluminum alloys react so strongly to salt air. Aluminum masts, for example, are very popular on sailboats, but the alloy found in most aluminum flashing, roofing and siding does not stand up to salt, and should not be used near the sea. Aluminum performs much better in industrial atmospheres, although the top choices there are lead and copper.

www2.mtec.or.th/th/research/famd/corro%5Chowmetals.htm

[washboardchris]

Please understand that I have no problem with the guitar and am not worried by the finish, I just wondered if the salt air may have changed the composition of the cone and infact inproved the sound.

[bod]

Sept 7, 2013 19:12:55 GMT washboardchris said:

Please understand that I have no problem with the guitar and am not worried by the finish, I just wondered if the salt air may have changed the composition of the cone and infact inproved the sound.

Yeah, got that - was just addressing the reactivity of aluminium in salt-water environments...

[mitchfit]

did a quick goo-search. thin aluminum CAN safely be anodized. having been involved in repair of
aluminum boats for the military, can tell you that anodized re-coating is specified after metal
repair work on same. same required for salt water protection.

applying this refinish over your cone will seal the aluminum again, and protect it from further
damage that has already begun in the metal. [and doesn't go away by itself]

then did a goo-search asking if reso-cones are anodized. many are/were. dunno if a there should be
a concern about whether refinishing the cone will affect collect-ability. do know that it will be
near impossible to detect this without laboratory equipment if you choose a non-colored finish.

contact an anodizing company in your area for specifics. you will want a thin anodizing to keep
from altering vibration characteristics.

FROM BELOW LINKS:

..."You can specify a range of coating thickness from 0.00001" to 0.005" based on what your product is to be used for and how you want it to look. In general, thicker coatings are used for products to be used outside or in corrosive environments, and thinner coatings are used for parts to be used in interior applications."...

$0.02
mitchfit

www.google.com/#q=are+resonator+cones++anodized

www.anodizing.org/FAQ/faq_cont2.html

[mitchfit]

captain's log, stardate sept 10, 2013, supplemental....

go to below link "Dopyera family history". appears to be advertisement for Do-Bro's personal collection auction.


just before document center-[as indicated by slide bar @ right for page scrolling]- to detail about a "Dopyera
Lullabyka (1973)" model. as they were anodizing cones as early as circa 1973, i feel safe guessing national
has been doing same for quite some time also.

hope this helped,
mitchfit


[mitchfit]

tried to save failed posting above, but edit is nearly totally obscure @ bottom.

pls see:

www.lvdrga.org/news/wp-content/uploads/2012/11/Dopyera-family-History-2-13-2009.pdf