Scratch-built 15" CF Mono

[Jim Bob]

I got the bug!:buttrock: I decided to build my own. Waiting on a rudder. Sorry I didn't post pics during the build.

[calcagno45]

Looks great! But I think my gorilla hands would be too big to work on that...

Whats the powerplant?

[Jim Bob]

Ammo 24-35-4875. I will run it on 2s.

[Jim Bob]

I got the rudder shortly after posting the picks and she had the maiden voyage today. It is fast. I need to put ride plates on it to help with the stability. I will post a video soon.

[ace028]

Thats pretty cool, so you built the hull too huh? Looks pretty nice, can't wait to see some pics.

[Jim Bob]

Yes I did. Here are some pics of the "plug" and the molds.

[minigazz]

Hey, just stumbled on this - just what I was looking for! This summer I am going to attempt a very similar project. Is the best approach for building the plug using a wood over frame construction or would you use another method if you were to do it again? I.e. solid wood or even foam with a coating on it? Any vids?

Thanks

[G1ST]

Have you thought of offering the hulls for sale?
I'd be interested in one.
Greg

[HibridO]

Post a vid of the beast running.

[Jim Bob]

I believe wood over frame construction is best.Be sure to use gel coat to coat the plug and then sand and buff to the finish you desire. The more time you spend on the positive(plug) the better your negative (mold) will be , and will require less finishing in small tight corners. I used paint and the resin attacked the paint on my first attempt.

[Jim Bob]

Greg,
I originally intended to make some to sell but after all the troubles I had with mold release I gave up on that idea. The original deck mold got trashed when a part stuck and I haven't made another one yet. I haven't run this boat in a while. I made a new strut and rudder and it doesn't handle the way I would like, so it has been on the shelf since I built my little rigger. I may build a new rudder and take it out for a video shoot.

[minigazz]

Thanks for the tip, I wouldn't have known that! Is it a special type of gell coat? as i know that it is quite thick usually and would be quite difficult to get a nice finish with. How did you go about joining the two halves of the hull? Do you know of a good way to eliminate the lip you end up with?

[martno1fan]

You can get special sanding gelcoat,this is ideal for plugs because it sands easier than normal gelcoat.If you wish to make seamless hulls then you need two perfectly matched moulds that you then bolt together with the two parts in.You use a resin bog mix to glue the two haves together.When set take apart the two moulds and you should have a joined hull that will just need the seam wet sanding after removing most of the exess resin that squeezed out after joining,it should just snap away.You should then glass the seam inside where you can using glass tape.Sounds easy but if it were everyone would be doing it hehe,that said a lip or a shoebox join is actually stronger as theres more gluing surface.
Mart

[Jim Bob]

Martin,
Sanding gel coat will not produce as nice a finish as using regular gel coat due to the filler in the sanding gel coat and regular gel coat is not difficult to sand. If you use regular gel coat and sand and buff it to a perfect finish it will make your mold much nicer. it is almost impossible to get into the inside corners of a mold this small and buff them. Your method of making a seamless hull is spot on, however...this hull is only 2" deep at the vee and 3/4" at the freeboard and 4-3/4" wide. getting inside to glass the seam would be extremely difficult. I am sure that someone with more patience than me could do it. I have built several 39" hulls and followed the same procedure you mentioned and they turned out great. What I found was that a boat actually needs some sort of spray rail.

[martno1fan]

You are right sanding gelcoat wont give as smooth a finish as normal gelcoat it will need painting,but i dont agree that normal gelcoat is easy to sand far from it.Actually rather than use gelcoat your best using Duratec but its so expensive.

[martno1fan]

You are right sanding gelcoat wont give as smooth a finish as normal gelcoat it will need painting,but i dont agree that normal gelcoat is easy to sand far from it.Actually rather than use gelcoat your best using Duratec but its so expensive.Ive also used durabuild primer,this sands to a high gloss sheen and can be used and gives a nice finish to your plugs and can be directly moulded off after waxing of course.
http://www.ecfibreglasssupplies.co.uk/p-867-durabuild-surface-primer-grey-inc-catalyst.aspx

[minigazz]

This is really helpful stuff guys, thanks! So if you make your plug and then barrier it up, lay up you lower mould, remove the barriers, then lay up your upper mould you should get the perfect two parts for a seamless join (in theory!)? Surely as you lay up you two halves in the moulds you end up with scruffy overhangs which can only be cleaned up when the resin has set, which would prevent you from closing the two halves together? Is the fibreglassing on the inside really vital as I am only going to be making hulls of around 16" or 400mm in length so access could be an issue! Can anyone explain the pros/cons of polyester vs epoxy too, both seem to be used for this application? Thanks again, gazz.