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Fuel tank rear baffle

Arie

Arie

Well Known Member
Good day all,
I posted this under general discussion ,and not under model spesific as I think this relates to most RV models. I have read here about the rivets that attach the baffle to the skin have a tendancy to sometimes set a bit skew, I think it might be that, when the skin gets countersink with the baffle in place during initial asselbly ,the holes in the skin might enlarge slightly ,as the skin is only .032in thick and cause some allignment problems when the baffle is then finally installed.
My plan with the rear baffle on the tanks is not to countersink the fuel tank skin before the baffle is finally installed and prosealed and then 100% clecod in place. The assembly would then be left for a few days to cure. After the proseal has set only then remove every second cleco, countersink and rivet in place and then repeat the process for the remaining clecos still left over.
What do you guys think of this idea? Good ,or a waste of time ,causing some other problems.
Regards
Arie
 
Arie, I know some have posted about this being a problem, but I just did my right tank baffle and had no problem with the rivets being skewed in the countersinks. I made the skin c/s's with the baffle in place to keep the tool straight, then made sure everything was straight and aligned when clecoing after applying the proseal. All of my rivets are good and straight. Just wished I'd gone a few clicks deeper to provide more room for the proseal. About 2/3 of my rivets are flush, and the others just a little bit proud, but not enough to cause me heartburn. I'll go just a tad deeper for the left tank.
 
Stalldog said:
Just wished I'd gone a few clicks deeper to provide more room for the proseal. About 2/3 of my rivets are flush, and the others just a little bit proud, but not enough to cause me heartburn. I'll go just a tad deeper for the left tank.
Click to expand...

Don't do it.
 
I can say on my end, I did go a click deeper for proseal on only one tank skin thinking it was a great idea too. I can tell you in my experience that the tank I did do this on has been my "problem tank". It opens the hole in the skin up more & I had some alignment issues during final assemble. The sealant started setting and the baffle was not pushed in all the way even though the ribs & z-brakets were riveted & the skins were clecoed to the baffle. I pushed ahead and got it seated correctly. I definately would NOT recommend the seal, cleco, wait & rivet on this section of the tanks!!! Plan a whole day of messyness for each rear baffle. I'm slow but each rear baffle took me about 8-10 hours... Mad wifey but happy tanks.
 
Arie,

That sounds like a reasonable idea to me. If you go that way I'd suggest not even final drilling until after the sealant has set (maybe a week, unless your shop is REALLY warm). That would give you the best possible alignment. I think you'd still want to wet set the rivets.

Most of my skin to baffle rivets are proud enough to feel, but the countersinks were knife edged as it was, so makiing them deeper would only make alignment more difficult.
 
Daniel S. said:
I can say on my end, I did go a click deeper for proseal on only one tank skin thinking it was a great idea too. I can tell you in my experience that the tank I did do this on has been my "problem tank".
Click to expand...

Thanks, Dan, you've convinced me to leave my countersinks just as they are and not go any deeper!
 
Oh, one other thing before you in stall the rear baffle... build up between the skin & baffle flang definitely needs to be avoided. I did all of the rear baffle rivet encapsulations last night. If you have a slight build up, I'm not sure the tanks will fit over the inboard main spar cap. It freaking tight in there!!!! I'm very lucky i wet riveted while installing the baffle & cleaned up excess sealant as i went because I'm an excessive pro seal applier.
 
Daniel S. said:
Oh, one other thing before you in stall the rear baffle... build up between the skin & baffle flang definitely needs to be avoided. I did all of the rear baffle rivet encapsulations last night. If you have a slight build up, I'm not sure the tanks will fit over the inboard main spar cap. It freaking tight in there!!!! I'm very lucky i wet riveted while installing the baffle & cleaned up excess sealant as i went because I'm an excessive pro seal applier.
Click to expand...

I taped wax paper over the spar reinforcement bars. After wet riveting the tanks I installed them on the wing with the proseal still soft. This resolved any interference issues as the proseal deformed any place there was a conflict.
 
Between using enough sealant to prevent a leak, but not enough to keep everything from fitting, I'm not sure it's possible to build one of these things!!! :D I agree, when I fit my right tank on the spar, it was a tight fit, but it did fit. I did have to clean up the sealant at the root end where the spar cap is thickest -- the edge of the baffle just did clear the spar cap.

Robert, the wax paper thing wasn't in the instructions -- that's cheating. :rolleyes:
 
You can dimple the rear baffle instead of machine counter sink. I think it looks better and certainly locks in the alignment. Probably quicker too.
It's not difficult to push the baffle into place and it snaps right into alignment automatically.
 
Yep , I did fit them to the wing & clecoed them in place before the sealant set. I let them be for about 5 days before removing to do all of the shop head encapsulations... Using waxed paper in other is a darn good idea!!! May be we should have this discussion moved to the building tips section. I do like the idea of not match drilling / counter sinking the skin / baffle till after final install. I enjoyed the challenge of the tanks but definitely would not do it without a pro seal gun.... I'd gladly build a set for someone else knowing what I know now. :D
 
Dan, what gun did you use? I used a syringe for large jobs and it worked okay, but there's always a better mousetrap.
 
Wax on, Wax off

Didn't you guys build model airplanes before instant CA glue? When building with yellow glue we always put wax paper over the plans, otherwise we glued the work to the plans. If I build another RV I'm going to enlarge the plans and build the structure directly over the drawings :)
 
CA Glue

Dang, I must be a young'in. Because I started building RC planes at 5 and only ever had CA... what's this yellow stuff you refer to? :D

The pro seal gun is this one... Absolutely awesome btw!!! Well worth every penny!!!

http://www.yardstore.com/browse.cfm/4,4780.html

The cartridges, nozzles & plungers are here:

http://www.aircraftspruce.com/catalog/appages/nozzle.php?clickkey=12425

http://www.aircraftspruce.com/catalog/topages/tech_wiperplunger.php

http://www.aircraftspruce.com/catalog/topages/tech_cartagige.php
 
jimgreen said:
You can dimple the rear baffle instead of machine counter sink. I think it looks better and certainly locks in the alignment. Probably quicker too.
It's not difficult to push the baffle into place and it snaps right into alignment automatically.
Click to expand...

Jim,
I am at this stage on my build. The idea of dimples rather than countersinks is appealing. Did you have any clearance issues installing the tank on the wing? It seems the spar clearance may be the main reason for countersinking the rear baffle row.
 
M McGraw said:
Jim,
I am at this stage on my build. The idea of dimples rather than countersinks is appealing. Did you have any clearance issues installing the tank on the wing? It seems the spar clearance may be the main reason for countersinking the rear baffle row.
Click to expand...

Marvin, I don't know what differences there may be in the -14, but on a -7 there is no clearance issue between the spar and the rear baffle rivet line. Funny thing is I dimpled instead of machine c/s by mistake, but am pleased I did!
 
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