Alan Gorham_

I think that any so-called safety isolation device will have it's limitations.   I simply posted the link to the Emcotec unit in response to Michael Smiths' query regarding using high power MOSFETs in this application. I do not think that the products specifications imply or suggest that it is suitable for long-term isolation (F.E. as some have suggested while the model is transported from home to field in car. Having considered fitting the Emcotec unit to my high powered scale models where the primary motivation was to cut down on the amount of handling the model received while fitting and removing the LiPos before and after every flight, I came to the conclusion that the benefits did not outweigh the purchase costs and there was also the matter of the unsightly safety switch to conceal. Personally, I never viewed a unit such as this as offering 100% percent foolproof isolation. Just as I wouldn't view a Dean's connector or other such device as being suitable. I concur that the only guarantee of complete safe isolation is to only install the battery into the model and then connect up electrically immediately prior to flight. And obviously to immediately disconnect and then remove the battery after landing. In my case, I always use a separate supply for the Rx in any case so I did not view that factor as a limitation or disadvantage of the product. In conclusion, I would suggest that if the battery is fitted to the model then there is always the potential for it to become live inadvertently (however small that risk may be). So the old adage about viewing such models as 'live' would be a good idea. Edited By Alan Gorham 2 on 10/01/2014 17:21:37 Edited By Alan Gorham 2 on 10/01/2014 17:25:35

Such devices are commercially available and have been for years. German manufacturer Emcotec offer a range to suit different voltage/current ratings. here is one type: **LINK** Not cheap, but proves the concept...

Model shop Leeds sell all the spares for Chris Foss kits and hold them in stock. For example they list an acro wot canopy for 12.99 pounds. Have a google to their website.... I've been impressed withtheir range of stock and mail order service.

Chris The motor is definitely a DC Merlin. For info the prop nut needs to be 3BA. If you are worried about too much power, then you can't ask for a better motor than a diesel to test fly with... Even if you don't try the old trick of test flying with the prop on backwards, you can try a series of powered glides with the motor decompressed and burping, then you can increase comp. at will.

You have my details correct

Ben Buckle Diamond Demon, plans been in stock for a month. Rudder only and a DC Sabre for power.

Yes polyester resin will melt white foam. Suggest you get the foam as smooth as possible then apply brown parcel tape over it. This will act as a barrier to the resin. Also consider coating the tape with a release agent prior to laying up. I use Meguiars mirror glaze wax (good but expensive) but 2 or 3 good coats of pva will work if you can get it to stick to the tape. Personally I wouldn't use white foam as I prefer the smoother finish of blue or pink, but you should get a usable part...

Andy Is there any reason why you can't make the cowl in a similar way to your fuselage? I would be tempted to make a couple of thickish balsa formers, one for the front of the cowl and another for the rear. You could add a top and bottom balsa keel to space the formers appropriately and then fill in the gaps with foam and carve to shape. Then tack the extreme nose block to the front of the shaped cowl and sand/carve to shape. It's quite difficult to get my intent across in writing, but I can thoroughly recommend this book to you: http://www.myhobbystore.com/2799/Book-Radio-Control--Foam--Modelling.html It has a section on buliding and shaping cowls as well as loads of other foam techniques you will find useful. It's less than £7; perhaps it make make an ideal stocking filler for you. It's much more useful than socks!

Andy  I know that Phill's Models sells Sullivan stuff, but they don't keep the small, flexible ones I was thinking of. They should be able to order them in though - if you can wait that long Have a look here: http://www.sullivanproducts.com/GoldnRodContent.htm And go down the page until you find "steel cable type" no. S577. My reasons for avoiding two servos are the cost of the extra servo (granted that's a small cost if you use a cheapo), avoiding long servo cable runs (possibility of picking up noise from the powertrain and the fact that extension leads ain't cheap either). But each to their own. I always feel that two servos are better either in a very large model where you need the extra servo power or on something like a soarer where you want to do fancy mixing e.g. crow brakes or spoilers or the like. Not sure I agree 100% with Simon above re the landing loads being highest on your centre section. The Chilton has quite a wide undercarriage track and the legs will be quite close to the "dihedral break", so the landing loads will be highest here. I do agree though that you could use a single brace across the centre section and out to the outer wing panels. this brace would probably give you something to tie the undercarriage mount to as well.

Andy Good stuff so far. I would be tempted to use either a full depth ply spar (1/8" or 3/16" birch ply) at the maximum thickness point of the wing section. You can make the spar so that it sits just under the surface of the wing and use filler to make it good. This is probably the neatest method, but of course you need to be able to cut the slot for the spar accurately. The easier method would be to use a couple of layers of glass cloth and epoxy over the joint. Make the first layer extend (for example) 3" either side of the joint and the second layer could extend 2" either side of the joint. This would help you to fair in the cloth when the resin has set and also to spread out the stresses along the wing.  I do think you need some reinforcement in this area, not so much for flight loads, but to spread the shock loadings from landing...... Personally, given the size of the model and it's likely flight performance, I'd be tempted to use a servo in the wing centre section and the smallest and most flexible Sullivan Stainless steel Gold-n-rod snake to the ailerons. I think it's 0.032" diameter. You can cut a shallow channel for this snake in the top surface of the wing. Allow for a wide sweeping curve to minimise friction. Bury the plastic outer sleeve and fair over the channel with filler. Separate small servos would be ok too, but I don't see the benefit on models of this size.... My 2p worth. Hope it wasn't too rambling!

