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Jabiru UL to SP conversion

Postby Steevo » Wed Jun 17, 2015 12:39 pm

Just wondered if anyone had heard of or done a conversion of a Jabiru SPL/UL to a Jabiru SP.

From what I have been told is that the only difference between the SPL/UL and SP is that the SP is fitted with wings from an SK. I am not sure if there are any other changes.

I have heard of one aircraft that was converted the other way from an SP to a SPL/UL. That aircraft suffered damamge to the wings and apparently it was hard to get hold of SK wings so UL wings were fitted instead and it was re-registered as a SPL/UL.

I just wondered what would be involved in this assuming you could get some SK wings. How would it wash with the LAA and what else would need to be done.
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Re: Jabiru UL to SP conversion

Postby Steevo » Tue Jun 23, 2015 10:45 am

I have found the answer (Thanks Vic).

The SP-470 and SPL/UL-450 are identical aircrafts with the only differences being the wings/flaps/struts and aileron cables (different length). Although the SP-470 uses wings from an SK, they are not an identical match. The wing attachment points on the SK wings are different to the SPL/UL-450 wings so are not interchangeable without modification. The wing attachment points on the SPL/UL are higher up and the fuselage strengthened in that area (as is the case with the SP-470). The only way you would get SK wings to fit would be to manufacture some kind of bracket (good luck with the LAA on that one).

To convert a SPL/UL-450 to a SP-470 you would need wings that are designed for the SP-470 which you have about as much chance of getting as you do winning the lottery with only 7 SP-470 Jabs registered in the UK. It is extremely doubtful that the LAA would accept an SK wing that has been modified.

As far as is known, it has never been done before. Conversion the other way from an SP-470 to a SPL/UL-450 is a lot easier as wings for the UL can still be got and there are a lot of them around.
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Re: Jabiru UL to SP conversion

Postby BobP » Thu Jun 25, 2015 12:08 pm

When FD visited me several years ago to discuss my record breaking number of design modification applications on my UL kit( I submitted them a week before mod applications first became chargeable) he made a passing comment that the SP with its long fuselage and short wings was the best handling model of the then Jabiu range (SP SPL SP SK). A better handling plane that would fit into my present hangar appeals to me.

I have still to start my wings and have often mused about chopping the end couple of feet of of each wing to reduce it to SP length. I think the only other mods are that the flaps would need to be reduced by the same amount and the aileron shorter tele-flex cables would needed. An option would be to cap the sawn off wing tips with winglettes/ Horner type caps to increase the effective wing length a bit. Also i think (might be wrong) the SP Teleflex cables terminate at the tip end of the ailerons and it might be better to swap over the ailerons so they terminated at the inboard end allowing shorter (lighter) Teleflexes to be used.

I see LAA's main opposition to a mod of this type would be that the (length wise) centre of lift of the wing would now be closer to the fuselage as compared with the balancing force at the strut attachment point. But the new configuration would be closer to that of most high wing strutted LAA aircraft (as measured by me at an LAA Sywell rally), and the shorter wing would actually be stronger because the weakest point on a UL wing is immediately outboard of the wing strut attachment point (the reported failure point of G-SIMP when it broke up in mid air in France.)

If you are interested in talking to LAA on this possibility please let me know

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Re: Jabiru UL to SP conversion

Postby Steevo » Thu Jun 25, 2015 12:40 pm

Converting mine to an SP could mean the difference between having to sell mine or being the ultimate for me. The problem with the UL/SPL is no matter what I do to it, I will never get a usable load weight where I need it. I am not looking for mammoth usable loads but as it stands, I have to be choosey who I take up with me and even then have to skimp on fuel. If mine were an SP, then I could basically have a reasonable amount of fuel and take up any of the people that I associate with. With the extra 20kg and the slightly decreased empty weight, it would make all the difference between a fully usable aircraft or an aircraft that is restrictive.

The problem is that all my dealings with the LAA have not been a particularly stress free experience. I have no doubt they would come up with a multitude of excuses as to why this mod cannot be done. I think the only chance I would have would be to find either someone that wants to convert their SP to a microlight and hence swap wings with me. Or somehow find some SP wings. There are unlikely to be salvage wings as there are only 7 SPs registered in the UK. I suppose they could be imported but I imagine at a huge cost.

I think that trying to get the LAA to approve chopping down wings would be like banging your head against the wall. I suppose I could be surprised but even simple mods have taken me months to get through let alone a major control surface change.

The other alternative is to sell mine and buy a bigger version. The four seaters don't come up very often and you are looking at almost double the price of my one. The J160 is just very expensive for what it is and still only come up once in a while and it would still be a 2 seater at double the cost of mine. Plus the fact I have got my aircraft the way I want it in almost every other respect with avionics etc so wouldn't want to do all that again.
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Re: Jabiru UL to SP conversion

Postby diablo » Thu Jun 25, 2015 12:50 pm

The mod although reasonable, would not be easy to get through the LAA.

There are all sorts of caveats and arguments that would have to be considered (to put it diplomatically). If you end up with "you know who" it is likely end up as who can outwit who which is what I ended up with when trying to increase the SK MTOW by 20Kg ...

On the same note, I had a lengthy conversation and email exchanges with Kevin Pearce and did a lot of work on getting MTOW increased on the SK based on the fact that the SK was flight tested at 450Kg (i have documentation) and that the MTOW increase of the UL 430 (same wing mount points and cross member as SK) to 450 was granted by re-enforcing the cross member and moving the position of the 1/4" bolt (moved up by 1/2").

They would not have it ...

ps: IMHO, the SK is one of the best handling jabs out there ...
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Re: Jabiru UL to SP conversion

Postby Steevo » Thu Jun 25, 2015 1:20 pm

Dean,

That makes sense. The difference between the SK wing an SP-470 wing is the attachement bolt (slightly higher). If they have approved the weight upgrade on a UL-430 by moving that, then there should be no reason not to approve the SK wing on the UL-450 making it a SP-470. Mine has already been re-inforced.

Better keep your plane locked up Dean, I might nick the wings.
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Re: Jabiru UL to SP conversion

Postby diablo » Thu Jun 25, 2015 1:56 pm

I'll know where to look if I find my wings have grown by 1.5 foot ...
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Re: Jabiru UL to SP conversion

Postby Steevo » Thu Jun 25, 2015 2:25 pm

I wouldn't have bothered putting my wings back on yours. Too much effort. I would have converted yours in to an overpowered golf trolley.
Jabiru J160 & Jabiru SPL-450
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