Tom Wilson

Yes Chris, you have taken the words out of my mouth.. i think it should be flown sedately as it is for observation purposes. We know that drag increases with speed and speed needs more thrust to achieve, so the faster you go the more thrust force above the drag force is going to push the nose down. One thing however that has not been mentioned (well on your model it has) is the wing. On Tim Hooper's version it has quite a thick wing section and an increase in speed will cause more drag on the wing, which is much closer to the thrust line and higher than the main source of drag at the front canopy, so will partly cancel out the lower source of drag. So I think there will be an optimal speed for this model, which will only be found by flight testing but good to know that the free flight model flies OK without human intervention

Yes, this would make sense, particularly as with the big flat fronted nose giving a very high drag factor, it is inevitable that this is going to happen. Martin. Maybe that's why the Germans never adopted it. Fight testing should be fun then. New silicon wire arrived today and hopefully the heatshrink tomorrow and I will get the original bell motor refitted, but weather forecast is not good so there won't be any flying this week again.

OK, I respect that advice and I will avoid,Thanks. It is a difficult one with the thrust angle as the thrust line is so high above the CG point and centre of drag line, that increasing it could tip the model even further down, but so also would upthrust, so maybe up elevator would be a better option. I think only flight testing will find the best options. I'll have a further look for the battery Dr.

Hinted?........Yes, the high thrust line and the low drag line caused by that big flat front looks like it could be a problem. Maybe needs more than the 4deg. downthrust or trim in a bit of up elevator, but we will see how it goes when the weather improves. at least I have the power problem sorted now I think Tim that you said it might be helpful to move the u/c forward a little for take off on rougher strips.One of my chargers is a balance charger, and the other is not but gives the option to force charge on 1 cell setting. Whether or not it can select the low cell or not ,I don't know. I had a look on ebay and there seems to be quite a number of suitable battery doctors for around £16.00-£18.00 like the "Max B6" eg Can you recommend it ?

Now reading 12.7 off load, 1 cell a bit low at 4.15 v, others 4.30 v, and 4.28 v, total 12.7 V On Wattmeter 12.8 V showing off load. Now drawing 12.7 A and managed to reach 149 W. Have now put battery on different charger to try and balance cells. That middle cell doesn't want to come up. I have ordered some more silicon wire and when it arrives I will re-fit the original Bm2409-18 bell motor and see how that goes. The original problem was the ESC which I hadn't set by firing it up with the throttle fully open, and then the battery really need a charge. I have another new one but will need to change the plug on it, and that should give me the full 150 w. Model weighs in at 30oz which is surprisingly (for me) a couple of ounces below that quoted. As an ex Clyde shipbuilder I have always tended to build a little on the heavy side . Thanks for your help.

Battery is showing 11.4 v but 10.3 v under load. Now on charge and will post results later thanks.

Since last night i have partly solved the problem. I happened to notice my Piwakawaka ( which I had forgotten about)on top of the wardrobe which had a similar type of bell motor. On checking , It was a 2408-21 as mentioned by Leccyflyer. with the watt meter in place it was reading over 200w initially and settled around 180W. As I said in my original post the Bm2409-18 is a bell motor. I swapped it over for the 2409-18A shown in leccyflyer's post. I then remembered seeing instructions for the HobbyKing ESC lying about and after consulting it I tried the Siebel again but this time setting the ESC as per the instructions and this time the power went up 107W, running at 10.5A. A vast improvement but still well below that quoted in the original build text. I will switch back to the original bell motor and try the slightly larger prop( a 9 x 4.7 which just clears the tail boom. Plan shows 4degs upthrust but I would call that downthrust as it is a pusher.

Can you please explain how you managed to get the 150 W power listed in the text from the 2409-18 bell motor, as the most that I can get is 61 W when using a 3S LiPo with an 8 x 6 prop. I even tried changing the motor for a 2409-18A outrunner but the maximum power was only 72 W.

