By continuing to use this site, you agree to our use of cookies. Find out more
Forum sponsored by:
Forum sponsored by CML

Aeromaster

Simplified version of the classic biplane

All Topics | Latest Posts

Search for:  in Thread Title in  
Bob Cotsford13/07/2020 09:51:59
avatar
8646 forum posts
483 photos

That sounds a good weight for a 62" bipe Martin. The GP Super Skybolt kits at 58" regularly came in at 9-11lbs depending on the finish and power plant, I've not weighed my WotsWot (50" but the quoted weight is 7lb.

The orange and white looks good together, you've done a very nice job trimming the paintwork and colour matching.

Martin McIntosh13/07/2020 09:59:13
avatar
3472 forum posts
1216 photos

Thanks Bob. I doubt if the model could have been built much lighter. The `orange` is actually Ferrari Red. I had some water based paint mixed up a few years ago to match the HK red.

Nigel R13/07/2020 10:05:36
avatar
3987 forum posts
722 photos

The muse has not been with me much this week, and I've been making some slow progress getting the throttle hooked up.

The throttle arm on the engine is - like many four strokes - close to the firewall. I decided I would do one of the standard dodges and use a rocker arm, to give me some breathing space with the linkage. However, I was constrained a bit on this - I couldn't just bolt a bellcrank to the outside of the engine mount (like the commercial offering) as the offset (from rightthrust) on the engine mount places the mount very close to where I believe the inside of the cowling will be. So the rocker needed to be mounted somewhere else. This is what I initially came up with:

20200710_140655.jpg

20200710_140704.jpg

The bracket is a steel right angle used for putting cupboards together, I think. It came from a DIY shop years ago. Bellcrank is a normal right angle bellcrank.

It needed a bit of trimming from that point. After trimming the M3 bolt and cutting off the surplus bellcrank arm:

20200710_142018.jpg

Getting there. Next up, a link, closed:

20200710_213329.jpg

and open:

20200710_213342.jpg

And then time to get the throttle cable itself in place. I like bowden cables, although they need a solder job to attach a threaded adaptor they result in a nice solid link and can be routed around things if needs be:

20200710_224817.jpg

Spot the deliberate mistake... servo is in back-to-front - oops.

At the engine end:

20200710_224825.jpg

All seems to operate smoothly enough, and, I can install it from above (access will be a bit restricted with the cowling).

It needs a bit more fettling yet - trim the rocker arm bolt down a little, and put a slighty bend in the link arm.

For next time, a better mousetrap would involve a slightly longer bracket, so that the rocker can be in front of the two engine mount screws/bolts, instead of half way between them. This would give a longer link arm.

I did then look at getting the tank in place, but there is a lot of room and it will only need packing in place with foam, so the only job to do there is to make some holes in the firewall for the fuel tubing.

As far as gear install goes, I think that just about concludes the work I need to do before I can get back to the remaining woodwork and think about fuelproofing the tank bay and closing up the fuselage with the underside sheeting and undercarriage mounting plate.

Nigel R13/07/2020 10:13:55
avatar
3987 forum posts
722 photos

7 3/4lb is fair weight for the model I think. If you've gone for both wings at 52" then you have the far side of 900sq in to carry the weight. Even allowing for a 10% reduction (to fudge the issue a bit because it is a biplane), the cubic loading is still under 10.

I guess like any bipe there's a bit of weight penalty to cabanes and all that sort of stuff.

Martin McIntosh13/07/2020 16:15:40
avatar
3472 forum posts
1216 photos

I have found easier ways although the first option has not been used much.

aeromaster 065.jpg

aeromaster 066.jpg

Bob Cotsford13/07/2020 16:31:20
avatar
8646 forum posts
483 photos

Having tried both variants over the year I settled on the big 'ole in the bulkhead (second) method, though with four stroke throttles every installation ends up with it's own issues. I often ended up with a wire pushrod with a big bend to allow it to avoid the tank. The bend never caused any problems as there's no load on a throttle pushrod.

I don't think I've seen anyone else use Bowden cable since about 1985, do you have any problem getting it now Nigel or do you just raid the kids' pushbikes?wink

I remember it getting gunged up and needing regular cleaning, though that was back in the days of castor based fuels.

