New Scratch built fibreglass/carbon mono build

[minigazz]

Argh, I have been having one of those days! This is the second time I have typed this and solidworks was being an absolute swine earlier too. Nothing seemed to be going my way with the boat work either so I have stepped back and left it for today. I am currently trying to assemble the tray which the hatch will sit in on the deck of the hull - this is proving to be a bit of a pain and shows a lack of planning - I will get through it though and sort it out! I need something like your cigarette hull top you are making Mart, but because the compound curves and planked frame its a bit awkward.

When you say split the mat in half, do you mean like when you split tissue paper into its layers, or just plain tearing or ripping? I couldn't work out what you meant cause I didn't think you could thin mat.

[martno1fan]

Hi mate yes mat can be split just like tissue paper just start at one corner and once it starts peel it carefully into thinner layers.450 mat can be split into 2 even 3 layers i know because i do it regularly,can be tricky sometimes but can be done.
Dont worry we all have off days m8 ,you will sort it.If you look how i made the hatch opening i made a frame arround which makes a nice lip inside or will once the parts made and trimmed.You could maybe do similar or you could use thin plywood glued under the opening to form the lip,do it in two halves and it should work fine.
Mart
ps dont beat yourself up we all make mistakes keep at it.

[minigazz]

Yer, just got to get things in perspective! I think I have wrapped my head round it now so I can go and tackle it tomorrow! How badly does the CSM show through the cloth? I just really like the idea of really clean hulls inside as well as out. Im not expecting a great shine on the inside, just fairly flat more than anything. I really didnt think you would be able to split csm, the only time I have used it is repairing boats at my local rowing club though and that was just some left over from a halfords repair kit. Couldn't I just buy lighter grade CSM? I am considering making the hatch from a shaped piece of expanded polystyrene covered in car body filler because then I can make some really nice shapes without worrying about how the structure below will support it all.

Do you know how much of a market there are for reproductions of these hulls?

[martno1fan]

The csm shouldnt show through if you do it wet on wet but as your only making a small boat id suggest just making it in cloth,you can get thinner csm lightest is 100g which would work fine under 1 layer of cloth and save you some money should you wish to try it on your first one.Like i say do it wet on wet and save on resin and keep it light,the matt will form to the shape easier just be sure to tear the pieces and not cut or the fibres wont blend where youve cut.I usually tear off 3 pieces one for each side and one for the bottom, the edges need to be torn so the fibres blend into each other better ,cut edges wont do this and weakens the laminate.By the way dont use polystyrene get some of the yellow insulation foam called cylotex its usually covered in foil,it wont melt when covered in resin ,sands reasonably smooth and is easy to work with,id sand it then coat it in sanding gelcoat or gelcoat mixed with talc to make it sand easier (talc can be found at glass suppliers its cheap) then sand smooth and wax it.You can pick pieces of this foam up free from most building sites even full sheets hehe,dont forget to ask though lol.Cant help you with a market for your boats but if you build it well and it runs well then people will buy them.
Mart

[minigazz]

Today I progressed a bit with the hatch tray. I cut into the ribs to let in the hatch tray with a dremel - unfortunately it scorched the wood and it was pretty difficult to clean up. In the end I managed this with a stanley knife blade, probably not the safest method but it seemed to work followed by a little sanding. Initially I was going to make a ring to make the sides of the tray using laminated 2mm ply bent around a former, but I thought they would warp in places and could end up not being perpendicular to the base of the hatch tray. In the end I decided to go for a 9mm balsa block (made of 3x 3mm sheets laminated) cut to form the sides. To ensure that the sides were exactly the same I double sided taped them together and cut them at the same time. I then made a base for the tray out of 3mm ply which slotted inbetween the ribs. This is all clamped together at the moment and the glue is currently drying!

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I think I will use try the two different methods I think, it shouldn't be difficult! How many layers of 200g cloth would I need for this thing? It is 400mm long near as damn it. I have used that foam before actually, its good stuff, I used to make rc hovercraft and I remember the pink/yellow foam didn't need nitro fuel proofing like the white expanded polystyrene does.

[martno1fan]

Id try 2 layers to start with and see how that turns out,be sure to leave it in the mould a good 24 hrs to fully cure,i actually leave my hulls in for 3 days this avoids any warping due to shrinkage,if you do demould it before this time then at least sit it back in the mould afterwards to keep it as straight as possible.
Mart

[minigazz]

I just went out to the shed to take the clamps off to see how it was all looking and instead ended up doing more work at 00:15, nevermind! I sanded the balsa surround of the deck tray to a smooth curve to follow the shape of the ribs and then decided to add a solid bit of balsa at the stern to give shape to the deck as it wont have all the ribs in between which would result in a flat rather than a nice curve. Tomorrow I will start the deck planking. I am not looking forward to it at all, getting it all to stick is going to be a nightmare. I am contemplating cutting the 2mm balsa into ~8mm strips and planking it that way - at least then I will know each bit is stuck down properly. It may make sanding a little more difficult though.

