XL-79 progress

[Jeff XL79]

Between the wing tank is a viable possibility  at least for volume. 

Tank Volumes
0% Full
Total
Capacity
Filled
Volume*
U.S. Gallons
4.94
0.00
Imp. Gallons
4.11
0.00
Liters
18.69
0.00
Cubic Meters
0.0187
0.0000
Cubic Feet
0.6602
0.0000


I calculated a tank 6.5" x 6.5" x 27".
My actual measurements were 7" deep at the front spar. And 5 7/8" at the rear spar. 27" in-between spars. Adjustments to height so the tank would clear the wing fittings could be made. It would give a tigermoth look to the profile.  

Interesting idea. The foam composite tank would be the easiest to make. I'll try drawing it out for a study.

Jeff 

[Jeff XL79]

Center fuel tank sketch.  Please feel free to give input.

Jeff

[Jeff XL79]

I'll try to get a tiger moth picture for example.

[Jeff XL79]

Tiger moth.

[pappyadkins]

Yep Jeff - I agree... This is what I've been planning.... 

[Jeff XL79]

Thanks Pappy Adkins. I'll look forward to your ideas..

I was going to order some Divinycell foam to start. Is 1/4" the right thickness for tanks?

Jeff

[Kamcoman77]

I used 1/4" thick Divinycell. It seems very strong once covered on the outside with fiberglass & epoxy. Be sure to use Vinyl-ester resin on the interior. It is much more alcohol resistant than epoxy. All my seams are filleted with a mixture of flox and VE resin. So far, there have been no leaks.

[Jeff XL79]

Nice looking work Kamcoman. I'm excited to try something new.  Working with foam and composites has been a goal. I see the vinyl ester resin in the Aircraft spruce book . What outer coating material are you using for the glass cloth? Do we still need to use the home depot drain parts or is there an option?

Anybody have an idea for a sight glass gauge? This will be right over your head so it will need to be electronic or offset somewhere. 

The most exciting thing in this design to me is getting the tank outside of the wing. It also centers the weight and makes repairs and service to the tank possible without disturbing the covering.

Jeff

[pappyadkins]

Following.... Great questions... I was about to ask some of the same... So y'all are looking at buying from ACS? 

I thought about getting a gauge, although very affordable, that just seems to add weight & complexity to it, so I'm leaning toward sight glass...

As far as sight glass I'm looking at possibly an 'indented' section with maybe tube at an angle... just don't know till I start whittling away at my foam template....

I so agree with you... I'm super excited to give this a go for some of the same reasons...

[Kamcoman77]

I used the Derakane vinylester resin, 1/4" Divinycell foam, Rutan bi-directional 7725 8.8 oz FG cloth, and flox powder, all from ACS (30 miles away). I already had some Aeromarine 300/100 epoxy from a boat project, but any laminating epoxy should do (not T-88). Be very careful ordering VE resin, it has a very short shelf-life and is expensive. I did not buy mine until the basic box was already glued together with 5-min epoxy. The petcock is from Throttle Addiction and the quick drain is Curtis (ACS). I VE/floxed an aluminum plate in my sump and threaded it for the petcock & drain.

[pappyadkins]

Ok y'all made me do it...

As I've stated many times before BEAUTIFUL!!! Question looking at the tank it appears the fiberglass will be very clear, right?  Just thinking I might leave part of the underside unpainted for a sight window... Of course the rest I'd paint red...

I went out quickly and made a temp mold - will have to make final mold once I get the wings mounted And know my actual clearances...
The 1st pix is side view with my cardboard template
the 2nd from pilots perspective
the last is slightly from lower side

[Kamcoman77]

Yes David, the fiberglass is crystal clear if you use a good epoxy. Here's a photo showing how you can see every detail under the FG.

[Jeff XL79]

Yes David, the fiberglass is crystal clear if you use a good epoxy. Here's a photo showing how you can see every detail under the FG.

I see where you built your sump. It looks like you built it by stacking layers.  I assume that you cut out the interior of each layer and coated it with VE . I read in the Aircraft spruce product description that the divinycell was formable with heat but hot wire was not allowed.  Have you tried heat forming for any shape adjustment?
Do the plates get any special surface treatment or are 5hey glued to the surface then glassed over?
Thanks for showing your work Kamcoman.
Jeff

[Kamcoman77]

You are correct about stacking layers to form my rear sump. The plates are glued into the foam with VE resin and flox, then glassed over. I did not need any curved surfaces except the top and it was such a gentle curve no heat was needed.

[Brock]

@kamcoman77
How did you do the VE/flox when installing (closing) the top of the tank?