Martin McIntosh13/07/2020 16:41:06
avatar
3472 forum posts
1216 photos

I now just use 16swg piano wire or maybe a 2mm pushrod, neither of which requires any tubing support and does not gunge up. At least the throttle does not require to be perfectly linked. I cannot remember the last time I bought quick links, the small SLEC ball links are all I use now. Flying an old model the other day the throttle nylon quick link pin broke off nearly spoiling my day.

Edited By Martin McIntosh on 13/07/2020 16:48:59

Nigel R13/07/2020 17:37:51
avatar
3987 forum posts
722 photos

No problems getting it! Most model shops stock it.

It's definitely a bit old school but I'm happy using it. The nylon outer avoids any problems with snagging stuff like tanks or formers. It always needs a solder job if some sort - unless you use those screw fixtures - but that's no big deal.

I will convert the links to ball joint though. The nylon snap links are OK for some applications. But there is a sideways component to the movement here. I just don't have any ball joints handy...

Martin McIntosh13/07/2020 17:54:00
avatar
3472 forum posts
1216 photos

The SLEC translucent snap on ones are what I use. They need a bit of doctoring before use though. Hold a brass ball in long nosed pliers and get it hot with a heat gun then snap on the nylon link and wiggle it about briefly. They will then pivot freely with no friction or play. I use these on quite large models for everything.

Nigel R15/07/2020 09:53:00
avatar
3987 forum posts
722 photos

Do you mean these ones?

**LINK**

I have a packet in the post to finish off the throttle links with.

On the bench, I polished on with a few noodley little jobs these past few days;

Finished up the fin by adding 1/4 edge LE and TE strips; sanded down the excess sheeting on fuselage decking ready for sorting the elevator and fin fairing block; sanded down the excess wood in front of the firewall, ready for building a cowl, opened up the main mount holes in my throttle rocker arm bracket a touch to allow complete clearance for the screwdriver to get to the front engine mount screw, and, corrected for a drawing error by adding some scrap 1/8 sheet to both tips of the upper wing (I drew out the wing panel just a tiny bit too short in span). Nothing particularly photogenic in that lot, although it all takes up shop time.

And also made a start on building up the elevator and rudder:

20200714_224442.jpg

This be my hardwood joiner; I don't like wire joiners as they seem to flex rather easily. My joiner is 1/4" x 1/2" spruce. The disc sander makes getting a nice accurate scarf joint a snap:

20200714_224500.jpg

I will scarf the hard(ish) balsa stock to the 5" length of spruce joiner before butt joining the end result to some lighter 1/4" sheet pieces to form the whole elevator assembly. The spruce is a lovely hard mount point for control horns. It takes less time than you might think with the sander.

I will do a similar assembly on the rudder; a 3/4" wide "leading edge" of balsa, scarfed to a short hard section made from a sandwich of 1/16" ply - 1/8" balsa - 1/16" ply (the balsa is there to receive a hinge).

Onwards... slowly...

Martin McIntosh15/07/2020 11:31:29
avatar
3472 forum posts
1216 photos

Yes, those ones.

I am going to take my model up this afternoon. Hope I have enough clearance on the wheels which only protrude 1/2".

Robert Welford15/07/2020 12:10:40
205 forum posts
4 photos
Posted by Nigel R on 13/07/2020 10:05:36:

20200710_142018.jpg

Nigel - I'm probably missing something here, but couldn't you rotate the throttle arm on the carb so the linkage is above the engine mount. This looks as if it would give you enough room even for a link/ball-ink if you made an appropriately sized hole in the firewall.

I recently finished putting together an Acrowot XL with a 3w 28i petrol. The reason for using this engine is it's both powerful and very easy to start.

Anyway on trying to start the engine in this airframe it would not start easily - lots of head scratching! In the end I found that the linkage to the choke servo was fouling the firewall and thus didn't close the choke fully.

Nigel R15/07/2020 13:03:56
avatar
3987 forum posts
722 photos

With the arm on top and pulled back at full throttle, there was little clearance to the firewall.

If I was using a solid pushrod I could have cut a girt big ole in the firewall, but, I was intending on using a cable. As per previous post I figured it was probably six of one when comparing making an extra support for the cable an inch or so back from the firewall, vs knocking up the bracket and rocker arm.

