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Mike.K

Midwest Extra 300S 80" kit & build

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Another eBay win for me.

This is an expensive American kit which I collected from Stourbridge yesterday. Of unknown vintage, the model came to me part built and what has been constructed appears to have been reasonably well executed. Clearly the kit has passed through several hands before my acquisition. The eBay seller bought it a couple of weeks ago for £140, then decided he wanted a 120" version. Back on eBay it went again and became my win for just £75 plus £40 of diesel fuel in the car! I`m a happy chappie! I looked on the internet to get some idea of the new price. Well over $1200 US which currently converts to around £963. That is a fair amount of dosh for an 80" model.....

Images below show the core model. A large box full of all the usually needed completion parts was included in the deal. This includes a two part ABS cowl and wheel spats, unmarked canopy, a massive Dural undercarriage, control horns and push rods. some timber stock, plans and a very good instruction build manual. All parts seem to be present.

The models appears to have been kicking around for several years. There is a bit of black mold in a couple of areas and the timber has that rather yellowed appearance. Glued joints appear tight with a good adhesive bond. Sheeting joints require sanding and leading edges of the wings are as yet, unprofiled. Someone appears to have started the project but never finished it. At £75, it looks like something of a bargain.

The prototype model was powered by a 1.80 Moki two stoke. Finished weight is stated as being between 14 & 17Lbs. There appear to be some similarities between this Midwest model and that of the one produced by Great Planes. Wings are of conventional balsa build and still require to have the ailerons cut from the construction. They also require main spar dihedral joiners to be fitted. The fuselage is of typical space frame stamped ply of about 3mm thickness. Tail feathers are of typical balsa truss with over sheeting on the tail-plane and fin and open areas on rudder and elevators. The whole model requires sanding and bringing to a covering standard. Controls, radio gear and engine layout are still to be planned and installed. As it is, the model would appear to be something of a bargain but perhaps not quite a big a bargain as the model Ben bought at the Club summer auction this year!

So, this appears to be my next project. All advice and comments in respect of this model would be appreciated. Vids on Youtube of flying examples are encouraging. The model appears quite docile at slow speeds and stable on final approaches and landing.

I`ll add more images to this thread as the build progresses.

Mike K

 

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Quite a tidy kit, Mike. With regards to the engine; I think that I'm right in saying that Moki engines aren't all that easy to come by, and if you stick "Moki 1.80 2-stroke" into Google or the like you'll see what I mean. 

As an alternative, I believe that ASP make a 1.80 2-stroke that retails for around £200, or if that doesn't appeal an ASP 1.80 FS (that is of "similar" power) goes for around £280.

Look forward to the build,

 

B ;) 

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Thanks for the comments, Ben.

The only big engines I presently have are the two ASP 1.08 two strokes I acquired at the recent auction. The similar sized Great Planes 300S  states their model will be suitable for just a .91 or 1.08 two stroke. I appreciate that a 1.08 may be a little small especially as the model will be quite weighty. It will certainly lack the performance of a larger engine model. Obviously I could fit something rather larger later. Lets get Christmas over first! The first thing to do though is get this thing finished and covered. Advice and comments appreciated. What do you guys think about fitting one of my 1.08 motors as a starting point? A shame no one markets a mini super-charger. I like "blown and tweeked" engines like the one in my 600hp Jag!!

I quite fancy a two cylinder motor. Something about 2.2, four stroke peeks my interest. There is masses of room in the cowl which measures 280mm/11" long, a similar width and a height of 180mm/7" in depth. Centre lineto inside top of cowl at the prop opening is about 40mm/1.5".

