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Member postings for Martyn K

Here is a list of all the postings Martyn K has made in our forums. Click on a thread name to jump to the thread.

Thread: 2018 Mass Build - Voting Thread
23/11/2017 17:32:24

Here are the results of the 1st stage of the Vote. Scoring as usual is 3 points for 1st choice, 2 for 2nd, 1 for 3rd.

Only 20 people have voted for a choice of 17 model groups...

Top 3 are Grumpy Tiger, 17 points, Ghost Rider 14 votes, CAP/Dalotel combo 11 points. More details on the votes below

We normally go to a second vote but assuming those who voted for one of the top 3 models actually build it then this would probably only give a maximum of 12 participants (for the top 3 models) of which historically/statistically only about 1/3 actually really take part that leaves err 4 builders. Not really a mass build.

I suggest that this years MB comprises of the top 3 models unless you want a second vote to run over the next 7 days. Answer quickly - we ain't got much time for discussion..

2018mb results 1.jpg

We'll make a call on this on Sunday 26/11. Is that OK? If you are categorically NOT going to build one of the top 3 please let us know now. No problem its helps get a better understanding.

Personally, I am still happy to build a Dalotel - possibly scaled up for a bigger engine.

Martyn

Thread: Mama Mia!
23/11/2017 09:16:18

Hi David

I was very tempted to slim the fuselage down. As you say its very easy to lose 30-40mm in width. However, to me that is not what Classic Aerobatics is all about. I think if you build a classic, you should stick to the outline at the very least - including any warts you may not like. When you deviate then quite simply, its no longer the aircraft that the designer intended.

Anyway, last night I moulded the canopy. I gave up with the PVA release agent and reverted to good old fashioned beeswax. Several coats and lightly polished smooth.

Canopy layered from 60g Carbon fibre in 5 longitudinal strips plus 1 additional edge reinforcement and two traverse bands and a little extra reinforcement where the inlet and outlet orifices will be.

canopy2.jpg

and after leaving overnight to set but before the resin was fully hard, I carefully removed it from the plug

canopy1.jpg

Its still a bit floppy so its gone back into the plug and is now sat on a radiator for a couple of days for the resin to fully harden. (Hopefully)

Huge sigh of relief was heard 4 miles away.

Martyn

22/11/2017 15:22:08

Too much power is never enough. SO I have been told. laugh

22/11/2017 15:16:00

Thanks John

Sorry Nigel - your other point. I don't want to make this model too much out of character. It would probably take a petrol engine and I did consider a 120FS and a bigger prop. I am limited though by the size of the undercarriage retracts. 14" is about the biggest diameter I can go to with the current setup. If it too revvy on a 14x8, then I'll try a 14x10 or a 13x10.

Martyn

22/11/2017 15:07:20

Hi Nigel

The Webra 91ABC is actually BNIB but about 30yo. I bought it last year for the princely sum of £70. I still haven't run it. When I get the manifold, I'll bench run it and experiment to get a good combination.

I am hoping to get 10k rpm using a 14x8 prop. I have a Graupner 90 sized tuned pipe for it, Anything in that area should be OK though

Martyn

22/11/2017 14:59:23

Thanks Geoff

My daughter would probably shy away at that although I wouldn't dare make her mind up for her.

I have never been really happy terminating pushrods to the wire bits. Especially in this case they had to be done in situ or risk damaging the wood trying to fit them afterwards. I think (hope!) they will be strong enough though. Not especially neat, but secure.

I tend to leave the covering until last. The next big job will be to glass the fuselage then I'll get the sealing iron out.

The fus length now the cowl and rudder is attached is just less than 2m It dwarfs my Aurora which I thought until now was pretty big

Martyn

22/11/2017 14:27:36

A bit out of step.

