Ian's Savannah Project

[Cloud Warrior]

I are going to ask a dumb question:

What are those copper coloured things sticking out of the wing? Are those the rivets? I always see them sticking out of kits being built but have never found out what they actually are.

[grosvenor]

There is never a dumb question.

They are clecos - "temporary" rivets, which can be put in and taken out before final riveting takes place. Put in and taken out with cleco pliers.

[Ian]

What are those copper coloured things sticking out of the wing? Are those the rivets? I always see them sticking out of kits being built but have never found out what they actually are.

They are called Clecos. They are like temporary rivets that, when squeezed come out again. Each colour is a different size. So you line all up with clecos, then replace them one by one with rivets. - Could'nt do without them..
Below you can see the cleco pliers squeezing the cleco.


RV4ker wrote = Question is thus how complete and idiot proof is the kit/maunal? What else would be required?

I think ive answered 'what else is required' before, as for how complete, I can answer the kit is very complete to date , havnt had to buy 1 bit of hardware yet.. as far as idiot proof I cannot answer as I dont know the span of the definition of idiot ... I can say the AP was impressed with the contents of the manual (he, unlike me has seen many manuals). Will pdf a few pages here some time of the manual.

[Cloud Warrior]

How very clever - thanks for the info. Looks like once you build the first plane you need to keep on going otherwise all the tools go to waste.

[Ian]

How very clever - thanks for the info. Looks like once you build the first plane you need to keep on going otherwise all the tools go to waste.

Nope, you sell them to the next adventurer ! (thats my plan at least)

[RudiGreyling]

Why is the priming limited to the surfaces that touch? What do you do about corrosion prevention on the inside surfaces that are not painted or protected in any way??

Yep, did a lot of research into this one. The Allie used is 6061T6 which is very resistant to corrosion, enough (so many 'experts' say) not to cause problems in JHB. Also priming adds weight, so I've decided to spray internally once a year with a CPC like CorrosionX or Dinitrol Av8 which seems to be 'the new way' to protect. (Google the above words and get as confused as I did)
I'll tell you in 10 years time if it was the right decision.
cheers

OK I can add here, got some experience with the RV...

Aircraft aluminium is an alloy hence it does corrode, but they put a layer of pure aluminium "ALCLAD" 1 thousands of and inch on the surface to help it be corrosion proof. So if you scratch the surface it will start to corrode.

The reason some people only put it on the mating surfaces, is because that is where you will get relative movements and it might start to corrode there first.

Priming does add weight and more work to an airplane, but typically it will last longer and hence it will fetch a higher price on resale.

You can use corrosion prove fogging product like corrosion X or what ever to help with it, it does have some negatives, like forget about trying to paint after treating it with it, it goes everywhere, so use as last.

That all said many airplanes from the 60's still is fine without any corrosion protection.

The picture below is picture of bomber rear fuse from the 1940/50s. You can see some surface corrosion but functionally stil sound. Check the top skins vs the bottom. Bottom is mostly covered by gunk and dust.

My RV is painted with an epoxy primer on some strategic skins, like the bottom ones, my plane is going to outlast me! You can see most of the gunk goes on the bottom.

Kind Regards
Rudi

[Sonex711]

Aircraft aluminium is an alloy hence it does corrode, but they put a layer of pure aluminium "ALCLAD" 1 thousands of and inch on the surface to help it be corrosion proof. So if you scratch the surface it will start to corrode.

Hi Rudi,

I stand to be corrected, but 6061T6 does NOT have an alclad layer. Not needed since it's corrosion properties are much better than 2024.

[Ian]

Rudi Quoted =
"OK I can add here, got some experience with the RV...
Aircraft aluminium is an alloy hence it does corrode, but they put a layer of pure aluminium "ALCLAD" 1 thousands of and inch on the surface to help it be corrosion proof. So if you scratch the surface it will start to corrode."

Agree Rudi, fogger goes on last, the stuff creeps everywhere..
The difference is I think your RV is made using 2024 alli which is Alclad coated. Below extracts from Aircraft Spruce catalogue.

The Savannah uses 6061 T6 and the alli supplied is not coated with Alclad (as far as I know and have experienced) (T6 means solution treated, then artificial ageing) Maybe John W can comment further ?

Cheers

[RudiGreyling]

Hi Ian,

very interesting...if the 6061 of the Savannah is the 6061 type that is NOT alclad coated then why would one still primer the top end of the ribs and spars? There is no coating to wear out??

Anycase I went and did some homework to check out the differences and do some google-ing
http://www.whittsflying.com/Page3.13Fly ... ntrols.htm

Aircraft Aluminum
All aluminum alloys have the same density, one size sheet will weigh the same, regardless of the alloy. Plain aluminum has about one forth the strength of 2024 alclad aluminum but is the MOST resistant to corrosion

6061 has about 85 percent of the strength of 2024 alclad aluminum. 2024 is clad (alclad ) with a thin coating ( about .001 inch thick ) of pure aluminum for corrosion resistance.

