tooling gel and two pcs mold

Discussion in 'Fiberglass and Composite Boat Building' started by brokensheer, May 17, 2012.

  1. brokensheer
    Joined: Jun 2009
    Posts: 201
    Likes: 3, Points: 18, Legacy Rep: 14
    Location: So. Md

    brokensheer Senior Member

    Hello, friends, I am building a small boat that has two items that stand off the hull a tumblr home guatd and a chine,, the guard is one inch tall by one inch wide and is perpendicular to the hull surface, in the images below the tumble home guard is not installed.
    the chine is the same in the aft section with a healthy radi looking down fron the top, as the chine wraps forward it gers a bit of an angle making it not perpundictular to the hull side I am planning on building a two pcs mold joined on the keel, might I consider a four pcs mold?

    tooling gel question:

    I am spraying with a dump gun, 22mils-26mils ?then here on the forum been told to roll / brish a second coat of t/g at what time and how heavy should the second coat be?

    Attached Files:

  2. Herman
    Joined: Oct 2004
    Posts: 1,618
    Likes: 94, Points: 48, Legacy Rep: 1240
    Location: The Netherlands

    Herman Senior Member

    Are you building in Australia, or are your pictures up-side-down?

    As for the number of mould pieces: Keep as little as possible, a split on the centreline should do. Just make sure your hull is designed such that it is easy to pull.

    On the tooling gel: consult the datasheet. It must be on there.
  3. waikikin
    Joined: Jan 2006
    Posts: 2,439
    Likes: 179, Points: 73, Legacy Rep: 871
    Location: Australia

    waikikin Senior Member

    Ha Ha Herman, thats the thing mate, in tooling you have to be able to think upside down & inside out. I hope Brokensheer that the rails on the chine etc are coming off for the tool. All the best from Jeff.
  4. tunnels

    tunnels Previous Member

    Ok first the mould ! are you trying to make those spray rails ? its really a waste of time !! first they are not the easyest shapes to mould and second they will create a weak line in the actual boat its self . Personaly thoughts are they are ugly and need to get rid of them ! they also date the boat and put it in the 1960's !!latsly why do you want to make a mould ??
    do you intend makng dozens of them oR just 1 ??:?::p

    Tooling gel is ok if you are intending to make a mould to make a 100 if not save your money and use just ordinary gel coat !! Theres nothing wrong with it at all !!. read the instructions from the gel coat supplyer and use the right ratio !! 1.5% and the right catalyst they recommend for that particular product !! :cool:
    If you want to second coat then use 2% catalyst so its goes of quickly and done get alligator or styrene attack !! Rather than spraying a second coat i would use a 6" pint roller to apply !! a LITTLE trick is to add 20%laiminating resin to the second coat of gell !! Its easyer to roll and gives a smooth finish and are far less likely to get Styrene attack !!Remember also to make you first layer of glass a little on the resin rich side !! you are building a mould not a boat so you need thickness with every layer you apply . DONOT USE ANY WOVEN OR STITCHED GLASS int your mould of you stand to get fibre print if its not far enough away from the gel coat !! a good waay to buld thickness it Core matt ! 5 mm core matt is a good thickness builder !! and dont try and skimp on the resin It will take a lot of resin but the 5 mm is a lot less than if it was 5 mm of solid glass !! It must look wet !! its it not keep wetting all th bleed holes need to be full of resin ! you cannot over wet core matt but you sure and hell can under wet it !! and that dangerous and at the end of the day it could be soft and not very ridged !!.
    Lets know what you decide and give us a step by step report of what you are doing and going to do next !!
  5. brokensheer
    Joined: Jun 2009
    Posts: 201
    Likes: 3, Points: 18, Legacy Rep: 14
    Location: So. Md

    brokensheer Senior Member

    Thank all

    this will be a production mold, tunnels I hear ya on the rails howqever its a signature part of a Carolina Sportfish, and kind of has to be there, I can cover the strength issue in the boat hull

    Thanks for the gel coat tips its been a good while scince I built a mold "2000".
  6. midnitmike
    Joined: Apr 2012
    Posts: 257
    Likes: 20, Points: 18, Legacy Rep: 167
    Location: Haines and Juneau

    midnitmike Senior Member

    An interesting design that might pose problems in demolding. With any amount of reverse draft in the tumble home you're going to need a two piece mold at a minimum. You'll also want to make sure your chine line has a positive draft or it will be a problem area on every pull.

    As far as the spray rails are concerned I've been a strong advocate of them for years having added them to some 20 or 30 boats here locally. Mine are somewhat triangular in profile and have proven very effective at increasing cruise speed, while dramatically decreasing the snappy roll characteristics of most modern deep v hulls.

