Flea Fli Build Blog

[Martyn K]

Flea Fli

Just in case the Flea Fli gets selected for the 2014 mass build (sadly not looking very likely unless a lot of tactical voting goes on), I thought that I had better actually make an electric version.

So in the lull between building the Magic, flying, essential maintenance and actually earning a living, I have made a start on no.1 of possibly 2 Flea Flies.

Unusually for me, I have made a start on the wing. Potentially, this could be built by a beginner so there may be a few more 'obvious' construction notes.

 

The Wing

Create a 1/16" ply template from the section shown on the plan. The master template is used for all the ribs, the specials are modified from this

.

Use 1/16" quarter grain wood for the ribs (if you can get it). It is much stiffer than straight grained wood. It has this characteristic speckled 'Mackerel Sky' appearance.

Note the template only has slots for the spars cut. The full slot is removed when the rib is ready to be inserted. Use a good scalpel and a new blade, it makes life much easier.

I thought that I had better check that there is space for a LiPo. This is a 3S 2200 but there is sufficient space for a 4S if required. Access will be via an upper hatch so the model can be kept assembled. I have selected a rear mounted 2837/18 (about 1100kV) brushless motor from Giant Shark - this should drive a 9x5 prop and give comparable performance to the original if I keep the weight down. Target weight will be 2.25lbs ready to fly.

Making a real start on the wing, you need to make 3 of these little jigs to support the LE at the correct height. Make 1 accurately and then pin it to another piece of balsa and cut round it using a razor saw. Seemples.

The lower spar is pinned down and 3 ribs (each end and middle) are located but not glued. Put the LE onto the jigs and push back into the ribs so that there is a nice firm fit. Check that the ribs are all the same way up. The chances are that the upper and lower spars may not quite line up as accurately as you would imagine. Leave the spars slightly too long at this time, you can cut them back later.

When pinned down, start glueing the ribs in - don't worry about the ailerons at this stage, the excess ribs will be cut off later. Check that each rib is vertical using a square

Note that the first rib in from the root is specified as 1/16" ply. I have used 3/32" lite-ply. I will use seperate aileron servos - I'll worry about how they are fitted later.

More to come

Martyn

Edited By Martyn K on 06/10/2013 23:06:14

[Biggles' Elder Brother - Moderator]

Very nice Martyn - watching with interest.

BEB

[Steve Dunning]

An excellent choice Martyn. The fact that you look like using a 3S, 2200 lipo puts it in the popular size/very affordable model category. Great for putting in the car in one piece, especially in cold weather. Following with interest.

Steve

[Martyn K]

Hi Steve

I don't do much electric, but what I do, I have standardised on this power setup. This will be the 4th model with this battery size.

And yes - keeping it in one piece is the objective..flying 'incidents' excluded.

Martyn

[Martyn K]

So far this week, I have made a bit more progress. Sadly my Olympus shack camera has died so I has to redo some photos using a phone camera - no flash so shadows are rather obvious and a couple of build shots have been lost.

Add the upper rear and upper front spars - leaving them slightly too long and repeat the build process for the opposite panel. There is a dotted outline on the plan - its quite easy to follow.

Note that the other front spar has not been added at this stage.

When both panels are dry, turn either panel upside down - actually right way up and pin the panel flat (on the plan) with pins through the spar. You should check it is flat by measuring the height of the TE centre line above the board. The height of the centre line on the LE should be the same. Use a couple of wedges to keep it stable.

Cut the LE and lower spars vertical over the centre line. I use a razor saw.

Cut the other panel spars to length, pin a 1.5" prop under the front spar at the tip and carefully sand, cut all three spars and LE to a good fit (on both panels). They will all need a slight taper .

Use a couple of pegs or clamps to hold it all stable while you check the joints and when happy, glue them up. Use a bit of polythene to stop the pegs sticking to the glue while it sets.

I used a PVA based adhesive - and lots of it smeared over the joint as well. It will be quite fragile at this stage.

The wing waiting for the glue to dry.

While you are waiting, cut out the ply dihedral braces. I use good old fashioned carbon paper, but I only mark the corners and the centre line and join the dots using a ruler and pen.

This is about the only use I have for a Stanley knife now - with a new blade. Don't try and cut through in one go - use a straight edge and a series of score lines and it will soon go through. Just be patient.

More to come

Martyn

[kc]

Martyn didn't give details of the plan, but I assume he is building the standard size 39 inch plan. That is a 66percent version of Kwik Fli 3 by Phil Kraft. This plan is a MyHobbyStores plan number RC 897 and has been re-numbered recently. It was RC 987 when it was a MAP/ Nexus/ Argus plan before MyHobbyStore typed it as RC 897 in their listing.
It was also a Model Airplane News ( USA) plan from October 1968.
I think there was a larger.40 size version too.

Edited By kc on 12/10/2013 17:09:25

[Martyn K]

Hi kc

I am building the 39" span model which was a free plan in 1968. Thanks for the clarification on numbers etc.