Hi Tony, I have never actually finished mine yet but had a look at it just now and I'm a bit confused. I said in my last post that I had fitted Tower Pro 9g ie SG90s. I also said that they were too high in the fus. On checking it appears that I must have changed them for smaller servos as they are fitted as I described on a liteply plate on approx. 10mm thick spacers on the floor. This puts the servo arms about 26mm above the floor and the wires for the push/pull rudder and the control snake for the elevator come inside the tail boom quite nicely. I have used the same servos in the wing for the ailerons. The problem is; there are no markings on any of the servos to tell me what they are. I have compared them to an SG90 and they are smaller.They measure 20mm lg by 8mm thick by 26mm from bottom to top of servo arm. I also said that I would use a single servo for the flaps but on trying it tonight I found that if one flap is a bit stiffer than the other then the easy going one pulls down and just twists the "A" frame out of position leaving the other with virtually no movement,so I will have to re-think this one. Any suggestions will be most welcome.I can't even go into my old Giant Cod / Giantshark account as they have now stopped trading. Similar micro servos I am sure will be available on ebay

Does anyone know the CG position for the old Chris Foss Hi-Phase. I can't find my plan at present . I reckon that it should be around 90-100mm from L.E.

Does anyone have any experience of repairing a glass wing. Due to a high impact landing, glass skin has separated internally from the balsa and inner skin. Any thoughts on this repair would be welcome . One tip panel has a L.E. section broken off for the first 8" tapering from the main spar out to the L.E. The crumpling has left ridges along the outer skins where the separation has occurred.I recently repaired a "Tracker" wing tip which had a piece broken off from the mainspar to the T.E. by cutting a foampiece to the rib profile anf fitting it in then re-skinningand it came out very well but the Pike panels are much larger.

Yes Brian, I like the idea of fitting carbon tube over the rods. I have just modified my Hi-Phase which had a bicycle spoke type rod inside the fin for elevator control. The problem was the flex in the rod more especially as it had a kink in it for clearance. I used 2mm carbon rod but made up aluminium end adaptors which were araldited to the rod and threaded to take a small piece of the threaded spoke to allow standard clevises to be screwed on , but your idea is much simpler. You have a point erfolg , When this model was originally designed and built in 1982 they wouldn't have had computer txs, so maybe I should just go with letter box spoilers and see how it reacts. It would certainly make life easier.

Some very interesting posts here. I want to try the eliptical dihedral which rules out crow brakes. Do the lower brakes not get damaged on landing, or do you close them before it hits the ground ?, in which case it sort of defeats the object of brakes. I have now manged to design a scissor brake that will come down to the required 23mm wing thickness but am worried of the same problem of the lower brakes catching on landing. The only thing holding me up at present is the building board I managed to get a 50" x 20" x 3/4" plywood for the base board, but need to fit 2 pieces of angle iron to the underside as there is slight buckling over the length. I have cut the curved pieces for the elliptical dihedral to be fixed to the upperside, but now need something to go on top that is rigid enough not to twist but flexible enough to bend to the curve and preferably soft enough to stick pins in. Has anyone built one with elliptical dihedral?

Crow brakes would not be possible with this wing without re-designing completely. I do intend however to install scissor brakes behind the mainspar. Designer reckons that the model will pitch severely with top brakes only and either bottom brakes or better stil top and bottom should be used. The problem is that the wing section is only 23mm thick so I am trying to make up brakes on the lines of the "Schemp-Hirth" brakes which would be ideal except for the fact that they are only manufactured at a minimum of 30 mm when closed.If you know of any others ,I'd like to here about them.

My preference is thermal. I have never flown from a slope and I don't have any inclination to do so, it just doesn't appeal to me. So from that point of view, I'm not really interested in flying inverted except perhaps to get me down out of a thermal or down quickly. the designer claims almost instant stall recovery , and excellent pitch control. Thanks for your input.