bt dh mosquito

[chris meek 1]

https://youtu.be/udQ7RYM67DQ

 

https://youtu.be/udQ7RYM67DQ

 

Have used latex to make the molds for my crewmen. it's taking a while to set so I've connected up the rudder/elevator servos work nicely - I always like the stage on a build when the flappy bits start flapping!!

Edited By chris meek 1 on 06/11/2016 18:14:04

[chris meek 1]

A brief update, not much visible progress over the last few weeks - the first molds for the aircrew didn't work out too well. I put them in the oven to speed up the setting process and the result was that they didn't take the shape very well - they were also a complete p i t a to separate from the clay masters. When I filled them with foam the best result I got was half a head that looked ok with the other side a complete mess. will have another go at some point. Have also been tinkering with the tail end - made up the steerable tail wheel and connected it up before adding a bit of scale detail, now working on the tail cone to make it removable so I can get to the rudder and elevator linkages if I have to!! all small jobs that take an age to complete, but might as well do them now!!

[Martin McIntosh]

Sorry, but I do not understand what you are trying to do here. Do you mean the spinners, not airscrew?

[Kevin Mander 1]

Reading this thread with interest, I have the BT Mossie 71 plan and parts, next years project, after the FW190 that is, mine will be electric power, have the motors and such but looking at the retracts at the moment, not sure what to do, air or electric ones. The brown paper covering is interesting, I remember Chris Golds I think using it on his scale projects, anyway great to see your efforts, cheers.

[Danny Fenton]

Hi Martin I think Chris is referring to the aircrew he was molding in latex.

I think you may have trapped air in the mold. Try using a different casting solution, such as PU resin, fill your mould about a quarter full and then seal the mold. Tumble the mold while the resin sets, this will leave a layer of resin on the inside of the mold. Then once set remove from the mold. If you have made the subject too fragile it may not be possible to extract the casting. If that is the case then you may have to make several molds of the parts, torso, arms etc. I used this tumbling technique to cast scale wheels ,a exhausts and dummy engine cylinders. I did use Silicone rubber for the mold not latex.

Cheers

Danny

[onetenor]

Make your moulds solid and in two halves with a joint line going across the subject i.e from side to side giving a front and backhalf Here is how. 1) make two matching ply or balsa boxes to give about 13 mm ( 1/2 " ) clearance from the size of your pilot and as deep as he is front to back

2) Using Plaster of Paris or moulding plaster after cutting a piece of the thinnest cling film you can find to give about 1" clearance across the box. Mix a nice creamy consistency of the plaster and half or just over fill the box

3) Lay the cling film over the open top and press on it till it touches the surface of plaster. Then take the male mould ( figure of the pilot ) and press it into the plaster with the cling film as well until the plaster is half way up.Pull the cling film in so it touches all round the model. Allow to go off to a stiff consistency ( very quick) then pull the cling film down flat Gantly .half fill the other box with a firmer but still soft mix on top of which lay another piece of cling film an quickly bring the two boxes together lined up with each other and clamp together or weight down . Roughly wipe away the excess .

4) Allow to dry . 24 hrs is best then separate the boxes .May need to run a knife round the edges and using the cling film to help lift out the model.You should now have two halves of a mould .Allow to sit somewhere warm for a few days then dope, varnish what have you all the inside surfaces a few coats as well as the the joint faces which you have sanded level to get rid of any grooves etcYou can now mould solid or half and hollow ,LATEX ????figures.. The latter by the pour and roll technique.DON'T forget the release agent . If I am teaching Granny etc I apologise Ragards John

[onetenor]

Make your moulds solid and in two halves with a joint line going across the subject i.e from side to side giving a front and backhalf Here is how. 1) make two matching ply or balsa boxes to give about 13 mm ( 1/2 " ) clearance from the size of your pilot and as deep as he is front to back

2) Using Plaster of Paris or moulding plaster after cutting a piece of the thinnest cling film you can find to give about 1" clearance across the box. Mix a nice creamy consistency of the plaster and half or just over fill the box

3) Lay the cling film over the open top and press on it till it touches the surface of plaster. Then take the male mould ( figure of the pilot ) and press it into the plaster with the cling film as well until the plaster is half way up.Pull the cling film in so it touches all round the model. Allow to go off to a stiff consistency ( very quick) then pull the cling film down flat Gantly .half fill the other box with a firmer but still soft mix on top of which lay another piece of cling film an quickly bring the two boxes together lined up with each other and clamp together or weight down . Roughly wipe away the excess .