Andy  Thanks for that - I know where Blue box is. I will take a look at it. Good plan for the panelling. Looking forward to seeing your progress.

Andy What kind of foam are you using and where did you get it from? I've used blue foam a few times now, but the stuff you have looks to be lighter (i.e. less dense). How are you planning on covering it? Iron-on film? Glasscloth? Brown paper? Jim, lol that explains it!

A man of excellent taste, Jim. You've even used my initials (AFG) in the registration! How on earth does it fly with no engine and prop? To stay on topic: Andy, that's an interesting method of construction. I've heard that some of your clubmates are fond of doing it this way. I'll be watching and learning.....

Phil  As an option for light silver covering, you could look at Solarfilm Solite. I used it on a Peter Rake Isaac's Fury see here: http://www.manzanolaser.com/id37.html It's much thinner and lighter than normal Solarfilm, but it does slacken a bit in hot sun. Worth considering?

Hello Jeff Take a look here: http://www.rcmf.co.uk/4um/index.php/topic,43726.0.html For a very comprehensive build thread. Not mine I hasten to add, I've just read it a few times. You might have to join the rcmf forum to view, but I am sure you will enjoy as it's a very active and helpful place! Best of luck on the build. Kind regards Alan

It is looking lovely Fred. Can't wait to see it finished. I do like the beaching gear you have made.

Hello Fred Just to give you some background on the cable length issue, have a read here: http://www.rcgroups.com/forums/showthread.php?t=903326 and follow some of the links, especially those from ESC manufacturers. It's not a clear cut science this cable length malarkey, but hopefully this will explain the issues so you can make an informed decision. Note that just because one particular installation has "got away" with long cables twixt battery and ESC, this wont always be the case. It a classic "Your Mileage May Vary" situation and the only reason I mentioned it to you in the first place is that I would hate to see all of your hard work with the model go to waste due to an ESC failure.....  Kind regards  Alan

Hi Fred I have been following your build with interest as I also have the plans and parts for this model. I am interested to see that you are planning on fitting the ESCs in each nacelle. This will mean having four sets of very long cables between the battery and each ESC, assuming you are going to fit the battery as shown on the plan. I.E. in the fuselage. Is this your plan and if so, are you anticipating any problems with large voltage spikes being generated in the long cables? Many speed controller manufacturers advise against long cables between the battery and ESC, instead they recommend extending the cables between the ESC and the motor. I'd be interested to hear your thoughts on this issue!

PS Aeroproducts sell Brodak coloured dope.  See: http://www.psaeroproducts.com/ Hope that helps.

Hi Matt  Your picture does show a Bunch Scorpion. In fact it is the model that was built by Dave Kirby who I mentioned above. I did ask him where he got the plan from - he remembered that it was from the USA but couldn't remember where. The only thing I could find was the scaled up Bunch Scorpion Major that I posted the link to. Apparently the model is capable of a few amusing stunts such as a curving take off on one float. Not bad for a model which is only rudder/elevator. If you do get the plan, bear in mind that the model was originally free flight and as such has a lot of positive wing incidence that you should reduce by packing up the trailing edge of the wing. This will stop the model from climbing madly under power. Also you will have to add a rudder and elevator but it's all straightforward stuff.

Jim I am cursed with a memory for planes/plans etc. I hope I'm on the right track with this one for Matt, because I remember seeing the Bunch Scorpion fly off water many years ago and it was lovely! I've got your offer of a pint in writing

I think the model Matt is referring to is the "Bunch Scorpion". I was talking to a chap called Dave Kirby at Kielder last weekend who built this model many years ago. I have found that Bob Holman plans in the USA do drawings and laser cut parts for an enlarged version (Scorpion major):  http://www.bhplans.com/GMPg4.html  Any good?

Lol! No bother Jim, glad you found it. It's a lovely looking model. I used to fly with someone who had one with a Taplin Twin fitted. Can't wait to see the finished article...

Jim Mate!  I've found one for you. You'll have to buy it though I'm afraid! If you visit: www.modelactivitypress.co.uk and then click on the magazine picture for AMI magazine, you will be able to see a menu across the top of the screen. One of the items in the menu is "Plans" - click on this and a new screen will open. There will be a list of plan categories down the left hand side. You need to click on "free flight sport" and when you look down the list of plans you will find this:  "Mercury 3 96" (2438mm) of sheer elegance for free flight or R/C assist and engines of .60-.90 cu.in. Rudder and elevator control surfaces shown. A real beauty!" Plan £20.00 Next time just ask me at our club meeting ;-D Cheers

Alan On the same forum you will find a Norwegian chap named Stian who has also built an 83" Spit. He has a working 4-blade prop made by a company called Soloprop. Forget using multiblade props meant for I/C engines as you need to be able to adjust the pitch to suit your motor/battery combo and also to get the wattage and current levels right. It's a whole new world so best of luck if you go ahead!