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Two layers seems very thin! Would it not be like ply wood where you have to have odd numbers of plys or layers to stop warping?

[minigazz]

Just ordered all the stuff I need! Had a chat to some bloke at ECF too, he was very helpful! Apparently cloth doesn't laminate so well with polyester resin so I am going for 100g CSM with a top layer of either cloth or tissue - not yet decided which. I will use tissue on the mould which will allow me to see if i like the finish. The other alternative was to use epoxy resin, but it was around 4x the price and is less forgiving with your moulds as it is far more adhesive (which is why it works with cloth!). He also recommended PVA at least to start with so i ordered some just to play it safe. I also bought a respirator - maybe it'll stop me coughing all the time! It was all very expensive so I hope it works! It has spurred me on to get the plug finished now.

[martno1fan]

Of course polyester works with cloth its all i ever use,i wont use epoxy because its hazourdous to health,poly might smell but it isnt a health issue.Ive been building hulls for 3 years now and have a 100% good feedback on all of them.PVA is ok and will make it easier to remove from the mould but ive never had good results with it because your parts come out dull,id use it for the first part then forget it but thats me.
Mart

[minigazz]

Today I planked the right hand side of the deck working my way out from the centre. I decided to use ~10mm planks to help bend around the compound curves better. As I mentioned earlier I ordered my composites today, so I thought it was high time to clean out the shed! Not the most exciting job ever, but I found some interesting things like manuals for tools bought before I was born and have long since burnt out! Tomorrow I am out most of the day, but if I get time I hope to finish off the planking and begin sanding the deck to smooth out the joins between the planks. I will then varnish the whole thing and then prime it ready for pulling some moulds!

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I was told that polyester doesn't bond as well as epoxy which can result in de-lamination? It was entirely the cost in my case - I'd love to make it from carbon fibre because it looks so nice! Thanks for the advice Mart, its all helpful as ever!

[martno1fan]

The only way it should delaminate is if you dont do it right,for example if you add layers one on top of the other after each layer has cured,do it wet on wet and get all the air out and it will be fine.I only ever do one layer of cloth all my builds are csm with cloth on top plus carbon if im using any,but all my hulls are bigger and heavier so never had need to do layers of thinner cloth.Actually ive seen two epoxy hulls recently that came apart at the seam,carbon kevlar to be exact,i was asked to repair one and both had the same issue caused by hitting a good old fashioned polyester hull so epoxy isnt all its cracked up to be .
Mart

[minigazz]

Today I finished the planking, sanded it all off to form the shape (roughly) and then cycled to town and bought some varnish ready to coat the hull with. I then remembered I haven't done the strakes yet. I am really not looking forward to doing them and am not yet sure how I am going to do them! Balsa seems too soft to make them from at this scale and ply would be too difficult to shape well and consistantly. I am thinking they want to be about 4-5mm across and taper to a point. The spray rail brings a similar problem too and since I have already trimmed the side panels I won't be able to use the car-body-filler method. Any ideas would be greatly appreciated!

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Im pretty happy with polyester choice now! The accuracy required with epoxy when mixing if far greater too. The stuff didn't come today which was a little disappointing given it was supposedly next day delivery but never mind. They recommended varnishing before durabuilding - does this sound familiar?

[martno1fan]

Hi,you can get triangular softwood stock from most timber supplies to make your strakes,id suggest having a look at a few hulls to see how theyre done .
Ive never used varnish on my wooden builds,but you can use sanding sealer or thinned varnish to seal the wood before you paint,you could also just use a thin coat of resin ,if they suggested varnish im asuming it wont react with the durabuild.Im surprised you didnt get your stuff ,asuming you ordered before mid day it normally arrives on time.Plugs taking shape now,i might not be online much over the next week as we go away for a few days so ill look forward to seeing how you progress while im away.
Mart

[minigazz]

This is the fourth time of typing this! ARGH!!! Today I made the strakes and spray rail. I used 2mm birch ply cut into 2mm wide strips superglued onto the bottom of the hull. Once it stuck in place I carved them into a triangular profile and used car body filler to make the right shape. My fibreglass supplies also arrived today which was exciting! I am away now for a week, but when I return I will varnish the hull and make a start on the canopy! I might also have a go at making a canopy for my old yellow boat out of fibreglass as a test run!

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[Chenige]

Could someone explain the theory behind strakes. I would have thought they would go all the way back to the transom. I thought on my Electrified the boat runs on the rear strakes which end at the transom.