All the best,

Mike

Edited by Mike.K
additional info added

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I can't comment on the specific details, but most of the engine working out I do (or sometimes eyeballing) is based on the displacement of the engine. With regards to the "ASP 1.08 vs ASP 1.80" argument - 

The ASP 1.08 has a displacement of 17.2cc, and weight of 862g (depending on the age of your engines), and the ASP 1.80 has a displacement of 29.9cc, and a weight of 1528g. This means that although the 1.08 is pretty much "half" the size (56%), it is also pretty much half the weight (56%).  However, this doesn't mean that the relationship is linear, a good example being the OS 35 and the ASP 36 engines that have powered two of my cougars. Whilst the OS was a 5.8cc engine weighing 280g vs the ASP at 5.9cc and 354g, the OS' performance was pitiful compared to the ASP'. I have since learnt from eyeballing, and this error cost me around £200 to rectify, as well as some modifications to the model.

I would think that a 1.08 is possibly too small a powerplant, especially seeing as it looks to be quite a chunky build. A 1.60 would cut it fine, although it should be ok I would have thought. As for the 1.08 as a starting point, a good rule is to  "start as you mean to go on" I.E pick an engine and stick with it. You won't enjoy the model if you're constantly buzzing around the ground at full throttle :) 

Keep in mind also the important factor of the balance of the model. For context, your 1.08 weighs in at 862g, whereas the Moki 1.80 is a much chunkier 1170g (308g difference). Whilst this doesn't sound like much on a model weighing around 6.35-7.7kg, it will most likely make a difference, especially considering the position of the wing (moments + pivots).

On the topic of weight, keep in mind also that the maximum weight limit at Fickleshole is 7kg, so I would suggest that you would want to try and keep the model as light as possible, seeing as you are sailing in shallow waters with the models quoted weight.

Finally, with regards to your desire to fit a twin cylinder powerplant - One of the most viable options would be the ASP 1.60 FS twin. However, it weighs approx. 1256g, and costs quite a healthy £430.

 

Lot's to think about ;) 

 

 

 

Edited by Pilot Ben

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A seriously well constructed appraisal, Ben. Thank you very much. Loads to think about. One thing is sure...its going to cost money!

Mike

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No problem Mike.

The only thing that I failed to mention was where I obtained the pricing and specifications from :)

All were quoted from Just Engines -(https://www.justengines.co.uk)

I can say also that I've only ever had a positive experience with them, so they may be worth a look.

Keep us updated on your progress, and I promise not to moan about servos!

B ;)

Edited by Pilot Ben

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I`ve just had offered to me an AGM 55 two stoke petrol motor. New, un-run, still in packaging, £130. New, retail is £196. Would this be suitable? It would be a cheap answer if ok. 5.5hp. Spec as per this link.

New AGM 55 RC Plane Aircraft & Muffler Gasoline Engine-agmhobby.com.

I`ll be at the EGM tonight. Perhaps we can discuss further.

Mike

 

Quote

 

 

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I much enjoyed the EGM last night.

I must thank the brilliant Committee member (sorry, I don`t know his name) who came over to me after I asked for help and advice in respect of a workable engine spec for the Extra. He spent a good half hour with me and assisted me towards making a correct and informed decision. The consensus was that the model was crying out for something like a petrol two stroke 40cc flat twin. The obvious choice was the DLE 40 with several other less well known makers also being run past us on my laptop. Obviously I wanted to buy a well known and trusted motor with decent sales and service for future back-up and maintenance. I accepted I was once again going to have to spend some fairly serious cash to get this model off to a good start. The closest main DLE dealer would appear to be Mac Gregor Industries in Maidenhead. That sealed the idea completely for me.

The twin cylinder motor retails at £430 in the UK. Yes, they are available for lesser figures direct from China. But, and it is a big BUT, the price does NOT include 17.5% import duty and carriage when the package eventually arrives in the UK. Only when you have stumped up on demand the VAT and settled the UK carriers fee will the package be delivered. You can make a stab at the additional costs but you might be way off the mark and end up paying more that a UK price. Like most people, I like to know where I stand before committing to buy.