It's a nice easy build - just need to get on with it. I wasn't aware of a Phil Kraft produced 40 sized model, however, I would imagine that there have been a few derivatives over the years

Thanks

Martyn

[Bob Cotsford]

 

I have an airfame that I think is a 40 size Fli, at least the dimensions and layout match those given on the Trenton site. It came as a part completed airframe with a foam wing, and looks to be 80s from the state of the veneer and the 40 size mount fitted. Whatever, it is now referred to as KFC (Kwik Fli Clone) and with an ASP53 in it's snout it flies an absolute treat. The barn door ailerons create a lovely screech on full deflection

 

Edited By Bob Cotsford on 12/10/2013 21:49:10

[Martyn K]

Work on this has been progressing while waiting for resin to dry on the Magic build - so not really that much done..

Continuing with the wing..

The TE ribs where the ailerons will sit have been sliced away. Phil Kraft advises to cut the ailerons out after the wing has been built, I think this way is easier.

Blurred photo (must be one of BEB's) showing the TE sheeting going on. The sheet is very light, the clamps need to be very lighlty loaded or you will end up with dings in the wood.

The centre section showing the centre rib, lite ply outer ribs and dihederal braces. A bit more sanding is required on that rear brace,

Cut the TE too wide - trim it back when the glue is dry. The lower sheeting is chamfered so that an extended line from the wing ribs passes through to a point, I think that is too much, mine is thinned to about 1/32" of an inch thick. Any thinner and you may end up with the TE warping.

After the rear part of the ribs where the ailerons fit have been removed, add 1/16" sheet across the rear spars - grain lengthways. Sand it flush with the upper and lower spar.

While waiting for the glue to dry, cut out the doublers (ply) that will support the outer U/C block. The original was only half a rib wide but 1/16" birch ply, I have elected to use a 3/32" lite ply doubler.

More to come.

Martyn

[Martyn K]

A couple of extra photos and a bit more progress.

The upper TE sheeting is added when the lower sheeting has been cut to size and chamfered correctly.

Work then starts on the ailerons. Phil Kraft hinged his using film - there are no aileron hinges shown on the plan. I am planning to use the kevlar cloth for all hinges on this model and the build will be modified to accommodate this (or use mylar hinges).

Because the hinge is on the top, the lower part of the aileron is narrower with a gap to allow it to deflect downwards. The correct gap is shown on the plan and an additional piece of 1/16" sheet is glued to this and angled forward so that it touches the upper rear spar.

Make it a tight fit between the last rib of the wing and the completed TE. The last rib will eventually be removed so that there will be a nice even 1/32" gap when the aileron is fitted. The aileron ribs are cut using the standard ply template and then trimmed to fit. Don't add the upper sheeting yet..

A start can be made on adding the very light 1/16" sheet balsa LE "D" box sheeting. Leave a short gap (1/32" where it overlaps the width of the spar so that the cap strips have got something to glue to. Note that I am using pins to protect the delicate sheeting from clamp damage

More to come.

 

Martyn

Edited By Martyn K on 01/11/2013 14:37:22

[Martyn K]

A bit more progress.

I have continued with the LE sheeting (3 out of 4 done) and added the Undercarriage mounting blocks.

These are quite simple to do in situ. From the plan, measure back from the main spar to the front of the block. I think it was 30mm from memory.

cut a slot using a razor saw with the u/c block as a guide (resting on the ribs) to make sure that the cut is at the right angle. Don't try and cut it in one go, take it in stages. Then move the block fractionally forward so that it is very slightly (the width of the saw blade) in front of the slots that you have just cut and cut the rear slot - again using the block as a guide. Don't cut too deep. Use a scalpel to remove the wood between the two slots. Keep easing the wood away (extending the slots) until the block sits nicely in the cut outs (across three ribs) but sitting 1/16" proud - so that it will sit flush with the sheeting - I used a bit of scrap sheet to get the depth right.

Before you glue the blocks in, drill the holes for the undercarriage leg and cut a slot. These are quite easy to cut with a Stanley knife held at 45 degrees and against a straight edge using the hole as a width reference.

Glue it in and allow it to set.

You can see from the photo the nearside thicker lite-ply rib and the next but one rib out has the lite-ply doubler added.

More to come.

Martyn

[Martyn K]

A bit more progress on the wing.

The lower centre section sheeting has been added. the gap between the LE sheet and the TE sheet is actually 3 pieces, one in front and one behind and a small piece to the inside of the u/c blocks

The 1/2" very soft sheet wing tips have been added and the LE planed and sanded to shape.

Note that the final carving of the tip wont be completed until the cap strips and ailerons have been fitted..

The aileron mounting rails have been added. These are simply 3/8" x 1/8" spruce inlaid into the ribs and the front one butted and glued to the spar. The servo has been inserted from underneath to keep the profil low and airflow over the wing as smooth as possible.

(A bit blurred - just too close for the phone camera...)

Lower cap strips added and the servo boxed in with 1/16" sheet. Access (if required) will be from the upper side of the wing through a suitable orifice - created when needed.

