Nipper composite fuel tank

Use this forum to discuss technical points relating to the Nipper and its ancilliaries.
JimCrawford
Posts: 65

Nipper composite fuel tank

Postby JimCrawford » Thu Mar 14, 2019 5:54 pm

I've tried the LAA forum and even emailing LAA engineering with no response so I thought I try here. My fuel tank has developed a leak along a riveted seam. I've been searching for a composite system compatible with E5 mogas in order to lay up a fuel tank. The most likely candidate I've found so far is Spruce and Speciality part number Part Number: 01-01109. A vinyl ester system. I'd be interested if anybody has any suggestions or experience with this problem.

Jim

ragson
Posts: 2

Re: Nipper composite fuel tank

Postby ragson » Thu Apr 11, 2019 3:06 pm

Good morning.

There is a very popular french brand, "Restom" (restom.net), rather specialized in collectible motorcycle, selling a very efficient product for leaking tanks. I personnally used several times and never failed.
The site is in french but they speak english and sell worldwide. Regards.

JimCrawford
Posts: 65

Re: Nipper composite fuel tank

Postby JimCrawford » Thu Apr 11, 2019 10:55 pm

Hello ragson.

That is a very interesting website, I'll certainly chase up some of their paint products.

The specialist composite tank repair product isn't suitable for my purpose as it is essentially a sloshing sealant and I'm not happy with using sealants on a tank which has started to fail. I cannot guarantee the stability of the surface of a 1960s composite tank after exposure to mogas. Also many of the reports I've read on such sealants in aero and marine tanks have indicated that less than perfect preparation will lead to the sealant peeling from the tank. My enquiry is for a composite scheme to build a new tank that is compatible with mogas incorporating alcohol. A secondary issue with mogas causing failure of resin systems, is that the products of the interaction will also be carried into the fuel system with uncertain results.

I've trawled through many resin systems and haven't managed to find any which are completely compatible. There is one vinyl ester product which is a possible but I cannot find it in other than industrial quantities. If I could source something that looks promising I'd make up some test coupons with the tank and test them year by year immersed in mogas.

It looks as if the quickest solution to my problem is to remake the composite part of the tank in aluminium.

Jim

Neil Spooner
Posts: 512
Location: Ardleigh, Colchester, Essex, UK
Contact:

Re: Nipper composite fuel tank

Postby Neil Spooner » Mon Aug 19, 2019 5:54 pm

Hi Jim,
I would think that removing the rivets along the seam, cleaning the surfaces of the seam and using Proseal or equivalent ( https://shop.vansaircraft.com/cgi-bin/s ... ct=proseal ) would do the job.
I am not sure what resins the original fuel tank were built with, but they clearly withstand the presence of Mogas. (I ran my Nipper exclusively on Mogas with no issues)
Neil
A little help goes a long way.
Nipper G-ONCS and G-BALS
RV4 G-IKON

JimCrawford
Posts: 65

Re: Nipper composite fuel tank

Postby JimCrawford » Wed Aug 21, 2019 10:28 pm

Hi Neil,

My concern with repairing the existing tank by doing as you suggest, de-riveting the seam and using Proseal to re-assemble it, is that the original tank would have been made before ethanol in fuel was even thought of as a good idea. In an era of Avgas and no ethanol mogas there was unlikely to be a problem using readily available resin systems. Alcohol seems to be the devil and to be able to react with these older systems with the consequence that reaction products end up in the fuel system with the potential to cause problems like gumming up. If you can deal with the faff of checking mogas for alcohol to find a source of alcohol free fuel then that's fine but I am hoping to rebuild my tank and system to be resistant so I don't have to worry. Otherwise it's Avgas or ul91.

I'll check with Vans about their Proseal equivalent sealant shipping costs but I notice that Spruce & Speciality do Proseal so it should be easily available from Light Aero. I've investigated getting the composite part of the tank remade in Aluminium although that would still end up with a riveted seam. The price quoted was attention grabbing!