The wheel wells have been a bit of a pain. I used a 3" dia jar as a mold and wrapped damp 1/16 balsa around them and glued them directly onto a piece of 3mm balsa

That worked really well and I was certain I would get round wells.

wheelwells2.jpg

I didnt get them . They are not too bad but still look decidedly angular in places

wheelwells.jpg

The canopy has been fun

plug3.jpg

 

 

 

The canopy is a glass fibre item that contains the tuned pipe.A foam core cut on the bandsaw then covered liberally with three dollops of plaster of paris. What a mess. Great fun. When dry, a surform was used to shape it then finished with sandpaper. About 5 coats of polyurethane (not water based) varnish to seal it. A very liberal coating of Beeswax and a plug was produced using Fibre Glass Tissue and Mat

plug4.jpg

This has turned out quite well but unfortunately the plug got damaged when I tried to pull it.I am also having a problem with blue PVA rel;ease agent not flowing very well - or rather condensing into clumps after application..I darn't try and make the final canopy unless I am sure it will release OK.

cowl.jpg

The cowl is again fairly straightforward and formed from thick balsa sheet triangle etc and then carved to shape.

My daughter came round at the weekend and this is what is currently looks like.

barebones.jpg

Coming along nicely I think. I need to get a manifold for the exhaust next.
 
More to come.
 
Martyn

Edited By Martyn K on 22/11/2017 14:50:40

22/11/2017 14:19:16

The wing was fairly straightforward except it didnt fit either my building board or my bench.. Not the span, but the 20" root chord..

wing3.jpg

Apart from the use of Depron ribs and additional ply reinforcement around the retract bay its fairly straightforward. Again - its not complex, just big

wing4.jpg

To make sure that the TE was straight. I aligned it vertically. The plan shows two separate halves joined with FG bandage - as you would use for a foam cored wing. I have used a 3mm ply dihedral brace

The fus sits in the gap at the LE - you can see the 1/16 ply doublers for the UC blocks here

wing5.jpg

Sheeting the wing was very straightforward, surprisingly not that much was used as many of the cutoff pieces were reused

wingfitting.jpg

Wing fitting was entertaining. It was at this point I spotted another error on the plan. The LE gap  for the fus fitment was about 12mm too wide. So additional thick ribs were added to fill in the gap. There are lots of errors on this plan. None insurmountable but it looks like Joe passed the model to the draughtsman and said "draw that". Just fundamental errors all the way through where basic reinforcement is missing for example. I gather that this was not as the top of the Bridi 'Must Fly' list.

ailerons.jpg

The ailerons were laminated from 1/2 and 3/16 sheet balsa (seriously), glued then planed to shape.Very satisfying when you can plane accurately like this

 

 

ail-servos.jpg

Aileron servos have been exercised and I have fitted them internally. One thing I did notice was that they tended to flex the ribs so the two adjacent ribs were linked with 1/8 balsa which stiffened them up nicely. The servos are screwed to a ply backing plate that is glued to the ribs.

bellypan.jpg

The wing bellypan area was fitted with wing attached. It uses a M6 bolt at the front and 2 x M4 steel bolts at the rear. Needs quite a bit of interpretation regarding wing mounting plates etc. The front bolt is guided into place down a length of 12mm internal diameter brass tube. Otherwise it would likely get lost in that bellypan area

More to come

 

 

Edited By Martyn K on 22/11/2017 14:48:31

22/11/2017 14:05:08

errrr. Apologies. I had forgotten I had started this blog. Spotted it yesterday while I was looking for another build blog.

So there is a bit of a catch up.

The fin. Its big - very big for a classic F3a. Quite simple construction and built directly off the plan except I have used Kevlar cloth as my hinge material

fin3.jpg

That's a 300mm rule to give some idea of bigness.

As expected, there were no real problems with this, a simple cut and glue exercise.