More to come

Martyn

[Colin Leighfield]

That's a proper model. Oh for more time to build them all.

[Martyn K]

Thanks Colin

Surprisingly, there is not a lot of interest in it though. Still I am not worried, I am enjoying the build and I don't mind writing it up for posterity a couple of times per week.

It's actually quite handy having a small model on the go (so to speak), its cheap and I can spend 30 minutes here and there and make some real progress - working on the Magic is much more time consuming and needs much more thought and space. (Due to its size and complexity).

This is a perfect foil for the Magic.

Best wishes

Martyn

[David Rothwell]

well I`m Watching and building

[Martyn K]

Thanks - that's great and reassuring.. When I get round to hinges, if you want some of the Kevlar hinge material that I use, let me know and send me an SAE and I'll get it straight back to you. (Ditto - any other Flea Fli builders out there).

Martyn

[Steve Dunning]

You might have got me motivated with that Martyn. Thought about it for a while and the 2200/3S battery brings it into the cheap to run area and great for putting it in the car in one piece. Keep going mate!

[Martyn K]

Thanks Steve

Will do - remember I have to build an IC version afterwards. Got a couple of period engines that will fit nicely..

Martyn

[Colin Leighfield]

Martyn, over the last couple of years I've expanded my collection of small i/c motors with the view of re-creating some of these classic models. I've got a Cox .049 with r/c throttle to go into the Jr. Sklark referred to recently. Also a few months ago I managed to build a Doug McHard Wee Snifter, fitted with r/c on rudder and elevator, with a Mills .75. I'd forgotten though that Solarfilm and diesel fuel don't go together (!) so need to re-cover that before I try to fly it. I've also picked up a promising new Norvel .06 which looks very useful.

While I'm well into electric, I want to use some of these engines (2 Mills 1.3s, one of them a new Irvine example) and these smaller models don't break the bank, do they?

I have determined though to stop flitting from one project to another and actually finish things in sequence, this is taking time but I hope to make progress and get some flying in as well! Nil desperandum, but I'll get there.

The Flea-Fli is a real classic, you definitely need to do one with an I/C motor though.

[kc]

I am also watching the build, it's just that you covered every point so there is no need for us to add any comments!
It is just a little on the small side so if it's also quick and a bit twitchy I might build one a bit bigger, say 125 percent. A dimensioned Kwik Fli drawing is somewhere there on the Trenton site and this would make a percentage change of size a piece of cake...mostly straight lines too.
OK one comment I can make is I was surprised that the u/c mounting blocks didnt meet in the middle to reinforce the wing and so that the u/c upright blocks can reinforce each other.

[Bob Black]

Hi Martyn

This brings back mems, during the 1970`s I built the Kwick Fli 3 from a Graupner kit, it had a foam core wing, it flew well but was well under powered with a Merco 35 I had up front (could not afford another motor) so it had to stay.

The radio I had was a Simprop 5 , wonder how many remember those early proportionals.

Bob

[Martyn K]

Hi All

Colin - This really needs a decent powered 19. The first one I built (mid 70's) had a clapped out McCoy 19 - the lack of power plus the model being slightly overweight led to a very early death. I agree about getting models finished though. I do tend to prevaricate a bit when selecting a model, but once started, I tend to get them finished. I'll probably put either a Veco 19 or an OS 20FP in the next one.

kc - I am following the plan regarding the u/c blocks although mine are slightly larger 1/2 x 3/8 0 the plan is 1/2 x 1/4. One area that does worry me though is that the dihedral braces are very short - one bay each side - so I will add a webs out for a further 2 bays - I don't like structural discontinuities.

Bob - my first radio gear - bought second hand in about 1973/4 was a Simprop 5 with 4 servos and DEACs. I paid £60 for the outfit from the model shop on the Bath road at Isleworth near Hounslow.

It was a bargain.

Best wishes all and thanks for the feedback.

Martyn

[kc]

The reason the u/c bearers stop short of the centre is because the centre was needed for the servo. In the original design a 1/16 ply box around servo in effect joins the u/c bearers together. Using 2 aileron servos means the bearers could meet in the centre. Various articles have pointed out that letting the u/c vertical blocks join together is much stronger than having them some distance apart.
I reckon a birch ply dihedral brace linking both u/c bearers would be a good idea if you didnt make the central 1/16 ply servo box.

[Martyn K]

Hi kc

yes very good point... I'll take a look and see what I can come up with.

Martyn

[kc]

On actually reading your written description I realise that what looked like balsa ribs are 3/32 liteply ( instead of 1/16 birch ply on the plan)I suppose this is almost the same as 1/16 birch. But just a simple cut alongside the bearers would allow a 1/16 ply dihedral brace to be inserted one side and another of different length the other side. Many american designs for built up wings specify a glassfibre bandage too but I cannot see anything in the USA plan or article which says this. I hate that idea and much prefer just a ply dihedral brace.

Edited By kc on 07/11/2013 12:08:19