The 2024 is alloyed with copper. The copper increases the strength but makes it subject to corrosion that causes the sheet of metal to thicken up and get spongy. 6061 is alloyed with zinc. It is resistant like pure aluminum but as strong as 2024. The strength differential of 2024 vs 6061 is that for the same strength given by the use of 2024 alclad, 18% more aluminum sheeting would be required using 6061."

If you primer you suppose to only add 3% to the weight of the part if done right. so it looks like the 6061 is the less work intensive route for the best protection. 2024 needs to be handled carefully not to scratch to surface coating or more work is required to prime it, but is lighter, even with 3% primer on it. One learn something every day!

Anycase please keep your updates and pictures comming

Regards
Rudi

[Ian]

Hi Ian,
very interesting...if the 6061 of the Savannah is the 6061 type that is NOT alclad coated then why would one still primer the top end of the ribs and spars? There is no coating to wear out??
If you primer you suppose to only add 3% to the weight of the part if done right. so it looks like the 6061 is the less work intensive route for the best protection. 2024 needs more work but is lighter.
Regards
Rudi

Rudi, good research, I have to plead ignorance here, I guess its because the lapping parts can retain moisture ? If not I do it because the manual says so .. he he . The average weight of the Savannah 912s is about 275KG, so Im aiming to come in in the 260's (less instruments, no primer but fog etc..). One thing RC taught me is the lighter it is, the better it flies.

And Rudi... well done on the quality workmanship on your RV, it looks stunning, out of my league !, Andrew take note of Rudi's QA inspector... (you will soon have no excuse)

Cheers

[Ian]

Question is thus how complete and idiot proof is the kit/maunal? ?

As promised I show 2 pages of the manual, first is the first build page, after quite a few pages of general info of do's dont's and bolt etc charts.

So each new assembly starts with the part numbers you need (each part has a numbered sticker on it) Second page shows you get CAD type drawings along with artists (?) dwgs sometimes. There are also plenty photographs


I guess you can decide on 'idiot proof' or not..

Cheers Ian

[Wingless Nut]

As corrosion engineering is my area of business, I wish to also draw attention to the following;

Aluminium surfaces overlayed and joined together, as in this case by means of rivets, creates potential corrosion problems due to;
1) The steel wire/shaft that remains inside the rivet is of a more noble metal, thus transferring the corrosion to the alloy, which is the less noble metal/alloy. Commonly known as the anodic effect.
2) Cyclic expansion and contraction, allows for moisture ingress between the aluminium surfaces during expansion, and moisture entrapment during contraction.

As I am not familiar with the abovementioned products, I cannot comment on their effectiveness in terms of combating corrosion. I can however suggest that an aluminium primer of which the LOW MVT (moisture vapour transfer) rate is indicated on the datasheet, is opted for. This is also referred to as the permeation rate. Coupled to that, it should also have good elongation to break properties (flexular properties). Be carefull however of epoxies, as they generally have poor chemical bonding to aluminium. Some epoxies specifically engineered for use as primers for concrete, bond well to alloys. Some "tin aerie kits" are supplied with epoxies as an adhesive to be used in conjunction with rivets to increase bonding strenght between ribs and skins etc. How good they are as corrosion inhibitors is not known to me, but I suspect that they have proven bonding properties and would provide leafing barrier protection against moisure ingress to some degree. Further also guard against the occurance of non-epoxies being sold as epoxies. Often the guy behind the sales counter regards anything that is a two-pack or three-pack system to be an epoxy. Many Vinyl esters and Polyesters are sold as epoxies, which in fact they are not.

I hope this is useful

[RudiGreyling]

Hi Wingless-nut,

thanks for the info, I agree when you choose a product know what you are using. The epoxie primer I use conforms to a military spec DTD 5567A Heavy Duty Corrosion inhibiting paint primer, that can be used as primer or final coat: EPIWASH STRONTIUM CHROMATE PRIMER AW-255.

Problem with some primers is they are fine as primer that will be top coated, but not fine by themselves for corrosion protection without top coat.

Anycase, Ian when can we get an update with some photos again??

Kind Regards
Rudi

[Ian]

As corrosion engineering is my area of business, I wish to also draw attention to the following;

As I am not familiar with the abovementioned products, I cannot comment on their effectiveness in terms of combating corrosion.

Hi Wingless Nut, Thanks for your comments, well at least half my guess regarding the moisture was right, and yes it does dry with some flexibility. Below is a pic of the can of paint you get in the kit. The numbers at the top have been 'primed' but on close look they say '5313/A SM ACQ /OP NERO' made by a company called ALBESIANC SISA VERNICI.


Then for Rudi, my day job is demanding at the moment, so all I've done this week is finish off all the plastic tips, then logistics to pack all in bubble wrap ready for the trip to the painters (in a few light year's time)...
Below you can see some flapperons and slats complete, and below that they are wrapped up.


Cheers Ian

[Wingless Nut]

Ian & Rudi, it's a pleasure guys. Shout if you require more info on this subject. Hopefully I can help. Good luck with your project Ian. I am absolutely green with envy, and hope to place my order for a Savannah or possibly an Oribi kit soonest. I don't care much for 2-strokes and is toying with the idea of an Oribi / HKS combination. The HKS seems a little light in the pants, especially in the torque department. If anyone has experience with these engines and can advise me on it, please do.