Growing a Grumman - Part 14


Wow! - another month and more has flown by and it seems almost nothing acheived!

Sometimes it is hard to keep the motivation up and running at a high level - along with the 'one step forward and two steps back" syndrome which of late has been common, there has been Easter and sundry other public holidays getting in the way during April. The result of that is that many firms and suppliers close of course, and then one cannot get hold of stuff you need, or get things done by said firms.

The plan outlined in Part 13 to use mandrel bends, a longer and more tortuous inlet tract (well, two tracts actually since there are two carbs) and for this inlet manifold to be mounted to the aluminium manifold is proceeding but slowly. What I found is that the adaptor plate carrying the inlet pipes cannot be bolted to the mounting surface of the manifold since the aluminium is too thin to take a thread which would provide strength. After tapping threads, I found that the bolts would immediately strip the thread in the soft ally since that is only about 5 mm in thickness - even tried helicoils but they also would suffer the same lack of grip into the metal.

So back to the drawing board yet again! I have made up a 10 mm thick aluminium plate to be welded to the manifold and this plate will give the necessary thickness so that threads can be tapped which will actually have some strength and then the actual manifold pipes, plus their adaptor plate of steel can be securely bolted down with a gasket for sealing.

With any luck this can all be completed soon and then we can figure, once the new inlets tracts are in place with the carbs mounted and throttle linkage connected up, just how the cooling water reticulation system of piping will have to be modified, since this previously passed through the area at the rear of the engine where the carbs will now repose!

Had a visit two weeks ago from Andrew, who has a Grumman AA1B, the only legally approved +6 - 3G AA1 in the world, and who is a director of a company that builds big military vehicles for a living - he pointed out that the problems of 'packaging' everything is one common to his development work - and even though his company has engineers, mechanics, welders etc etc available in abundance, it still is a trying job sometimes.


What with life getting in the way, a move to a new hangar on the airfield and many complications arising out of the decision to relocate the carburettors, we have not been able to make much progress on the job of finalising the manifold design and fully testing it.

Just a few weeks ago however I did mount the new manifold and carbs and cranked up the motor - it ran, after a fashion, but I could not get it to run satisfactorily and the reason was pretty clear - there was air being sucked in at the manifold, either at a defective weld, and/or, as I later found, by the fact that previous welding operations had caused the mounting flanges to distort so that they are no longer flat!

So now it is time to file those down flat again and to check out where the welds might have pinholes.


After a lengthy lay-off over Christmas and into the new year, I made the decision to move the aircraft from the airfield where it costs money to rent a hangar and more money and time to get to the airfield every time work has to be done - which is every time! After a very poor final half of 2011 business-wise some economies must be achieved whilst we hang on for better times - whenever those may arrive!

Then a malady set in! Oh dear me, the move appeared in my mind as such a giant task, and in fact as an admission of failure to be honest, that I actually harboured thoughts of selling the project and getting the hell-out! Indeed I advertised it at what I thought was a low price, feeling so frustrated on many fronts as a result of the 'one-step-forward-two-steps-back' effect!

I won't bore you with the details but the appalling experience of dealing with potential "buyers" who actually have no money at all, or are deeply,deeply ignorant in the extreme about aircraft, especially experimental, or seem to think that my aircraft has zero value so I must give it away, has led to another but welcome state of mind - the bloody-minded state that says "no way will you sell it - finish the bastard!"

Today, working on the aircraft to install some delicate interior components rather than carry those loose and removing the wings in preparation for the move has made me realise what a fabulous airplane this littlest Grumman actually is - built solid, built honest and a great flying machine, it cannot be sold under these circumstance - end of story.

But it is coming home to my garage - saving me the ongoing expenditure of the hangar and travel costs and I will be continuing to 'fettle' the motor - which is about all that needs sorting out now and even that does not look like a massive job, consisting mostly of getting my inlet system working well.

As a buddy at the field said - "You have had time now to experiment deeply over the past few years at the airfield with the auto-powered concept - and you now know that it will work and what is needed to make it fly"

And you know what? - he is right!


Longer inlet pipes to put carbs where they need to be - down low and tucked behind! And made of aluminium!
Lots of cutting and welding - someone who can weld will be able to remake these properly.
Carbs as previously mounted on top