I'm still interested in making a composite tank using a vinyl ester system so I'll have to make my mind up soon as all the undercarriage and engine work is progressing apace.

Jim

Bumblebee Girl
Posts: 11

Re: Nipper composite fuel tank

Postby Bumblebee Girl » Tue Sep 10, 2019 8:58 pm

I had a new tank fitted last year as part of a complete overhaul of the fuel system. The seal in the old tank had started to perish so we fitted a new aluminium one. Cost about £800 and needed LAA approval.

Neil Spooner
Posts: 512
Location: Ardleigh, Colchester, Essex, UK
Contact:

Re: Nipper composite fuel tank

Postby Neil Spooner » Thu Sep 12, 2019 10:57 am

....what have you done with the old tank please? It may be useful as a donor for developing a mould for future composite tanks. I am working on a larger capacity tank that has a triangular extension on the bottom that fits between the brace bars. It will have a divider to allow it to be fitted with a flop tube for inverted flight, and only one fuel outlet to preclude having to switch tanks.

Regards,

Neil
A little help goes a long way.
Nipper G-ONCS and G-BALS
RV4 G-IKON

Bumblebee Girl
Posts: 11

Re: Nipper composite fuel tank

Postby Bumblebee Girl » Thu Sep 12, 2019 6:29 pm

Hi Neil

I gave the old tank to John Brompton, G-XD. I believe he still has it.

Kate

JimCrawford
Posts: 65

Re: Nipper composite fuel tank

Postby JimCrawford » Sat Sep 14, 2019 1:55 pm

Hi Neil,

I've been working on a scheme for a composite tank, also with a triangular drop to increase the capacity and to provide a sump to the otherwise flat bottom. I hadn't thought of the possibilities of a flop tube but it seems a good idea even though my VW isn't adapted for inverted flight. Building in the option now could be useful.
My cunning plan of the moment is to build the tank using the most likely and available composite scheme and also make up a set of test strips. I'll fly restricted to Avgas and UL91 for a couple of years while the test strips sit in alcohol and mogas and can be frequently checked. That will give me at least two years heads up on alcohol problems. If the strips deteriorate then I'll stick to alcohol free (fuel not me!) and I'm no worse off that I would be anyway. If they don't suffer then I can move on to mogas without worries.
I'm keen to try the composite tank as I have experience as a BGA inspector with composite repair authority and quite like working with the stuff. A composite tank will also be considerably cheaper than getting an aluminium version professionally made and it is worth a go as an experiment.

Hi Bumblebeegirl,

It was good to see your Nipper at the rally, it certainly is very smart, and also that the LAA took it seriously. I took a couple of photos of your exhaust arrangement as I thought I might copy it, mine are cruder and with a little corrosion so they will have to be replaced within a couple of years. Do you have any drawings of the exhaust and the aluminium tank? The latter in case the composite solution falls over and I have to revert to metal. I noticed a 'hydraulic type' line fastened to the fuselage frame in the cockpit what is that for?

Regards

Jim

Bumblebee Girl
Posts: 11

Re: Nipper composite fuel tank

Postby Bumblebee Girl » Sun Sep 15, 2019 9:44 am

Hi Jim

Glad you liked the Bee. I had the fuselage recovered a few years ago and that smartened it up: she probably looks the best ever at the moment and I propose to keep it that way.
I'm afraid I don't have any drawings of the exhaust or tank. The tank was made by Motorsport Revival in York who used the old tank as a template. It was sprayed locally. It's made from 1.5mm 3031 aluminium and then tested to 1.5 psi. The LAA approved the mod. The mod number is 14837. The tank was replaced as part of an overhaul of the whole fuel system following my two incidents with a faulty fuel pump. ( see photo of first landing in a field of crop.....). The new fuel pump is a Citroen Dianne 2CV, part number 3241/1. I'm now getting a very respectable 11 litres an hour.

Not sure what the line is : could be the primer or the oil pressure gauge? You will have noticed how "crude" the cockpit is compared to other Nippers, so it can't be many things!! Did you take a photo?

Hope that helps....

Kate
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