Getting back home after the EGM, I hit the internet again in the search for a reasonably priced complete DLE40 package. I wanted the full kit with the motor, Pitts mufflers, ignition module, back plate and all other knobs and whistles etc. If I could some how improve on the retail price, then so much the better. Good second hand used, out of packaging products and fully overhauled options were investigated. I knew second hand examples would be few and far between and that if I did find a good example, its price would still hold up well in the market place. Then I found a DLE 40 on the MacGregor main agents listing on eBay. A fully refurbished and tested motor, bench run and offered with a short six month warranty on a buy it now listing at £330 including postage. I tried a phone haggle but it was unproductive. So I bit the bullet and paid up £329.99. I`d have liked 10% off but there was no shifting on the price. Knowing there would be little difference between this motor and a brand new one, I have to be satisfied that I did obtain what I wanted but for £100 less than a boxed, new unit. Tonight, I`m quite satisfied, if somewhat poorer than I was this morning.

In perspective, buying a twin seems the favoured option for smoothness, throttle response and semi scale like flight characteristics. I could have gone for a single banger DLE35 which would have given better vertical performance but at the expense of rougher running. Midwest also make a CAP232 kit which has marked similarities with theExtra300S kit. It is of similar size and indeed uses the same wings. One of the Forum sites discussed the fitting conundrum of DLE40 twin v DLE 35 single cylinder engines in action. The discussion ended with the views expressed above in this paragraph. I reckoned that as I was going to spend a fair amount on an engine....more than I ever envisaged, that I might as well go for the twin option which will fit with ease within the cowl of the Extra. If you`e got it, then flaunt it. That is what my old Granny used to say.

I`ll be a petrol leper banned to the other side of the pits with this model and armed to the teeth with fire extinguishers and fire blankets. So be it. A small price to pay for what promises to be an interesting and ambitious forth coming project. If I don`t buy you a beer for Christmas, it is because I`m seriously skint!

As always please gents, your comments and opinions please.image.png.e426859b4887c9a4e77f8ec85fe6e956.png

Mike

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A bit more on this Extra 300S from Midwest.

Planning is all. Its always good to know what size target you have and its properties. On the basis of that, I check weighed all the kit components including the ones already built. In addition, I`ve estimated the weight of the coverings knowing what the Hobby King material weighs per metre length, less its backing sheets. The manufacturers weights for the now ordered DLE 40 twin and ancillary components have also been factored into the total estimated predicted all up flying weight. My list also included typical servo, Lipo, NiMH batteries etc. I`m hopeful that the compiled weight schedule will not be far off what this model will eventually weigh.

The all up weight will definitely not be less that 13.9Lbs/6.3Kg. This seems comparable to weights for this Midwest model quoted on various other internet forums. Whilst my estimate cannot be guaranteed, it doesn`t seem to be unrealistic. I suppose the model is likely to accumulate another 5% or so additional weight for items that may get added as the build progresses.

Mike

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Mike, I have sent you a Private Message as this section of the Forum is PUBLIC.

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I`ve replied with a private email to Dave.

In his PM, Dave emphasized the importance of keeping weight down to the 7Kg limit and also detailed the mandatory maximum 82Db sound limit. I wish to confirm that I take both matters very seriously and will not fly this model if weight and noise issues cannot be addressed.

As in all things in life which pose a problem, in many cases issues can be overcome by using logic and rational. In short, one has to diagnose the issue, understand the issue and then address the issue. The process is infallible and needs to be be applied to this particular model, its equipment specification and its final flying detail execution. Otherwise the project will stay, as my young grand-daughter would say..."An exquisite little ornament"!

The diagnosis is that the standard DLE40 exhaust "mufflers" are known to be little better than exhaust collectors or deflectors. They do nothing to help control noise levels and are to all intents, useless. In addition, some propellers, prop speeds above 0.7Mach, vibration and loose air-frame objects, such as push rods and sloppy wheels and axles do nothing to help. Solid engine mountings may also be a major cause of high noise levels together with the poor quality exhaust muffling.

