Wet install or 100% cleco cure?

cjensen · Post by **cjensen** » Mon Jun 05, 2006 10:33 pm

I started installing fuel tank ribs tonight (well, I did one anyway), and I've decided that I don't like the wet install method. It may be the preferred method of most people, but the other method that I know of is to butter the ribs, install the ribs with 100% clecos, and let cure for 24 hours or so, then set the rivets as you would the leading edge, but dab a small amount of sealant in the dimple before the rivet goes in.

Thoughts??

JohnR · Post by **JohnR** » Tue Jun 06, 2006 12:50 am

Chad,

I donl't have a response for your question but am following and will be watcing to see what people think. I'll will probably go wet but am willing to change my mind if someone shows me why I should.

tshort · Post by **tshort** » Tue Jun 06, 2006 3:43 am

Ditto!
I'm almost there myself and have been wondering the same thing. Will be interested in your experience.

It seems like you could install all the ribs, wait 2-3 days, then come back and rivet in a session or two and things would go faster.

Thomas
-8 wings

captain_john · Post by **captain_john** » Tue Jun 06, 2006 5:52 am

The cleco fastens the joint at no more than 300 psi and IS NOT going to perfectly align the sheets.

A rivet holds at almost 3,000 psi and will be sure to perfectly align the sheets.

When the sheets have an air gap, the driven rivet will not be driven to spec. In other words, the rivet will bulge in between the sheets. This is a structural part and that is not "spec" grade work.

Also, some rivets will inevitably be cocked or crooked. This is likely in a few spots unless you are totally LUCKY! That leaves an end product that I am not happy with.

That being said, many people have done their tanks that way with success! I am sure it was a fast method. It just isn't the way I chose to do it because of those reasons.

Also, it isn't the "standard" means of assembly. Not that everything must always be "standard"... I just think this step should be.

FWIW... my $0.02... YMMV... do what feels good to you. See you in the sky!

CJ

JohnR · Post by **JohnR** » Tue Jun 06, 2006 7:19 am

Good coments CJ. I think you convinced me to stick with doing it wet an pay my dues.

cjensen · Post by **cjensen** » Tue Jun 06, 2006 9:29 am

captain_john wrote:The cleco fastens the joint at no more than 300 psi and IS NOT going to perfectly align the sheets.

A rivet holds at almost 3,000 psi and will be sure to perfectly align the sheets.

True, but the rivet only holds that pressure once it is set. It holds 0psi when it's just sitting in there waiting to be squashed. All other parts get assembled with clecos holding the parts in the same fashion, just with no sealant. I understand that once the sealant takes hold, there is no adjusting from that point on, however, with clecos in EVERY hole, there should be little chance of the holes not lining up, especially since the dimples keep things aligned as well.

captain_john wrote:When the sheets have an air gap, the driven rivet will not be driven to spec. In other words, the rivet will bulge in between the sheets. This is a structural part and that is not "spec" grade work.

This is true as well, but the layer of sealant between the rib and skin is gonna be no more than 1/16th thick after it's squeezed by the clecos. There's a thread http://www.vansairforce.com/community/s ... php?t=7602 on VAF that describes in detail about how the pressure bulkhead on C-17's are built this way...

captain_john wrote:Also, some rivets will inevitably be cocked or crooked. This is likely in a few spots unless you are totally LUCKY! That leaves an end product that I am not happy with.

Yeah, but this happens on other parts all the time anyway...at least with me it does, and I've been able to deal with it to get it to set straight.

I'm not trying to start an argument here AT ALL, but the pros and cons of each method are weighing equally in my mind, and if it comes down to mess or no mess...I'll choose no mess.

Wicked Stick · Post by **Wicked Stick** » Tue Jun 06, 2006 10:24 am

Awh come-on now Chad... Are you trying to tell us your building a metal airplane and are worried about getting a little messy

cjensen · Post by **cjensen** » Tue Jun 06, 2006 11:23 am

Nope! I actually like getting messy...looks like I've been doing something that way!

Sealant is another story, however. I DON'T want sealant all over my arms, face, whatever...I'd get funny looks the next day with gray sealant on my nose.

I talked to my shop guys about this method, and all of them agreed that it's a fine and acceptable method.

CJ, one suggestion by one of the A&P's was to use a nut on the cleco to get a tighter grip. That way, the spring is actually pulling harder. He showed me a set of clecos that they have set up this way, and it does grip quite a bit better...

tshort · Post by **tshort** » Tue Jun 06, 2006 1:06 pm

Where do you put the nut on the cleco?
I have some of the wing nut clecoes but they are in the 1/8 size... don't think I'm gonna buy any silver ones just for this.

T.

cjensen · Post by **cjensen** » Tue Jun 06, 2006 2:18 pm

Here's a couple of pics of where the nut goes. The guys say this works great, and can really add some pulling power to the cleco spring.

Pay no attention to the metal used, it's just scrap from the shop.

The nuts are 6-32's for 3/32 cleco's, and I believe 8-32's will work for 1/8 clecos.

tshort · Post by **tshort** » Tue Jun 06, 2006 4:34 pm

OK ... I see. I couldn't picture it - my nuts are too big.

(Sorry Spike - please no demerits or anything, couldn't resist)

I'll have to see if I have any that size and test it out. There are some other areas where a little more pull would be helpful.

Thanks for the tip!

Thomas
-8 wings

cjensen · Post by **cjensen** » Tue Jun 06, 2006 4:37 pm

Funny!

I didn't have any either, so I ran to Menards while getting some lunch today, and bought a little over 200 6-32 nuts for $6. Plan on using my nuts tonight!

cjensen · Post by **cjensen** » Tue Jun 06, 2006 10:25 pm

Well, I installed the remaining inside ribs on the right tank tonight using the 100% cleco method. I did a lot of reseach today on this, and found that there are quite a few RV builders doing tanks this way. I feel confident in my decision, and there was NO MESS! I didn't even put gloves on tonight!

Here's the clecos with the nuts in between-

captain_john · Post by **captain_john** » Wed Jun 07, 2006 5:50 am

Looks good Chad.

Q. Your setup is resistive senders and no return lines?

CJ

cjensen · Post by **cjensen** » Wed Jun 07, 2006 9:04 am

Resistive senders, yes. I need to do a little research on the return line. Actually, I was thinking about this last night, and it's something I guess I don't really understand, nor do I know when to do it. I'll start a new thread...