4) Allow to dry . 24 hrs is best then separate the boxes .May need to run a knife round the edges and using the cling film to help lift out the model.You should now have two halves of a mould .Allow to sit somewhere warm for a few days then dope, varnish what have you all the inside surfaces a few coats as well as the the joint faces which you have sanded level to get rid of any grooves etcYou can now mould solid or half and hollow ,LATEX ????figures.. The latter by the pour and roll technique.DON'T forget the release agent . If I am teaching Granny etc I apologise Ragards John

[chris meek 1]

Thanks all for the advice, much appreciated. john not teaching granny at all - never done this before so all advice gratefully received! I've decided to put the aircrew on the back burner for now and get the airframe finished first, although when I do go back to them I think I'll make up a new set of molds for them, either plaster of Paris or silicone rather than the latex ones I started with.

Anyway, plenty to be getting on with - anyone got any advice on making your own exhausts for 2 strokes????

All the best

Chris

[Denis Watkins]

Many avenues to work new silencers Chris. The simplest would be copper, easy to work and solder and numerous shapes and pipes already available from DIY shops. Aluminium is lightest, easy to work, but is best welded at an alloy wheel repair centre. Or modify the existing silencer, splicing in where needed and then weld

Edited By Denis Watkins on 25/11/2016 12:20:26

[chris meek 1]

Posted by Denis Watkins on 25/11/2016 12:19:19:

Many avenues to work new silencers Chris. The simplest would be copper, easy to work and solder and numerous shapes and pipes already available from DIY shops. Aluminium is lightest, easy to work, but is best welded at an alloy wheel repair centre. Or modify the existing silencer, splicing in where needed and then weld

Edited By Denis Watkins on 25/11/2016 12:20:26

Thanks Denis. was thinking of trying copper - want to keep the silencers within the cowls. Are there any rules to keep to over minimum size etc or is it more like make one and see how it works? On the plans it shows what looks like fairly simple cannister exhausts but they look a lot smaller than the stock ones..

[Merco 61]

Hello Chris,

A pic of the silencers for my Mossie,1/16" brass,silver soldered,quite heavy at 3 ounces each,but effective on OS 25 FSRs.Quieter than standard silencer and the silicon outlet tube will help further.As per plan.Also a pic or two of the UC,again as per plan.More on the album.Hope this helps.

[chris meek 1]

Posted by Merco 61 on 30/11/2016 12:56:48:

Hello Chris,

A pic of the silencers for my Mossie,1/16" brass,silver soldered,quite heavy at 3 ounces each,but effective on OS 25 FSRs.Quieter than standard silencer and the silicon outlet tube will help further.As per plan.Also a pic or two of the UC,again as per plan.More on the album.Hope this helps.

Hi yes it does help - nice to see that it's possible!! any more photos of the exhausts would be appreciated.

Progress has slowed, have just about sorted the tail cone out - not perfect but it's ok when viewed from a distance and is removable so I can get to the linkages if needed. Anyway as I keep reminding myself, as long as at the end of the build I have something that has a passing resemblance to a mosquito I'll be happy. Although I may have developed a slight case of Mr Fentons scaleitis, there's always something else to add that won't be visible, but I'll know if I don't add it!!!

[DIGGER]

Be very careful with the weight , someone I know wanted his Lancaster to look very scale, now it's to heavy to fly and has ended up with a very expensive and large car.