To understand the problem, one has to gather information. This is relatively easily sourced on the internet and by direct discussion with prime players in the modelling fraternity. It is well known that whilst the DLE40 and its brother motors are good, reliable motors but that is where it stops. It would appear that the Chinese makers of the DLE series and indeed many other model engine makers together with the International distribution network, have jointly and severally failed to ensure or perhaps understand the significant requirement that Internationally and Universally demands acceptable product noise levels. In other industries with perhaps the car sales industry being a good example, to be able to export/import products, it is a requirement to have those products conform to accepted and realistic standards required by local market areas. ie BS classified or other appropriate standard certification before the product is allowed onto the often widely differing requirements of the Global market place. I therefore understand this lack of certification to a necessary standard has seemingly been missed by so many model engine manufacturers. A common standard appears to be lacking generally across the industry and supply chain. I do accept that there are many variable factors involved, again prop selection, air-frame resonances, mounting selection, etc, etc make it difficult to publish particular engine installation noise levels.

To address these issues, one has to find industry support and attendance advice, practical knowledge and experience together with eventually obtaining correct parts to help drive down noise levels. So what is required for me to have reasonable chance of obtaining typical UK maximum noise levels or more desirably less noise, is to approach the modelling after-market and seek assistance. Surfing the net, there are businesses that supply these motors as agents and also hold after-market silencing systems or can build a bespoke system on demand. Cheap it may not be but mandatory it certainly is. I`ll be talking to Just Engines, MacGregor Industries and any other knowledgeable people that may be able to help address this engine noise issue. Needless to say, if anyone has contacts that may be able to assist me, please make contact with me. Personal referral is just what I`m looking for.

As regards final air-frame weight, that can really only be controlled by me. I`ll have to work hard to keep the eventual sum of the parts down to within that 7Kg limit.

Mike

 

 

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S

Quote

So here we are some three days after I wrote the above post.

Things are moving slightly. The DLE40 has arrived from MacGregors. To all intents, it is indistinguishable from a brand new motor. It doesn`t even look as if it has been run. MacGregors assure me the motor has been tested and found satisfactory. They were however un-able/un-willing to disclose just what had been done to this motor by way of refurbishment in their service department. It could well be that this motor has previously been a demonstration or display item. I can see no evidence of it having been seriously dismantled. A few units are known to have had carburetor issues which agents have sorted by fitting new carbs to replace some defective examples. May be this engine is one of those.

I`ve now contacted Josh at Just Engines with a view to having them make a custom exhaust for this Extra. We all seem to acknowledge that the standard exhaust cans supplied with these motors are quite useless as silencers. Thin, tinny and with no baffles. They are only really suitable for the bin. I`ve sent vital model dimensions to JE together with images of the trial fit of the DLE on the model. Some of those images are loaded on this post for general interest. Of note is that the standard motor stand off units at 25mm, are too long for this model. You will see brass compression fitting nuts of 10mm have been fitted temporarily to act as correct length stand off units until a design specification and costing for this motor installation has been agreed with JE. I`ve given them a free hand with the design but said it MUST be capable, together with correct prop, mounts and other ancillary items of fully meeting the 82Db requirement. If noise can be reduced to lower levels, then so much the better.

So I`m taking a big gamble with this project with the un-certainty of throwing a fair sum of cash at a difficult area of RC modelling and with no guarantee of an acceptable result at the end. Am I likely to win? Again, your comments would be helpful.

I`ve been working on the two part ABS cowl ensuring it is well joined. It is now under primer and looking reasonable. The wings have had leading edge stock planed and sanded to profile and will be joined shortly. I`m taking my time with this model. Some issues will not be easily solved so I`m not going to belt it just to get it finished in record time.

Mike

 

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Some 24 days have passed since I last posted on this build. A lot has happened over the period. Images attached tell some of the story to date. All your comments and observations gratefully received as always.

