I was fixing the fuel tank into the fuel tank compartment of my new Avistar 40 and was thoroughly disappointed with the poor vibration isolation. First of all no mention of rubber foam padding was made in the manual. Second, the tank is push fitted into a plywood holder, which simply means that the engine vibration is directly transmitted to the tank !

Is there any Avistar flyers that have mounted their tank without any modification and found no problem with fuel foaming ? Would like to hear experiences out there and what modifications done..........

I plan to sand out the plywood holder so that I can squeeze in some foam in between the tank and holder. Also adding foam all around tank, including the front part which touches the firewall.

I flew my avistar for 115 flights without a problem. I sold it and the guy who has it doesn't have any problems either. SO I guess it is OK.

Geistware, did you use any rubber foam to wrap the tank ? I am not sure if the older versions of Avistar did not use the plywood holder. Can you remember if your tank was secured with plywood at the rear part of the tank ?...........

I had no problem with my avistar tank, flew it for over a year and then sold it. Mine was the ARF version, not the ready to fly version with the radio, etc. Used 5 different engines on it, each with its own vibration characteristics (became the engine break in plane because of its flight characteristics). All of them used the stock tank. I wrapped mine in foam, and used a small piece of balsa spanning the fuse at the rear of the tank to keep it from sliding back (foam padded as well). I didnt use the SIG foam, I just used some packing foam that we had at work from a parts shipment.

Hope this helps,

Steve

I have an avistar 40 and have been flying it for 10 years. I just foam wrapped the tank and butted the front of tank to the fire wall. no need for foam at the fire wall. I never had any type of fuel foam problem with my os fx 46.

I just took a shot of the tank. Can you see the plywood "holder" in contact with the top of the tank ? The holder at the bottom cannot be seen in this shot. Do you guys have the same type of design ? I can't even wrap the foam rubber BEFORE I fit the tank because the plywood holders are obstructing. So I will have to creatively fit the foam inside the fuel compartment first and somehow push the tank through the plywood holders and putting a finger through the firewall hole to manipulate the foam to fit around the tank !!! ................

I too used the suggested method of installation without any problems.Been thru three different engines. OS.40FP,TT.42, and
OS.46 FX. HEY, Can we all agree on what a fine little plane this is??
Oh yeah, don't forget to add a stiffening wire between the mains to stop the bouncing on landings. Sure helped me !!

Happy Flying !
Ugo

Yes this is a great flyer! Where is the pick of the tank and fire wall. If i was you i would just lay some foam in the fuselage in the shape of a U and then push tank down and then cut a piece of foam to cover the top and screw the hatch down. No problem!

ok guys. sorry about that. here's the photo. the top plywood holder can be seen in direct contact with the top rear end of the tank. there no hatch in my avistar btw. that must be a much earlier version I suppose...................

Just stick foam in the opening and push the tank through you will be fine.The foam will isolate vibes enough to were there is no foaming even if the tank touches the supports.

Yeah, they are really great planes. I am trying to get mine back from its second owner, but looks like I'll have to take out some of the center of the wing to repair it. I used mine for all kind of neat learning experiences. I had virtually no dihedral in it, enlarged the rudder, wing bolts, glassed center section of the wing for strength. The funnest thing was building a wing mounted release mechanism to tote hand launch zagi wings up. Pop channel 5 on the radio and release the lil rc zagi.

I think my tank/ply setup was a little different than yours is in your pic. You might want to even try to move the tank back a little and see if it clears some. What size tank is it?

Heres a pic of my avistar, with the zagi affixed to it.

300 flights on my Avistar so far, no foam anywhere near the tank, just followed instructions. No problems.

If I am not mistake, I shoved foam into the compartment so the tank could not fall out but the tank came in contact with the bulk heads. No vibration reduction was used and it worked great.

Works fine. Follow the instructions. No foam needed.

I did have problems with the rubber plug on the fuel tank. The screw for the plug was stripped. The fuel spilled out into the plane. Sure was a fun flight with the CG changing with every move of the stick.

I used a little carpet cleaner to get out most of the fuel. The tail is now warped and twisted but the plane still flies great. I still love this plane.