The Fus - despite my misgivings was almost built as per plan. It is still stupidly wide and boxy but I have increased the depth of the 1/6 ply doublers so that the whole of the inner fus to behind the wing has extra reinforcement. the plan only shows a 30mm or strip which seems to be asking for trouble.

fus3.jpg

All the formers except the firewall are built up. The upper side has a 1" Triangle which doe its length is in 2 pieces. I am using harder wood at the front - lighter at the rear which as you can imagine caused a few problems when I pulled it together at the rear.

fus2.jpg

Lines up in the jig and overhanging front and back.. Note the tailplane has been aligned level at this stage with the top of the fus. All very simple and typical build method of the boxy models of the era.

fus.jpg

Now with the 12mm top deck added and the fin and tailplane fitted.

fin.jpg

I added extra triangulation around the side of the fin for strength but also to improve the airflow over this area.

pushrod.jpg

The elevator push-rod is a length of 6mm C/F tube with two M3 steel push-rods epxied then bound with Kevlar thread and more epoxy. It seems quite stiff strong and light.

horns.jpg

These terminate with some decent horns on the elevators. The rudder will have a closed loop cable system.

More to come

Thread: Pilot RC Sbach 100cc
21/11/2017 09:22:25

A bit intrigued. On the Firewall to Firewall box junction, does the balsa triangle strip actually add any noticeable strength or other structural benefit or is it there for aesthetic reasons? I would have thought that aluminium angle strip and multiple bolts would be where the strength lies.

Anyway.. Watching this. I love to see how these things go together

Martyn

Thread: 2018 Mass Build - Voting Thread
19/11/2017 21:43:43

bump

Thread: RAF's Finest Biplane? Hawker Fury MkI
18/11/2017 11:42:34
Quote. Even my hero Brian Taylor enlarged tailplanes.....

Nooooo. I am mortified
18/11/2017 11:26:07
Hi Chris
Excellent work. Thanks. How does the 3v westbury compare with K1930 around the cabane and upper wing location? That looks like it is different to the plan as well.

KCs point is very valid. The correct longeron length can be calculated using pythagoras using a generalisation that the rear fus sides are straight
17/11/2017 17:43:38
Been trying to overlay but failed miserably despite cropping the plan and 3v to the same physical dimensions. I'll try again later but at first glance, Dennis plan looks a little more porky.

Edited By Martyn K on 17/11/2017 17:44:39

14/11/2017 18:19:56
Yes. The inaccuracy mention was the bit that bothered me as well. Implied it was mainly around the fus area

Martyn
Thread: The 2018 Mass Build Ideas thread
13/11/2017 20:04:34
Thanks Jack, but i think its too late for this year. I would be intetested as i fly gliders but i don't think we would get many subscribers to the idea. The fact is that no one suggested a glider is a good indication. My experience with the glider build blogs i have done is that there is little interest. Most people here want powered sports fliers and that was reflected in the nominations. Not my choice and personally I would prefer a higher performance model but this generally is not what people want here.

Martyn
Thread: RAF's Finest Biplane? Hawker Fury MkI
13/11/2017 17:46:48
Posted by Danny Fenton on 13/11/2017 17:45:49:
, but if you dont watch the grams next thing you know they become kilos....this is meant to be a scale model not a sport model

Cheers
Danny

Very true..

Martyn

13/11/2017 17:24:37

Just had a quick read through the articles. Would appreciate others views on this. I am certainly looking forward to making a start

Best wishes

Martyn

13/11/2017 17:00:52

Hi Chris

See the previous posting for the download link.

G10 is a very thin fibreglass board sold by Mick Reeves and can be used for skinning. It gives a very hard edge and helps maintain stiffness. A posh and possibly better way of doing what I want to do and possibly lighter but I can use PVA to glue spruce rather than epoxy needed for G/F.

Martyn

13/11/2017 16:45:31

Hi Richard,

 

Another forumite has very kindly sent me copies of the articles. Thank you Jose Luis..

 

Download from HERE

 

Best wishes

 

Martyn

 

 

Edited By Martyn K on 13/11/2017 17:03:43

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