The model is now hinged and covered, the motor installed together with the spark ignition module, kill switch and all the radio gear. Direct action, no snakes, twin servos for elevator and rudder all mounted both sides under the tail plane, singles for the ailerons. The rudder servos push and pull in opposite directions so that worked out fine. The elevator servos, one working each elevator section, required a same direction, push or pull. This entailed having to reverse the direction of one servo by un-soldering and swapping over two wires on the motor and two on the feed-back pot. All connections re-soldered, to my astonishment, it worked first time and the elevators went up or down in the right direction together! I spent a fair amount of time carefully hinging this model with Kavan pin hinges and have the pleasing result that all control surfaces drop under their own weight without any stiffness or binding. Just for once, the digital servos don`t sing like an orchestra as they fight against hinge stiction.

Power for the RX and servos comes from a 6.6v 1100mAh LiFe cell with another identical one being recommended by DLE as suitable for the spark ignition module. Servos appear very responsive and fast acting as a result of having this type of battery installed. An interface for the kill switch figures. More on that below.

A separate smoke tank is in place and awaits the delivery of a smoke pump. Just Engines are due to begin fabrication of the exhaust when they get back from the Christmas break on the 3rd January 2019. This will include building in smoke injector fittings in the appropriate locations.

Fitting the "Dummy at the front" and the canopy are the next items on my to do list. All coverings are from Hobby King. A small price increase occurred in line with the new CEO taking up his position....... Even so, about £9.50 plus post for a 5 metre roll is still excellent value when compared to about £18+ for a 2 metre Oracover equivalent. Hobby King covering colours though are rather limited. It is excellent stuff to apply and very easy to get around curves without puckers or creases. It shrinks up well and is best described as being of medium weight and density. It is highly opaque and even white over dark blue works well without much dark colour bleed through. It is a great covering material at a sensible price. Any white glue spew on overlap joints is easily removed with a cloth and a drop of acetone.

This model has not been a terribly cheap build. OK, the already built, second hand but un-finished air-frame was cheap as chips at £75 and the motor was well priced from MacGregor Industries at £330 as a dealer "refurbished" unit. I suspect it was a demo unit which had been sitting on a shelf. It clearly hasn`t had any air time and is almost indistinguishable from a new motor.  The other major additional expense is the Just Engines quiet exhaust which with all fittings and fixtures plus a 3.5" spinner and a smoke pump, adds another £250 minimum to the project costs. Total expenditure to date? About £650. It is amazing though how all the small parts add up in cost. These itches I get, just have to be scratched so I have to dig deep into diminishing available funds! As we used to say in the marine industry...no cash, no splash!!

Other jobs still to complete are 2-pack finish painting of the cowl, landing gear and the spats. The ballasted weight of the complete model is likely to be in the region of about 14.5Lbs. So still under the legal limit which is pleasing. Within that total, on the basis of trial C of G testing, has seen that about a pound and a half of nose weight will be needed. I used a carrier bag loaded with metal drills, bolts, spanners and other junk hung off the prop to get some idea of what would eventually be required. So everything that it has been possible to shift forward, has been done. The build on the exhaust can be quite weighty but even then I expect to have to add some lead sheet. The predicted build weight would appear to be fairly typical of this model.

I have placed another post in the "Petrol" section of this site asking for anyone with some experience of the function of optical kill switches to please contact me. No point in me repeating what I said in that post, but any pointers on kill switch operation would be appreciated.

With the winter now in full swing, I`m taking my time with this model. No more 04.00am finishes for a while. There is little point in busting myself with the new flying season still three months distant. I`m due a back operation soon so will be slowing down the building for a while after I get the job done. I like to think installation of the proposed electronic gadget will help my sciatic nerve pain somewhat and make me more enthusiastic about getting stuck into some significant flying this coming year. Lets face it, I`ve enough built kites in stock now and my efforts should be towards getting them all into flying condition rather than just hanging them off the wall!

Cheers guys. Enjoy the images.

Mike

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A bit more completed.

