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/attachment.php?attachmentid=550&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!

[Dave S]

BM.

Regarding possible hard points for lifting at the rear of the aircraft - Kitfoxes have through tubes at the rear - get to a kitfox and it is pretty easy to see where they are - One short through tube at the front of the Vertical Stab has is designed to take the wing lock back bolt to secure the wings when they are folded - it's a pretty well reinforced point. Additionally, there are two longer through tubes at the bottom of the fuselage at the rear of the aircraft under the horizontal stabalizer - these are sometimes used for a tail dolly during building; or, a tail dolly when the wings are folded on a trigear (due to the lack of a tailwheel - my plane seems to lack a tailwheel to the chagrin of many of my peers:o) A trigear sits on it's butt with the wings folded too due to the CG shift with the wings folded)

OK - on the windscreen mods - where the rear spar bolts are located for the wing attach the windscreen (unless a builder has already made a modification) will be underneath the corner of the windscreen on the port & starboard corners - Again - find a kitfox and this will make make itself clear. On the front spar pins, there is normally a small aluminum cuff which goes over the area and over a portion of the windscreen at this position. Unlike the rear spar bolt location, during the build this corner must nave relief cuts around the pin under the cuff so the pins can be removed for wing folding - in all likelyhood, a person will need to provide a little more relief to accomodate the added hardware. You'll want to become familiar with cutting/working acrylic or polycarbonate (whichever the plane has for a windscreen) and become familiar with aircraft hardware as you will likely want a longer bolt for the rear spar location and replace the shear nut with a thicker standard aircraft castellated nut; and, on the front spar location, you will want to use aircraft bolts similar to the rear spar bolts with castle nuts rather than the pin secured with a hairpin (which is not designed to carry any load at all) used for keeping the pin in place.

Best bet is find a kitfox with an owner who will let you examine these points on the aircraft...plus you will end up doing some minor engineering with the hardware needed. :)

Cheers,

Dave S
KF 7 Trigear
912ULS Warp Drive
St Paul, MN

[Esser]

What ever Kitfox you decide, if you are on floats make sure it has loads of power. Personally If you want a good combination between solid and sporty I was say the Model 7 with the new STOL wing might be a good choice. More money than the 4 but it is bigger, hauls more, and can probably handle rougher water (That is just an assumption on my part)

HIABs are awesome so I dont think you have to worry about your crane!

I think I would lean towards trying to lift it on the boat with the wings out but if that's really not going to be practical I would say the suggestion to lift through that rear carry through is the best one. Kitfox is now putting handles on both sides of the 7 for moving it around. If your 7 had those two handles you could just run a sling under the handle, over the fuse, and then under the other handle with out much fuss. The whole rear fuselage is pretty sturdy.

Now for the question we've all wanted to ask....Where is the picture of your Yacht!

[jdmcbean]

First.. we are not putting handles on both sides. We did on the STi for another reason.

I would think the best way to lift with be with lift rings from the spar attach points.. However, if possible I would lift it with the wings out for CG reasons, place it on the deck then fold the wings. If that is not possible then using the wing tie-back location could be an option for an aft point.

[Tom Waid]

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!

Speaking as one who has quite a lot of time in yachts I think alongside towing of a float plane could be a disaster. Even a small chop can get both the yacht and airplane rolling out of sync with each other. Passages between islands in either the Bahamas or the Keys can be rough.

[t j]

When you fold the wings...or spread them...on the water for the first time please make a video. be sure to wear your life jacket.:eek:

[jdmcbean]

Forgot to add this...

[av8rps]

Badmash,

So here are my thoughts on what you are trying to accomplish...

Aircraft choice:

A Kitfox makes for an awesome floatplane, so it certainly would be a great choice for what you want to do. I love my Model 4-1200 with a Rotax 912 ul on floats, so I know that one would be a great choice.

But if you are a bigger person you might enjoy the slightly larger cabin of the Kitfox 5 through 7, along with more useful load. It too would make a great choice.

But in reality any Model Kitfox will make a good float plane. However, some will be better than others. To determine which will be the best performer, just find the model that will provide the lightest weight with the most horsepower, and the wing that provides the most lift/ wing area (and one you fit in comfortably). The earliest airplanes with their 2 stroke engines and high lift undercambered airfoils were real hotrods on floats mostly because they were so light. But now that we have lightweight 100 hp+ Rotax 912 engines, even the later airplanes are good performers on floats. So for those reasons, if you do the math you will discover the Model 4 fits right between the earliest hotrods, and the latest models, taking the best features from each. My 912 model 4 is light, so it performs really well off the water like the early airplanes, but yet will easily cruise 100 mph when on floats, like the later airplanes will do. That's why I like my 4 so much:)

And the floats are a big factor for operating off big water, big waves, and swells. The number one thing is to make sure they are big enough. Too small a float would be dangerous in rough ocean water conditions. Of course, you also will need a strong float, so stay away from the cheap junk you so often find for sale cheap. The cool thing is that we have good choices that 20 years ago we didn't have.

If I were doing what you are, and I wanted to keep the price reasonable, I would find a model 4-1200 with a 912s and put it on a set of Zenair 1150/1200 amphibs, and run a warp 3 blade prop with nickel leading edges.

If I was ok spending more, I'd buy a newer model Kitfox with a 912s Rotax and a warp prop and put on a set of Zenair 1450 amphibs. If you were ok spending more, a set of Czech 1300/1450 amphibs (if you can find any?), or maybe even a set of the new Aerocet 1500 amphib (big bucks). Clamar 1500s also could be used.

And if you just want to try something inexpensive to start, find an early Kitfox (or Avid) that is bare bones lightweight with a 532 or 582 2-stroke Rotax and put on straight floats (1150 Zenair). That would be a great little floatplane, and a very inexpensive option.

Also worth mentioning, a Just Aircraft Highlander would also be a great option. I have one, and know it makes a great floatplane. But will be more money than the other options.

Oh, and based on my experience with Full Lotus, I would not want to operate that float in rough water.

There's my take on the aircraft and floats.

Tomorrow I'll share my ideas on how to lift it the airplane with a crane...

Paul Seehafer
Central Wisconsin