Waiex Project

[LarryMcG]

Hi RV Sometime

You're very welcome to have a look, hopefully will be very close to tasting the air by the time you get here!

Can also direct you to PE, where they are building 3 RV 7's.

Give me a shout -0825746102

Larry

[RV Sometime]

Wilco, thanks Larry.

My Twinco's port engine broke the crank a few weeks ago so I am sadly grounded, but I estimate that it will be back in the air within a week. It would be an honour to be there when you do your 1st flight. When do you estimate this happening.

[joraua2]

shlarry Mgilawi, call me re your egt probes and that bad bend in the wing - I think I have found a way to fix it.
Is the medication working.

pb

[AndyCAP]

HuH?!

Larry, whats going on? Havnt heard from you in a while?

Cheers

AC

[LarryMcG]

Hi All

Bad time of the year, Festival in GHT, been away for a while again, but hopefully back on track soon.

Windshield in, Busy with fairings for main gear, back end etc. Canopy frame done, lock mechanism sorted, hoping to tackle final canopy fitment this weekend, but need extra hands, and hot weather! Then, to airfield for fitment of wings etc. Seems like only about a week of work left, but cannot fing the time.

OH, one problem. Jab factory must have over tightened a fuel drain nut on the bottom of the tank, so the brass nut now turns in the plastic of the tank, and have a fuel leak, right into the cockpit. Any suggestions on how to seal this??

LM

[grostek]

Hi Larry,

Find out what type of plastic the tank is made from.

Then make a plastic "Heliccoil/Threaded insert "from the same material with a larger OD and the same ID that was in the tank.

Next enlarge the hole to tap size in the tank so that you can cut a thread equal to the OD thread of the new plastic insert.

Then apply epoxy onto the new insert and screw the new insert into the new larger tapped hole in the tank before the epoxy dries.

Let the epoxy cure for a day or so.

Screw in the original brass fitting and leak test the tank.

All this assumes you have enough meat in the original tank to drill a larger hole for the tapped insert to start with.

Also check which type of epoxy will glue the two plastics together.

Also remember that pipe threads are taper threads so dont tap the hole that the tap falls through.

Hope this helps.

Kind regards,

Gunter Rostek.

[LarryMcG]

Thanks very much, Gunter. Will have a good look, will have to take out tank again, and check thicknesses etc.

One step forward, two back!

Larry

[AndyCAP]

Hi Larry

The other option to consider is plastic welding. from the pics I have seen it looks like the tank is blow moulded from Polyethylene (Just a guess on my part ). If it is, you will probably not find an epoxy which will stick to it. (PE is the same stuff 2l trancelucent milk bottles are made of) If the hole in the tank where the fitting attaches, was threaded, it may be possible to build it up with some plastic welding and then re-tap the threads? In my limited experience with plastics, a weld tends to work better than 'glue' - unless the latter was specifically designed to bond the material in question. Perhaps Sonex will tell you what material is used and then you may be able to find a local Co which can do it for you.

If not - be brave and try doing it yourself Plastic must be very clean - use something like acetone to degrease the area where you want to plastic weld. then you can use a pencil torch to heat the affected area and some build up material up to the point where it is almost liquid (but not quite - PE turns clear as it heats up - from its normal ) before pressing it together. Finding the 'build up' material can be tricky - particularly if you dont know 100% what the tank material is. 1st prize is to cut some material from a moulding burr or mounting lug on the actual tank (if there is somewhere where you can cut some material off without weakening the tank).

I must say that I have use this technique many times on model aircraft fuel tanks and have managed to successfully repair multiple puncture 'wounds' following crash damage. I am not sure if it will be acceptable for use in a fullsize plane tank, but the principle is the same and in the model plane case, the fueltanks are pressurised by exhaust gas which makes it even harder to seal. I never had a leak after repair though!

Good luck!

[grostek]

Hi Larry,

I Think Andy CAP has the better method, always better to return something to original size by welding than by trying to adapt.

Have a look at this link where they discuss repairing a PE fuel tank.

http://www.cruisersforum.com/forums/f54 ... 12306.html

May help you.

Kind regards

Gunter Rostek.

[AndyCAP]

I am happy to see that my idea was not too far off! Thanks for the link Gunter

LARRY! (yes I have to yell to ensure I get your attention - sorry )

It just occurred to me that I should highlight the inherent danger in the procedure I suggested above. Your fuel tank has already contained fuel, so at the risk of stating the obvious, I would suggest the following: Drain the fuel, remove the tanks & fill it with water, leaving it over night. Then drain the water and flush it a few times to ensure you dont have any petrol residues left. Then let it lie in the sun for an hour or so to ensure that there are no petrol fumes left in the tank BEFORE you try to do the repair - i.e. bring a naked flame close to it. Similarly ensure that the acetone you use to de-grease the repair area should also be allowed to dissipate before attempting the repair.

At the risk of stating the obvious, I am highlighting this, since i know one can sometimes be so focussed on the repair that one forgets about the inherent danger involved!

Gunter, your link is very interesting and helpful, I would just like to highlight the following quote from it:

"You don't have to worry about igniting the diesel fuel. There is no flame and it doesn't get hot enough to ignite diesel fuel."

This is a very dangerous statement to make, because it can create the wrong impression. Yes I know diesel is not nearly as volatile as petrol, but it is flammable none the less and all you need is the right vapour/air mix and an ignition source to have a very nice bomb! Obviously Petrol is a lot worse since its more volatile, but one should treat all flammable liquids with respect

Sorry for the slight hijack and accompanying sermon Larry!

Good luck with your repair

[AndyCAP]

Another thing, If you dont like the idea of using an open flame, you can use a large soldering iron as a heat source, but make sure the tip is free from solder - or buy a new one. I have used this as well as the pencil torch, and found the latter easier since you can heat a larger area more evenly. You have to be careful however that you dont melt the plastic completely or set it alight.
Cheers

AC

[grostek]

Hi Andy CAPP

All good, valid points.

Kind regards,

Gunter Rostek

[LarryMcG]

Hi Guys

Many thanks, this seems like a sound option. Will hopefully get the tank out this weekend.

Damn festival in this town is making us madder!

L

[LarryMcG]

Ok, so I broke my canopy!!

Fortunately the factory automatically send two, knowing that most people will break one. So, now building a wodden framework, to hold the canopy. This thing is EXTREMELY brittle, and cracks / breaks for absolutely nothing!!

Also busy with fairings, wheel spats etc.

Pics below

L

[LarryMcG]

Broken!