The canopy is on and the result quite pleasing. Hingeing is boring but canopy fitting is a nerve jangling once off, get it right first time or it looks dreadful situation......this time it all went very well. I cut back the covering down to the wood where an adhesive bond was required, carefully made sure the canopy was exactly the right size and in places blended to ensure it sat well against the fuselage. I used a clear Evo-stick adhesive product, Serious Glue, ex Halfords, in a small and manageable tube. It is solvent free and has a very fast initial grab time. Before committing to this glue, I trialed both this glue and the typical and common yellow tube Uhu balsa type cement. I made two test pieces of balsa and a couple of canopy material off cuts. Glued and clamped over night, I tried to pull both samples apart. This included a peal apart test..... a sure fire way to test whether a bond is good. There was little to choose between the two glues but I went for the Evo-stick product because of its fast grab time. Once adhesive had been applied to the model, I pushed the canopy down into the bead of glue and held it in place with masking tape for ten hours. To my astonishment, the job came out perfectly with the canopy not showing any signs of wanting to part company with the model. Of note now is that I sanded off the edges of the canopy in order to remove the abrupt 90degree cut line all round the edges of the canopy. Essentially then, I rounded off the hard corners. I then ironed on blue Hobby King covering in strips to disguise and tidy the joints all around the canopy. The front of the canopy required the cutting of several strips of covering because of its compound shape due to the angle of the front of the screen. It wasn`t that easy  but I seem to have made a passable job of it and the result is a great deal better than I was expecting. The fitting certainly went better than with the Super Chipmunk canopy! That nearly drove me nuts!!

The two part ABS spats (what a cheap and hateful material ABS is) have been joined using domestic Osma plastic pipe cement and internal land strips. A tad of plastic filler and sanding corrected any mismatch between the two halves followed by severe abrasion of the plastic and the use of some quick set epoxy and very light weight e-glass cloth strips. Filled and faired and with the wheel slots cut out, the spats are due for two pack priming tomorrow. Whilst not the best bonding job ever, the e-glass, abrasion and epoxy might just hold these pats together for a while. I favour proper epoxy or Kevlar material to work with. I can get an assure glue bond with glass material but I totally distrust ABS plastic bonds. Perhaps I should invest in getting one of those plastic stick welding units. The motor trade use them to repair plastic bumpers. Anyone have any experience with one?

The ali landing gear was abraded and given three coats of acid etch U-poxy two pack, aircraft grade, high build ali primer. Blue, two pack finish colour painting is due to be another job for tomorrow.

As regards the cowl, I`ll get the fixing holes drilled before painting. I`m a bit held up on final cutting of details. As Just Engines are presently closed over the New Year, I can`t get their ideas on spacing's and distances for the new exhaust within the cowl. I`m reluctant to paint the cowl if I then have to cut great lumps out of it. I`ll just have to be patient.....not so easy when the completion of the model is so tantalizingly close.

I created a thread on my Jaguar Enthusiasts Club web site when I joined CAMFC as I thought some of our members may be interested in what I`ve got up to with these models. I started the thread back in February. Some ten months later it has received over thirteen thousand hits! Quite incredible but also very pleasing. I was quite amused to note one comment this morning in regard to one of the cockpit images. The member thought I`d given the pilot a laptop! He didn`t realise it was a tachometer for the DLE 40!!

Happy New Year, guys.

Mike

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A bit of bling added this morning. Two registration letter runs added to the fuselage sides.

Not cheap though. £16 for the two stickers to my own sizing. 65mm in this case with the length being dictated by the font and style. Something like 390mm for each sticker. Ordered on line from The Sign Builder. A quick and efficient service. Recommended.

The cowl and spats are now under two pack white paint. The landing gear is now painted blue and looks good.  I`ll not touch any of those parts now for another day in order for the paint to harden before adding blue and grey over the next few days. Painting is a long slow process and requires patience and the ability to walk away for a while when adding contrasting different colours. I always remember our accountant at Kemble having a moan about the length of time paint took on full sized aircraft. My reaction was "OK then, you come and have a go and see if you can get a top result any faster"! The accountant shuffled off across the hanger mumbling and cussing......his issue was justifying the size of the invoice to the aircraft owner!!

