Thanks Nigel for your informative thoughts. My reservations come from the use of rivnuts in what seems to be a structural application, but I am far more used to working on spam cans than on plastic birds.
Michael On Sep 4, 2017 7:33 AM, "Nigel Baker" <[email protected]> wrote: > Hi All. > > I am answering several mails in one hit so excuse if disjointed. > > > > This mail is probably the best description of the procedure so far. I like > the reference to wiggle as it is the best description. > > > > There are 4 variants of the tank fitted to the H36. > > The original 60 litre. > > Then a 70 Litre. > > And finally an 80 Litre with all variants being in FRP. > > Then the alloy version which bears no resemblance to the previous 3. > > They are all different but the wiggle principle works for me. > > There is a good explanation of the technique of removal in the maintenance > manual if anyone cares to read it. > > Removal of the canopy ( a small job as Ian mentioned) is essential. > > > > The front retaining flanges mounted to the rear of the spar bridge are > indeed removable as previously mentioned in the later variants but fixed in > the earlier versions. While there is a distinct version I and version II > there is a whole heap of variations in between them all that is not > reflected in the MM or certification of the type. Things obviously worked > differently in Austria under the LBA at the time compared to now under > EASSA. > > > > As for strength for retaining consider the following. > > > > The Tail boom of the H36 is 4 layers of 92-125 and 1 layer of 92-110 with > 4 roving stringers to add extra strength in 2 directions for ground > loop/heavy landings. > > The cover panel for the inspection portal at the rear of the luggage shelf > is from memory made of 3 layers of 92-125 and held in by 4 X M5 bolts going > into rivenuts mounted in the bulkhead. The bulkhead is quite heavy for > torsional stiffness so the panel is the week point. > > > > The tank weighs about 12KG again from memory. > > Assuming constant mass over length which is conservative given its shape > this means a load about its Centre to create a moment resulting in a load > of 6KG at its aft point. > > Assuming a fuel load of 80litres (Tank choker block) this adds 57.6 KGs to > the load. > > Given the shape of the tank it is safe to assume about 1/3 is aft of > Centre. > > Thus working on the same moment principal the fuel load at the aft point > will be 19.2 KG’s > > So total load at the aft point would be around 25.2. > > Now turn the aircraft upside down at minus 6g. Load is now 151.2KG. > > So do I reckon me and the Mr’s standing on the tank inverted at the rear > edge held up by 3 layers of 92-115 in an angle shape as a support close to > the tank edge. Yep I do and more. > > The reason the H36 is 100K lighter than a G109 is because of attention by > Wolf Hoffmann to keep the weight down in all areas of design and > construction. And it works. None have failed in the air except for the > prototype and it simply couldn’t handle the abuse it was enduring at the > time. Every aircraft has its limits. Respect them or suffer the consequences > > Cheers. > > Nige. > > > > > > > > > > > > > > *From:* [email protected] [mailto:[email protected]] *On > Behalf Of *Greg Wilson > *Sent:* Monday, September 4, 2017 11:52 AM > *To:* [email protected] > *Subject:* Re: RE: Re: [DOG mailing list] Fuel tank removal > > > > Removing the tank is tricky. After removing the angle flanges and the > luggage compartment base: > > > Remove the fuel gauge sender and earth wires > Remove the fuel intake pipe off the tank and fuselage > Lift the rear of the tank until the tank is vertical > Reach over and under to disconnect the fuel hose and fuel drain hose > Rotate the (vertical) tank 90 degrees to the left (I think this is correct > -rear should now be at the left. Once I worked it all out I wrote a diagram > & instructions on the top of my tank in texta.) > Lift and wiggle tank up and top forward to remove it through cockpit > > Good luck, > > Greg. > > > Greg Wilson > > > > > ---- On Mon, 04 Sep 2017 11:17:43 +1000 *Michael Stockhill > <[email protected] <[email protected]>>* wrote ---- > > Thanks all. Whoever installed my tank didn't install any sort of flanges > or other restraining devices at the rear bulkhead to secure the baggage > compartment covers, so their back edges and the tank are floating. If > anyone gets a chance I would appreciate a photo or two so I can fabricate > something. > > > > There are two fiberglass angles creating a flange at the front of the tank > under which the covers fit. These are attached to the back side of the > seat bulkhead with rivnuts and machine screws. Naturally the machine > screws were seized or the rivnuts spun so I spent an hour or two grinding > off the screw heads so I could remove the flanges. I have a hard time > believing that rivnuts are a solution for a structural application. > > > > Looking forward to pulling the tank tomorrow. May be an issue due to some > fiberglass buildup behind the shoulder harness fittings from someone's > indeterminate repair. Currently an interference fit. I hate cleaning up > other people's messes on airplanes. > > > > Thanks for all of your insights. > > > > > > M > > > > On Sep 3, 2017 6:08 PM, "Ian Williams" <[email protected]> wrote: > > The reason I suggested to remove the canopy is that it is real easy to > remove and yes, I did crack the rear window !@#@#$ . > > Best regards > > > > Ian W. > > > > *From:* [email protected] [mailto:[email protected]] > *Sent:* Monday, 4 September 2017 10:44 a.m. > *To:* [email protected]; Mike Collins > *Subject:* Re: Re: [DOG mailing list] Fuel tank removal > > > > I forgot to mention that we have a fibreglass tank that replaced an ally > one and same method worked with both. > > > > > > > > > > > > > > > > On Monday, 4 September 2017, 8:28:14 am AEST, Mike Collins < > [email protected]> wrote: > > > > > > If you have a new aluminium tank it just rests very snugly on (from > memory) five or six fiberglass covered supports that are attached to the > fuselage. > > The passenger luggage panels are what hold the tank in place together with > the fuel filler system - there are no bolts! > > Mike > > > ------------------------------ > > *From:* [email protected] <[email protected]> on behalf > of Michael Stockhill <[email protected]> > *Sent:* 03 September 2017 18:52 > *To:* [email protected] > *Subject:* [DOG mailing list] Fuel tank removal > > > > It looks like I need to pull my Dimona fuel tank to route ADS-B antenna > coax. For the life of me I can't see how the tank is secured to the > airframe. Where are they hiding the bolts etc.? > > > > Thanks > > > > M Stockhill > > Polson MT > > > > >
