Here is a list of all the postings Spitfire fan has made in our forums. Click on a thread name to jump to the thread.
|Thread: Maximum motor current question|
I have finally carried out watt meter tests on my motor using multiple watt meters, three to be precise, as it was earlier suggested I should do. As it happens I have to report that i got very similar results with all three meters and the overall result was that the motor gave me a lot less power than specified. So I am grateful to Ken and others for their suggestions/comments.
This is a great forum.
I have returned the motor and without question I was offered a full refund including the return postage, so they could not have been fairer.
|Thread: TN 46" Spitfire|
Hi Paul. That really is very good news about the watts produced, the current drawn, and how the plane flies. I have seen the underwing filters on other build logs but I thought that because of their rearward position that they might actually create a pivot point so more likely to produce a nose over or at least bring the nose and prop closer to the ground increasing the chance of damage. Adding the air intake as well would help but of course this is just adding more weight. Did you include the air intake ?
I will buy that motor if i can find it or something to give me a similar output, so i can complete the nose build and see how the AUW estimate is looking then. After that i can decide about the under wing additions.
Thanks for your help. I will think about posting some pics sometime but i don't feel ready to yet.
Hi Paul. I have not had much chance to progress the build since Nov., however as will be detailed in a different post my choice of motor did not work out, so I'm now looking for a different motor, possibly the same BL2815/09 you used. Did you do a wattmeter test to confirm the output as I noticed that 380Watts is the specified output for that motor /prop combo. If you actually achieved 380W then it seems model flies well at 100W/lb which is really good to hear. I assume this means you can do all the manoeuvres you would expect of a warbird, and thats what I want and nothing more. It is always possible to get a more powerful motor and i have read before that 130W/lb is required for a warbird, but adding watts just means shorter flight times for the same battery, not a good idea.
Have you flown it many times ? Have you experienced any issues with damaged props, bend motor shafts or nose overs because of the prop digging into the ground during a belly landing ? Many thanks in advance for any comments.
|Thread: Maximum motor current question|
Thanks for the replies. I had hoped that the current drawn in flight would be less the static test but i was not sure, so now I'm happy. In any event I don't want to be flying drawing at or near the max current of 35A, that would not be good. If I can't get the watts I need then I will change motor.
I've not had time to do for a watt meter test yet on my OS motor but I wanted to ask how the current drawn during a static watt meter test will compare with the current drawn when the plane is flying and hence the prop is cutting through the air.
Does anyone have any knowledge how the current might change ? Thanks.
Point taken Phil thanks.. I will be sure to use a couple of watt meters, however an error of 100 watts is likely to be a lot more than 10%.
Hello Ken. Many thanks for that info. I will carry out a watt meter test asap incase I need to return the motor for a refund.
Hi. Thanks for the explanation. You are spot on about the document causing the issue. Fortunately I have chosen a 10x7E prop, as I wanted something over 400W, and this should give me 428W at 34A. I will definitely do a check with a watt meter though. Thanks again.
I do not understand the details relating to the overall electric motor power train.
Please can someone help me understand my motor specification and propeller data chart. The motor in question is the OS OMA-3815-1000. The motor specification gives Rated current 35A and Max current 45A, but no mention of the number of seconds allowed at 45A. On the same document is a chart detailing 16 different propellers from a 9x6E drawing 25A and producing 315W up to a 12x6SF drawing 64A and producing 806W.
How can it possibly draw 65A when the spec says rated current is 35A ?
I would appreciate any help to understand this.
|Thread: TN 46" Spitfire|
Hi Paul. My turn to be sorry, I had not realised you had replied. Many thanks for the info.
I'm covering the model using Deluxe Eze-Kote in combination with light glass cloth or light tissue paper.
I am aiming for a flying weight between 3 and 3.25lbs without any lead in the nose. I have roughly balanced the model with some items taped in place and I think I can get the correct CofG position by adjusting the final position of the battery without any additional lead.
What did you cover your model with ?
I am using 3S 3200 lipo and OS3815-1000 motor and 10x7E prop giving 428Watts and I have a 60 A esc. Your numbers encourage me that I should have enough power.
I am still to pass my A test so I will be getting someone else to maiden it for me and I will be praying that it does not tip stall on release, either from hand or from a dolly, copying your design. I hope I have managed to build in the small amount of washout that TN suggested on his plan so I hope everything will go OK.
Thanks again for the reply.
Hi Paul. Just found your log. I am building this model,also without undercarriage, so very interested in your dolly. Please could you advise:
What is the all up flying weight;
What motor have you use;
What capacity 3S battery have you used and roughly how long a flight time do you get ?
|Thread: Carbon tube/snake push rod|
Thanks for all the comments/alternative suggestions. They will be very useful for future builds.
Hi Matt. I could not find these adaptors you referred to when I did a web search. Please could you post a link.
Hi. I want to try making push rod assemblies with 5mm OD carbon tubes because of their stiffness and lightness but I have not found any useful threads with pics showing how the end connections are completed. Quite by chance however I found that the inner plastic of Sullivan type snakes is a perfect light push fit into the 5mm OD carbon tube. I inserted about 15mm of snake inner into the tube and applied cyno. It seems to hold but not wanting to take a chance I decided to pin it with a split dowel which was easy enough to do. Now it is easy to screw a short length of 2mm studding into the snake and attach a clevis or swivel link, or whatever is reqd.
I think the result is a lightweight, very stiff, and easy to finish push rod. I will use two each approx .5m long.
Does anyone see a reason why this should not work ?
|Thread: Wing covering on 46" Spitfire|
Having completed the wings I am unsure how to proceed with covering. I want to add some strength without adding too much weight. With this in mind I thought to use Deluxe Eze-Kote with either 24g/sqm or 18g/sqm glass cloth.
I have looked at previous related posts however i am somewhat confused by the various replies. Someone in a similar post said it was imperative to use sanding sealer first but did not explain why. Also someone told me water based resin like Eze-Kote could easily warp the 1.5mm sheet balsa that is used to cover the wings.
I would appreciate it someone can explain the best way for me to proceed.
Many thanks. Peter.
|Thread: A TN 46'' SPITFIRE by an Intermediate builder|
Hello again Henri and thanks for the confirmation on the access and fixing of the battery. Great paint job, it looks really nice.
Hi Henri and thanks for the both replies. Yes you covered all three points. I am not adding retracts and I may now only partly glass the modeI so I figure a 3S x 3,200mAh battery will be Ok. I would still like to try the same battery location as you, however can you confirm, is it necessary to remove the wings to change the battery or can this be done from the front access ? If the wings do need to come off I might look for an alternative method of battery location and fixing.
|Thread: Two or three hinges per aileron on Tony Nijhuis 46" Spitfire.|
Will do Richard. Thanks.
Thank you all for your comments. I am not an experienced builder which i why I asked for your input/advise. I will use at least three.
Thanks for all the replies and it seems I should stick with three hinges. I have a day or two before I will need to decide so I will wait and see if anyone who has built this model replies.
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