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No More Mystery - it's a BipaBlast 2


andy watson
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Still no one has got it.

Here it is with wings roughly  in place (I think the top wing shoud actually be further forward, but it is just sat in place.

And another angle:

There are no ailerons, rudder or elevator in place. These are all built from solid wood sheet (well the ailerons are triangular TE stock, but you know what I mean). Little thought seems to have been given to keeping the weight down! The cockpit and canopy has also been ommitted for now. Also it might help to know there are some pretty hefty wing caps to add- almost semicircular.

Actually the whole kit has been a bit of a pig in some respects. I have decided I hate foam wings. You cannot get them to match perfectly like nice balsa ribs and sheeting. The join is clearly visible. In fact the join is clear whereever the foam pieces are used along the turtle decking too. I am not sure how much filling will be needed, but the thin veneer will limit my ability to sand it smooth. The instructions have been better than that in many ARTFs, but not by a huge amount. The plans are a halfway house between a proper set of plans and a sketch. Both the plan and instructions take quite a bit of thinking about- luckily these days I have the experience to work it out. I am putting the fixings in place for the interplane struts. These also involve digging huge lumps of polystyrene out (a very messy job) and glueing wooden blocks into the wing. Although the positions are well marked out there is no indication of depth- I have guessed the blocks are sunk to the level of the skin at each end- but that leaves a raised section of wing in the middle. This seems to be the logical place, but maybe I am out by several mm. Top and bottom might make it a snug fit if I am wrong- a few details on the plan would help a lot, since there are no photos in the instruction.

Having said that it's a nice looking plane. Short and chunky. I have a 3HP petrol engine for it, so hopefully it will have enough oomph to do it justice. I do have some questions about completing it though.

1) No one has answered my earlier question about the best way to run servo wires down a foam wing.

2) What are my options for covering it? I don't really want to use film as I am hoping to paint it, but I am worried about sealing the wood- I guess sanding sealer would dissolve the polystrene through the veneer? Unfortunately not sealing it could cause warps.

Edited By andy watson on 20/03/2012 20:58:43

Edited By andy watson on 20/03/2012 20:59:47

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Andy,

Regarding covering - as long as the veneer isn't cracked or split

it should take a coat of unthinned sanding sealer in preparation for poly-C

without risk of melting the foam underneath. I've never had a problem

doing this (but there are apparently reports of it happening).

If you're worried you could try oil-based polyurethane varnish

instead of cellulose sanding sealer. I gave this a trial recently & it seemed fine.

Anything water based straight onto veneer will ripple it as you say.

 

To make a channel for servo wires one method is to use a sharpened

piece of metal tube to bore out the foam & another is to use a hot screwdriver

but I haven't tried these.

I did once cut out channels from servo boxes to the centre section, fitted the

extension wires & then refilled the channel with balsa strip & sanded smooth.

Wires are trapped forever of course with this method! - but it worked.

 

 Same as Alanyes

 

Edited By Richard Wood on 20/03/2012 22:12:49

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Cheers guys,

I think that gives me some ideas. The wires sound straightforwards then.

The covering is a bit more problematic. I might have a go at glassing, but it doesn't look like the easiest model to practise on. I might get some help from an expert who lives close by. However I do like the sound of the oil based varnish- presumeably through glass cloth. I doubt I can depend on the integrity of the veneer, so best not take chances with it.

Alan- this thread must be making you want to explode!! And just for info the incidence angles are taken care of with the mountings.

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Knew I'd read it somewhere:

Cellulose can soak through to the foam core if the manufacturer

has used cheap, thin veneer or has sprayed a very thin layer of adhesive

to fix veneer to foam. Thick adhesive can act as a block to the cellulose

reaching the foam core.

I'm fairly sure oil-based varnish won't attack foam or ripple the veneer -

best perhaps to try it first on scrap or an unseen areawink 2.

My idea though was to use the varnish instead of cellulose sanding sealer

as an initial preparation on the bare wood prior to using Poly-C & tissue

or glass cloth.

Hope this helps.

Blast .....??

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Got you- you were suggesting the varnish as a replacement for the sanding sealer, rather than as a replacement for the epoxy in glassing, or the water based poly C varnish.

Just a question though- why layer the poly C over an oil based varnish. Since I have started with the oil based is there a reason not to just use that for several coats? Is it more brittle etc?

Andy

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With veneered foam wings/deckings It possibly depends on the type &

quality of the veneer. It may well be fine to use water based varnish on

sheet balsa - certainly worth a try.

I once left an untreated veneered foam wing in a damp garage overnight

& found the veneer had absorbed moisture & was very badly rippled.

Continuing with the oil-based varnish instead of Poly-C might work ok -

I haven't tried this method to complete a finish - only as an experiment

on a piece of sheet balsa in place of the initial coat of cellulose sanding

sealer.(Cellulose vapour gives me a very bad headache!)

Could be worth a try to use varnish to completion - but not sure how

well it would sand to a flat finish after several coats. Poly-C is certainly

very good in this respect.

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Well Alan was the auctioneer in charge of selling it to me- so he is disqualified! Actually he ought to get a prize for remembering one of over a hundred lots at each one the club does.

Luckily I am on holiday for the april auction, so the silver tongued devil will have to leave my wallet alone this time.............although I do need a few servos......!

Hmm, silver and blue does sound nice! I want a colour scheme away from the usual drab camoflage I seem to be drawn to!

I will have to have a word with the mods to change the thread title.

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Even remembers the price!

It was £30 and I had to promise to build it, not flog it on ebay or similar. I didn't really want it, it's not really my thing, but things get to a certain price and you just can't say no can you?

I haven't really liked the kit- I am taking a real dislike to foam. The parts don't fit to the same tolerances as balsa, and it feels like I have only stuck about 8 pieces together to make the thing! But I am taking a liking to the end result- I think it's a nice chunky little (actually slightly impractically big again!) plane.

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  • 3 weeks later...

Whatever you do make sure you cover the foam wings before painting. I would use tissue

and dope then a barrier coat of water based PU followed by paint finish.

A paint finnish on uncovered veneer will be hopelessly heavy and liable to splitting.

proctor

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get jonesy or Alan grebo to show you how to glass it--properly, some of the foam and bone models these 2 guys have glassed are beutufull, and the are lightweight glassers par excelance, tissue is yesterdays tech, its brittle, smelly, and the wife will kill you, then rub back, prime, and paint, but me? i would film it, but for many, thats too dear, and the biperblast will use a lot of it

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  • 4 weeks later...

Progress update:

Well there hasn't been any for a couple of reasons.

1) I have given up smoking, and my workshop is somewhere I used to potter around in and have a fag. Because of this I have been keeping away from the garage altogether.

2) I have to be honest- I have lost a lot of motivation for it. I have the plans for a ME 163 that is burning a hole in my build list, and I am about to get a seaplane delivered to me that should be interesting. I am really tempted to put it to one side, but I don't know if I would ever pick it back up again.

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