Engine Doctor

Good luck with build, hopes it goes well . Pics ?

Pics for making a Balsa cowling . A Davids plane then a sanding block to shape . This took a couple of hours .

Best way to glue PP is to find another material. Its too waxy to glue. Have you tried gluing a candle stick? It can be welded but not glued. Why are you useing it ? Virtually any shape cowl can be built using balsa block method. You should be able to find a post with pics on here with a search . Tack Glue blocks of balsa to the front of fuz filling inside with blicks were you want to sand to shape and might sand through , especially on corners. This can be done very quickly with cyano . Then plane and sand to shape. When happy with exterior cut from fuz and carve out inside . A dremel is very handy for this it can all be toughened up by appling some cyano or finishing epoxy before final sanding and finishing.

As far as i know it doesnt. In laymans terms for our model size a single bladed prop is the most efficient as used on speed models. The air in the arc has time to recover before the blade takes the next bite. The single blade is counter balanced by a wieght. Two bladed props are easier to balance and give good all round performance. I think in simple terms , air is a constant and on our sized models the more blades spining in an arc will disturb the air flow for the following blade causing poor thrust. With bigger props as per full size the air isnt disturbed as much due to bigger distance between blades and so a gain in thrust can be achieved. The huge multi bladed props as used on later spitfires and on Corsiars were used to tame and load the massiive engines. There will no doubt be someone on the forum who can explain the theory and in better detail . In practice three blade props dont produce the same thrust like a two blade prop on our models. So multi bladed props for display and two bladed for flying. Last year i was given a Durafly (or similar ) spitfire with a three bladed prop . While landing it nosed over breaking a blade off . No prps availabl locally so i fitted a two nlade and plane flew much better with more power. Then found a three bladed prop and fitted it to move it on. One last fly and it was , as before very tame.

Agreed Ron . Its a disgrace but doesnt little Johny have to be 18 ? The CAA I think are just empire building and making a case for increasing their remit. Those in power who know little or nothing about our hobby will of course hang on their every word while ignoring the Likes of experienced flyers , BMFA, LMA and any opinions from polls they set up to make it look like they are listening. The general public who buy toys for their children will just ignore it or just wont know about it anyway so its a piontless excercise thats being paid for with our flying tax (CAA annual fee) . I had a similar discussion a few years ago with a local Park Ranger about youngsters flying at a loca park . He told me that small children throwing a toy glider or small flying toy would be stopped at a local park! His words, although ive never heard of it actually bring enforced. If we had a minister in office who was a devout aeromodeller it would be a tottaly different storyI'm sure ; the same as lord Young ,now deceased, who pushed for our driving rights for heritage vehicles.

Hi Dave . Ask your mate if he can spray the cowl with single stage 2k paint. If painted with base and clear the base coat can be attacked on edges by glow fuel residue then bubbles and lifts slowly creeping underand lifting the fuel proof clearcoat. Ask me how I know? Water based base coats may be ok but polyester just melts with glowfuel (methanol) .

Time to eat my words I guess.😳 After looking at the Yamamoto add and comparing the pic its not the " plastic pig" Yamamoto as tailplane on that was not mounted on the bottom of fuz ! Oops ! So Superfly it is. The earlier mk1 yamamoto with a balsa fuz was a delight to fly as it was much lighter. Had one of those with an Enya 35 in it , great flying model. As Gary said I should know as finished his Superfly for him earlier this year. Note to self ...look more carefully before you leap. The superfly flys very well but the GF Yamamoto was just toooooo heavy and fast for a trainer as GF was just to thick and heavy.

Definately a Yamamoto Mk 2 by MFA in Folkstone Kent. Comonly refered to as the " plastic pig" as it was heavy and had to fly relatively fast compared to its contemparies. Simlar to the Ely superfly but a bit bigger . About 60 inch wing span ? It was my first trainer bought as a started / messed with kit from one of my sons mates. It flew ok on an Bluebird 46 also distributed by MFA .

Some heat shrink that fit over the plug serves as id from whatever colour you use and for ease of unpluging without putting all the strian on the wires. Use heat shrink with internal adhesive so as to adhere to the top of the plug. Similarly ordinary non adhesive heat shrink is ideal for locking extention leads together .