Martin McIntosh15/07/2020 16:20:16
avatar
3472 forum posts
1216 photos

Flown it and very pleased indeed, straight as a die and just three clicks of up so I must have done something right.The only snag was that the pressure feed from the silencer kept falling off despite a very strong fuel clip round it, but easily fixed. Tried without pressure but the motor quit when pushing down from inverted due to the low carb.

Way too much aileron throw but since I was using a lot of expo I hardly noticed. Loads of power as expected and on a stall test it did not drop a wing. Landings were a doddle, even the dead stick ones.

Why do you not simply use a wire pushrod on throttle as I suggested? You would then not need the bellcrank and the wire would not require any support.

Nigel R15/07/2020 16:55:17
avatar
3987 forum posts
722 photos

"Flown it"

yes

As to the bellcrank and wire, it's sort of done now, I don't see a lot of point revisiting the arrangement... next time maybe I'll do it different.

Edited By Nigel R on 15/07/2020 16:55:43

Martin McIntosh15/07/2020 17:03:33
avatar
3472 forum posts
1216 photos

Thanks, I think that my heart has at last slowed down.

I may post a thread to see if anyone has any bright ideas on how to fix a windshield to polyester covering. I need to be able to operate the switch so a canopy is out of the question.

Nigel R15/07/2020 19:46:40
avatar
3987 forum posts
722 photos

Small brackets and small screws, I would say.

I'm planning on a canopy and canopy glue but I'm not sure how secure that would work out with just a screen.

Steve Dunne15/07/2020 20:02:46
avatar
170 forum posts
94 photos

Nicely done, Martin!

Great to see another Aeromaster in the sky.
They live a long time, too!

Steve.

Martin McIntosh17/07/2020 23:24:05
avatar
3472 forum posts
1216 photos

Back in the air today with a modified exhaust pressure nipple. Fine until the motor coughed so I landed, only for it to stop when the model came to a halt. Strange. On carrying it back I found that the spinner and cowl were swimming in fuel and the tank was empty. Found a huge hole in the fuel feed due to the pipe getting pinched between the motor back plate and mount. Easily solved and everything now hunky dory.

I reduced the aileron throws by removing the servos and re tapping the arms a couple of holes further in to take the ball joints. A little Tx tweaking and I now have the roll rate I want. I shall now concentrate on elevator travel and making sure that it will knife edge from one end of the field to the other.

The fairly strong slight crosswind today did not bother it at all when landing.

FlyinBrian18/07/2020 08:24:50
645 forum posts
4 photos
Posted by Bob Cotsford on 13/07/2020 09:51:59:

That sounds a good weight for a 62" bipe Martin. The GP Super Skybolt kits at 58" regularly came in at 9-11lbs depending on the finish and power plant, I've not weighed my WotsWot (50" but the quoted weight is 7lb.

The orange and white looks good together, you've done a very nice job trimming the paintwork and colour matching.

I think it is actually 52" span rather than 62" but 7/3/4 lb is fine - there is close to 1000 sq inches of wing!

Martin, your model looks great, make me want to build yet another.The Ferrari red against white is rather visable eh?and with the B&W checks underneath there is little chance of confusing which way up it is.

Was checking mine over yesterday, it has not flown for a while - found a/ the battery IR is high so when it is under load it drops voltage and the capacity is well down - replaced it with a 5 cell 1500 2/3 A (not AA) pack which seems to hold up.

The u/c mounting ply has got a bit fuel soaked now and the wood above it is going soft (must stop doing so many T&Gs - so looks like another refurb coming on soon

 

Edited By FlyinBrian on 18/07/2020 08:32:55

All Topics | Latest Posts

Please login to post a reply.

Latest Forum Posts
Support Our Partners
Sussex Model Centre
Slec
CML
electricwingman 2017
Advertise With Us
Sarik
Latest "For Sale" Ads
Has home isolation prompted you to start trad' building?
Q: The effects of Coronavirus

 Yes - for the first time
 Yes - but Ive bashed balsa before
 No - Ive existing projects on the bench
 No - Im strictly an ARTF person

Latest Reviews
Digital Back Issues

RCM&E Digital Back Issues

Contact us

Contact us

Magazine Locator

Want the latest issue of RCM&E? Use our magazine locator link to find your nearest stockist!

Find RCM&E!