Kitfox Yacht Tender/Built in Lifting Rings/ Best Model

[badmash]

For a while I have been playing with adding a small float-plane to act as the tender to my 20m Classic Motor Yacht, currently based in Florida, which I've just finished restoring. (The benefits of stopping flying winged death for the govnmt to found my own company)....

My intent would be to use the deck crane to lift the Kitfox onto and off the boat, so my first question is:

Does the forum hive mind think it would be possible to weld lifting rings onto the aircraft frame (covered with zips/press stud flaps of aircraft covering material) to attach a lifting harness directly to the aircraft when it needs lifting, or will this bend the airframe? I'm thinking 3 rings ahead of the c of g and 2 rings aft, attached to keep the aircraft in balance when it's lifted.

Further, I guess you could weld a plate between a number of stringers and attach the lifting ring to the plate to spread the load?

The alternate is to use a sling under the fuselage, which would take an awful lot longer and be a lot more hazardous.

2) Whilst due to the size of the aircraft there will be float limitations, are any particular Kitfox models known as better Floatplanes/Amphibs than others? As this is an experiment my preference would be to buy an older and cheaper model to test the concept, then look at building an aircraft once I know whether it will work or not and what tweaks for the application need to be made. Ideally I'd like to keep empty weight below 400KG, though am happy with keeping it on the experimental register, as opposed to the LSA register.

Thanks in advance for any help.
Badmash

[badmash]

Having just looked at a picture, perhaps what would actually be best, might be to use the 4 points where the float connects to the fuselage as the lifting points, using padded straps to avoid damaging the fuselage fabric, KISS.

http://www.teamkitfox.com/Forums/att...0&d=1251942389

[Av8r3400]

IMO, easiest would be the 4 spar pins where the wings attach to the fuselage.

Replace pins with bolts and include a tab with an eye to attach to lift rigging.

[Dave S]

Badmash,

I second Av8r3400's opinion.......your CG will be within the rectangle described by the 4 attach points and it is a very sturdy location - plus no slipping of a sling to damage the sides. A person would have to modify the corners of the windscreen...but that should not be a big deal.

FWIW - the ends of the upper carry through tubes (which is adjacent to spar pin/bolt points discussed) are where the BRS folks design the attach points for the straps for their whole plane parachute for the Kitfox - which would certainly expose those points to far greater stresses than your lifting rig ever would if the parachute were deployed.

Sincerely,

Dave S
KF 7 Trigear
912ULS WArp Drive

[Esser]

I vote where the spar pins are as well.

[herman pahls]

Since I often fly into road less strips, I thought it would be a great idea to already have the bolts with eyelets that Larry suggested installed in especially the rear spar and a pre-made sling so in the event a helicopter is the only way out it would do very little or no further damage.
I have seen full size float planes in the Puget Sound, Washington lifted on and off yachts in this same manner.
I have a 950 pound gross model 2 Kitfox for sale that would be close to your weight range.
Herman

[dholly]

A sling typically goes underneath something for support, not the best application here. Most seaplanes are lifted from above using either a 2 or 4-point hoist bridle that connects to eye bolts in the wing spar to fuselage pin/bolt attach bushings. I would think a 4-point hoist bridle to your crane line, along with two guy ropes from the tiedown rings underwing to keep the plane from twisting, would work fine. Bigger issue might be sufficient crane arm reach. You would have to lift with the wings unfolded and parallel to the ship, nose toward the ship, for the shortest crane reach. One badly timed swell and OOPS there goes your new IFA prop and spinner! Maybe trade in your yacht for one with a rail system that pulls a folded Kitfox into a stern toy garage?

[badmash]

Brilliant, thank you all for your wisdom!

It looks like a 4-point hoist bridle attached to the spar pins, with two guy ropes from the tiedown rings is the winning concept, simple and effective.

The crane has the reach, as I transplanted a HIAB lifting boom from an old Army truck, avoided the sticker shock of buying a yacht crane (the word yacht always adds at least 50%), looks vintage, far easier to maintain and is designed to lift more than a feather!

One of the mods to the yacht I will look at it is modifying the swim platform to be able to 'lock' the floats into it, so I can fold the wings before lifting and then lift with a guyline from the nose and a guy from the tail, if this would still be possible with the spar pin lifting attachment?

Dave S, can you clarify what mods would you have to do to the windscreen?

Finally, I have flown a Kitfox 2, a 4 and a 7, the 2 was in the understated British manner 'sporty', the 4 from memory felt like the best balance between feel and agility and the 7 felt a lot more solid, what model would peoples preferences be for making into a floatplane, we so far have one vote for a 2 from Herman, is that plane already setup with floats?

Thanks once again for everyone's engagement.

BM

[Av8r3400]

Lifting with wings folded will require different lifting points as the CG will move to the rear quite a bit. Folding once on deck and secured would be much easier and less likely to cause damage, also.

[badmash]

Lifting with wings folded will require different lifting points as the CG will move to the rear quite a bit. Folding once on deck and secured would be much easier and less likely to cause damage, also.

Thanks, that's why I had assumed I would have to put in lifting rings before the cunning plan of using the spar pins as lifting points.

Perhaps I should rephrase the question:

If you had to locate a lifting ring at the rear of the aircraft, where would be the best point?

My thinking is a) options are always good and it could be that it is easier to drop the aircraft into the water and unfold the wings once the aircraft is in, as my boat has a full-beam (5.5m) swim platform, from which to work from, we just need to make sure the platform itself is wider than the wing-root to make the operation reasonably safe as you can slide the fuselage up and down the side of the yacht to help unfold.

b) For short transits such as in the Bahamas or the Florida Keys, it could be easier to raft (tied to the side of the yacht with floats still in the water) the kitfox parallel to the hull of the boat with wings folded so the engine is better protected (rear of aircraft due to weight of the wings would raise the nose), though in addition to being secured over the wingbox, it would need lines fore and aft to ensure it does not try and twist against the hull. At this point, I'm thinking a bridle running from the front two float legs should secure the front of the aircraft and make sure the nose stays high.

All really interesting stuff and actually started to think this idea might not be as daft as it sounds!