Just Engines are due to start building the muffler on Monday and it should be with me in a couple of weeks. The two bladed prop has been balanced. It weighs 0.4Lb so it is a fair old chunk of blade. My fathers prop balancer was given additional magnets to stop the prop falling down into the balancing rig. A bodge fit mod but a quick answer in preference to having to buy a larger unit. A 3.5"/89mm ali spinner is awaited.

So the model is progressing well with no real issues. More updates in due course.

Mike

 

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Looking very smart! Do you have an approximation of the flying weight yet?

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Hi Ben,

About 14.25Lbs seems to be an early figure. Added lead until the C of G appeared right. The total weight figure will be less than I added because the exhaust is still to be built. Just Engines are starting on Monday. Two week delivery is expected.

The cowl and spats are cooking in front of an infra red lamp presently. I have to spray outside, then dash the parts inside to prevent paint bloom. Not perhaps one of my finest finish jobs but that is how it is with somewhat inadequate facilities and current low ambient temps. It is amazing how much spray paint gets used. All the white and blue now used. £30 so far just to finish the cowl and spats. Grey pin strip to be added in a couple of days. A long, slow and sometimes difficult process. How I crave for my old spray booth at Kemble Airfield.

I`ve just received a 90mm Krumbshield? ali spinner. Heart in mouth, I`m now hacking out for the prop blades. Images of that shortly after I`ve made a mess of it!

More updates soon.

 

Mike

 

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It is fairly hard going at present. The paint on the cowl is giving problems despite my relatively high skill level. The cold temperatures don`t help. In addition, I had masking tape glue left on the surface of the white paint. I should have used insulating tape. With the goo removed, the white paint has suffered. Flatting down again and cussing madly, I now have a couple of coats of brush pained, water based white applied over the damaged areas. This will need flatting back tomorrow and a further thinned coat applied. More drying time then required before it will be set up enough for grey trim. This is likely to by sticky back vinyl in an attempt to reduce possibilities of further paint troubles. I just have to find a sign writer locally to cut me some appropriately coloured 1/4" strips. I`m not enjoying this paint saga much....

Red self adhesive trim tape from Halfords over white and blue on the fuselage, tail feathers and wing has been applied. It pops quite nicely with the red on the Union Flag. Quick and easy to apply....now if I can just get some grey to match the Hobby King grey covering...

The prop is balanced and a Krumshield 90mm spinner has arrived. Not cheap at £27. Careful cutting and filing has been required to get it to fit the propeller.

Total weight looks like being about 14.5Lbs with the Just Engines silencer and probably some ballast. Check C of G testing with a bag full of metal hung off the prop gives me some idea of what will be required.

Mike

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Images show the further work carried out.

The going has got tougher but I have a result although not quite what I expected. The predicted weight of the model once the muffler has been constructed and fitted is now likely to be no less that 15Lb 12oz. So the model will be over weight for many flying sites limited to 15Lb 7oz/7Kg. Despite my best efforts, I cannot reduce weight any further so that is that. The model will not and cannot ever be flown at Fickleshole and alternative flying sites will have to be sought. Disappointing, but that is how it has panned out. There is only so much weight reduction on air-frame components that can be achieved and I`m not prepared to compromise structural integrity or safety. There are many over 7Kg models out there flying but it is quite clear to me that some traveling and membership of another flying club or two may be required if I ever wish to see this model fly. Weight wise, it is within the manufacturers figures ie 15-17Lb. This is a chunky model and is typical of American kits of about 25 years vintage. Had this been a modern laser cut kit, no doubt the end result would have been different and somewhat lighter to boot.

I`ve moved the servos from the tail. The weight of the servos and push rods was an astonishing 8oz and in the wrong place! I moved three of them to forward of the wing TE which has helped C of G. The fourth servo has been removed to save weight. The move meant installing carbon fibre push rods and outer sheaths. Not cheap but effective. Installation after covering wasn`t easy. Retro re-fits are far from fun. Seemingly, I learn something new, every time I build a model. This one has been a steep learning curve.