[Denis Watkins]

As you have found Chris, heavy thick walled silencers are the quietest, and as you pointed out, weight is our enemy. If the weight benefits the Moss then all well and good, but there is still the possibility of shaving off some meat from the silencers. Great job so far and we are all following with interest.

[chris meek 1]

Tail end finished apart from getting a coat of primer.

[chris meek 1]

Have to say, I'm really impressed with the service from slec. Ordered a new supply of wood from them on a Saturday morning - arrived with me the next Tuesday. Now I should have enough for the wings. I've spent time working out the retract operation so have made some slight alterations to some of the wing ribs to fit the servos in. They're behind the c of g slightly but I think with an onboard glow and battery right behind each engine it should balance out. The plan shows the spars made up of 1/4 inch balsa but I've read somewhere that some bt mosquitos have had wing failures in flight, so I've substituted them with spruce. Next step is setting out the spars and ribs for the first wing - will add photos as it goes together.

Chris

[Martin McIntosh]

I expect that you have seen the photo in the back of the July mag. Worth keeping in mind re strengthening. Another reason why I shelved mine.

[chris meek 1]

Start made on the wings, nearly finished the webs connecting the upper and lower front spars. Next job will be adding the leading edge then it's on to the upper sheating.

[onetenor]

I would put in a short spar, up to the,4th rib with another 1/8 th ply dihedral keeper .I had a set of wings of similar construction clap hands. so during the rebuild. not much damage luckily .so I did this . It survived anything I could throw at it Including a cartwheel after a signal loss from a nearby lightning strike.. Luckily again she was low on the landing approach. Coming in because of the storm.

[chris meek 1]

Just after posting the last photo I had another look at the plans, turns out the upper and lower spars are both made up of 2 quarter inch square strips for the first 7 ribs.... Obviously I realised this after all the glue holding the spars into the ribs was well and truly set!!

Anyway, after setting to with a hacksaw and some files I was able to add the second strips to both spars and re did the webbing. Now on with the upper sheeting. Am toying with the idea of glassing the wings to add some strength to stop any 'clapping' moments.

[Martin McIntosh]

If that wing sheeting has not been glued on yet, I would seriously think of using some light but thicker balsa. I seem to remember that the plan states 1/16 only.

[Kevin Mander 1]

Hi Guys, Looking for some advice here, I have the plan/pack for the BT 71 inch Mossie, the intention is to electrify it using the set up as per the TN one that is of similar size, has anyone built a BT one with electric power? where is the best place for the batteries? I have not seen the TN plan at all being out in the colonies its hard to source these things, the cost of the TN parts is quite high and the freight cost is an arm and a leg, but is this the better option do you think? any help/advice would be most welcome, Cheers. Kevin.

[Martin McIntosh]

I posted a long time ago on my Mossie build thread that I attempted the BT 81" but found the fuselage construction difficult and potentially very weak and the wings to be very flimsy indeed, so scrapped it. I believe that TN tried one and came to the same conclusion. Some `details` like the nacelle outline were missing from the plan as you were expected to buy the GRP mouldings.

I would have thought that ordering the TN plan and canopy should not be too expensive. The rest of the bits are fairly easy to make.

[Kevin Mander 1]

Looking at the plan I see what you mean about the fuz, it relies on the bolt on wing to hold it securely from what I see the TN one has plug in wings, what I will do I think is order the TN plan and have a good look at that, then see what parts from the BT one are usable, I have the TN 62in Spit to build next so there's no real hurry, we are only a month from spring here and the better weather, I cant believe its almost August, unreal!

[chris meek 1]

Progress has slowed with it being summer again... Have been sorting out the flaps, lots of bending piano wire to the shape on the plan, once set in the flaps there's loads of testing them in place to check the geometry and then adjusting slightly to fit. Instead of making up the hinges out of paxolin as shown on the plans I used pin hinges set on an angle.Once I was happy with the fit of them I added the flap Shrouds. I plan to epoxy the paxolin push rod in place on the wire, if it won't work I'll end up making one up from copper and soldering it (carefully!) on.