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M5 is a big jump in size for the bolt head. Why not fit a helicoil thread to keep original bolts ? Kits available on Ebay for not a lot of money

I thought they were M4x 0.7 ?

Here on ebay

Did you keep the layup in a warm dry atmosphere while it cured ? I had some finishing resin that wouldnt cure as the temp fell too low. Once the cure stalls I find it wont start again even if warmed up.

Thank for putting GC piston ring web address up. For one dreadful minute I thought that we had lost a trusted member of our ever decreasing spares suppliers. I have made many piston rings over the years but to be honest G C rings are so good and at his prices its not worth the hassle of making them . Glad you got sorted Derek.

As jon says leave tops off but use pippette tips and change when clogged as per Shaun2.4 post

I have just tried to look up the site I recommended in my last post and its appears closed !!!😧. I have messaged the seller to see if they will be continuing to supply parts . I used his products on a few occasions as it was far quicker and easier to buy a piston ring from him than it is to make them . If he has packed up it looks like ill have to fire up the lathe more often !!

Yes look on ebay . A seller named Gaviscool sells piston rings for many discontinued engines. They are excellent quality and very well priced . An OS 48 will cost around £12 the last time i was on his site. Ill have a look and pm you later.

The sellers words " its compatible with Nitro and glow fuel" ? He probably doesn't know anything about the hobby . He says its from a house clearance and is just a chancer like so many on ebay. Sad if someone get caught out ☹️

👍I've used them for years and fitted correctly as you say there are no problems. I support the middle loosely just to stop them vibrating and flapping about. Control snakes are my preferred system . Securing ends can be an issue as no glue really fixes the plastic. To overcome this I wrap the ends tightly with Masking tape then seal this wit a thin coat of cyano . when its fitted and in position I then glue the ends to the airframe. and jobs done . Any issues I've ever come across has been due to one or both ends sliding .

Dont forget that petrol contains ethanol and WILL absorb moisture from the air . The longer its left the more it absorbs and eventually you will have water at the bottom of the tank causing poor running and corrosion to any vulnerable parts in the fuel system . Obviously if its a diesel this doesnt apply although even diesel fuel can go off if left for long periods in cars as bacteria can grow blocking the fuel way and especially the fuel filter. Take it for a run and use the fuel . If left standing again replace fuel with shell V Power or BP / Esso Equivalent as this apparrently doesnt contain ethanol.

If you make an eflux tube with the ammount of taper you require it doesnt matter if the end is made to fit the shape of the outlet. I did yhis to a Tomcat model wi5h a single 70mm fan that looked like it had two outlets/ engines . It made no difference and had excellent power. I dare say the theorists will disagree but in practice it works. The model was a " Highend technology F18 Tomcat " from around the late 90's to mid 00's.Eflux tube was made from acetate sheet made into a normal tube with taper then fitted through the elongat3d outlet and fitted to fan in the normal way. The oulet end had to be supported as there was a gap either side . I made an infill to sit insde tge dummy motor outlets to support the tube.

Hi john we used the plastic cup . The foam ones seem to have a bit more of a taper from memory .

Not sure about the formula but a small plastic coffee cup fitted pushed over the back of a 70mm fan and the bottom cut off about 1 inch up works very well. Tried this at our field when a member turned up with a EDF zagi . Running on 4s it didnt have any power to maintain flight . He had left off the inlet flare , or whatever its called off and had no eflux tube. We fitted the inlet flare and thrust improved slightly then tried the coffee cup as a experiment as it was all we had in the club shed . It was pushed on and held in place with some insulating tape . The trust was so improved that flight was maintained at less than half throttle . The coffee cup idea has now been used in a few models .

Yes all bets are definately off judging by the driving displays on our local roads let a.one on our motorways! ! Its inconcievable to me how people can drive in fog , around a tight bend or in heavy rain with associated spray at speed without being able to see a thing let alone consider. braking distance ! Anyway off subject . Give us the answers please 🧐 Shaun beat me to it