    Since the weight and trim of commercial fishing boats can vary dramatically from one boat to the next I've always custom built each spray rail specifically to the demands required by each hull. Although over the years I've sort of settled on certain design aspects of the rails themselves their width and length continue to change according to customer wishes and my own intuition as to what the hull needs.

    Some years ago a prominent boat builder in Seattle started added spray rails to his boat as well, but they were molded separately from the hull and added later using 5200 and stainless screws.

    When I worked for Crusader boat works in Florida back in the 80's we added chine/spray rails using extruded PVC of their own design, again they were attached using 5200 and stainless screws. The shape of these PVC pieces was such that they couldn't be easily molded so having them extruded was the only option.

    I know you're well along in your build, but you may want to consider the alternatives to building that chine into the might be more trouble then it's worth in the long run...especially if this is going to be a production mold.


    BTW installing the PVC rails took two men about three or four hours... probably a lot less time then you'll spend trying to lay them up in the mold.
  7. tunnels

    tunnels Previous Member

    Can you give some closer details of the spray rails and some good pictures if the hull taken from the back and the front , Spray rails its the shape from the hull bottom that is the bit thats doing the work thats all ,so some slight changes in the design of the rail could be adventages and make demoulding and the moulding of that part easyer!! like i said the shape and size is hard to make and is a weak part of the boat . Simply filling them and moulding over the top is bad manufacturing practice specially if its a fishing boat !!
    Means the hull has a design problem and or the internal loading inside the boat needs seriously looking at !!. Things that have to be added to boats to hulls are just quick fix things that shows up the poor design of the original boat !! Leave the rail there by all means but fairing it out into the topsides so the hull will look better and release from a one piece mould . Two piece mouls as time goes by change in shape abd can become a problem as one part changes differantly to the other . Its been many uears since split moulds were the in thing to mould off odd and strange shaped hulls . they were usually Yachts from a by gone era Slowly designers caught on and started doing designs that were more mouldable and the boats went better and even looked better .
    I am sure if people see better pictures you will get better help as well :D
  8. tunnels

    tunnels Previous Member

    After sitting playing on the computer with those Australian upside down pictures ! those spray rails are just bits a timber plant ons any way so just and fair then into the topsides and it will save you one hell of a lot of extra work latter on !! you say its a signature part of a Carolina Sportfish then its time to up date and rethink its is 2012 and before you know it 2013 !!
    If you knew all about these spray rails in the very begining why didnt you build them in while you were making the boat ??
    Some forward thinking and planing will save yourself a lot of heart ach and having to sort some ducy ongoing problems in the future !!
    Is this boat loaded nose heavy ?? with those strange looking things up on the gunwhale to shed water i suspect it has some serious inherated fore and aft stability problems .To have water getting up that far the nose of the hull !!, wow dangerous !!!! :(

    There is a possability of rather than making a spit mould, make the transom so it comes off and draw the boat out the back all in one piece !!

    If you make a mould of a boat the inherant problems that boat has are and will be repeated over and over again as long as the moulds get used and in the many boats that come out of it . If you change and improve the product before the mould is made is a good thing . Getting plugs made and finished and making moulds is many long hours and is always very exspensive !!
    Also complete new Glass boats hardly ever preform like the wooden plug it came from So be warned !!
    Theres no good sticking to your guns and saying no this is what i am going to do and them 12 months down the track wishing you had done some simple updating and alterations that would be beneficial in the long run .Because you make a glass boat you are making it easyer for some one to splash and slightly change a boat ,maybe with the changes you didnt want to do and theres not much you can do about it !! Just a few things to think very seriously about !!

  9. brokensheer
    Joined: Jun 2009
    Posts: 201
    Likes: 3, Points: 18, Legacy Rep: 14
    Location: So. Md

    brokensheer Senior Member


    this boat is only 15' long I will mold the transom a a 3rd mold peice, the chine / spray rails have a large fillet mating them to the hulls topside, and the horizontal "guard" is just that water is never intended to creep up the hull that far,
    the chines ae flat i the mid to aft section and angle downwards slightly as they near the forward section. with the transom mold being desgined to be removable when remocing the boat from her mold aft section first and with upwards pressure she should demold fine!

    or I'll just build a 5 pcs mold ! two sides two bottoms and the transom!
Similar Threads
  1. itchyglass
  2. aaronhl
  3. garrybull
  4. RTM
  5. jiggerpro
  6. weldandglass
  7. Erwan
  8. nicste
  9. Tim McCraney
  10. John Slattery
Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.