The cowl paint was difficult. The predominate issue was masking tape residue left on the paint after the tape was removed. Insulation tape would not have caused the problem. The fine line tape did not cause problems but the common masking tape did. A lesson learned and not to be repeated. Paint is a combination of two pack, single pack water based acrylic, self adhesive vinyl, and motor trade pin stripe tape. Whilst not one of my better jobs, it is passable enough. As we used to say in the marine industry, "Stand back six feet, Sir"!

So the muffler construction should begin at Just Engines tomorrow. They have been instructed to build a unit that stands a chance of getting the DLE40 Twin down to or below 82Db. Other factors of course affect the noise generated, prop pitch, diameter, construction and prop speed. Pointed tipped props constructed from carbon fibre seem to be preferred by other users aiming at low noise levels. At around £25 for a prop, getting this aspect right could prove an expensive game. In addition, a noise pressure meter has been ordered and this is awaited.

A Rcexl ignition kill switch has been fitted. I have a Futaba 7C transmitter and FS617/606 receivers in my stock. Whilst the transmitter switch G will kill ignition, switching the transmitter off does not. The fail safe facility is only functional on Ch3 throttle ie acting directly on the throttle servo to close the carb in the event of transmitter failure. The user manual states that fail safe is only on Ch3 only. So is this a problem? Opinions please. I would rather not at this stage have to go and buy a new Tx/Rx set up.

I`m the first to admit that I`ve pushed the envelope limit with this model. I had the itch to build bigger and I`ve copped a difficult project in the process. I`m not out of the trees yet with it as you can probably surmise. "When you are at the cutting edge of development, you can regularly expect difficulties and disappointments"! This model is one of those cases. My challenge is to overcome those difficulties one by one and hopefully see this model fly.

Mike

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Shame about the model being over 7kg Mike, although it does look very sharp indeed!

With regards to the kill switch; whilst some models at our field DO fly without the correct failsafe set up, it is highly unadvisable to do so. This failsafe protocol also become mandatory and enforced above 7kg too, so you will need that to kick in when the tx turns off. However, I'm not sure if it states that the engine must be killed, or simply idled, perhaps a check in the bmfa handbook could clarify?

I actually tried setting up a failsafe, where when signal was lost, the engine would remain idling for a few seconds, in case the signal came back. This was changed however for an instant cut, and a gentle up elevator. I know that Rod used to use full defections on all surfaces too.

 

B

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The BMFA handbook, page 32, section 15.12(a) states,

"For models 7 to 20Kg, A serviceable "fail-safe" mechanism should be incorporated to operate on loss of signal. or detection of an interfering signal. For example on a power driven model this should operate, as a minimum, to reduce the engine(s) speed to idle".

So there we have it. I have the switch G on the transmitter available to cut the ignition manually with the transmitter operating and transmitting and also the mandatory fail safe on Channel 3, throttle servo to be set to retard the throttle to full close in the event of transmitter signal failure. It seems I would be in compliance. It would appear that if I wish to also have a fail-safe on the ignition, I would hae to upgrade transmitter and receiver packages. That will have to come in time.

Mike

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Sounds good. In my opinion, as much as having the engine cut is good, I always prefer to keep it idling so that there is a change of recovery. I also can't imagine there's much of a difference being hit by a 7kg lump of metal vs a 7kg lump with an idling engine - either way your day is going to get a lot worse...

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It is a legal requirement for ALL powered aircraft (whatever their weight) fitted with a receiver capable of operating in failsafe mode, to, as a minimum reduce the engine speed to idle on loss or corruption of signal.  In other words nearly all modern radios have this function so nearly every model you fly must have the failsafe set correctly, whether the model is greater or less than 7kg. This is legally required by CAP 658 and has been for some time. Failsafe operation should be checked on a regular basis.

This is also one of the mandatory questions that are asked for the A and B Certificates.

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I wonder then, how some of the rtf ultra micro models fit into that? My first model actually went to full throttle on loss of signal, and I could barely fly, let alone worry about something I did not know about.

There ought to be a set of regulations on the packaging of models like that, or perhaps radios, similar to the packaging of air rifles I would have thought...

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